Propane, propane , propane

[MConnelly]

A side from a leak in the line and colder than normal temps, has anyone run into their heaters all of a sudden using more propane than they used to? And, what was the fix?
I have a 2009 Fuzion 403 and we are currently using it. The temps here have been as low as the imd 20s at night and the mid 60s in the daytime. This has been the norm save for a day or two in the high 30s over the past three weeks.
All of a sudden I have gone from 6-7 days heat etc on a 30lb bottle to 3 days on a 30lb bottle. The heater seems to be operating normal. Cycles on and off properly and sounds normal. It doesn't seem to be running an inordinate amount of time either.
I smell no propane in the bottle area .
Any ideas as to why I am using almost double the propane would be appreciated.

[saxgod]

Maybe the place you went to didn't full your bottles completely? Speaking from experience, I had a place fill my bottle weighing for a 20lb not a 30 before.

[JRTJH]

If the furnace was misadjusted (unlikely since it was working and hasn't been tinkered with) you would probably see black soot on the side of the RV and/or smell propane at the furnace exhaust. If you haven't "tinkered" with the furnace, it's probably the propane bottles (as suggested) that weren't completely filled the last time. I'd watch next time and make sure you get the "full measure" that you're paying for. Also realize that at 20* you're going to use significantly more propane to keep the RV at 70* than you will at 40*. In fact, you'll use about two times more propane to maintain the 70* temps.

It's amazing how much heat loss there is through the RV single pane windows and even through those "vacuum insulated" R7 or R9 walls :)

[ktmracer]

there are several things that could be affecting your consumption, or apparent consumption.

1) bottle wasn't filled full, pretty common in my experience.
2) bottle not completely empty on switchover. This is common in cold weather. As you get near the end of the tank, say the last 1-2 gallons, and it is cold out (near or below freezing), the propane can't boil fast enough to keep up the pressure and the changeover thinks the tank is empty. Mine does that if I get near that condition first thing on a cold morning and turn on the furnace and HWH. I just switch it back over later in the day when it warms up and let it draw the tank fully down.

In all reality, I believe that a 30lb tanks is actually not the recomended size for a typical 30-45K BTU furnace, it should be bigger. But given the constraints for tank size that's what we get. Normally there is a formula for BTU draw/hr and temperature that gives the minimum tank size to make sure that the propane can boil off fast enough without to much of a pressure drop. Propane boils at about -40F/C IIRC.

As an example, a 100lb tanks with 10 lbs of propane left at 20F can barely supply a 35KBTU/hr furnace. It will only vaporize 38KBTU/hr. So as you can imagine, a 30lb tank is going to have trouble at 20F supplying 30KBTU/hr as the tank nears empty. So even a 100lb tank as you get down to about 3-4 gallons at 20F will go "empty" on you with propane left in the tank. one of two things will happen. (a) it will switch to the other tank (b), the furnace will shut down from lack of propane.

Combine (1) and (2) and all the sudden you can think your running through a lot of propane when you aren't.

3) How many hours is the furnace actually running?? Your furnace probably uses 30-45K BTU/hr. A gallon of propane is about 80KBTU. so 2-3 hours of run time/gallon of propane. HWH is similar.

[bobbecky]

We have the normal 30 lb tanks, one on each side, and last week, when temps over night were in the teens, filled a tank every other day. This has been normal from the beginning. You have to understand, you are not only heating the living space, but are also protecting your plumbing and tanks. We are about to leave our current location in about a week, but I'm afraid we will be in the single digits a couple of those nights prior to departure, so we will be filling tanks a lot again. Our 3402RL stays comfortable, but takes quite a bit of propane to do that. Much better than freezing your.....plumbing.

[theeyres]

Sure don't know for sure but would guess you are just experiencing the joys of inefficient propane trailer heaters. It's colder, takes longer to warm up the space, including walls, furniture, etc., plus all the ways a trailer lets the heat escape, and a 10* difference in temps at those low temps will make a big difference in how much propane you use.

[ktmracer]

Another thing to be aware of. The heat loss through the walls of a dwelling does not increase/decrease linearly with dwelling square footage. It actually increases as a cube root function of the dwelling square feet, all else being equal. Thats because the heat is lost through the walls and the wall area increases roughly as the cube root of dwelling space.

As an example, our 2400 sqft house has only a little more than 3 times the wall/ceiling/floor area of my roughly 240 sqft trailer, even though it has 10x the living square feet. and the trailer has much less insulation.

In my house the 80,000BTU furnace will run about 30% of the time at 20F. On a 20F night, the inside of the house will drop from 68F to about 58-60F overnight. In my trailer, with 1/10 the living area, the 35,000BTU furnace will run for almost 3 hours full time in the morning to get the temp up to 68F when it is in the mid 20's outside. And it will drop from 68F at 10pm to 45F by about 3am when the furnace starts cycling.

A result of the large wall area/sq ft and the much lower insulation and higher heat loss.

Same thing applies to the AC in the summer for heat gain.

so a small house/small trailer is going to go through lots of propane to keep it heated!!

[Ken / Claudia]

Did you change your camping altitude to a higher level.

[MConnelly]

Thanks for al the input. I am now writing down the temps and the days per bottle I am actually getting. It "seemed" that during the last cold snap three weeks ago, I used less fuel. It is warmer now so fuel use will be much less.
I think I am going to put a hour meter on the heater. Just another measure device.
I was watching the fills so that wasn't the issue this time. 1-2 lbs of propane left in a bottle could be a day or two at 2 hrs a pound.
Like I said I am keeping better track of temp and use.
I will admit we like the rig comfortable and if it take a few more $$s to make it so no issues.
Again thanks for all the input

[bobbecky]

If you are spending a long time in one spot with those temps, it is much easier to have a 100 gallon tank set up by a local propane company, who will fill it on a regular schedule. The gas should be a bit less in price, plus saves the hassle of filling and emptying the tanks 3 or 4 times a week.

[abneynormal]

when I am at home which is in the winter I live in my TH inside a metal building. I plumbed a propane set up into my 500 gal propane tank. open 3 valves and shut off one and I don't fill those small bottles. I also don't have the waste of not using all of the propane in the small tank. so for you I would rent a 120 gal tank from a propane company they can plumb it in also. if you would rather have a system like mine I got my hose and quick connectors from a hydraulic hose building company nearby. they can order large propane hose and connector too. most propane companys will tell you they cant get it. along with other rip offs.