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Thread: Upgrade or repair oil boiler?

  1. #1
    DIY Junior Member ess's Avatar
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    Default Upgrade or repair oil boiler?

    Hi - I've been lurking on this forum quite a bit gathering all sorts of tips on boilers, insulation, etc. etc., and I was hoping that if I posted my situation, I might be able to get some of the great advice as well.

    Summary: We have an newish but kind of mediocre boiler, and I'm trying to determine if it's worth improving the current boiler or taking the money that we would put into the existing boiler and putting it towards a new (better) one.

    [House]
    - Location: North of Boston (01810)
    - Family of 6 (4 adults, 2 children)
    - House built 1968; 2 story colonial with mostly "finished" basement, ~1500 square feet / floor (I believe the deed has us around 3200 not counting the basement)
    - Blower door test: 4202 cfm50 (mid-high, but that's down from 6200 before MassSave air sealing!)
    - Blown in cellulose in attic floor and eaves; mostly (but not all) replacement windows; basement heated but almost certainly not well insulated (on our plan for before winter); 1960s insulated walls (fiberglass; IR tests seem to show that it's mostly still there and hopefully helping a bit)
    - We installed a Carrier Greenspeed (ducted) heat pump last winter/spring in the attic for the second floor to help with non-design day heating (at least for the 2nd floor zone) and provide summer cooling.
    - We tend to keep the house on the cool side - 68 is about max for us, and I think our setbacks go as low as 62.

    [Boiler]
    Hydrotherm PB-105-WT boiler, installed probably about 3.5 years ago (not by us) and currently used only for heat
    http://www.drillspot.com/products/51...l_fired_boiler
    Beckett 7505 GeniSys Control; Watts Model ETX-30 Pressurized Expansion Tank with Diaphragm
    0.65 x 80A @ 140 PS Nozzle = 0.77 GPH
    Rated ~85% new; Latest combustion test: 82%
    Three zones (2nd floor, 1st floor, basement)

    - The boiler is in an unheated garage room (boiler definitely warms it up).

    - Fin tube baseboard radiators (some in less than stellar condition). Upstairs heat has a lot of pinging, banging and clicking sounds that may be due to badly installed baseboard (missing dampening pieces?) or damage (fins touching each other) or...something else.

    - Rooms far from the thermostat on the second floor are quite cold, although we do have issues with the thermostat being placed incorrectly (all the way at the other end of the house) / damaged baseboards / furniture probably interfering, so I'm thinking that it's more of a repair issue than an issue with the boiler itself. I checked and the pipes for the baseboard in one of the cold rooms do get warm / hot (although not burning to the touch immediately). That seems to have ruled out air in the pipes (I think?), although I've been meaning to check and see if individual baseboards have bleed valves (I'm guessing unlikely).


    [Energy use]
    I have tried my best to do a bunch of the necessary calculations, but I'm not sure I've done them 100% correctly.

    We use about 1000 gallons of oil per year overall; the numbers here are a bit lower because I was trying to match up the degree days to oil deliveries.
    Closest degree days station: Osgood Street, Andover, MA (71.19W,42.63N) KMAANDOV3

    For 10/1/12 - 5/30/13, I got:
    Heating Degree Days: 6034
    Oil usage: ~845.7 (we got a delivery of 108.5 gallons on 5/23, but I kept the 10/3/12 delivery of 21 gallons...it's not perfect)
    Calculated K-Factor: 7.13 (this is my number - our oil company does not provide on invoices)
    BTU / hour @ 80% = 41907
    BTU / hour @ 85% = 44526

    For the calculations I made during 11/01/13 - 01/31/14:
    Heating Degree Days: 3213
    Oil usage: ~534.4
    Calculated K-Factor: 6.01 (this is my number, same as above)
    BTU / hour @ 80% = 49730
    BTU / hour @ 85% = 52839

    Is this showing that the boiler is oversized for our heating needs (about 2x, give or take)? Especially considering that it is feeding three separate zones and doesn't modulate?

    Basically, I'm trying to figure out if it would be overkill to spend a lot of money to upgrade the current boiler to something right-sized and efficient, like an Energy Kinetics or Firebird boiler. If we can get ROI even within 10-15 years, I could see a point, but it's unclear to me how much we could expect to save each year (we might need to save like 30%), especially since we're hoping to lower some of the energy costs via the new heat pump.

    This is made a little more complicated by the fact that with the current boiler, there are some changes to be made (see below - chimney, heat purge control, possible hot water tank, etc.), so we'll be spending money on the heating system either way. It might be that the true difference between improving / fixing the current system and installing a new one is more like half of the full upgrade cost (and thus a much easier ROI), but that depends on which fixes would be worth making on the current boiler.

    For potential replacements, I've been looking at Energy Kinetics EK1 and Buderus G125be, and I saw a Firebird boiler mentioned as well. The smallest available appear to be around 80k BTU / hr - so closer to estimated heat load range, but not -that- much better than what we have now (about 15%?).


    [Questions]
    1) Thoughts on whether the better sizing and benefits (integrated smart controls, better venting, better insulation, etc.) are worth the rather steep upgrade cost versus retrofitting the current boiler? Is the current boiler worth improving? I keep thinking that it's only 3ish years old, so I'd hate to rip it out, but it really does seem mediocre when compared to what else is out there.


    2) Our current electric hot water heater likely is the reason why our electric bill is higher than we'd like, plus it's about 18 years old and we do run out of hot water with multiple serial showers. I've been very happy with indirect hot water in the past, but since our boiler isn't that efficient (and oil is expensive), would we be better off getting a heat pump / electric hot water tank (maybe oversizing it a little if we're worried about capacity)? Is this mitigated by indirect hot water heaters being so efficient at holding temp?

    (For the heat pump hot water heater, are there any that you'd recommend that are quieter and/or more efficient / reliable than most? The current hot water heater is located fairly near the basement recreation room, so having extra noise down there didn't seem like a great thing.)

    If we went with the indirect option, would we be able to cold start the existing boiler, or would it need to run all the time (warm start?) - and if the latter, would there be a lot of extra oil used over the summer?


    3) We currently have a powervent out the side of the house that is somewhat smelly (slight burning oil smell - we've been told this is normal?) and in a location that's close enough to an inside corner / porch that we want to move it. The suggestion from the oil company representative was to install a double-wall insulated stainless flue (we can go straight up through the roof of the garage). I'm a little concerned about chimney draft hurting the already mediocre efficiency of the boiler, but it does seem to be the only other option, assuming we stay with the current boiler. Does the chimney sound okay, or is this another reason to consider a new boiler that might be able to vent more efficiently?


    4) Are there cheaper upgrades that we could make to the current system that would help efficiency as well as fix the comfort / coldness issues (assuming we find someone qualified who will actually look at the baseboards)? Would that potentially make it worthwhile to consider an indirect hot water tank instead of the heat pump?

    Some of the items I've been considering - which of these would you recommend, or are there others you would suggest?
    - Intellicon HW+ or other heat purge control (am I correct that this would work better for us than an outdoor reset, since the temp needs to stay about 140 anyway?)

    - Thermostats that can interact and coordinate zone calls
    --I have no idea if the boiler is short-cycling - I definitely don't think it's running all the time. I'm assuming combining zone calls would help, but is there anything else that can be done?

    - Insulate the boiler plumbing, or the boiler itself (or at least add insulation to the boiler "room")

    - Stop using setbacks as much (don't use them at all?)

    - Slow close zone valves? Variable speed circulator pump? I think one of these was suggested as potentially helping with the pipe / baseboard noises (by the oil company assessor).


    5) We're considering adding heat to our 3-season porch - ideally radiant (in-floor), although we have other options. We'd have to add another zone to the existing boiler to do so. Is the efficiency of the current boiler low enough and/or would the radiant zone be so small (as the boiler doesn't modulate) that we should consider something else (pellet stove, ductless unit, etc.)?


    Also, I would be very grateful to receive any HVAC contractor recommendations in my area (via PM), especially ones familiar with retrofitting oil boilers.

    Thank you so much!

  2. #2
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    Bock oil-fired 33E with with a Taco XPB, and annual maintenance by a qualified oil-burner service technician.


    If you have a proper Manual 'J' heat load performed, measure your radiation and have the systems designed properly your comfort will improve while the fuel bill goes down. There are always ways to improve the envelope...last would be new windows by the way.

  3. #3
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by BadgerBoilerMN View Post
    Bock oil-fired 33E with with a Taco XPB, and annual maintenance by a qualified oil-burner service technician.


    If you have a proper Manual 'J' heat load performed, measure your radiation and have the systems designed properly your comfort will improve while the fuel bill goes down. There are always ways to improve the envelope...last would be new windows by the way.
    Thank you so much for replying! We do get annual maintenance under our oil service plan, and I agree that new windows will not help us as much as some other areas (I'm thinking air sealing around badly installed replacement windows, replacing the badly leaking front door, and basement insulation per Dana's excellent instructions, at least for this year).

    Were you suggesting the Bock 33E + Taco XPB together for the water heater replacement, or also / instead to support radiant heat (which on a quick glance the Taco XPB can do)?

    I hadn't considered a straight oil-fired water heater. If the Energy Factor for the 33E is only .68 (and a warranty of only 5 years), wouldn't it end up costing more overall than either a heat pump water heater or an indirect, or am I thinking about the efficiency and lifespan incorrectly?

    I completely agree about the system needing to be specced and designed properly, in theory. However, what sort of redesign could we do while keeping the current boiler - would we be adding / removing baseboard, tweaking the boiler? Or were you talking about getting a Manual 'J' and designing properly if we went ahead with a new boiler? Also, the difficulty is figuring out who will be willing to come out and consult when we're trying to spend a couple thousand if possible rather than the bigger bucks of an entirely new system (unless retrofitting really is a losing battle).

  4. #4
    In the trades Dana's Avatar
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    The EF of an oil hot water heater is irrelevant when using it in space heating mode, since you'll be running the burner at a much higher duty-cycle than for just heaiting ~63 gallons/day of hot water. The steady state combustion efficiency is still going to be in the mid-80s, but unlike an oil boiler it has a lot of thermal mass to work with, which allows you to micro-zone without short-cycling, and it's better insulated than almost all oil boilers.

    But if the current boiler is in good condition it's probably worth waiting. The fact that it's in the garage and outside of your conditioned space means that the standby losses don't fully accrue to the conditioned space, which is bad for net efficiency, but for estimated sizing you should be looking at it's I=B=R output, not the D.O.E. output number.

    The Intellicon would be a cheap & reasonable retrofit for the boiler if you decide to keep it for awhile, and it would cut that 850 gallons do the high 700s if you opted not to heat with the heat pump. Putting at least 1" fiberglass pipe insulation on all of the heating system plumbing in the garage would be cost effective too.

    The Greenspeed is going to have about half the operating cost of 85% oil at your mid-winter binned-average temp of ~25F, and it may even be able to support the entire load at that temp. Even the 2-ton Greenspeed is good for about 25,000BTU/hr @ +15F. Your 99% outside design temp in Andover/Lawrence is about 0F, a temp at which even the 3-ton unit is barely delivering 20,000 BTU/hr, which means you'd likely still be using some oil.

    At a K-factor of 6 and a design temp of 0F is 65F heating degrees (since 65F is the modeled balance point between heating & cooling) implying a heat load of ~50K @ 0F with an 80% burner, 53K with an 85% burner but since it's out in the garage the true heat load is going to be in the mid-40s. As a sanity check a 45K load for 3200' of house is 14 BTU/foot, which would be about right for a somewhat leaky 2x4 framed house with decent insulation and clear-glass (not low-E) replacement windows, or storms over single-panes, and less than stellar foundation insulation & air sealing. Odds are pretty good that your heat load can be cut to at least the low 40s after insulating & air sealing the basement.

    That means the heat pump can deliver half or more of your heat at design condition, and can deliver the lions-share of the load at the average outdoor temp. Since it's operation cost is lower than oil, and it's efficiency is higher when modulation it may be best to "set and forget", the thermostat on the Greenspeed to something like 70F, and set the oil-fired zone T-stat to 65F as the backup, minimizing the fraction of the heat load carried by the oil burner. If after further house-tightening heating with the Greenspeed cuts your annual oil use to under 200 gallons it may not be worth replacing the boiler from a financial point of view (until its really dead), but it would still be worth insulating the pipes, and adding an Intellicon as a DIY.

  5. #5
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by Dana View Post
    The EF of an oil hot water heater is irrelevant when using it in space heating mode, since you'll be running the burner at a much higher duty-cycle than for just heaiting ~63 gallons/day of hot water. The steady state combustion efficiency is still going to be in the mid-80s, but unlike an oil boiler it has a lot of thermal mass to work with, which allows you to micro-zone without short-cycling, and it's better insulated than almost all oil boilers.
    Right, I think that's what I was missing - BoilerBadgerMN was suggesting the Bock heater if we went with a radiant zone, instead of plumbing a new radiant zone on the existing boiler (please let me know if I'm still incorrect). It's a really neat idea, and in that case, I agree that comparing the efficiency of the Bock to indirect or heat pump hot water is irrelevant.


    Quote Originally Posted by Dana View Post
    But if the current boiler is in good condition it's probably worth waiting. The fact that it's in the garage and outside of your conditioned space means that the standby losses don't fully accrue to the conditioned space, which is bad for net efficiency, but for estimated sizing you should be looking at it's I=B=R output, not the D.O.E. output number.
    Okay, so the I=B=R is 79,000/98,000 - would I be looking at the first number for the sizing, since we're supposedly set to use 0.77 gph (at the low end of the range)?

    Besides the piping, would it be helpful to look at insulating the boiler itself or the walls of the room that it's in, to help cut the standby losses, or would that time be spent better elsewhere? I wasn't sure if the boiler would run better at a more stable temperature versus in a colder room.

    Quote Originally Posted by Dana View Post
    The Intellicon would be a cheap & reasonable retrofit for the boiler if you decide to keep it for awhile, and it would cut that 850 gallons do the high 700s if you opted not to heat with the heat pump. Putting at least 1" fiberglass pipe insulation on all of the heating system plumbing in the garage would be cost effective too.
    Great, I was hoping you would say that. Would you believe that when I asked the oil company efficiency expert about insulating the heating plumbing, he told me not to bother? That didn't really make much sense to me.

    Quote Originally Posted by Dana View Post
    The Greenspeed is going to have about half the operating cost of 85% oil at your mid-winter binned-average temp of ~25F, and it may even be able to support the entire load at that temp. Even the 2-ton Greenspeed is good for about 25,000BTU/hr @ +15F. Your 99% outside design temp in Andover/Lawrence is about 0F, a temp at which even the 3-ton unit is barely delivering 20,000 BTU/hr, which means you'd likely still be using some oil.

    At a K-factor of 6 and a design temp of 0F is 65F heating degrees (since 65F is the modeled balance point between heating & cooling) implying a heat load of ~50K @ 0F with an 80% burner, 53K with an 85% burner but since it's out in the garage the true heat load is going to be in the mid-40s. As a sanity check a 45K load for 3200' of house is 14 BTU/foot, which would be about right for a somewhat leaky 2x4 framed house with decent insulation and clear-glass (not low-E) replacement windows, or storms over single-panes, and less than stellar foundation insulation & air sealing. Odds are pretty good that your heat load can be cut to at least the low 40s after insulating & air sealing the basement.

    That means the heat pump can deliver half or more of your heat at design condition, and can deliver the lions-share of the load at the average outdoor temp. Since it's operation cost is lower than oil, and it's efficiency is higher when modulation it may be best to "set and forget", the thermostat on the Greenspeed to something like 70F, and set the oil-fired zone T-stat to 65F as the backup, minimizing the fraction of the heat load carried by the oil burner. If after further house-tightening heating with the Greenspeed cuts your annual oil use to under 200 gallons it may not be worth replacing the boiler from a financial point of view (until its really dead), but it would still be worth insulating the pipes, and adding an Intellicon as a DIY.
    We have a 3-ton, but I agree about needing the oil heat for backup (plus for heating the basement and first floors, although the staircase is open enough that there should be some airflow). We're still figuring out at what temp it makes sense to swap over from the upstairs heat pump to oil, but hopefully we won't hit those temps again until next winter. We've also thought about adding ductless units on the first floor (which is much more open plan than the second floor) if we need them for summer cooling - I hadn't really thought about using them for heating on the first floor, although it sounds like it could be more cost effective (for about the same price) than upgrading the boiler?

    Thank you for the thermostat suggestions - that sounds like a valid way to coordinate the different systems without actually having something actively managing them.

    So if we did go ahead with the Intellicon / pipe insulation / basement insulation, what would you recommend for replacing our hot water tank? The tank will be in the conditioned basement, not out with the boiler. Would a heat pump hot water heater be a better choice than something like a Superstor (which I've had before and loved, but that was off of a high efficiency gas boiler), as long as we can deal with the extra noise near the playroom?

    Also, do you know if switching from the current power vent to a direct vent stainless chimney would hurt the efficiency of the boiler? I'm not getting a great deal of information either way.
    Last edited by ess; 04-01-2014 at 10:04 AM. Reason: missed parentheses

  6. #6
    In the trades Dana's Avatar
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    If the I=B=R output is 79K and your true heat load is 45K, it's less than 2x oversized, but not a lot less. If you insulate and air seal the boiler room bringing it inside of conditioned space the D.O.E. number is valid, since the standby losses aren't all 100% lost.

    In practical terms building out the boiler room with insulation so that it's inside the thermal envelope of the building probably isn't going to be worth it unless you continue to use the boiler as your primary heat source. Since there is probably an insulated wall between the boiler and the fully conditoined space the benefits won't be quite the same as moving the boiler completely inside. It may be possible to add insulation to the boiler itself, but you have to be careful not to interfere with any combustion air, and use rock wool (which can't burn or even melt at oil-burner flame temps.) It's probably only going to be worth insulating the boiler if the original insulation on the boiler jacket is an inch or less. Most boilers would be a real PITA to retrofit insulation onto in a meangingful way.

    Heat pump water heaters are a bit noisy and cool off the space that they're in, but they also dehumidify the space a bit. Recovery times are long in heat-pump-only mode, and for a family of 6 you'd have to get a pretty big one like the AirTap ATI-80 or Stiebel Eltron Accelera 300, either of which are pretty pricey. The ATI-80 is all-stainless, and will probably outlast the others, and may be worth paying a premium, but it's hard to say for sure. Otherwise a much cheaper 80-100 gallon electric tank like the Marathons are pretty good, but they use 2x the electricity.

    To extend showering time a drainwater heat exchanger might be useful for your situation. A 4" x 48" will return slightly more than half of the heat going down the drain into the incoming water stream, pre-heating it to roughly room temp. This means you end up mixing in about 2x the volume going into the cold side of the shower mixer, and taking a significant chunk off the hot side flow, and the recovery time for the tank is cut in half. (The PowerPipe series is the only ones currently listed on the MA-approved plumbing fixtures list, and you can get them at wholesale through EFI by opening up an account with them over the phone with a credit card. They can also be ordered direct from the manufacturer or Home Depot, but it's more expensive that way.) With six people it'll have a reasonable payback if they're all showering daily.

    The 3-ton Greenspeed could probably carry ALL of the load at 25F if it were also ducted (and separately zoned) for the first floor.

  7. #7
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by Dana View Post
    Heat pump water heaters are a bit noisy and cool off the space that they're in, but they also dehumidify the space a bit. Recovery times are long in heat-pump-only mode, and for a family of 6 you'd have to get a pretty big one like the AirTap ATI-80 or Stiebel Eltron Accelera 300, either of which are pretty pricey. The ATI-80 is all-stainless, and will probably outlast the others, and may be worth paying a premium, but it's hard to say for sure. Otherwise a much cheaper 80-100 gallon electric tank like the Marathons are pretty good, but they use 2x the electricity.
    We do run a dehumidifier in the basement during the summer, so that is a side benefit (I don't know if it would be able to replace the dehumidifier). Would insulation help with the dehumidification needs as well? I've bookmarked a bunch of posts about using EPS / XPS foam, no vapor barrier, etc., but I wasn't sure if that would reduce humidity levels (by raising the temp) as well as keep mold from forming. We don't actually get water in the basement; it's about half exposed cement walls to the outside (walkout) and half dirt surrounded.

    Should I just forget about the option of adding an indirect unit off the boiler? I like the idea of purging boiler waste heat into it for better winter efficiency, but would the summer running costs for the existing boiler be a lot more than electric (since oil prices likely are going to stay where they are / go higher)? I'm not concerned so much about additional upfront cost for an indirect, since the stainless units should have a longer lifetime than standalone tanks (I'm assuming).

    Now that I think about it - our current water heater is about half the house and one story from the boiler - I don't even know if the leftover heat could be purged from the boiler to the water heater at that distance (or if what I'm talking about even makes sense)...Also, if we end up using the boiler less during the winter overall, there would be less boiler heat to save.

    There's no way to run indirect in the winter and heat pump (or even electric) in the summer, is there?

    Quote Originally Posted by Dana View Post
    To extend showering time a drainwater heat exchanger might be useful for your situation. A 4" x 48" will return slightly more than half of the heat going down the drain into the incoming water stream, pre-heating it to roughly room temp. This means you end up mixing in about 2x the volume going into the cold side of the shower mixer, and taking a significant chunk off the hot side flow, and the recovery time for the tank is cut in half. (The PowerPipe series is the only ones currently listed on the MA-approved plumbing fixtures list, and you can get them at wholesale through EFI by opening up an account with them over the phone with a credit card. They can also be ordered direct from the manufacturer or Home Depot, but it's more expensive that way.) With six people it'll have a reasonable payback if they're all showering daily.
    I've seen you mention this before and was intrigued. Does it require ripping into ceilings / walls to get at existing plumbing, or is it an easier retrofit than that?

    Quote Originally Posted by Dana View Post
    The 3-ton Greenspeed could probably carry ALL of the load at 25F if it were also ducted (and separately zoned) for the first floor.
    An interesting point, but at the time, we didn't really want to deal with ripping into closets and whatever else was required to get ducting down to the first floor. I'd still prefer not to, but it sounds like it's at least worth discussing. Is it tricky to add a zone and balance additional load to an existing system?

  8. #8
    In the trades Dana's Avatar
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    If you raise the temperature of the air, it's relative humidity falls, but that will be a very minor effect for the basement. The bigger issue is to stop the stack effect air infiltration that is pulling warm humid summertime air into your cool basement. The foundation sill and and band joist are typically a bigger air leak than all door & window crackage leaks combined, but there are probably a few other bigger leaks as well if you're over 4000cfm/50. The cfm/50 number doesn't tell you where those leaks are- and location is important. The leaks at the upper floor ceiling level and at the foundation levels are by far the most important, since those are the locations under stack-pressure. If you seal both the top of the stack and the bottom of the stack what happens in between doesn't much matter (except under wind loading.)

    A heat pump hot water heater will take some of the summertime humidity load off, but not all. But it will cut into the duty cycle of the dehumidifier by a good bit, and instead of dumping that heat-of-vaporization into the basement heating up the space, it'll be dumping into water inside an insulated tank instead.

    Heating hot water with an 85% efficiency oil boiler is roughly at par with a standard electric hot water heater at local oil/electricity rates. You'll get better hot water performance in terms of recovery times, but going forward I expect it to become more expensive to run than a cheap electric hot water heater. cood b rong, offen am- predicting future energy pricing is fraught with contingencies.

    But with more wind & solar coming on the MA grid with a marginal-kwh cost of $0 the cost of electricity isn't likely to rise quickly. The price of natural gas currently drives much of the ISO-NE regional electricity pricing, since annually about half of all power moving on this grid is sourced by combined cycle gas. Nukes are between a quarter and a third. At the moment non-hydro renewables is in low double digits on an annualized basis, but the installed base of solar in MA is doubling every two years, and will cut pretty deeply into the summertime peak power that would have otherwise been sourced by oil & gas fired peaker plants, and cut the peak-power marginal price to the grid operator very significantly. Peak power in summertime often breaks a buck a kilowatt-hour at the spot market price, and is a real factor in where the rate structures end up.

    The current levelized cost of energy for small-scale PV is below the residential retail rate in MA even without subsidy. With the SREC market kickbacks and tax incentives the lifecycle cost per kwh of grid-tied rooftop PV is conservatively under 8 cents/kwh to the home-owner, or about half the current residential fixed rate. That level of incentive is going to drive rooftop PV for quite awhile, and the actual installed price is still falling. (I reviewed a proposal for a 15kw system last week that was priced at $3.70 per watt. A single roof-top watt of panel returns about 1.1-1.2kwh per year in this area, averaged over the lifecycle of the panel. Residential retail electricity is about 15-21 cents. At 15 cents/kwh return on a $3.70 investment that's an after-tax internal rate of return (IRR) of 4%, but when that $3.70 is reduced by the 30% tax credit the IRR climbs to about 6%. Then when the SRECs are sold at another 4-6 cents/kwh you're talking after tax returns way better than an S &P 500 index fund, eh? In MA if you have a decent amount of south facing roof pitch it's becoming almost a no-brainer. But in about 5 years even the un-subsidized cost of PV will be under $2/watt, and no matter what the SREC markets look like and even without tax credits the cork will be fully out of the bottle, and the tsnumami of cheap PV installations will be breaking big-time.

    So what's currently a 1% slice of the MA grid (and largely invisible to the ISO-NE operators, to whom it appears as a lower load) will be well into double digits as a fraction of all kwh going onto the MA grid within the lifecycle of a hot water heater.

    Drainwater heat exchangers are a section of copper drain pipe with a slinky of potable-copper piping tightly wrapped around it. To work they have to be oriented vertically- in a vertical orientation the surface tension of the drain water causes it to cling and spread to the walls of the drain for maximum surface area/maximum heat transfer. If horizontal the much stronger gravitational forces keeps the water on the bottom edge of the drain, at maybe 20% of the surface area contact. With 100-105F water going down the draing, and cold water coming in at the bottom of the potable slinky at maybe 40-45F, it exits the top at 70-75F. If both the hot water heater AND the cold feed to the shower are being fed by the output of the heat exchanger you get the energy-return benefit.



    From a functional point of view it doesn't much matter how far away the heat exchanger is from the shower or hot water heater, but from an ease of installation point of view it's easier if the hot water heater is reasonably close to the heat exchanger, as it is with this tank HW heater:



    So it may matter where your main drain stack lives relative to your potable plumbing. In most basements (even finished ones) it's usually fairly accessible.

    I have no idea how difficult it would be to add a zone to your existing Greenspeed system, but it's usually do-able if you can give up some space somewhere for a duct chase.

    Even at 0F outdoor temps the efficiency of the Greenspeed is high enough that it is at least not much WORSE than heating with 85% oil (especially with a boiler that is in the garage rather than the basement.) I would estimate that a typical installation would have a coefficient of performance (COP) of at least 1.5 @ 0F, which means it's delivering 1.5 watts of heat for every watt of power being used. One kwh is equal to 3412 BTU, so 1.5kwh is 5118 BTU. A gallon of oil in an 85% burner delivers about 117,300 BTU/gallon, so it takes 117,300/5118= ~ 23 kwh to be equivalent to a gallon. Assuming 16 cents/kwh that's the equivalent of $3.68/gallon oil. Only if your power is a lot more expensive than that or oil is a lot cheaper should you bother re-calculating. At warmer outdoor temps your coefficient of performance rises significantly, and at 40-45F outdoor temps even at full speed you'd be getting at least 10,000 BTU/kwh out of the heat pump, and significantly more if it's modulating.

    There are cold-climate modulating mini-splits out there that will run at a COP of 2 even at -25C/-13F, but unless you have a fairly open floor plan on the first floor it's probably not an option. It's point-source heating, no ducts/distribution - think of it as a funky looking wood stove with a quiet blower. :-) But they're comparatively cheap relative to a GreenSpeed- a unit capable of delivering 18,000 BTU/hr @ 0F would still be under $5K, installed. They have become the most popular heating/cooling solution for super-high-R houses in New England, and can be put to good use elsewhere. (If your basement is fairly open a 3/4 ton mini-split would likely cover the heating load there, installed cost in the low $3Ks.) It's not as cushy as radiant floors, but more comfortable than most fin-tube baseboard heating systems.

    Oil heating is dead IMHO. There is no way it's going to get cheaper- oil is much to useful to the rest of the world as transportation fuel, and even those drunk on the frack-water will tell you that crude oil can't be economically retrieved from shale or sand at $50/bbl, even if they're getting rich at $100/bbl oil. If you're on the gas grid it may be worth investing in nicer radiation for a hydronic system, but if your options are oil & propane even low-temp radiant floors will be far more expensive to run than the better heat pumps. Hydronic output heat pumps can work OK with low temp radiation, but at a much higher cost than even the GreenSpeed.
    Last edited by Dana; 04-01-2014 at 02:31 PM.

  9. #9
    Master Plumber nhmaster3015's Avatar
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    You guys never ask the right questions which are. How much money do you have? How long do you plan to live in the home? How many years are you willing to take to pay for the upgrade? Is oil the only option or do you have natural gas available? How do you feel about solid fuel boilers? What is your estimated hot water useage?
    Don't believe everything you hear, go find out for yourself.

  10. #10
    Master Plumber nhmaster3015's Avatar
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    Drainwater heat exchangers are a section of copper drain pipe with a slinky of potable-copper piping tightly wrapped around it. To work they have to be oriented vertically- in a vertical orientation the surface tension of the drain water causes it to cling and spread to the walls of the drain for maximum surface area/maximum heat transfer

    Which is why in probably 90% of residential installations it just won't work.
    Don't believe everything you hear, go find out for yourself.

  11. #11
    Master Plumber nhmaster3015's Avatar
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    Drainwater heat exchangers are a section of copper drain pipe with a slinky of potable-copper piping tightly wrapped around it. To work they have to be oriented vertically- in a vertical orientation the surface tension of the drain water causes it to cling and spread to the walls of the drain for maximum surface area/maximum heat transfer

    Which is why in probably 90% of residential installations it just won't work.
    Don't believe everything you hear, go find out for yourself.

  12. #12
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by nhmaster3015 View Post
    How much money do you have?
    How long do you plan to live in the home?
    How many years are you willing to take to pay for the upgrade?
    I am willing to put money into this project as long as it will save us energy overall and pay back in a reasonable period of time (generally 10 years max). However, I'd really rather not spend the money if there aren't very clear benefits.

    So for example, if an oil boiler upgrade costs $10,000 but provides us with a new indirect hot water heater and save us $1000 in oil costs per year, then that would be worth considering, especially if the evaluation process while replacing the boiler fixes the cold room issues (replacing baseboard, balancing the system, whatever).

    Factors that are hard to predict: price of oil going forward, lower use of the oil boiler due to using the heat pump except on the coldest days (although only on the second floor), actual savings.

    If we keep our current boiler, I'm anticipating that we'd have the following costs anyway:
    - new efficient water heater of some sort (likely included in the cost of a new boiler - or at least as we had them specced)
    - Intellicon HW+ (equivalent or ODR comes with a new boiler)
    - Change from power vent to chimney (new boiler would also get a new vent)

    So this is $3-5k that's going into the heating / hot water system regardless.

    Plus:
    - Investigation of cold room issues / some baseboard repair or replacement (probably not included, but possibly fixed with proper system design)
    - pipe, foundation, and other insulation (not included with new boiler)

    I'm mostly considering replacing the boiler because we need a new hot water heater sooner rather than later, and I would like to use less oil both for environmental and money reasons. The heat pump hot water heaters have some drawbacks we don't like (noise, need to refill, units that cost twice as much for the same tank warranty as straight electric ones, pulling heat from an oil-heated basement - but the dehumidification and better energy factor in the summer are nice). My ideal choice would be a stainless indirect unit with a long warranty like a Superstor, except...mediocre oil boiler that would need to run during the summer.

    Ductless heat pumps might help get us off oil for heating (and add cooling), but they won't help us with hot water. They would be a possibility over time, though, if we didn't upgrade the boiler (I see no reason to put a lot of money into a boiler that we plan on using less and less).

    We don't have plans to move for at least the next 10 years (although plans can change). I do like to keep resale values in mind when putting money into the house, however.

    Quote Originally Posted by nhmaster3015 View Post
    Is oil the only option or do you have natural gas available?
    No gas, unfortunately, or I'd be switching.

    Also no solar, alas, as we'd have to cut down something like 10 trees to have sun on our roof during the summer. If we had a sunny South-facing roof, it would absolutely be worth it.

    Propane prices are high enough that it hasn't even seemed worth considering switching to that.


    Quote Originally Posted by nhmaster3015 View Post
    How do you feel about solid fuel boilers?
    Do you mean wood or pellet? I hadn't considered them, but it's an interesting option. I have no idea about the air pollution impact, efficiency, and cost of fuel versus oil. Would we be able to put a solid fuel boiler in the garage where we have our current boiler?

    The other question is price, just as with putting in a more efficient oil boiler. Also, I don't know if having a whole house boiler that's not oil or gas is weird enough that it might hurt the resale value of the house (which I wouldn't want to bite us down the road).

    Quote Originally Posted by nhmaster3015 View Post
    What is your estimated hot water useage?
    Interesting question - I'm not sure of the best way to find this out. I can check on the size of the existing electric HW tank later, but I have a feeling that it's never been maintained (and I don't really want to try and drain it now, as I'd rather have a plan in place first in case it fails ).

    Currently, we have a high efficiency dishwasher (but we may run it multiple times a day), a high efficiency top loading washer (although we mostly wash , and about 3-4 showers per day (not excessively long, and I think we have 1.5 and 2.5 GPM heads). There are a few baths each week, but they're not very deep (although I would love to add a 70-75 gallon soaking tub at some point in the distant future).

  13. #13
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by nhmaster3015 View Post
    Drainwater heat exchangers are a section of copper drain pipe with a slinky of potable-copper piping tightly wrapped around it. To work they have to be oriented vertically- in a vertical orientation the surface tension of the drain water causes it to cling and spread to the walls of the drain for maximum surface area/maximum heat transfer

    Which is why in probably 90% of residential installations it just won't work.
    Useful note. I think it makes sense to investigate whether we can put one in (if we end up going with a heat pump hot water heater, it might mean the difference between the Airgenerate ATI66, which has a Mass Save rebate, versus the ATI80, which doesn't), but I don't know whether it would fit - I'd need to verify where our drain line is.

  14. #14
    In the Trades Tom Sawyer's Avatar
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    Quote Originally Posted by ess View Post
    Useful note. I think it makes sense to investigate whether we can put one in (if we end up going with a heat pump hot water heater, it might mean the difference between the Airgenerate ATI66, which has a Mass Save rebate, versus the ATI80, which doesn't), but I don't know whether it would fit - I'd need to verify where our drain line is.
    Well, start at the start so to speak. You are pretty much stuck with oil although you might want to look into a solid fuel pellet boiler as an add on to the current system. IOW, keep the boiler, add a pellet boiler. They are expensive though. In the 10,000 dollar range. They certainly can be installed in the garage beside your current boiler though. I heat pretty much exclusively with pellets. The cost difference for me was from 8000 in oil per year to 2500 in pellets so it makes sense for a house the size of mine. Keep the power vent. Chimneys add to standby loss which can be mitigated with a power vent damper but you already have the power vent so keep it. A superstor SS40 makes a whole lot of sense both economically and you won't run it out of hot water. If you do go with a solid fuel boiler it will heat the superstor too. An intellicon always makes economic sense so definitely do that. Going with a heat pump is going to cost a whole lot of money both for the installation and the equipment. If you change the boiler, look into the Firebird condensing oil fired boiler. It does not need to condense to still give you very high efficiencies. Personally, me, intellicon and a superstor to start and see how things work out for a season. If you decide to upgrade the boiler you can use both on the new system.

    Unless you have about a 4' vertical drop from your shower drain to the building drain (and almost nobody does) heat recovery won't work. I'd estimate 90% of homes just can't use it because there is almost never enough vertical between the inlet and outlet but maybe you can get lucky. Still, the cost of the equipment and having it installed is going to take a whole lot of years to pay back.
    Last edited by Tom Sawyer; 04-02-2014 at 02:41 PM.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  15. #15
    DIY Junior Member ess's Avatar
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    Quote Originally Posted by Dana View Post
    If you raise the temperature of the air, it's relative humidity falls, but that will be a very minor effect for the basement. The bigger issue is to stop the stack effect air infiltration that is pulling warm humid summertime air into your cool basement. The foundation sill and and band joist are typically a bigger air leak than all door & window crackage leaks combined, but there are probably a few other bigger leaks as well if you're over 4000cfm/50. The cfm/50 number doesn't tell you where those leaks are- and location is important. The leaks at the upper floor ceiling level and at the foundation levels are by far the most important, since those are the locations under stack-pressure. If you seal both the top of the stack and the bottom of the stack what happens in between doesn't much matter (except under wind loading.)
    Sadly enough, Mass Save seems happy getting us from horribly leaky to just leaky (they sealed the upper floor in the attic and plumbing stacks, mostly). I may see if I can get (pay) someone to come out and test us again after we get the basement insulated and sealed, with the stipulation that they help find the leaks if we're still leaking air somewhere.

    Quote Originally Posted by Dana View Post
    A heat pump hot water heater will take some of the summertime humidity load off, but not all. But it will cut into the duty cycle of the dehumidifier by a good bit, and instead of dumping that heat-of-vaporization into the basement heating up the space, it'll be dumping into water inside an insulated tank instead.

    Heating hot water with an 85% efficiency oil boiler is roughly at par with a standard electric hot water heater at local oil/electricity rates. You'll get better hot water performance in terms of recovery times, but going forward I expect it to become more expensive to run than a cheap electric hot water heater. cood b rong, offen am- predicting future energy pricing is fraught with contingencies.

    But with more wind & solar coming on the MA grid with a marginal-kwh cost of $0 the cost of electricity isn't likely to rise quickly. The price of natural gas currently drives much of the ISO-NE regional electricity pricing, since annually about half of all power moving on this grid is sourced by combined cycle gas. Nukes are between a quarter and a third. At the moment non-hydro renewables is in low double digits on an annualized basis, but the installed base of solar in MA is doubling every two years, and will cut pretty deeply into the summertime peak power that would have otherwise been sourced by oil & gas fired peaker plants, and cut the peak-power marginal price to the grid operator very significantly. Peak power in summertime often breaks a buck a kilowatt-hour at the spot market price, and is a real factor in where the rate structures end up.

    The current levelized cost of energy for small-scale PV is below the residential retail rate in MA even without subsidy. With the SREC market kickbacks and tax incentives the lifecycle cost per kwh of grid-tied rooftop PV is conservatively under 8 cents/kwh to the home-owner, or about half the current residential fixed rate. That level of incentive is going to drive rooftop PV for quite awhile, and the actual installed price is still falling. (I reviewed a proposal for a 15kw system last week that was priced at $3.70 per watt. A single roof-top watt of panel returns about 1.1-1.2kwh per year in this area, averaged over the lifecycle of the panel. Residential retail electricity is about 15-21 cents. At 15 cents/kwh return on a $3.70 investment that's an after-tax internal rate of return (IRR) of 4%, but when that $3.70 is reduced by the 30% tax credit the IRR climbs to about 6%. Then when the SRECs are sold at another 4-6 cents/kwh you're talking after tax returns way better than an S &P 500 index fund, eh? In MA if you have a decent amount of south facing roof pitch it's becoming almost a no-brainer. But in about 5 years even the un-subsidized cost of PV will be under $2/watt, and no matter what the SREC markets look like and even without tax credits the cork will be fully out of the bottle, and the tsnumami of cheap PV installations will be breaking big-time.

    So what's currently a 1% slice of the MA grid (and largely invisible to the ISO-NE operators, to whom it appears as a lower load) will be well into double digits as a fraction of all kwh going onto the MA grid within the lifecycle of a hot water heater.
    Good point that even though we can't get solar without extra effort, there are plenty of people who are able to put it on their houses. Too bad we can't convince our neighbor (with a perfect roof for it) to put on solar and split the savings...

    And thank you for the comparison of an electric water heater to an indirect on our current boiler. I wanted to save on energy costs by getting a new water heater, not continue paying as much as we are now (although there are other variables, such as tank size and the likelihood that our current water heater isn't performing well).

    Quote Originally Posted by Dana View Post
    There are cold-climate modulating mini-splits out there that will run at a COP of 2 even at -25C/-13F, but unless you have a fairly open floor plan on the first floor it's probably not an option. It's point-source heating, no ducts/distribution - think of it as a funky looking wood stove with a quiet blower. :-) But they're comparatively cheap relative to a GreenSpeed- a unit capable of delivering 18,000 BTU/hr @ 0F would still be under $5K, installed. They have become the most popular heating/cooling solution for super-high-R houses in New England, and can be put to good use elsewhere. (If your basement is fairly open a 3/4 ton mini-split would likely cover the heating load there, installed cost in the low $3Ks.) It's not as cushy as radiant floors, but more comfortable than most fin-tube baseboard heating systems.

    Oil heating is dead IMHO. There is no way it's going to get cheaper- oil is much to useful to the rest of the world as transportation fuel, and even those drunk on the frack-water will tell you that crude oil can't be economically retrieved from shale or sand at $50/bbl, even if they're getting rich at $100/bbl oil. If you're on the gas grid it may be worth investing in nicer radiation for a hydronic system, but if your options are oil & propane even low-temp radiant floors will be far more expensive to run than the better heat pumps. Hydronic output heat pumps can work OK with low temp radiation, but at a much higher cost than even the GreenSpeed.
    That makes sense - considering a heat pump for the porch at the very least makes sense (even if we size it for heating and don't worry much about the cooling), or I guess even a pellet stove (although we'd need to find a very clean burning one and a place to store the pellets). The basement may be more of a challenge (there are some sectioned off rooms), but it's a consideration if we're trying to lower our oil usage in general.

    Thank you again for all your input so far!
    Last edited by ess; 04-02-2014 at 02:40 PM. Reason: clarification

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