New furnace isn't giving off much heat

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On Nov 5, 10:47 pm, snipped-for-privacy@snyder.on.ca wrote:

m...
Agree with all that.

But the total BTUs of heat the furnace is putting out is going into the living space, whether the heat rise is 20 deg with a fast blower, or 40 deg with a slow one. So, it should not make a difference in whether it can raise the house temp a reasonable amount in a given time. The only exception I see would be if the fan speed were so slow that the temp got too high and it caused the furnace to stop firing.
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On Nov 6, 10:00 am, snipped-for-privacy@optonline.net wrote:

com...
I know the what the problem is, its a bad installer, he needs a new installer.
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On Sat, 6 Nov 2010 08:00:18 -0700 (PDT), snipped-for-privacy@optonline.net wrote:

OK, since you agreed with the first part - are you dissagreeing with the final analasys, or just adding an observation?
Is there ANY other option, given the first conditions are met, than the furnace being defective (something else wrong) or too small??
The main complaint the guy had was not that the furnace could not heat the house. He FEARED it might not be able to heat the house because the outlet air temperature was lower than he expected (rightly or wrongly)

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On Nov 6, 4:35 pm, snipped-for-privacy@snyder.on.ca wrote:

Yes...
Poor installation techniques on the duct work would only make the issue of an undersized heating plant worse...
There is no excuse for newly installed duct work to not be 100% covered in foil faced R-9 insulation batting which is sealed at every seam with foil tape... And that insulation is applied ONLY after the ducts have been either foil taped or gotten a coating of mastic at every joint or seam...
Since this duct work is BRAND NEW, it SHOULD NOT be a factor in the "my house is too cold and the furnace can't keep up" complaint since the duct work was supposedly installed by a competent HVAC professional... Agree ?
The OP's problem seems to stem around insufficient thermal mass and a system without enough heating capacity to properly heat the space given the overall condition of the house...
~~ Evan
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On Sun, 7 Nov 2010 01:47:47 -0700 (PDT), Evan

The original post, in it's entirety: "New Grandaire furnace, gas high efficiency 40k btu in 1200 sft house near boston. All new insulated duct work, hooked up and seems to run right, but the air coming out of the supplies is only about 75 degrees. Any ideas why its so cool"
Also: "73 degrees is furthest away 82 for one that is right off the plenum., "
But you are right, he's also complaining about how long it takes to heat up the house: "It was about 60 inside. Took 90 minutes to raise the temp to 68 and thats with an outside temp of 55. I cant imagine this will be any better this February."
Now the fact that the copper pipe was stolen out from the house suggests the house may have been vacant and somewhat derelict as well, which means it COULD well be uninsulated and drafty - basically an old barn - in which case the furnace WOULD be too small, but in which case it would also be much more cost efficient to seal up and insulate the old barn, rather than throw a bigger furnace at it.
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On Nov 6, 3:35 pm, snipped-for-privacy@snyder.on.ca wrote:

.com...
Not enough gas supply is a possibility. Bottom line, this guy didnt hire a real pro.
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Measure the outlet temperature outside. It should be close to the exit temperature of the vents. Whats you inlet temperature for 75 exit ??
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I meant the air right out of the blower should be very close to the furnace exhaust temperature. 100% eff, equals same temp.
I had a thermometer inserted into the exhaust PVC pipe to constantly measure the efficiency of my old furnace.
A nice furnace would have that feature built in. Two probes and readout. Also helps to identify filter efficiency, or clogged filter.
greg
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wrote:

If you are getting 85 at one, and 75 at the other it sounds like a duct ballancing issue. How many outlets in the house???? If you partly close the 85 degree vent, does the temperature come up on the other one???
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On Nov 4, 12:14 pm, snipped-for-privacy@snyder.on.ca wrote:

Before the new furnace install my oil burner had over 140 degrees out the vents!!
My 1600 total cf home has a 70/50 installed. Its still overkill since insulating my home. I am further remodeling basement and more insulation downstairs, very important. Heats radiates in all directions. The old house had a 100K BTU and it struggled.
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On Nov 4, 12:14 pm, snipped-for-privacy@snyder.on.ca wrote:

Before the new furnace install my oil burner had over 140 degrees out the vents!!
My 1600 total cf home has a 70/50 installed. Its still overkill since insulating my home. I am further remodeling basement and more insulation downstairs, very important. Heats radiates in all directions. The old house had a 100K BTU and it struggled.
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On Nov 4, 12:14 pm, snipped-for-privacy@snyder.on.ca wrote:

Before the new furnace install my oil burner had over 140 degrees out the vents!!
My 1600 total cf home has a 70/50 installed. Its still overkill since insulating my home. I am further remodeling basement and more insulation downstairs, very important. Heats radiates in all directions. The old house had a 100K BTU and it struggled.
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I bet its to small for your homes load, I have 1200sq in he midwest where is goes below zero and has gone to -20. i have 75K input but could have squezed by with 55k if it ran 24x7 on the coldest times. If that is 40k input and 35k output I bet you need 30k more unless its super insulated, mine is super insulated and needs 50k by a load Calculation, it had 110000 btu in it before. But 40K input is to small for a normaly insulated house in Boston.
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wrote:

I bet its to small for your homes load, I have 1200sq in he midwest where is goes below zero and has gone to -20. i have 75K input but could have squezed by with 55k if it ran 24x7 on the coldest times. If that is 40k input and 35k output I bet you need 30k more unless its super insulated, mine is super insulated and needs 50k by a load Calculation, it had 110000 btu in it before. But 40K input is to small for a normaly insulated house in Boston. ========= "too small"
Not "to small". Write like an American.
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wrote:

WTF you the dam net nanny, an extra o never slipped by you. Keep proof readin because I dont bother, you ass.
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wrote:

WTF you the dam net nanny, an extra o never slipped by you. Keep proof readin because I dont bother, you ass.
============ It didn't "slip by you".
Be sure you don't ever complain about immigrants who don't learn English. When you live in a glass house, you don't throw stones.
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Jdog wrote:

I'm sure some/many people will correct me, but here's what I'd do.
Spend some quality time with the gas meter and a stopwatch. Verify that the gas going in is correct for the BTU rating of the furnace.
Log the percentage of time the gas is on in the steady state. In my case, it's 1.5 minutes less than the fan runs each cycle. Measure the difference between inside and outside temperatures.
Calculate the inside-outside temperature difference on the coldest day of the year.
Ratio this calculated future difference to the current measured difference and multiply by the percentage on time. If that is > 100%, you've got a problem. Yes, there are issues with wind, snow, SHG, etc, but you gotta start somewhere.
On a day with no wind, open one window a crack. Open all the interior doors. Turn on the furnace fan. Take a burning incense stick smoke generator to the window. A lot of air moving in or out suggests that you have a leak in the system somewhere.
You can do a similar test by turning on all the exhaust fans in the kitchen/bathrooms and use the smoke stick to look for air coming in the registers.
This assumes you don't have a fireplace...or you need to account for that major hole in the system.
I just replaced a 120,000 btu 70% furnace with a 60,000 btu 95.5% furnace. Air coming out of the registers went from 140F to 105F. And that's higher than it should be. Doesn't help that I have the registers closed in half the house, so the effective duct size is too small.
You have at least two issues. 1)heat loss thru insulation/infiltration. 2)thermal mass.
With excellent insulation, it takes little heat input to maintain the temperature. But if you CHANGE the temperature, it can take a lot more heat because of the thermal mass of the system.
After a major insulation upgrade, I started to notice a phase shift in the cooling load. The air conditioner worked harder around sundown than it did during the hottest part of the day. Fortunately, I can open the windows at night, so it's a good thing. Near as I can determine it's because of the increased thermal resistance coupled with the increased thermal mass of the insulation and the air trapped within.
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One fact, you dont even know what you have, and you need to start there. I just looked a Grandaire furnaces site and they dont make a 40k Btu input or output rated unit in 80 or 90%. They have in 80% 43/36 and 54/45. In 90% 55/35, and 60/38. So f you have the smallest 90% you get 35000 Btu, if its the 80% you get 36000 btu. Not very much at all, Two burners on my stove do 35000 BTUs !!!
You can check temp rise to see if its firing 100% or getting 100% needed supply, [ still a manometer test is needed ] Place a probe thermometer at the furnace intake and one just at the top of the unit [ you have to drill a hole so if you have AC dont do this unless you are sure of where the AC coil and lines are ] the difference of the two is a rise of only 30-60f for the 90% unit.
Bottom line, pay an experianced top line pro to figure it all out, your buddy is a hack. Did this guy get a permit or is he even lisenced, I bet not and that might help you to get him to fix it free after you figure out the truth. If he is at fault you could pull a permit now saying you thought he did it, the inspector will make him fix it. Ive done it.
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One thing not mentioned is the calculations. The size is on the bottom end, but in a well insulated house, it is very adequate. OTOH, in a poorly or non-insulated house, it is very undersized. We just don't know enough.
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If the old system was a hot water boiler, the house is probably pretty old and therefore not very well insulated.
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