[asking]

Inspired by a thread here on propane furnace efficiency, I went to the basement and changed the filter on my propane furnace and tried to find out what kind it is. It is a Day and Night and is 16 years old. But it has no information that I can find saying how efficient it is or how many BTUs or what kind it is. There is another one in my attic I know even less about.

I read that new furnaces are much more efficient. Should I consider a new, more efficient heater? How do I find out how efficient my old ones are?

I'm not rolling in dough, but I want to lower my propane bills and do anything I can to reduce my carbon footprint. I am going to get new weather stripping and possibly put up thick curtains in some rooms. Should I save for new heaters?

Just Asking

[NorthernHeat]

I need to know if there is a draft inducer blower motor in it to tell if it is a natural draft (around 75% efficient) or induced draft (80+% efficient). If you are installing a 90+% efficient on LP please please please have it checked annually. To many times 90+ furnaces are ruined on LP due to the excessive moisture and soot problems if there is gas pressure problems or insufficient combustion air.

But to answer your question a 90% is 20+% cheaper to operate than a natural draft if installed and maintained properly.

[asking]

Thank you!

I don't know if it has a draft inducer blower motor. Can you tell from the following?

I went into the attic and found a package of information from when it was installed. The one in the attic is a Day& Night, 376C horizontal and the one in the basement looks like a 395C upflow, and the air comes into it from the bottom left. "Series B Sizes 040 -130, Gas-fired, induced combustion furnace"

The blower fan in the basement furnace is covered with fine dust.

I suspect they have not been properly maintained...

For the attic furnace, there is a throwaway filter at the air intake in the ceiling, but if there's another filter inside the furnace, it's never been changed in 16 years... I assumed there wasn't. The box is insulated and sealed.

The service instructions say that each furnace should have two filters, but I think each was installed with just one filter. The basement furnace had one nylon mesh filter that didn't do much. So after about 4 years, someone replace it with a 5 inch thick Trion "airbear," which was poorly sealed. More recently, I added a throwaway 1 inch "Filtrete Ultra." at the intake and sealed everything better. I just reinstalled the nylon mesh one that came with it, so it now has three. Too many?

As far as I know, the attic furnace still has just the one inch throwaway filter, unless there's a nylon mesh one inside (that hasn't been cleaned in 16 years!). The box is sealed and insulated.

Both furnaces have been checked two to three times, because I kept reading I was supposed to do that, but the furnace guys always say, "There's nothing wrong, why did you call me?" I would say "for maintenance" and they would say it didn't need maintenance, So I stopped calling them after a while... Bad?

[therinnaiguy]

Keep in mind that you could increase your furnace efficiency and still use as much fuel. Here are a few reasons. By design a 90% efficient furnace is not 90% efficient all the time. It may be rated 90% A.F.U.E. which is tested as an average under certain conditions, many conditions you may never experience. Typically you could expect to use less fuel most of the time. Shoot for efficiencies above 93%.

Another factor is the tightness of your dwelling. Installing a new furnace without tightening up your buildings envelope will not help one bit.

I suggest that you investigate systems that stage or modulate to compensate for external temperature dips and can adapt and run at it's optimum (not highest) output. Also do what you can to tighten up your home with insulation including your ductwork.

[asking]

Thanks, again!

I just adjusted all the weatherstripping, so the doors are better sealed, windows are doubled paned metal windows. The house is reasonably tight, being newish. All the heating ducts are insulated. I did notice that the attic floor is insulated (ie. The ceiling), but not the underside of the roof, so the furnace sits Above the insulation, heating the attic (which was very warm). Unclear if it would be worth installing a second layer of insulation on the underside of the roof. It rarely gets below 30 here. I'm not sure what else to do...

What is a system that "stages or modulates to compensate for temp. dips"? Can you explain or give an example?

[therinnaiguy]

Picture your car, you probably regulate your gas pedal to compensate for hills and valleys on the road, or are you from NYC and just floor it! Lol. A furnace that can compensate for differences in temperature use both much less fuel and electricity. The typical one-stage furnace turns on at 100% of it's rated output whether you need all that heat or not. A dual or triple stage system turns on at a much lower output and intelligently seeks the optimum stage to run at, thus helping to keep fuel usage at it's lowest. Typically these systems will use less than 2% of their total fuel cost for electricity. As an example, compare a single stage system as a 600 watt lightbulb and a triple stage system as a 40 watt bulb.

[asking]

I get it! That was a great explanation.