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View Full Version : Who makes a boiler thats small enough for a 1000 sq ft house??



Gnfanatic
08-06-2010, 08:10 PM
Hey guys, my house is very small (1000 sq ft) and very well insulated. I am still working on the heat loss calc but I am confused about the sizes of these oil boilers. I have not seen any smaller then 70k btu. I am not going to be using a tank either. So make believe my calc comes out to be 25k btu. what do I chose??

thanks

jadnashua
08-07-2010, 09:18 AM
Do you have natural gas available? I know that there are modulating (mod-con) gas boilers that can fire as low as about 12K or so, but I am not familiar with oil burners at all. Propane is an alternative, if natural gas isn't available. If you use the boiler to fire an indirect WH, you'd want at least 60K BTU.

Gnfanatic
08-07-2010, 04:23 PM
Hey Jim, funny you ask. There is a gas line in front of my house in the street. I was thinking of converting to gas but the damn town is anal about who is the plumber, licensing, permits etc. If I need to go to gas I will. Propane is out of the question

Doherty Plumbing
08-07-2010, 09:21 PM
Hey Jim, funny you ask. There is a gas line in front of my house in the street. I was thinking of converting to gas but the damn town is anal about who is the plumber, licensing, permits etc. If I need to go to gas I will. Propane is out of the question

Like Jad said you should convert to NG then you will have PLENTY of options to chose from.

Gnfanatic
08-08-2010, 04:22 AM
I know. the Triangle Tube solo boiler is a killer boiler plus I will get back $700 from the gov. I am just worried about cost of installing the unit. They make a 60k btu and then the next one is 100k.

jadnashua
08-08-2010, 01:07 PM
I have a small Buderus. Solid device, very quiet, wide modulation range, standard outside reset, nice unit.

Gnfanatic
08-08-2010, 07:39 PM
Jim, installing a HE boiler is complex?? totally diff from a std boiler?? Which Buderus do you have?

thanks

jadnashua
08-08-2010, 08:29 PM
Mine is very similar, but they tweaked the max efficiency slightly (mine is maybe 3-years old). I think that it qualifies for the 30% federal energy credit (up to $1500). http://www.buderus.us/products/gasheating/gascondensing/logamaxplusgb142.html Some localities also provide rebates...mine is now giving $1300 for a qualifying boiler and indirect WH.

I live in a condo, and needed a licensed plumber to install because of local codes. It's not much of any different than most, and easier than some. It comes with a primary/secondary loop already included, so all you need is to get a circulator(s) and zone valve(s? many not be needed).

Dana
08-11-2010, 03:04 PM
If Manual-J says your peak heat load is 25K, reality is more likely to be 20K. At that point there's little advantage to going with a gas-fired mod-con over running it off an 80%AFUE forced-draft gas-fired hot-water heater combi like the Bradford-White Combi2 (http://www.bradfordwhite.com/products2.asp?id=13&product_id=183)

You'll end up spending about 5 grand less up front, but you'll use about $100-150 more in fuel. With the $5K delta you can buy a Cansolair (http://www.cansolair.com/) or SolarSheat (http://www.google.com/products/catalog?hl=en&q=solarsheat+1500g&revid=522263049&um=1&ie=UTF-8&cid=18033562600887400528&ei=ABxjTIGlG8OB8gb9_rWACg&sa=X&oi=product_catalog_result&ct=result&resnum=3&ved=0CCsQ8wIwAg#) thermal air panel and easily recoup that $100-150 (in most US locations) and still have couple grand left over to play with.

High efficiency heating systems are for low-efficiency building envelopes. If your ACH50 numbers are less than 1 and your true design day heat load is as low as you're calculating, there's scant rationale for a mod-con. Even the lowest modulating boilers will have less than a 25% duty cycle on average- to achieve the real AFUE at your load it needs to be down there in the 5KBTU range at lowest modulation. The thermal mass of the combi is sufficient to keep it's efficiency pretty much at ~80% through the heating season despite a low duty cycle- you'd have to add thermal mass to a mod-con to keep it happy, and you'd be only 10-12% more efficient.

But the gas hw/heat combi will be a huge improvement over even the smallest oil burners out there (unless you have buffer tank and smart heat-purging controls on the oil boiler.)

Dana
08-11-2010, 03:12 PM
Forgot to mention- in a house as tight as yours don't cheap out and go with an atmospheric-drafted version. The forced-draft version can't backdraft, and you can seal up the flue for the old oil-burner to make the house even tighter.

There are condensing combis out there, but the extra 10% in real-world efficiency just isn't worth it.

Also, what do you have for radiation? If radiant floors/panels or high-mass radiators of reasonable size you can heat the place just fine at 120-125F domestic hot water temps, but you may have to crank it up to 140F in the winter to get the heat out of fin-tube baseboard convectors. The additional heat loss from the tank would still end up inside the house, so it's less of a loss than if you were looking at hot-water only. The rest of the year you can save a bit of fuel by backing off the storage temp to ~120F.