View Full Version : Boiler Decision: Oil or Natural Gas? 80%? 90%? Condensing? Tankless?

02-12-2012, 08:00 AM
I am in need of replacing my oil fired boiler, it heats my hot water too. I live in Delaware in a 2200 square foot, 1900's farmhouse with original radiators. I have 2 heating zones, and I am planning, sometime in the future, to put in a third zone, which would operate more radiators, (before me, some radiators were removed, and electric baseboard heaters installed). I am on well water, and I think it to be rather acidic, and I have a submersible pump.

I have the ability to hook up to natural gas

I am fairly conservative with my heat, and hot water.

All this being said, any suggestions on a gas fired replacement system for my heat, and domestic hot water?

Thanks, in advance, for any input, and until someone can straighten me out, I shall remain,


My existing OIL FIRED BOILER set up shows a metal plate, on the front, of the boiler:
HB Smith - FD 12 Smith Pac - Boiler Burner Unit
5 Section Boiler (heats my domestic hot water)
144,300 BTU/HR
1.5 Burner Capacity
186 Valve Capacity

There is an 80-1241 on the metal plate, as well. The 80 may be for 1980, but I have a fact sheet, from the Realtor, stating the boiler was replace in 1985. I have lived in the house since 1994, (18 years), and up to now, have never had any problems with the heat, or hot water. I do not remember ever having to replace any external controls, parts, or either circulating pumps.

I have two circulating pumps, as there are two heating zones
Grundfos Circulating Pump
B & G Circulating Pump

Also there is a never used, by me, electric hot water heater, all plumbed in, it was there, when I moved in. This is being noted, for the fact that it is plumbed in, I would not want to use it, as I am not sure of its condition.

02-12-2012, 02:34 PM
Is it possible that they're using the electric WH as an indirect tank? Some models, especially those designed for solar, could do this.

That aside, the first thing you need to do is figure out what your actual heating loads are. There are ways to do this that aren't onerous, and it is required to decide on what is the best fit for you. Generally, NG will end up being less volatile in pricing, and probably less expensive, so I'd plan to go that way when replacing things.

If you can accumulate your oil usage and then get the heating degree day info for your area, you can calculate how many BTU's you actually used. Then, you can relate that to a good approximation of the size of the boiler you need to get. You'll probably find that the boiler you have is at least twice as large as what you need, and maybe even more.

Radiators work quite well at lower temperatures than baseboard, and lend themselves to a modcon boiler. The lower the temp you can supply, the better the efficiency, and a modcon can adjust the burner size to accommodate your needs IF and only IF you size it properly. If you also then install an indirect WH, your boiler won't need to maintain temp all year long, further increasing your efficiency. With mine, in the summer, it generally only runs maybe once in the morning after baths, then cools off to ambient for the rest of the day. Much more efficient than running and maintaining temp for that occasional hot water use. A modcon can survive with cool returns. You may find that for many days, it could run in the 130-degree range and keep you perfectly comfortable and be reaching in the mid-90% efficiency range. You can't lower the temp of what you have because it needs to be hotter for the hot water issues, plus, that low would put it into condensing range and the burner byproducts combined with the moisture would eat it up along with the flue.

As to brand, it's more important to find an installer that can put it in properly and adjust it for your real needs. I ended up with a Buderus unit, partly on recommendations, and partly because their US headquarters is about 15-miles from my home, but there are a lot of them out there that could serve you well.

02-12-2012, 09:09 PM
Thank you for the information.

The existing water heater has not been discussed as use for an indirect tank. I never used it, and I have been her 18 years. I am not sure when the previous owners last used it, or if it was even drained after its last use. I assume it is no good for anything. I just thought it could be removed, and a gas fired one could be put in its place. I fully understand the waste of a gas hot water heater to continually keep the domestic water hot, or using the condensing boiler.

I am kind of confused on the working of the indirect water heater, what happens when you need hot water? Does something happen to kick on the indirect,, and then, does it acts sort of like a tankless hot water heater, so that the water is heated on demand?

I got this information, but not sure what to do with it to calculate the BTUs used. Never was good with math calculations. Delawares heating degree day information is 638 for January, and I used about 100 gallons of oil.

I never mentioned, I am one person, in the house, so the hot water demands are not great.

02-13-2012, 02:38 PM
100 gallons of oil in 638 heat degree-day is a K-factor of 6.38, which can be used with the NORA FSA calculator (http://www.nora-oilheat.org/site20/index.mv?screen=home) to come up with a design condition heat load.

Or, you can just do the simple math:

Assuming 80% combustion efficiency and 138,000BTU /gallon you get (0.8x 138,000=) ~110,000BTUs out of every gallon. You're using 100/638=0.157 gallons per heating degree day, so that's (0.157x 110,000=) 17270BTU/HDD. For every heating degree HOUR that would be (17270/24=) 720BTU/degree-hour.

The 99th percentile heating design temp (http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf) for Wilmington is +14F. Assuming your balance point between heating/cooling loads occurs near +65F (typical for non-superinsulated houses), so that's (65-14=) 51 heating degrees, so at 720 BTU/degree-hour you'd need a heating system capable of delivering (51 x 720=) 36,720 BTU/hr.

Since your fuel-use estimate/K-factor numbers are very crude estimates, so is the above result, but this is a realistic number for a house that size with conventional levels of insulation and air-tightness, maybe even slightly to the high side. And yes, the existing boiler has at least 3x the output needed for heating your home, making it's average as-used efficiency well below any AFUE rating it might have. (This is actually pretty typical.)

Modulating-condensing boilers or a condensing hot-water heater set up as a combi-system would deliver high efficiency, and your heating costs would be about half (maybe even 1/3) of your current costs heating with oil with an oversized boiler. If you replaced it with a 2-3 plate cast-iron gas boiler instead of a mod-con it would run longer burn cycles than the oil boiler, but also cut the heating bill in half. But a better heat-load analysis is required before doing any of it. You want to be sure to have enough boiler, but JUST enough, with the most minimal oversizing factor to be able get the best efficiency and longevity out of it. If you go with condensing boiler, oversizing the radiation for any new zones has a very positive effect on condensing performance too, but that's a whole other design aspect.

As a sanity check on heat loss, how many windows/doors, (and what type of windows), and what type of wall construction/insulation does this place have? Full basement (insulated, not insulated?), slab on grade?

02-13-2012, 03:39 PM
Thanks for the information...

I wonder if I got the wrong degree day info, whatever I found, I think it was a total count for the month of January, I did not add up 30 day increments. I know you say your calculation is a realistic number, but that ends up being 1/4 of my current BTU capacity of 144,300 BTUs. I usually get 100 gals of oil a month, and I usually stretch it to last the month. Not sure if this makes sense, but would you not have to factor in what the thermostat is set at, another words, if I leave the setting at 55 degrees, and your calculations show 36,720 BTU/hr, than to have it set at 68 degrees, would we not add in a factor to increase the BTU calculations?

The house is full of windows, first floor has 21 plus the sun porch has 10, upstairs has 14. Out of the 45 windows original to the house, but the have the aluminum storm windows, the rest are updated double pain, but are 20 plus years old. Most the windows are standard size, except 6 are about one third the standard size. The basement has 8 more windows in it. There are 3 french NEW exterior doors, and 1 solid exterior door. I would say 3/4 of the basement is a concrete slab, and 1/4 is dirt. No insulation in the basement. Attic has insulation in the floor, not the rafters. Walls have the old fashion "cotton like insulation" There is new insulation in the ceiling, of the first floor rooms. The walls, I guess are 2/4's with cedar shakes, then german siding, than asbestos siding. The roof has a new 50 year architectural shingle, with ridge and soffet venting. I have not had time to plug in the info to a heat loss calculator but I know my house looses a ton of heat

Again, many thanks for your time, and all the information, it is very much appreciated.

02-13-2012, 04:14 PM
An indirect is usually treated like a separate zone. The whole tank is heated when its thermostat calls for heat, so when you want hot water, it is just drawn from the tank. If you use enough to drop the temp enough, the boiler comes on and reheats it. Sort of like an electric or even gas WH...the tank is maintained at temp, and the heating system turns on to reheat or heat it depending on use. Because the boiler is usually a lot higher heat capacity than an electric or most gas WH, you can usually use a smaller indirect than a standalone tank. Some are available with SS construction, and for practical purposes, should last nearly forever. Mine is a SuperStor Ultra. A good tank, once hot, can often remain hot for over a day or more without having the boiler turn back on. Mine in the summer usually only runs once in the morning after baths.

It is very common to have a boiler way oversized. A lazy installer will ask one question - did it keep you warm, and if the answer is yes, probably just put one in about the same size. A good installer will run the numbers and put one in the proper size. The only way to maximize efficiency and comfort is to get one the proper size. you have a chance to do it right, and the cost of fuel is always a question, but economy usually pays in the long (and often the short) run.

02-13-2012, 06:25 PM
Thanks for the help, it is very much appreciated.

Sounds like an in direct is a good thing. Would set up costs (material and labor) be considerably more on an indirect then a conventional electric, or gas water heater?

I just need to do my homework to make sure the sizing is right.

Thanks again.

02-13-2012, 06:34 PM
What is a 2-3 plate cast iron boiler that you refer to, can you give me an example of one? Can you tell me what the efficiency rate is?

Is a modulating -condensing boiler the same thing as a unit that hangs on the wall that gives the 95% efficiency?

Thanks again for your time, and help.

02-14-2012, 01:21 PM
That would be a two or three plate.

eg. A higher-efficiency 3 plate: ES2-3, 51,000 BTU output (http://www.pexsupply.com/Burnham-ES2-3-ES2-3-70000-BTU-High-Efficiency-Cast-Iron-Boiler)


Mid efficiency 2-plate Weil McLain CGA-25, 82% 38,000BTU-out (http://www.pexsupply.com/Weil-Mclain-381-357-335-CGA-25-Natural-Gas-Boiler-Standing-Pilot-52000-BTU-5070000-p)


Modulating-condensing boilers start at 92%+ efficiency, most are wall hung or have that option. There are a few hybrid non-modulating cast-iron + condensing boilers out there in the 92% efficiency range too.

Yes, the temperature you keep the house at makes a difference, especially if you're keeping it under 60F, but it's not likely to be more than ~25%. The lower you keep the interior temp, the more crazy the oversizing factor is, and the lower the as-used AFUE. Upsizing to something in the ~50K range like an 85-86% 3-plate cast iron beast would not be an efficiency-disaster.

Mind you, with any boiler over 83% you won't be able to use the flue or you'll have flue condensation issues, and if the flue is sized correctly for your 144KBTU beast it's going to be oversized for any ~38-60K boiler. The 85%+ power vented 3-plate beasts can be side-vented, getting around that issue. Going to a lower-BTU 82-83% boiler means you'd have to put in a narrower flue liner to avoid backdrafting risks, so it's often cheaper/easier to go one better on efficiency and side vent it and just brick-in where the old boiler vented into the flue.

With high mass radiators and a smaller boiler you may have condensation issues in the boiler unless you plumb it with a system-bypass/boiler bypass scheme and tweak the flows so that it never runs very long with return water entering the boiler at sub-130F temps. Many/most cast iron gas boilers can tolerate extended 130F operation, but not 125F. Spec on 'em is usually 135F or 140F for minimum extended time return water temps. With oil boilers you really need to hold the line at 140F, since condensed oil exhaust is far more acidic & corrosive than natural gas exhaust. With a mod-con boiler you WANT the return water temps to be as low as possible, to get as much condensing efficiency out of it as possible.

It doesn't sound like an insane amount of windows, and they're all double-glazed or stormed, so you don't have a gia-normous additional window loss. Fixing any weather stripping on old windows is worth it though, unless it's so far gone that the frames are warped or rotting. Before replacing any of them, consider tightening them up and going with tight low-E storm windows.

Indirect HW heaters cost ~2x what a standalone tank costs, but they also tend to last 2x as long and run more efficiently.

It sounds like your house is pretty air-leaky. The biggest problem areas to address are the upper floor ceiling/attic floor interface, and the foundation sill/band joist, since stack effect drives infiltration. It may be possible to dense-pack blown cellulose in over the older insulation, and well worth it if air is moving freely up the studbays through the old stuff. In many areas retrofit air sealing is highly subsidies (I don't know about Deleware), but air-sealing is by far the best bang/buck for upgrading the building envelope. To seal the band joist and foundation sill reliably it may take 1-2" of closed cell sprayfoam, which isn't cheap, but cut'n'cobbled rigid foam insulation cut loosely to fit then sealed at the edges with1-part can-foam (Great Stuff, or similar) also works. Seal up any electrical or plumbing chases that run from basement to attic too, any old flues, etc. It all adds up. If you have a lot of air-sealing to do it's worth buying the foam guns and 1-part foam cans that come 20+ ounces that screw onto the gun rather than the cheezy plastic-straw throwaway cans, or even a 2-part foam "Froth-Pak" kit or similar. Start with big holes first, sweat the small stuff later. The foundation sill/foundation interface is usually a big hole, despite appearances- usually bigger than all window & door leakage, but not as big a hole as a wood fireplace with a broken or missing damper. Recessed lights in the upper floor ceiling can be HUGE air leaks, but you can box over them from the attic side with 3" of clearance, foam-sealing the box to the ceiling gypsum or lath/plaster, and insulate over the box.

There are likely to be local insulation companies who specialize in air sealing, and once you've nailed every hole you can think of, hiring one of them to show up with a blower door & infra-red camera to find& fix the other 8 square feet of hole that you never imagined existed is worth it, especially if the state or utility subsidizes it.

02-14-2012, 05:20 PM
Thanks for your reply.

Knowing what you know about my house, would you have any recommendations on the type of system for heat and hot water for my house. There seem to be so many types of boilers, it is hard to figure out what would be the right choice for my situation. And, yes, I know there is not just one answer to the question, but what would you lean towards?

Remember, 1900's farmhouse, drafty, 2200 square feet, 2 zone heat, 1 bath, very little laundry or dishwasher demands, well water, and my chimney has NO liner. Also the basement wall is 6'3" high plus 9" of joist space, not sure if that is enough room for wall hung unit?

Thanks for the insulation checklist, it will come in handy.

If you can touch on natural gas cast iron boiler vs natural gas steel boilers that would be great too. Not sure if you are just limited to steel when it comes to a natural gas boiler. Anyways, if there is a choice, can you point out any pros / cons.

Thanks again for your time, and knowledge, it is very much appreciated.

02-15-2012, 08:08 AM
There's no significant difference between steel or cast iron gas-fired boilers in an application like this. Most atmospheric-drafted gas boilers out there are cast iron. There's a huge difference between these and low-mass modulating condensing boilers, but whether it's worth spending the extra money on a mod-con as opposed to spending it on air-sealing & spot-insulation isn't always an easy call, but in your case I'm thinkin' it's better spend on air-sealing, which will reduce the boiler output requirements, and be more comfortable, but still that's just a guess. It's much easier to make that call when inspecting it on-site. In general spending the money on improving the efficiency of the building-envelope is a better investment than a higher efficiency boiler when there is literally ANY low-hanging fruit to be had.

An atmospheric drafted 2-plate boiler might look cheap until you add in the cost of installing a flue liner, and you'd have to do the low-temp return water protection with external plumbing and some system design. For about the same money you can get better efficiency out of something one-better without the expense of a mod-con, which would be at LEAST $500 more up front, and may not save enough on fuel.

I suspect the best value for you would be to put in a ~50KBTU/hr forced draft 3-plate 86-88% AFUE boiler and side vent it, closing up the old flue, and spend another grand or two on air sealing + insulation. Get quotes on both an indirect and a power-vented tank to determine which works the best for your budget. The indirect would be more efficient and provide more hot water, but your hot water needs aren't very high. Something like the smallest Burnham Revolution 3-plater (http://www.pexsupply.com/Burnham-RV3NI-2-Revolution-48-000-BTU-Output-High-Efficiency-Cast-Iron-Boiler-Nat-Gas) is easy to hook up, and self-protects against low-temp return water issues. The smallest of the Weil McLain hybrid cast/condensing (http://www.pexsupply.com/Weil-McLain-GV90-3-GV90-56000-BTU-High-Efficiency-Gas-Boiler-Nat-Gas) boilers is similar money and also inherently protected from low-temp damage, but I have no idea what it's track record is.

02-17-2012, 11:48 AM
Your house may not be quite as leaky as these folks, but the process for chasing the low hanging fruit is the same, and well worth it, whether before or after the boiler swap, but should give you confidence that even a smallest in the line cast iron boiler could cover the peak load:


See also:


In thinking about it, with your modest hot water usage, an electric HW heater may be the better choice, since it would take a lot of time to pay off the costs of installing an indirect, or even the additional gas-line plumbing and venting for a standalone gas fired HW heater.

02-17-2012, 06:37 PM
Again, many thanks, lots of useful information. So much to take in. I will be looking at it all.


You gave me a link that took me to the pexsupply.com website. I found that they had a "btu" calculator. Do you think it realistic? I plug in my info, and I get around 108,00 btu's.

When you calculated 37,000 btu's, based on the 100 gallons, and the degree day info, I supplied for the month of January, that gave you 37,000 btu's, this is the amount of btus of oil I actually used for the month, right? Meaning, that should not be the actual btu rating of the new boiler, right?

I have gotten two HVAC companies that have actually gotten room sizes, window sizes, house orientation, etc, etc, so I think they are doing an analysis with the heat loss calculator. I wanted to do my own heat loss calculation, just as a double check, but I find it perplexing. If you have any suggestions on heat loss calculations I can do on my own, please let me know.

Some of the estimators want to match the btu's, with what is there, one wanted to increase it by about 15,000 btu's, and some have said they would drop it to around 100,000. So who's right, and who's wrong. Anyways, I am waiting on the 2 that requested the most information, and I expect they should be more realistic on the sizing - I hope. If they both come in around the same btu's, than maybe I have something better to go on.

I have not made a decision, but I think the modulating condensing units might do the trick, if I can afford it. The Rinaii E110C will do up to 110,00 BTU's, as well as the domestic hot water. If I understand correctly, the domestic hot water delivery acts just like their tankless delivery system, which is on demand only. With this type unit, I think money might be better spent, since I do not have to hook up an indirect, or a gas, or an electric hot water heater.

The other thought on the Rinaii, if I understand correctly, is it can expand to anticipated BTU's, that is, if future demand is put on the system. I have about 600 square feet of space (4 rooms) where radiators were taken out, and electric baseboard heat was put in. When I am able to, I want to remove the electric, and replace them with radiators and have them on a separate zone. The expanding capacity of the BTU's will allow me to do this.

I understand, that a multi zone system, which I currently have, upstairs and downstairs, will have a negative effect on any of the 80% rated systems, because the boiler is going to heat to capacity, even if a zone is not being used. Also, I understand whenever you go from oil to gas, using and 80% rated systems, you need a liner in the chimney, of which, I do not have. To put one in would be costly, so I am thinking that money would be better spent on bumping up to the 90% rated systems.

Also, since these units modulate, I guess, I don't have to hit the nail, on the head, by perfectly sizing the btu's.

I am also thinking, with a more efficient unit, I might get more motivated to do all the proper insulation, and caulking to help keep all that expensive, but efficient heat, in the house.

Anyways, I think, a lot of this you already explaned, but it takes me awhile to take it all in. If I got something wrong, or if there is something, I am not thinking of, I welcome any comments.

As always, I thank you for your time, and well thought out responses.

02-17-2012, 09:15 PM
The amount of heat you actually put into the house is much more accurate than an estimate that can't take into account actual leaks, voids in insulation, the real performance of the windows and doors, and how you use your house. But, if you're also using those rooms, and they were heated with electric baseboard, the amount of heat they used needs to be added to the calculation. So, taking say a mild spring month verses a winter one, preferably the same one you had for your oil use, try to see how much more electricity you used to isolate what was for heat, and what was for other things. 1Kwhr= approximately 3412BTU. So, if you averaged an extra Kwhr/day, that's about 56BTU/hr.

You'd have to have an almost uninsulated, really leaky house to need 105KBTU requirement.

Just for a rough idea, how long, and how often does the boiler run on average? If it's only on 15-minutes/hour, it's putting out sligthly less than 1/4 of it's ultimate capacity (less, because startup and shutdown lose some out the flue and maybe even less if it is turning on and off many times in that hour - talking about actual fire times, not when the circulators are running).

There are many calculators out there, and most of them are quite optimistic, the better ones maybe as close as 10-15%, but real life numbers trumps them all.

02-18-2012, 04:35 AM
Thanks for the info, really appreciate it.

The electric baseboard doe not really factored in because I do not use them, and two of those areas are shut off from the rest of the house. One of them shares two 5' openings, and in those two areas is a radiator for those two rooms.

I never mention the fact that I do not use my existing oil heat as the normal person probably would. I leave each zone, at its lowest setting, (55 degrees down, and 45 degrees up). So you can imagine, the house is cold, that why I dress warm. Anyways If I do call for heat, I will usually up the downstairs thermostat, it seems like all I need to do is have the boiler run for one to two hours, then I shut it down, and the radiators seem to generate a good amount of heat for hours after the initial 2 burning hours. All that just being said, the 37,00o btu calculation might be a little out of wack, because of my thermostat settings. I am thinking it should come in at around 74,000 btu's, if the thermostat was set at 68 degrees, rather than 45 and 55, although, I am not sure, if this is a logical conclusion. And then, of course, I need to factor in the 600 square feet of space which is really not even being heated, because there are no radiators in those spaces, and I do intend to put radiators back into those spaces.

I do not think the boiler is turning on and off a lot, maybe more like the 15 minuite interval, but I will be more aware of this.

Another thought, one of the estimators, took the nozzle off for measurements, and said, based on the nozzle's measurement, that the boiler was firing at 114,000 btu's. As I understand it, this reduced the 140,300 btu's down to 114,000 btu's. Not sure if that was done because of the radiators being out, or if the previous owners felt the boiler that was put in for them was oversized, based on the heat they were calling for.

In any event, I am thinking, if I end up with a modulatign condensing unit, that is rated between 35,000 and 110,000 btu's then this sizing issue becomes less important, because the system is going to figure out what it needs, when it needs it. Would that be a logical thought?

Thanks again for your time, and information, as always, it is very much appreciated.

02-20-2012, 09:15 AM
When I first moved into my house (similar in size to yours) it had ZERO wall insulation, 6-7" of rock wool in the attic, it leaked like a sieve, and it's heat load at 0F outdoor temps was still under 50KBTU/hr.

Given your comparatively modest outdoor design temps I'd be truly shocked if your design condition heat load was anything like 74KBTU/hour with the windows closed. If you put in a mod-con with a minimum firing rate of 35K, max of 110K it'll almost certainly be oversized, but if you enough thermal mass in the radiation it won't cut into efficiency much.

Short cycling isn't a function of how often the boiler runs, but how long it runs for each burn. The on-time to off-time duty cycle will vary with your actual heat load, but to be very efficient the burns need to be long enough to not be blowing away heat in startup cycles, and the total duty cycle high enough to not be blowing away a lot of heat instantby. In a high mass boiler any burn less than about 5 minutes, and a duty cycle under 25% (15 minutes out of every 60) means it's not running at peak efficiency, but in a mod-con or low mass combi half that can still be fine. With modulating-condensing burners the ideal efficiency is when it runs nearly continuous burns at low fire. But if you're heat load at design condition is only 35-40K (likely) and your burner's lowest fire is 35K, that means that MOST of the heating season it will be running at less than 10% duty cycle. Going to a burner with min-mod of ~15K would be measurably more efficient in most systems.

Doing all of that caulking and insulating and going with a "right sized" 82-85% non-modulating burner would likely lower your fuel use more than going with a condensing burner, for less money, at which point the cost-delta of going to a condensing burner won't be as cost effective. As a general rule on older homes like yours it's ALWAYS a better investment to tighten up and insulate the BUILDING to a high efficiency than going to ever higher efficiency on the heating systems. The first $2000 in air-sealing & insulation buys you a lotbigger reduction in fuel use (and increase in comfort) than the next $2000 in boiler efficiency, and that should be the priority.

02-29-2012, 03:43 PM
The boiler pictures are of low-efficiency non-condensing boilers. The Burnham is a Series3 with outdoor reset, but still a hot stack.

As stated; a proper heat load is first, then the condensing boiler with indirect (about three times the installed cost - and life - of a conventional tank-tip water heater - and the right guy to install it.


03-01-2012, 10:44 AM
True, the cast-iron-beasties are all hot-stack non-condensing but the heading of the title of the thread is still

"Boiler Decision: Oil or Natural Gas? 80%? 90%? Condensing? Tankless?"

Unless budgets are unbounded, there's room for splitting it between higher-efficiency envelope and high-efficiency boiler, and trying to figure a good/better/best investment strategy. Going with a right-sized 80-something efficiency boiler and spending the difference on dead-obvious heat leaks that can probably get the heat load down to within range of a smallest-in-class cast iron boiler seems like a better investment than a mod-con.

The efficiency of an indirect for a very low-volume user is pretty miserable, and the rationale for the upfront cost delta between his already-installed (but unused) electric tank and an indirect isn't likely to be justifiable. He's been there for 18 years- a single guy either already in retirement or will be within the lifespan of the boiler replacement. Turning the valves and flipping the switch on the electric tank seems like the right thing to do, worry about the replacement later. It's not clear that an indirect is going to have lower operating costs for him than an electric tank at his volume of use, and even if somewhat lower cost it CLEARLY isn't going to pay for itself even in 25 years unless he marries somebody with kids. Getting off the miserable embedded-coil oil-fired inefficiency should have happened back when oil was $2/gallon, given the piss-poor efficiency outside of the heating season combined with the fact that the electric tank has been there all along and has no installation cost.

03-02-2012, 06:31 AM
Always with the ROI! No room for the modcon Zealot?

The man that builds with stone, is a true philanthropist. :)

03-02-2012, 09:04 AM
Always with the ROI! No room for the modcon Zealot?

The man that builds with stone, is a true philanthropist. :)

I like mod-cons too, but the nature of the question seemed to be more akin to "what makes the most sense for me" (==ROI) rather than "what's the coolest and most-efficient solution for me".

At least I didn't try to sell him on a mini-split, eh? :rolleyes: