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Thread: May need to replace boiler What with?

  1. #16
    DIY Junior Member Heating in Colorado's Avatar
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    Dana,
    Some initial thoughts on your comments;
    I believe that the low heat loss is due to the fact that it is partially an envelope with a second wall on the south side. The entire outer wall is glass 5 ft in height the length of the wall, or about 150 sq ft of glass. That room often exceeds 96 F on a extreme sun mid winter day. It is currently over 90 in October and I am venting to the outside. As the sun angle gets better it will take in a lot more BTUs too. The next wall which is 4’ north is a heat sink and a couple windows to the living area plus an 8’ slider. The house has only 9 windows which are only 16.5 sq ft each, 4 facing east and 5 facing west. There are also three small windows with 5 layers of glazing. The ceiling has a ridicules amount of insulation partly because a friend in the business one day came by and gave me an additional layer of R 19 added to the already well insulated ceilings in return for a favor. I suppose that explains the low BTU loss even without low E glass.
    I figure the 4th zone must also always be added into the total load due to the fact that it is heating when the temperature drops.

    As for changing the radiation of zone 3, your are suggesting adding 13 to 15’ additional radiation making the total 35 to 37’ to the load? Somewhere in this brain, I seem to have forgotten some of these calculations. Isn’t the BTU/ft-hr you have calculated the BTU loss for the zone per ft of radiation? Or are you using the slant fin numbers for the different temperature?
    Remember Zone 1 is only ” pipe.
    Just to throw a curve here, in that zone 3 area, there could be some radiant heat added beneath the bathroom stone floors, it could be a pain because the joists run the wrong direction. There is piece of drywall there that may need replaced anyway. Just a thought here, I have never worked with that. I am too old, or it is too young!
    So far, there are several possibilities you have mentioned. The Bradford White 72 Gal - 76K BTU, Polaris hot water heater, Vertex, and you even mentioned the Burnham ESC3 with a hot water tank plumbed into the system. So my question at this point is why do you prefer “If it were my place I'd be inclined toward a Vertex or Polaris condensing hot water using the Taco X-Pump Block pre-engineered potable/heating isolation” Should these system be more efficient? How about trouble free life span expectations. I need to study these systems farther and will be back to you soon, probably with more questions.
    This house had AC installed a few years ago. It is a fan unit in the attic with the compressor on the roof, 10 ft away. Duct was run to the upstairs bedrooms from above and one duct through a closet straight below to feed the first floor, as well as a return on 1st floor. The 2nd floor return is on the ceiling in the center of the 2nd floor. As long as all upstairs doors are open and one office door on the first floor is closed, the temperature is balanced to within about 1 degree, bedrooms being coolest.

  2. #17
    In the trades Dana's Avatar
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    I calculated the ratio of the heat loss of the zones to the length of fin tube in each zone. Zone 2 as-is would be able to meet the load at the 99% outside design temp with 140F (or cooler) water according to SlantFin's charts. but zone 3 was still needed more to come into line. If the peak water temp requirement is 140F it means you can run it off a hot-water heater at a standard storage temp.

    The Vertex/Polaris would use about 12-15% less fuel than the Combi-2, the smallest forced-draft Burnham cast-iron (ESC3) would use about 8-10% less fuel than the Combi-2.

    The size of the pipe makes little difference whether 3/4" or 1/2"- you aren't bumping into any design limits. Adding 15' to zone 5 has negligible impact on the pumping head/flow rates.

  3. #18
    DIY Junior Member Heating in Colorado's Avatar
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    Dana,
    In understanding how the house currently heats, I know that the Zone 3 (2nd floor) is seldom on, but we are coming up with a need for additional radiation in that area I have gone back to look at my heat loss numbers for each area. I have seen that I did not add in heat loss / gain from the ceilings between floors. The only ceiling heat loss consideration is for the loss through the ceiling when it goes to the outside.

    I looked at these numbers again. I know there should there be heat loss from the basement through the ceiling to the first floor. But I also know that there is only a slight temperature difference. So I went ahead and added in those ceiling loses to each area, knowing it would not be a large number. Understandably, it lowered the heat loss of the zone 3, 2nd floor as well as the raised the loss of Zone 1 and 2 slightly.

    Here are the slightly corrected loses:
    House BTU loss
    Basement 1477 w 16’ of slant fin
    1st Floor 7844 w 46’ of slant fin
    2nd floor 5146 w 22’ of slant fin
    Shop 2900 w 20’ of slant fin
    TOTAL 17367 BTU loss/ hr


    Now, let’s see if I have this right…I have added 25% BTU loss for slab, infiltration etc. which was not in the BTU loss numbers. I then calculated the ratio of the loss to the feet of baseboard by dividing the BTU loss by the number of feet in each zone.

    Z1 = 1846 BTU loss per hr /16 ft slant fin = 115 BTU/ft - hr
    Z2 = 9805 /46’ = 213 BTY/ft - hr
    Z3 = 6432 /22’ = 292 BTU/ ft-hr
    Z4 = 3625 /20’ = 181 BTU/ft\hr
    Adding 12’ to Z3 will makes it
    Z3 = 6432 /32’ = 201 BTU/ ft-hr


    130F water in slant fin is 260, 140 F is 320
    As I see it, operating this at 130 is too cool at 99% outside design temperature, but is fine at 140 on all zones, with Zone 2 being the most demanding. Is that how you see it too? Operating at 130 will work when the outside temperature is warmer. I understand this system has no remote sensor for auto set back.

    I have done some looking at the Polaris and so far, it looks like they type of system I need. So the question at this point is how I determine the size of this hot water heater now that we know the space heating needs. I know on normal hot water heaters the sizes used for a 3 bedroom, 3 bath, home would possibly be 60 gallon and the BTU output will determine the recovery rate. But I am not so sure of either the tank size needed nor the BTU rating needed.
    I found this on line link which looks like a simple install example: http://solarhomestead.com/best-off-grid-heating-system/

    I will look at this and other systems we have discussed in more detail too, but I am sure liking what I see in the Polaris so far.

  4. #19
    In the trades Dana's Avatar
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    You're on the right track. Bear in mind that the SlantFin output is average water temp, not entering water temp. To hit 130F AWT you'd be looking at boiler/heater output of ~140F.

    The Polaris based system in your link uses potable water in the heating system which isn't advisable (or even legal, in many locations) for health reasons. (Water stagnating in the heating system tubing between 80-110 can grow legionella and other fun stuff.) To use a Polaris or Vertex requires an external heat exchanger and a potable-tolerant pump for isolating the potable from the heating system water.



    ^^^ not this^^^

    This:




    If going with Polaris you can the tank to the largest tub you need to fill. The burner on even the smallest Polaris is enough to heat your house and take a never-ending shower.

  5. #20
    DIY Junior Member Heating in Colorado's Avatar
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    Dana
    I here you on the Legionnaires stuff! I believed that this pictured system was not considering that, and the main reason I sent it to you. Although, they are circulationg all DHW through the heat zone, it would not work with zone valves.

    So my next question is about heat exchangers. How efficient? Size for the heating needs of the house? Quality? Brands that are better? Whatever else, that I do not yet know and need to!

    Back to the slant fin. I may need to add additional feet to the Z2 area too, since at 120 it is 210 BTU/ft-hr. There is still additional loss from this are with an open stairs to above. But that can be determined later too, since the numbers are still okay.

    System from you as shown. It looks as if this will need a circulator with shutoffs, a one way valve, and temperature sensors. I may be able to connect into my current stem without major work. It is just a secondary zone add here that is currently a part of the heatmaker boiler.

    System size seems to be the smallest Polaris 34 – 100. That is their smallest unit. There is only one bath tub in the house, a standard Kohler cast iron, currently only used by grandchildren occasionally. All three bathrooms have showers.

    So far, to me, this seems like the best possibility by far. How many problems are people having? I see that igniters are a problem. I had that problem in conventional forced air systems I had maintained. The best solution is to always have one or two on hand. I am more concerned about circuit board system failures. I know enough about them to understand what is causing most failures since my wife was in the circuit board manufacturing business a couple decades with a very large company. Gas valves are gas valves, and should not fail easily. Sensors should be easily diagnosed and replaced.

    On the Heatmaker the number one failure was the on board Grundfos circulation pump, about 10 in 28 years. The igniter failed about 6 times. The temperature sensors failed occasionally. Considering how complex the system was, I believe that it did quite well. The whole house Taco circulator pump failed once, just a few years ago, All of the original Honeywell zone valves are still in place. Everything is isolated with valves. It seems that I can pretty much hook into the current system. I may replace all of the valves with ball valves. So the system must be pretty much torn apart in order to do that. Maybe I should consider replacing zone valves and other things too. What are your thought on that?

  6. #21
    In the trades Dana's Avatar
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    You went through 10 Grundfos pumps in 28 years? Sounds like iron-impeller pump on the potable side or something?

    Polaris has a pretty good track record overall, but I don't have a lot of direct experience with them. (Ping BadgerBoilerMN on this- he posts here frequently, and has done quite a few heating systems based on Polaris HW heaters.)

    There's little downside to oversizing the heat exchanger other than a bit of pumping power. Since they are fully counter-flow the delta-T between the potable & system side (sometimes called the "approach" temperature) doesn't have to be much- most are BTU-rated at a 10F difference. But installing one rated for 2x or even 3x the BTU rate cuts that difference by quite a bit, and may even be more inline with your actual radiation flows. I suspect (but don't know without doing the full analysis on the actual pump and pumping heads of each zone) with one zone valve open you're getting at least 2-3gpm of flow and with all of them open you may be getting 8-10gpm. See the BTU rate & min-flow requirements of this series.

  7. #22
    DIY Junior Member Heating in Colorado's Avatar
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    Dana,
    How do I Ping BadgeBoilerMN?
    Do you know anything about the Phoenix Water heater?

  8. #23
    In the trades Dana's Avatar
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    Quote Originally Posted by Heating in Colorado View Post
    Dana,
    How do I Ping BadgeBoilerMN?
    Do you know anything about the Phoenix Water heater?
    Send him a private message using the service on this site. Or you could email him. He's done more than a few of these- this pic is from his company site:



    (The green blob is the Taco "X-Pump Block" heat-exchanger/pump unit, which is a pricey way to get there, with more features than you'll likely need or want.)

    The Phoenix water heaters are great units with modulating burners, but way overkill for your loads. There's no point to a modulating unit that in an application where would literally never exceed it's minimum 40 KBTU/hr firing rate. Your space heating load is half that, and with 119 gallons of thermal mass you'll never draw down the hot water to the point where it would need to ramp up either, unless you LITERALLY showered for hours at a time.

  9. #24
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    I did not realize yet that the Polaris was a modulating unit. That makes it even better. However that is the fact that the house only cost $160 per year to heat and $192 for all the rest of the gas for the year. However, so far, I do not see a lower price reasonable system that is better than the Polaris. People just do not have house that uses this little energy. The current Heatmaker keeps pretty warm year aroung, but always 190 + in winter. As I see it most of the “real” solar type houses the people for the most part will spend anything to save a drop of oil or gas, without much thought. It is all show. I just want a reliable system that works well and last for many years. That does not mean it need to be the lowest cost thing either.

    As for putting a system like this, I need to understand the design of what goes in the house. That is an interesting picture from badgerboilerMN. I sent him a message, not too sure if it went out. I will try an e-mail next.

  10. #25
    In the trades Dana's Avatar
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    The Polaris does NOT have a modulating burner.- the Phoenix does.

    The Vertex is quite a bit cheaper than the Polaris and in many ways nearly identical. But not being stainless, the anticipated lifespan is probably more like 12-15 years compared to 20+ for the Polaris.

  11. #26
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    Dana
    Is that an advantage of the Polaris having a modulating burner in my system? Both are Stainless, but a different kind of stainless,is one better with the temperature and water contact? I like the expected longer life. I am still leaning toward the Polaris, but can consider the Phoenix.

    I have had the Heatmaker for 28 years this month. Most repairs were done by me and they were simple part swaps. I did try a couple contractors replacing those circ pumps but with no added benefit in lifespan and more than triple the cost. I soon gave up on that and just swapped when it began making the noise of the failed bearings. Yes, they were cast iron, what would have been better?

    I need to begin looking at the total layout of the new system as a possibility too. Is Taco Flo Pro University a good place to look?
    Last edited by Heating in Colorado; 10-14-2013 at 01:18 PM. Reason: Bold question

  12. #27
    In the trades Dana's Avatar
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    As I said in a previous post, there's no point to have a modulating burner that never modulates. At your loads you will rarely or never exceed the min-fire output of the Phoenix, rendering it's ability to modulate moot. Were it's min-modulation 10,000 BTU hr there could be some advantage in your situation depending on how you set it all up, but not at (it's actual) 40,000 BTU/hr min-fire. It's a great unit- for somebody else/some other application.

    When pumping potable water you need to use a bronze or stainless types. Most of the Taco circulators have bronze or stainless versions, with compatible impeller cartridges. Fresh water has lots of oxygen in it, causing iron pumps to rust. If it's all on the closed system, with no fresh water coming in, the iron pumps should last for a good 20 years or more if properly specified for the application.

    I've never looked at the Taco Flo Pro University stuff, but it has to be better than a WAG, eh?

  13. #28
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    Dana,
    I have been looking at the Panel Radiators previously mentioned. So far, I have only looked at Pexsupply, which carries Buderus. Looking at the specks of them, they state the BTUH different temperature on the Buderus web site. As you know, I expect I will be running this system at 140 or 150. If I replace a 3’ SlantFin with a 2 ” thick Buderus Model 21 36” unit operating at 140F water the removed unit output was 960 BTUH, the inserted unit output a 12” height would be 1400 BTUH for a gain of 540 BTUH for $360, Monetarily, it certainly pays to put in both taller and wider unit per BTUH by far. Today’s cost goes down from 3.77 BTUH/$ to 6.58 BTU/$. With the wider Bederus being 4”, their narrower at 2 ” and the current Slant Fin at 2 ”.The Model 22 24” x 36” x 4” would give me a 2140 BTUH gain in the room with the greatest shortage. The other two rooms can each have an additional 1300 BTUH added the same way. It appears to be a good fit. Will this work okay with a one pipe system in series with the other slant fin radiation? I will continue to look at additional brands. I am unsure of which brand may be better quality

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