New furnace isn't giving off much heat

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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.
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On Wed, 03 Nov 2010 19:49:37 -0700, Jdog wrote:

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
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Is it possible that they gave you a high altitude model which has smaller burner orifices by mistake?
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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
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On Wed, 3 Nov 2010 23:41:37 -0700 (PDT), Evan

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.
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On Nov 4, 11:10am, snipped-for-privacy@snyder.on.ca wrote:

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
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On Fri, 5 Nov 2010 04:51:43 -0700 (PDT), ransley

aluminum siding with double glazed Low E argon filled vinyl windows and about 2 feet of loose fill fiberglass in the attic. The basement is insulated to about R12 - almost as good as the outside walls. We spend about $700 a year on natural gas which operates the furnace and the water heater. Changing from the original 35 year old furnace to an 85%+ 2 stage 35/50 TempStar with variable speed DC fan didn't reduce our gas bill at all.
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On Nov 5, 5:39pm, snipped-for-privacy@snyder.on.ca wrote:

If your new unit is only 85% eficient im not suprised, most old units are 80-82% efficient, going to 95% plus would help, but your gas bill is still minimal for yearly cost. Ive done about the same as you in insulating.
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If your new unit is only 85% eficient im not suprised, most old units are 80-82% efficient, going to 95% plus would help, but your gas bill is still minimal for yearly cost. Ive done about the same as you in insulating.
--


In Ontario you can no longer buy mid-efficient furnaces anymore.

Is your 85% new furnace considered mid or high efficient? Does it use a
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furnace that came out was "rated" at 75%, and the last time I had it tuned the tech checked it and said he thought he had made a mistake, so checked it again, and it was over 80%.
The ECM fan is so much more efficient than the old belt drive induction motor fan that the furnace needs to be more efficient just to maintain the same consumption.
The ECM fan draws 400 watts less on low speed, on average - producing a BTU deficit of about 1300 btu/hour just for the constant run consumption.
When running at high speed (heating) the ECM blower saves roughly 400KwH of electricity - requireing between 11 and 29 cu meters per year more gas to make up for the BTU deficit (approx 1,365,200 BTU) according to a Natural Resources Canada study (Google canmetenergy ecm effects)
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On Nov 5, 10:07pm, snipped-for-privacy@snyder.on.ca wrote:

Of course you are not saving any cash, you might have taken out a good 82-85% furnace An 85% furnace is not High Efficency, your manufacturer called it so as a sales gimmic. H.E. is a condensing unit 93-98% efficient, thats no marketing gimmic. 82-83% efficient heat has been available for maybe 70 years and more than 100 on boilers. 82% units are just not sold by law anymore. I have a 1955 1,300,000 btu Kewanee thats 83% efficiect steady state, continous running.
A contractor Can Not rate a systems efficency to the standard AFUE test in your home, it requires a test facility with near $50,000 in test equipment that is Gov certified and maintained, he can only test Combustion Efficency. And there he lied to you to sell you a new unit because to get 85 % combustion efficency you would hardly be burning the gas, or an oil burner would be all smoke. Its impossible for him to do the tests to Rate a systems overall efficency. He lied to you again.
Even if OPs blower is set to high he still would get the same Btus, but he still has no recovery in his temp rise number, realise he might be getting 37-39000 btus, just 3 burners on my stove-oven are 38000 and I could not heat my house with 3 burners on my stove stove or with the oven running giving more Btus, its just not enough Btus. 38000 might work on a super insulated house, one built to high Canadian standards, standards we dont have inplace in the US yet, some houses are built to them, not many not enough.
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On Sat, 6 Nov 2010 04:22:08 -0700 (PDT), ransley

I took out a 35 - or I guess 38 year old furnace so I'd be replacing it on my terms, instead of it's terms. It was a relatively cheap contractor grade furnace, and mine was one of the last 2 on the street still in operation. I was involved with the addition being installed on the neighbour's house, which required replacement of theirs - the other one still in service - so I negotiated replacing both at the same time. I think I got a good deal.

I have mine. It is a high efficiency non-condensing furnace. What makes it high efficiency? It has forced draft burner, not atmospheric burner, and it is a two stage furnace - with a variable speed electronically commutated DC blower motor.
7 years ago, or whenever it was we replaced the furnace, this was allowed to be sold as a "high efficiency non condensing furnace" and is every bit as efficient, over-all, as a single stage condensing furnace with an AC multi-speed blower. (counting combination of electrical efficiency and gas efficiency together)

He didn't lie to me to sell me a furnace. It was 5 years later that I had it replaced, and not by him or his company. He was surprised at how high the efficiency of the furnace was - and he measured inlet temp, outlet temp, stack temp and something else I can't remember to come up with his "efficiency" number. He said he had not seen one of that type of furnace running as efficiently as mine was - and he didn't make a single adjustment to it.

I didn't see the OP complaining about recovery - only the fact that the air from the heat outlets was much coller than what he had before - and then at the same time he said it was replacing a boiler - so I really don't know WHAT he was complaining about.
The fact that one was 85 degrees and the other only 70 something, from what I remember, is what makes me believe it is not JUST a furnace size issue, if it is a furnace size issue at all.
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On Nov 6, 4:28pm, snipped-for-privacy@snyder.on.ca wrote:

LOL...
Except the OP clearly stated that his home USED to be heated by hot water baseboard heat rather than the *NEW* forced hot air system... Therefore he has NO basis for comparison since he never had heat duct registers before...
Now, your point of duct size, duct balancing and duct insulation would make the problem of having an undersized burner EVEN worse than the suggestion that the houses insulation and windows were not properly accounted for in the heat loss calculations made prior to selecting the SIZE of the unit that was installed...
The fan speed setting at which the air in the ducts is circulated can not compensate in any way for an undersized burner...
This is an example of why field conditions in a home MUST be examined prior to doing ANY sort of work on the building...
The OP pointed out that the heating system was replaced because persons unknown stole the copper piping from the baseboard system... Well, I highly doubt that any analysis of the overall status of the building envelope was done by the heating contractor he called in to replace the scavenged heating system -- he would have better spent his money replacing the cut out copper piping than he seems to be with his idea of replacing the whole system with something new because he selected an unqualified professional who lacked the proper assessment skills to properly determine what size heating plant to install in the home...
While you have brought up some interesting issues which could explain SOME of the problem, you are not adding up everything that has been stated by the OP to see that while the concerns you address may bear some fruit, they can not add up to the entire heating gap the OP is experiencing from his clearly undersized heating plant based on his total lack of knowledge of the status of the insulation rating sealed up in his walls, or the energy rating of his window and door openings...
The shell of the building and the insulation values involved are of primary concern when doing heat loss calculations to figure out the maximum heating load that the heating plant must be able to accommodate on the "coldest day of the heating season"... Honestly it is better to have a system that is rated at 1/3 more btu's than you need than to have one that is just barely enough to heat a home which complies with the most ideal insulation conditions and would otherwise be clearly undersized because someone assumed an insulation value was inside your walls that doesn't exist...
The OP at this point in time needs to have a more qualified and experienced heating contractor come out and evaluate the overall condition of his home... He might be looking at either replacing the new heating plant with a larger one which can support the ACTUAL heating load present, or spending SERIOUS money replacing all the windows and doors and upgrading the R-value of the insulation...
~~ Evan
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All true, but it could be as simple as insuficent gas supply, and im sure a test with a manometer was never done yet. He does need a real Pro to come in and re evaluate everything.
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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.
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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.
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Colbyt
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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?
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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.
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Colbyt
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On Nov 5, 8:17am, snipped-for-privacy@optonline.net wrote:

.
40000 input and its likely 38000 output, 3 burners on my stove put out more than 38000 btu, my whole stove-oven might put out 60,000 btus, He cant have any recovery with 38000 btu. I say its undersized and not up to modern insulating standards or what you have. But if no load calculation was done everyone here is just guessing, and maybe his installer guessed also, from the old boiler size, which is different than forced air.
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On Fri, 5 Nov 2010 17:41:30 -0700 (PDT), ransley

He is complaining about vent output temperature. Even with 100,000 BTU, if the fan runs too fast the outlet air temp will be too low.
He has to start with making sure the temperature rize across the heat exchanger is correct. If it is not, the blower speed needs to be adjusted and/or the ducting corrected to provide proper flow and heat gain. IF with the correct heat rize the air flow is not enough to heat the house, the furnace is not putting out enough heat (btus) either because there is something else wrong, or the furnace is too small.
If he is getting high enough temperature at one duct, but not at another, he has a duct ballancing issue and the installing contractor needs to correct that.
According to a study I saw when looking to replace my furnace, the vast majority of furnaces in North America are oversized for the application, and suffer in efficiency because of that. I'm looking for the numbers, but CMHC (Canada Mortgage and Housing Commission) states "the majority" of homes in canada have oversized furnaces. The "consumerresearch.com" states "A recent New Jersey study shows that most furnaces are significantly oversized"
From http://www.bsr-vt.org/vbg/EDUMarch2003final.pdf
A recent study has shown that the average furnace installed in a new home in Anchorage, Alaska is oversized by 121%. The study was conducted by Phil Kaluza, a researcher with Arctic Energy Systems, and was sponsored by the Cold Climate Housing Research Center through a grant from Alaska Housing Finance Corporation....
The ALASKAN report indicates a "rule of thumb" 19 BTU per sq foot is on the high side. Boston would surely be significantly lower.
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