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New furnace isn't giving off much heat

Is it possible that they gave you a high altitude model which has smaller burner orifices by mistake?

Reply to
Molly Brown
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A 1,200 square foot house is small, but that is a lot of exterior wall and roof to contend with as far as heat loss... Is this a free standing house or part of a larger townhouse/condo building ?

It sounds like your unit was not properly sized...

Were the installed windows and insulation inspected before picking a furnace unit that small ? Heat loss calculations can be a real bitch and come back to bite you if you didn't do them properly...

You are most likely losing heat out your exterior walls and windows faster than your new small high efficiency furnace can keep up with...

~~ Evan

Reply to
Evan

73 degrees is furthest away 82 for one that is right off the plenum. Its a single stage *Are the ducts insulated? You could be losing heat to the crawlspace, attic or basement that the ducts run through.

I would contact the manufacturer to find out what the actual output temperature should be.

Reply to
John Grabowski

If its a 2 stage unit maybe only the 1st stage is opening, either the stat is wrong or the unit or its set up wrong, is it a modulating gas valve, maybe that is the issue. When you turn the thermostat up 10f or so do you get more heat at the register, does the unit kick on high, you can check the flame if its easily visable. Measure the return temp and register output, what is the diference normaly and when its set to a much higher temp, to check if its 2 stage heat and working. Maybe you just dont have enough Gas supply, that can be measured with a manometer. He isnt much of a pro if he doesnt check all things out and get you an answer, im just a home owner and dont know what pros know, I dont work on heating.

Reply to
ransley

That seems low to me - I think I got somewhere around 73 on my farthest one, too, but plenum temp was way up, and well over 100 degrees (it's been a year since I measured, so I don't recall exact numbers).

My return temp is pretty low, normally around 60 degrees (previous owner DIY install, and they just suck return air from the basement with a vent in the basement door - I'll get around to fixing it one day) - perhaps measuring that on yours so you can see the actual temperature gain is worthwhile.

I think my furnace is 57k BTU, so I suppose it'll have a higher output than yours.

cheers

Jules

Reply to
Jules Richardson

40K BTU for a 1200 sf house in Boston sounds mighty small to me. I have 2 75s for 2600 sf in Kentucky and they can not recover when the temp gets into the teens. Who did the load calculations?

I suggest you set the thermostat to call for 5 degrees more heat than it is currently set for and the watch the burners until the temp is achieved. Should the burners turn on and off before the set point is reached you either have an air flow restriction, a unit tripping out on high limit or a potentially defective control board.

While the poster who said that the limit controls are on the board is correct; there is in most cases a physical, high limit safety sensor that wires back to the board. I had to replace one of mine already.

Please do come back and post the solution in this same thread. That helps others who have the same problem.

Reply to
Colbyt

Measure the outlet temperature outside. It should be close to the exit temperature of the vents. Whats you inlet temperature for 75 exit ??

Reply to
zek

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

Reply to
zek

I have a 2 storey 1200 sq ft home on the endge of the southern ontario snow-belt and when the contractor sized my furnace and put in a 2 stage 50/35,000 BTU he said it was oversized for the house and would very likely never kick up from 35 to 50 in normal operation - so

40,000 does not sound like it is terribly undersized - and that would not affect the outlet air temperature at any rate. The specified temp rise, in degrees F, is rated at 35-65 If the air temp is too low (too low temp rise) the fan is running too fast. If the temp rize is too high, the fan is running too slow.
Reply to
clare

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???

Reply to
clare

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.

Reply to
zek

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.

Reply to
zek

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.

Reply to
zek

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.

Reply to
ransley

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.

Reply to
JoeSpareBedroom

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

Reply to
ransley

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.

Reply to
JoeSpareBedroom

If you go to -20f I bet your house is insulated to the highest standards possible, twice as much as an old house that had hot water heat. I bet he is undersized and the contractor went by boiler size, which is incorrect. I bet no Load Calculation was made

Reply to
ransley

I'd say his sizing sounds closer to reality than yours. I have a 100k BTU furnace with a 3200 sq ft house in NJ and it works fine. I can't imagine 150K BTUs in a 2600 sq ft house not being sufficient. Don't you have any insulation? What kind of heating bills do you have?

Reply to
trader4

I'd say his sizing sounds closer to reality than yours. I have a 100k BTU furnace with a 3200 sq ft house in NJ and it works fine. I can't imagine 150K BTUs in a 2600 sq ft house not being sufficient. Don't you have any insulation? What kind of heating bills do you have?

---- reply ------------ I actually have very cheap heating bills. 107 x 12 for the gas bill and I will most likely only pay 10.5 - 11 months of that. Mostly brick-veneer construction with R-13 in the walls with double-glazed windows and at least R-19 in the attic. I do plan to beef that up a bit. I figure the open floor plan and the story and half family room costs me some money. I did not include the unfinished basement but some heat goes there. I am also assuming that the upstairs unit is the same as the basement unit because they look the same and use the same igniter.

When I said "can not recover" I meant from a 10 degree setback in a two hour period of time which is the wake setting on my thermostat for weekday mornings.

Reply to
Colbyt

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