Just had the blower motor replaced on our York furnace this morning. Outside temps were 20F today with some wind. The new motor was assigned the task of warming the house from 45F to 65F. This took it
7 hours, which seems like a long time.How many degrees per hour is a usual rate of temperature rise for gas forced-air furnace?
2(+/-) F/hr unless _WAY_ oversized would be pretty typical....you're about right sounds like.
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You're joking, right? You expect somebody to give you a figure without knowing the size of your furnace or the size of house?
Hint: a twenty million BTU furnace is going to warm a dollhouse a bit faster than a bic lighter will warm up the taj mahal.
It depends.
steve
FWIW, I have my programmable thermostat set to let the house cool about
5 degrees during the day when I'm not here, and I think it takes about an hour to bring it back up to temp, so I would say 4-5 degrees per hour isn't unreasonable. Your experience seems to be in the ballpark, particularly given the cold outdoor temperature. As the other posters have pointed out, there are many variables involved -- furnace size, house size, insulation effectiveness, outdoor temperature, etc.
There are many factors. Size of furnace, insulation, number of windows, day or night, opening of the door, amount and type of furnishings, etc. No one can say for sure without a lot of calculations, but that does not seem unreasonable. There was a lot of sensible heat lost that has to be replaced and that takes a lot of time..
I guess mine is way oversize, i can pick up easily 10 degrees per 1/2 hour. I have the unoccupied downstairs set to 55 over night, & brought up to 68 at 6:30 am. I've never seen it not make 68 by 7:00 even when it is in the 20s outside.
I turn my heat off at nights and when we are not home. If it is 60 in the house, it takes about an hour to warm it up to 72. If it takes 7 hours to warm your house that much, I would wonder if your insulation is particularly poor or if your furnace is undersized.
Funny that you ask this question.....I have to have done the expereiment on three houses
Two in Orange COunty, Ca.
One is a 1 1/2 story 1930 ....no wall insulation but ~R30 in the attics.....on cold (for SoCal) winter day of about 50F outside, about 5 or 6F degs per hour
Second on is a one story ranch iwth blown in cellulose attic insulation......about the same performance
the last home is an eastern sierra two story lots of wall & ceiling insulation, propane heat...takes about 3 or 4 hours to go from 55F to
70Fyour temp rise of 2F deg per hours seems a bit on the low end in my experience but not hugely unreasonable...a furnace needs to be able to maintain the house at a reasonable temperature......how quickly it gets there isn't really all that important.
what is the out side temp (I'm guessing in the 20's?)
an important thing to check would be the temp rise across the furnace
But I'm sure Bubba will jumping right in with a helpful addition (along with his typical serving of insults) to this thread being the furnace expert that he is
cheers Bob
Usually the heat strips come on anytime you are more than about 3 or 4 deg low. If the heat pump is turned up about 2 deg at a time they will not come on , but if it is moved from 45 to 65 deg then they probably will. Also at 20 deg the heatpump is not too efficiant and it might as well be using the heat strips.
The length of time the temp was low makes a difference. The thermal mass of the structure and contents make a diference that becomes greater if it has all chilled to match the lower temps. That stuff takes a long time to heat back up.
Yes, the house was chilled for probably 12 hours (the motor died overnight, and the outdoor temps at that point were single digits). House was built in 1930, 2 floors, has numerous windows, full basement, full attic, not well insulated, but has storm doors and windows all around. Furnace is a York 2-stage Diamond Deluxe 95, installed in 2003. We live by Lake Ontario. But this new motor doesn't seem to be heating up as quickly as the previous one did; the old one used to be able to get the house from 60F to 65F in an hour, and we're still not up to temperature 1.5 hours later this morning, so I'll be calling the HVAC company to check this.
If I turned my furnace off & let the house get to 45- then turned it on [while it was 20 with wind] I imagine it would take 1 -1 1/2 hours of running to bring the house up to 65.
But my furnace was designed to keep the house at 70 when it was
30below outside- and that was with old, drafty windows & no insulation.If 20 is about as cold as it gets where you live- and if it was 45 for some time so all the mass had to be re-heated- and if you've got room for improvement in your windows and insulation- then don't worry about your furnace. Work on the insulation.
You say you "had the blower motor replaced". That implies that some guy who knows a whole lot more about your setup was in your house. What did he/she say?
Jim
With the house thoroughly chilled to around 50, with an outside temp in the 30s, I'd say my forced air will do about 4 or 5 deg an hour. So, I'd agree that 2 deg an hour sounds on the low side.
Measure the input and output temps of the unit while it is firing and blowing. Are they within the specification listed in the installation manual?
Depends how many BTUs the furnace output is, as well as how much heat loss the house has. Also depends how much thermal mass. If it needs to heat up a lot of masonry it will take longer than heating up a lot of stud-framed walls with good insulation.
A minor quibble: 20 degrees in 7 hours is (much closer to) 3 degrees per hour. -- H
You do know you have asked a trick question? With the information you have given, it cant be answered. Here let me give you and example or two so you might understand. Where I live, we design furnaces to maintain an indoor temp of 70 at a
0 degree outdoor design temp. What that means is: If my furnace is sized properly and my indoor temperature is 70 and the outdoor temp is 0, then my furnace will run 24/7 until the outdoor temp begins to raise. If the outdoor temp continues to drop to -10 or -20 below 0 then my house will begin to get colder and colder and I will need to add some type of supplemental heat. On the other hand, with that same furnace, if it is 50 degrees outside and 60 degrees in my home and I want to raise it to 70 I would probably take much less than an hour. What you are interested in is if the motor replacement you just got is set properly. It should be set so that you get the proper "temperature rise through your furnace as stated on the furnace equipment label. Usually a temp in the range of 35 - 70 degrees. More blower speed will lower this temp range. Less blower speed will raise this temp range. BubbaHomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.