Coldest day of the year

RobertSmalls · 01-23-11, 09:09 PM

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.

Daox · 01-24-11, 08:27 AM

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?

RobertSmalls · 01-24-11, 05:31 PM

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?

Daox · 01-24-11, 06:21 PM

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.

Piwoslaw · 01-25-11, 01:05 AM

Quote:

Originally Posted by RobertSmalls

Today will probably be the coldest day of the year in Buffalo, with a low of -7°F.

Don't worry, January 24 was also the Worst Day of the Year 2011

Quote:

January 24 is the worst day of the year mood

Month-end debt together with those acquired in December, aims and goals have not yet been met, a climate conducive to cold, gray day, and the fact that it’s only Monday, as reported by the newspaper “El Universal” from Mexico.

Arnalls calculated with the formula 1/8C + (Dd) 3/8xTI MXNA, where C is the climate, capital D debts last month, the d tiny amount of money received this month, I attempt to bring order out of Christmas, the T is the time elapsed since Christmas, while the positive side of the formula lies in M which is the motivation and NA is the need to improve, managed conclude that the January 24 is suitable for a bad mood.

Cheer up, it's downhill from here. Until mid-June, that is

benpope · 01-25-11, 03:35 PM

Quote:

Originally Posted by Daox

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.

Won't an over-sized furnace necessarily cycle quickly? As I understood, that's what makes an over-sized furnace inefficient. Before each cycle you have a warm-up period that consumes a lot of fuel without heating the house. Or in the case of AC you are cooling the evaporator each time you start up.

Daox · 01-25-11, 07:44 PM

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.

Xringer · 01-25-11, 08:06 PM

Quote:

Originally Posted by Piwoslaw

Don't worry, January 24 was also the Worst Day of the Year 2011

Cheer up, it's downhill from here. Until mid-June, that is

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..

benpope · 01-26-11, 09:18 AM

I was going to ask how the heat pump fared in the cold - How did the heat pump fare in the cold?

Xringer · 01-26-11, 11:36 AM

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..

01-23-11, 09:09 PM	#1
RobertSmalls Journeyman EcoRenovator Join Date: May 2009 Location: Buffalo, NY Posts: 344 Thanks: 3 Thanked 17 Times in 15 Posts	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
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	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? __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-24-11, 05:31 PM	#3
RobertSmalls Journeyman EcoRenovator Join Date: May 2009 Location: Buffalo, NY Posts: 344 Thanks: 3 Thanked 17 Times in 15 Posts	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
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	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. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-25-11, 07:44 PM	#7
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	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. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-26-11, 09:18 AM	#9
benpope Helper EcoRenovator Join Date: Jan 2010 Location: Little Rock, AR Posts: 95 Thanks: 16 Thanked 13 Times in 12 Posts	I was going to ask how the heat pump fared in the cold - How did the heat pump fare in the cold?

01-26-11, 11:36 AM	#10
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	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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