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Old 04-02-2013, 05:10 AM   #1
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What size boiler would you pick???

Hello again, Okay here's a quick question. I had two companys bid out an electric boiler system for the in-floor heat in my basement (1800sq) and garage (800 sq) The bids were about 40$ apart. However when I looked at their specs, one has figured a 15 KW boiler, and the other has a 20 KW boiler. Now, since the two bids are practically identical, which one would you chose? Seems like it might be a better value upgrading to the 20 kw for the same money. Would I see any added performance from the higher one? I would have thought the load calculations would have been the same for both companys, but who knows. The 15 Kw guy even used a design temp of 72 for both basement and garage, which the garage will not be that warm, so he felt pretty confident that 15 would be more than enough.


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Old 04-02-2013, 07:12 AM   #2
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whick one did a proper sizing for the heat needed to perform to specs for the most effiency...ben sr ..thats the one i would go with..


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Old 04-02-2013, 09:54 AM   #3
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Yeah, pick the one that did the best job calculating. We had a 180k NET Boiler in our ~4000 sq foot house (basement + 1st floor) from the 1950s. We got 6 bids, 5 of them basically picked ones in the 160k-200k range. One was 80k NET and they did the best job calculating everything, and we went with them. If you over size your boiler you short cycle it. I know for central air short cycling is bad because you don't remove as much humidity, but not sure if it's inefficient for boilers. My assumption is as long as it can heat enough on the coldest day, you're fine and would save money with a lower BTU boiler. But it also depends on your heating radiators, whether you have baseboard or cast iron rads.

The 80k has been fine, although it hasn't been too cold out either. But before it would take 30-45 minutes to go up 1 degree in our house. Now it's 15 minutes per degree in the house. Granted the boiler is hard set on 180* temperature, that might also play into it. But basically, don't oversize, boilers are much better than they used to be, and hopefully save some money.
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Old 04-02-2013, 04:14 PM   #4
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Guessing you have pretty cheap electric rates, that your not going with LP.

Is your electrical service big enough to handle an extra 15 KW.

15KW=51,195 BTUs.
20KW=68,260 BTUs.
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.
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Old 04-02-2013, 04:56 PM   #5
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Thanks for the reply's, I think I am going to go with the guy who selected the 20 kw, mainly because his company did the rest of the house ( new construction) Was happy with their work, and he said that we could easily drop down to a 18 or 15 kw if I wanted. which would lower the price.. I am in North Dakota, so we get pretty cold during the winters. My electric rate is $0.05 /kwh for all electric heat sources. This is in a rural setting, so we have don't have access to LP. The house should handle it fine, we have 400 amps in the basement panels... in case... i dunno... I open a welding shop in my living room.
Is their any good websites to figure out the btu/h needed, just to educate myself and give myself some credibility when talking with him?

Last edited by jusolson; 04-02-2013 at 05:02 PM.
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