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furnace BTU

Today's furnace specify btu. Is that input or output ?

Greg

Reply to
gregz
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They are advertising. You think they will give the bigger or smaller number? Bigger. So....

Reply to
Stormin Mormon

Mine quotes input BTUs (basically fuel consumption)

Reply to
clare

The input is the only thing the manufacturer has control over. Anything that effects the efficiency of the furnace will change the output BTUs

Reply to
clare

Yes, input and AFAIK that is how it has aways been.

Reply to
trader4

Input. Figure the output by multiplying by the efficienct rating.

Reply to
Ed Pawlowski

Is that true for oil furnace, too?

Or maybe the question is, Was that true for oil furnaces 35 years ago, too?

Reply to
micky

Yes.

Yes. It was stated as such, on mine. As others have stated, it can't be anything else. There are too many variables to state the heat output.

Reply to
krw

Read the spec sheet carefully.

My furnace is rated on output.

Reply to
Irreverent Maximus

The funny thing, output is what yo need to know in computing requirements. When I was young, I remember looking at the furnace specs in my teens. I'm pretty sure it gave specs at 120k btu out, and maybe 160btu in. I'll have to compute efficiency. I remember nights hearing the furnace shut off, then come back on in a minute. Before I sold that house, I made many improvements in insulation. A 100k btu 95% furnace was in place. Also nice that newer units have more cfm flow.

Greg

Reply to
gregz

Just out of curiousity, you have the make and model?

Reply to
trader4

Well, my furnace is a Carrier model 58HV085

And in the owners manual, it says Ratings, Input (1000 Btuh) 106 Output (1000Btuh) 85

So it not only rates the output, it named the model of furnace after the output.

I went shopping for a new oil furnace, but the brochures they gave me didn't show if they rate them by input or output or both now, of if the model number reflects either number.

(HV means it's an upflow furnace, and 58 is the series, a group of furnaces including downflow, upflow, loboy, etc of variious sizes, a total of 18 models, all of which are named after their rated output)

Plus the blueprints for the house, which I got fromt he architect, have 85,000 (or maybe 85,000 btu) hand-written in big numbers at an agle on them.

It was installed 34 years and a few months ago, and when shopping for a new furnace, I have to be careful NOT to buy one with 85,000 input, which won't give as much output as I have now.

Here's the spec sheet for all of them. The info starts at page 3.

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Reply to
micky

How long does your furnace run on the coldest day of the year? If it runs less than 8 hours, chances are very good the furnace is larger than required. If it runs over 16 there is a strong chance it is slightly undersized.

Reply to
clare

Even Carrier can't repeal the laws of physics. The only thing they have control over is the input (and that, only to the degree that specifications are followed). The output (efficiency) is left to age and those maintaining the system.

Reply to
krw

Yeah, I've heard about that, and I wish I'd kept track as much as I could have.

We don't have many days that are the coldest, and I kept NO track during those.

I could extrapolate maybe, if I kept better track on even non-coldest days, like most of last week. I did notice, without looking at a clock, that it often ran maybe 10 minutes, and then was off for only

10 minutes, but I guess those are estimates. Often I'm in the basement on the computer for hours during the middle of the night. It might be like that then too.

But it's in the 60's today and until Monday,. I'll have to start paying attention after that. High in the 40's on Tuesday, t hey predict now.

Thanks for the question.

Reply to
micky

True, but nonetheless, that's how this 34 year old oil furnace was rated, and named. I guess they changed but I don't know when.

Hmmm. Have they changed that much? I see that currently Carrier names its gas furnaces by the maximum effficiency they can deliver, Comfort 80, Comfort 92, and Comfort 95, model names for 80, 92, 95% efficiency. and it's probably no coincidence that model 59SC5, ending in 5, iis the one that they say is up to 95% efficient. And 59SC2, ending in 2, is the one they say is up to 92%.

Not all of them are exaclly like that. Performance 90 (not 92) goes up to 92.1% they say, but its model number is 59SP2, ending in 2. to represent 92%. .

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And in oil furnaces, Performance 80 ranges they say gp from 85.7 to

86.6% eff. but they are all called Perf. *80*. The model numbers have no numbers, only letters.

I havent' found the btu ratings, but I wouldn't be surprised if they have a rating for output, despite its dependance on age and maintenance. They'll say they're just rating it when it's new.

Reply to
micky

I used to have another thermostat when I had an oil furnace. It recorded daily on time. I knew it used 3/4 gallon per hour. Easy computations. Dam thing took 5 minutes before the fan came on !!

Greg

Reply to
gregz

My Tempstar(icp) is an ntv6050fb/vne050b12 input 50kbtu/35kbtu input, 40kbtu/28kbtu output spec 80+% 2 stage variable speed. On low fire it is better than 85% efficient (so puts out 30kbtu+) - not as efficient on high fire. The "smart thermostat" registers run time - I don't think it has ever run 10 hours in a day, even when it is a nasty -5F and windy out. Most winter days not over 8 hours out of 24. The furnace is slightly oversized for this1350sq ft plus finished basement 2 story 40 year old house. ( new vinyl double glazed LoE2 windows and R50 in the attic)

Reply to
clare

And in oil furnaces, Performance 80 ranges they say gp from 85.7 to

Oil heat for a home is a foreign concept for us down South because NG or LP are the most common fuels burned for heating homes. Of course there are heat pumps with a backup that can either be electric resistant heat or a fuel burning furnace, then there are wood or other solid fuel burning sources of heat. Many very old homes have coal burning furnaces that have been converted to NG but they're not as efficient as more modern forced air systems. We call the old coal burners, "Octopus" heaters because there is no blower, the furnace in the basement has large ducts coming out looking like a tree or octopus and the heated air flows by convection. The old homes have a coal chute from outside to the basement and when I've serviced some of the old coal furnaces converted to natural gas, there is often still coal in the coal chute. ^_^

TDD

Reply to
The Daring Dufas

Nat gas isn't available in much of the NE and LP is exceedingly expensive. Oil is there, now, too. We had oil-fired hot-water heat in our NY and VT houses. The latter we converted to Nat Gas as soon as we could (the gas company gave us a deal we couldn't refuse).

Sure, though not that not all "octopi" were coal-fired. There were also gas and oil-fired gravity fed hot-air systems. Their efficiency sucked so went away some time back (at least by the end of the '50s).

Reply to
krw

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