First off supply temps from 80% eff non condensing furnaces will be higher than high eff condensing furnaces.

Questions

What is your location?

Living area size this furnace serves?

Outside temp when you are taking these measurements?

Is thermostat setting being maintained?

Typical average runtime?

When was last time furnace had a checkup by HVAC pro?

What is your electric rate and current cost of propane? Adding a heat pump to leverage fuel cost against the more expensive propane might not be a bad idea,

IMO

Thanks for asking IMO.

I'm in northern Virginia (usda zone 7a).

This furnace serves a 2000 square first first floor of my home. It could also heat the unfinished basement, but I've closed off those vents for the winter.

Outside temps have been in the mid-30s when I took these readings.

Yes, thermostat is programmed and maintained at 69F and no one messes with it.

Average run time is about 5 to 6 minutes of heating. Then the system shuts off for about 10 minutes. So a full cycle, on and off, is approximately 15 minutes on a day like today (outside temps 36F right now).

Can't tell you last time of service, as I just bought the home last July and I haven't had it serviced yet. I suspect it's been a long while though, based on the state of maintenance I've seen with other systems in this house.

I'm paying $0.12 per kilowatt for electric, and $2.39 per gallon of propane.

I've had heat pumps in the past and am accustomed to the low relative temp that comes from the registers. This is my first propane furnace and it just seems that 115F from a system designed to handle up to 165F is a bit on the low side. Thus the reason for my question.

Thanks,
Mono

Furnace is oversized obviously...

I don't recommend closing off vents.

Ran some quick numbers on your fuel sources. Used a COP for HP of 2.25. Straight electric resistance is less expensive than propane.

Cost per 100,000 btu of useable heat
Electric baseboard: $3.16
Heat pump: $1.56
Propane: $3.27

What size and how old is your current AC for this zone? A HP in a DF application would have a measurable payback for heating. An 80% eff furnace using propane is not good.

I would get a HVAC PM run on this system. Filters are being changed regularly?

IMO

DF=Dual Fuel system, a heat pump with a backup fossil fuel furnace such as nat gas, propane, fuel oil.

Still do not like the idea of closing vents.

Your furnace is oversized, that's the reason for short cycling.

Basements below grade or even partially below grade carry small heating loads. Even the size of the AC may be problematic.

And first opportunity, I would add a HP to leverage electric against the more expensive propane and absurd 80% eff furnace. Someone dropped the ball here.

IMO

Thanks for the perspective. Maybe the furnace and AC are were oversized to compensate for the loose building and relatively poor insulation? Dunno.

I was entertaining the idea of replacing the furnace, and a dual fuel had crossed my mind. But I haven't done much research into it yet. I'll talk to the tech who's coming to check out my system next week. He installed the heat pump in my last home and I trust his work.

But back to my original question. Doesn't 115F at the supply end of the furnace seem a bit low for something that burns propane, and is designed to handle up to 165F?

Mono

IMO is internet talk for "in my opinion".