Air temp affects on LP boiler burner

tazdvlj

Any one have a problem with cold air affecting combustion on a LP gas forced burner

EdTheHeaterMan

How cold?
Is the LP tank outside above ground or buried?
What size tank?

As you use fuel, the propane evaporates off the surface of the liquid in the tank. If you are using 100# cilinders the surface area is very small. The cold temperature will have an effect on the evaporation of the fuel. This may cause a lower than desired pressure.

We are talking below-freezing temperatures for this problem. In northern areas they resolve this by using Butane or a mixture thereof

JUGHNE

Cold air in the furnace room?
Cold air comming in thru sealed combustion pipe?
How cold?

EBEBRATT-Ed

Cold air does affect combustion. I have seen technicians dial in a boiler and complain the net time that there combustion test has changed....of course it does. Colder air is more dense that warmer air so the fan moves more air on a colder day.

But a combustion test is use d to keep a boiler within a safe range not at a specific set point. What problems are you having? Colder air can cause ignition issues

EdTheHeaterMan

@tazdvlj just wanted to ask the question... does not really care about the answer I guess

Solid_Fuel_Man

Hold on @EdTheHeaterMan.....

LP vaporizes from the wetted surface of the tank. Not just the small surface area of the liquid. Therefore a 100#cyl has more vaporization capacity when it is fuller (more watted surface) the surface area of the liquid is the same circle no matter how full or empty the tank is. 

The metal tank absorbs the heat so the liquid will vaporize. 

100# cyl holds 25 or so gallons full. Sixteen 100pounders (400 gallons) can vaporize more LP than a single 500 gallon tank (400 at 80%). The 16x 100 pounders have more total watted surface than the 500. 

EdTheHeaterMan

@Solid_Fuel_Man , Do you really think the OP will understand that? He is not even interested is replying to our questions about “what temperature?” What problems are you having?” “Cold air from furnace room or direct vent?” Or “tank location?”

I know that the fuel volume in the tank matters and a 80% full tank gasses better than a 15% full tank. But the OP is not helping with the discussion of Their problem !!!

But thanks for pointing out the error. I could not remember that term “Wetted Surface”.

That is one of the things I forgot when people say “ He forgot more than you will ever know!”

I can tell from your posts that you have as much or more experience and “Forgot more Than I will ever know. “

Solid_Fuel_Man

No offence....I mean I'm not part of the National Sarcasm Society....although my wife would send me there for sure!

I know you knew that, and I was just poking the bear a little. 🤪

captainco

I am pretty sure there are rooftop and gas packs that are LP and work in the coldest of weather. They get all their combustion air from outside.
When dealing with combustion air temperatures, the colder the air the poorer the mix. This means if equipment is set up in warmer weather we have to set it up leaner than we would in colder weather. What about all the equipment that brings in outside air directly to the burner? This affects oil burners more than LP.
There was an ASHRAE study in 2006 that stated outside air piped directly into burners was not as great as previously thought.