01-23-11, 09:09 PM | #1 |
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Coldest day of the year
Today will probably be the coldest day of the year in Buffalo, with a low of -7°F. I took the opportunity to time my furnace for one cycle. I found approximately 32% duty cycle, with 19 minutes on followed by 41 minutes off. My thermostat is set for 1.5°F swing.
It's also the day of the year with the coldest infiltrating air, the greatest variation in temperature from one part of the house to the next, and the lowest indoor humidity. I figure I spent about a therm of gas due to air infiltration alone, in addition to heat conducted through the walls. I really want a tightly sealed house that uses a ventilation fan (with heat exchanger) instead of infiltration to provide fresh air to the occupants. Additionally, it might be nice to have a fan that filters and circulates air within the house. |
01-24-11, 08:27 AM | #2 |
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Well, it certainly seems your furnace is over sized for how much heat you require. Do you think it is reasonably sized for someone using all the space available?
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01-24-11, 05:31 PM | #3 |
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Yeah, I bet it's about twice the required size even in that case. However, given enough air infiltration though leaky windows et cetera, and a much higher set point, it might be closer to the right size.
This furnace was a waste of money for whoever bought it (should have sealed up the leaks and bought a smaller furnace), and the blower is inappropriately large. Aside from that, though, is there any efficiency penalty associated with an oversized furnace? Edit: I finally found the furnace ID tag, INSIDE the furnace. It's rated for 75000BTU/hr input, 78% AFUE, so about 58500BTU/hr (17KW) output. Do they sell furnaces as small as 30000BTU/hr? Last edited by RobertSmalls; 01-24-11 at 05:38 PM.. |
01-24-11, 06:21 PM | #4 |
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I'd imagine they must. You gotta have something small for cabins and what not.
I don't think theres a big efficiency loss from having an oversized furnace. Just the unnecessary cycling. Of course, I saw a decent gain from having mine not cycle as much. However, I do have some uninsulated ducting in my basement which isn't heated.
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01-25-11, 01:05 AM | #5 | ||
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Quote:
Quote:
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01-25-11, 03:35 PM | #6 | |
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Quote:
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01-25-11, 07:44 PM | #7 |
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That makes sense only if the parts you are heating up are in unconditioned space. In my case and probably most others, the furnace is in the basement and thus is probably quite true.
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01-25-11, 08:06 PM | #8 | |
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Hey!!
Quote:
HEY!! That was my Birthday! I'm 65 now and don't need to be bummed out by that fake looking news!! I have to admit, it was a hard day for the heaters.. |
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01-26-11, 09:18 AM | #9 |
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I was going to ask how the heat pump fared in the cold - How did the heat pump fare in the cold?
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01-26-11, 11:36 AM | #10 |
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I've been turning it off when it's going to get down to 10 or 12 deg F.
(And, we've been getting a lot of that lately). Since I know that single digits are soon to follow. Right now, it's working great, but it's a 24 deg F right now.. Later on, when it starts snowing again , I will have to turn it off, since the fan pulls in the snow, and we get a defrost cycle.. A defrost cycle is followed by an automatic call for a big temperature increase, and the dumb firmware tries to run up to 3 KW.. It's a PITA to baby this thing.. Worse than tending a fireplace fire! But, it does put out some good heat.. |
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