Furnace efficiency rating?

My furnace was installed in 1991. It is a York Stellar Plus High efficiency gas fired furnace. I believe its a model P2UD.

I have looked at all the literature that the previous owner (the people that built the house I live in) left us. Installation instructions, user's information manual but I can't find anywhere that gives me a number of the high efficiency. Ya know like 98% or something like that. I know it's not that high...but I am trying to figure out if its better to replace this unit...if we would save money. There is nothing wrong with the furnace...just wondering about cost of heating etc.

Any ideas or suggestions? Thanks for your help.

 

If it has white PVC pipes going out to the side of the home, it the 90% line.

if it uses the metal chimney to the roof, then it's 80%.

If it's 90% you won't gain a whole lot more in savings.. 80% to a 90% will save some. but not a whole lot if you are tight, and the current furance is working fine.

Just make sure the air filters are kept cleaned, blower motor/blade are clean, a/c coil and secondary coil (on 90%) are clean as well for good air flow.

If you are not sure, then may not hurt to get someone in to give it a good cleaning.

 

Wow...thank you so much! It does have the white PVC going out to the outside of the house....so its a 90.

When we bought the house we had them put in an April aire thingee and also a special filter thingee...so yes its got clean filters and I should probably call the furnace dudes to come out and give it a once over...we usually do that for winter furnace and summer AC...just didn't do this year -- oldest son got married and it was a hectic fall!

Thanks again!

 

What if you have a furnace that was made in 1982? If it works just fine what efficiency would it be (regular simple natural gas furnace).

 

It may be around 60% at best.

 

I think your furnace is higher than "60% at best". It's hard to estimate just based on the year, because 1982 is when Lennox released the first 90% high efficiency furnace. You could also have a mid-efficiency furnace which is around 80%. Or you could have a lower one, but that's not as likely.

My guess is that you're in the upper 70's.

Look at the nameplate ratings on your furnace. There should be input/output numbers listed. Such as 100000 BTU input / 80000 BTU output. Take the smaller number divided by the larger number and that'll be your efficiency.

I measured a gas Lennox roof-top unit from sometime in the 70's, and it was at 72.5%.
My old oil furnace that is now in the garage was originally installed in the house in 1954. It's efficiency is 73.75%

 

It only says nominal input 80,000 BTU
Doesn't give output or efficiency.

 

Even if it did list output, the division of input into output will only give you combustion efficiency, not Annual Fuel Utilization Efficiency (AFUE). Even 1930's models showed 80% combustion efficency. Throw a standing pilot into the mix & your efficiency goes right up the chimney along with the heat from the pilot.

 

That's why I turn off the pilot light around March or April and don't turn it back on until Septembet or October (although I waited until late November last year to light it).

 

I got my answer from emailing Trane:

The furnace in question has an input BTUH of 80,000, a capacity of 62,000 and is rated 82.8 AFUE. The CFM would depend on the external static pressure.

 

What's the full model # do you have on the furnace?