Excessive propane usage with high-efficient furnace??

Jeff2020

Hello, looking for some out of the box thinking here as I am racking my brain on what I believe is excessive propane usage on my high-efficiency Lenox furnace.

We moved into a 2200 sqft bungalow this past summer and this is our first winter in the house and on propane. We live in Ontario (Canada) but this past Nov & Dec has not been too cold. For the past couple of months, I am burning 650L / month (175 Gallons) in propane. I'm concerned that Jan / Feb / March is going to be multiple fills per month.

I have made some adjustments to the house / system but it doesn't seem to have helped at all.
- shutoff and blocked the HRV so no cold air is getting brought in.
- updated the insulation in the ceiling to R60.

We have a loft above the garage that is spray foamed and has a split heating system as the duct work did not run into this area.

Has anyone seem a high-efficient furnace consume excessive propane? It seems to go on all the time so not sure if it's shortcyling or if that's just because it's a high efficient furnace.

Looking for any thoughts or feedback on what could be checked. I have a thermal camera on order but considering the house was built in 2006, I don't expect it to be too bad from an air leakage perspective.

Thanks in advance.

Jamie Hall

Two things. First, has anyone maintained that furnace? They must be cleaned and adjusted, preferably annually, by someone with the proper test instruments and knowledge to use them. Oddly (or perhaps not) the higher efficiency furnaces are even more sensitive to this than the older clunkers, and it's quite possible to lose 10 to 15% efficiency just by being out of adjustment -- and you can't adjust them by eye or ear.

Second, you will use a certain number of BTUs to heat the house, and there's no way around that. For satisfaction, you could do a heat loss calculation on the house (Slant/Fin has an excellent on-line calculator for that) and compare that to what the furnace is doing.

Jeff2020

I have the company who installed the furnace in this week to look at it to ensure it's operation optimally. At this rate, spending 20K on geothermal would be a 5 year payback or less.

JUGHNE

Is furnace and ductwork in the basement or attic?
Anything else in the house use LP?
Do you have any history for comparison, from the previous owners or even the LP company?

Assuming you have a buried line, there is a simple test to pressurize the line at the tank to see if the UG could be leaking.
If it were an inside leak you would have known it by now.

pecmsg

What’s the actual heat loss of the building 
what size is that heater

Jamie Hall

Jeff2020 said:

I have the company who installed the furnace in this week to look at it to ensure it's operation optimally. At this rate, spending 20K on geothermal would be a 5 year payback or less.

Remember that a BTU is a BTU, and it doesn't matter where it comes from. Do the math on the geothermal very very carefully. Capital and running.

hot_rod

5 gallons a day?  Assume for calculating that it is. 92,000 btu/ hr furnace, that would be 5 hours of run time per day, as LP contains about 92,000 btu/ gallon. Minus the efficiency of the furnace.

in a perfect heating world , a properly sized furnace would run non stop on design day, so dies 5!hours of run time match to the temperatures you have been experiencing ?

The efficiency of the building envelope drives the heat load, as @Jamie Hall eluded to.

Jeff2020

All the duct work is in the basement and I have wrapped most of it in thermal tape before drywall so I don't expect too much leakage. Nothing in the attic from a duct perspective.

I have not figured out how much my house leaks BTU/hour. Is there an average or how would I go about figuring that out?

I have closed the vents in the basement and that did nothing from a consumption perspective which I thought it would help a bit as I'm not heating that area.

My furnace is a 88K BTU/hr and figured it's running at about 25% of the day based on burn rate but that would be at 100% burn rate which it never seems to be at full throttle.

Just trying to figure out if this is reality or if something is off. At this rate, I would be spending 3-4K for propane from Nov - April. My neighbors said they spend 1600/yr for a similar sized house.

Is there a rough guideline on how much time / day the furnace should run in winter?

Jamie Hall

Neighbours are a very poor guide to how much fuel they burn or how much it costs...

However, Slant/Fin has an very nice and relatively easy to use on-line heat loss calculator in their web site. Quite accurate - if you put the right information into it.

jacobsond

"We moved into a 2200 sq ft bungalow this past summer and this is our first winter in the house and on propane." There is most of the problem right there. New homeowners 1st heating winter. You can likely get usage data from the propane company to see the history. Maybe something has changed. Maybe not. 2200sf and 175gal to heat a month in Canada is likely right in line. Im in a 2000sq ft home in ND with baseboard hot water with a cast iron "efficency" boiler.I would be happy with that usage. Ive been in my house 40ys and I know what this house can use over the varied boilers I have had.

SkyBlue_123

Excessive propane usage in a high-efficiency Lennox furnace could be attributed to various factors. It's commendable that you've already taken steps like blocking the HRV and improving insulation. To further troubleshoot, consider checking the furnace's heat exchanger for any cracks or leaks that may affect efficiency.

Verify that the thermostat is functioning correctly and that the furnace isn't constantly running due to a malfunction. Ensure all vents and ducts are clear and unobstructed. Additionally, examine the loft's heating system to confirm its efficiency. While awaiting the thermal camera, observe the furnace's cycling patterns to determine if it's running more frequently than necessary.

If issues persist, consulting a professional HVAC technician for a comprehensive inspection and analysis would be advisable to pinpoint and address any underlying problems contributing to the excessive propane consumption.

EBEBRATT-Ed

Not sure blocking vents and the hrv is a good idea.

The furnace needs air for combustion. Where is that coming from?

Jamie Hall

I'm sure that blocking vents and the HRV is NOT a good idea. Not only do you need air for combustion, but if there is insufficient air change in the house the indoor air quality will be pretty poor.