propane and the cold

[schmism]

anyone have experience running a house on a 500 gal tank when temps drop to 0*F or below?

im concerned that my furnace isnt putting out max heat due to reduced input pressure from the tank due to the cold weather.

ps tank lvl at 67%

 

[beenthere]

Shouldn't be a problem due to the cold temps you mention.
Have had 30 deg F below zero, and no problem with propane.

Less output from the furnace may just be the size of the furnace vs. the demand for more heat when it is so cold. (we've been known to call it global warming, or global climate change now. )

 

[Willl]

0* F will get you about 23-24 PSI

Pressure - Temperature Chart for HC-290 (Propane)

ps tank lvl at 67%

As long as there's liquid in the tank, it'll be the same pressure be it 80% or 10% full.

 

[irvingj]

With small tanks, yeah! But with a 500, you shouldn't have a pressure problem.

 

[bp fick]

If this is your first time with zero weather in this house it may just be the reality you will live with or have to deal with. If the furnace is in otherwise good working order, zero weather brings out the weaknesses of one's insulation, windows, doors, bond insulation, basement wall convection and any problems with the furnace having been undersized a bit.

It's funny how most of these problems don't show in weather that averages in the teens or twenties. Zero weather exposes areas that need improvement in the entire package; insulation, weathertight seals, and the heating system. You find out how good your entire package really is or isn't.

 

[Kays Supply]

I just went to a $300,000 home yesterday that the shower head supply line was frozen. The ceiling in the shower had condensation on it that looked like rain. It had a poor insulation job to say the least. The cold will bring out many weak areas.

 

[kenstrac]

anyone have experience running a house on a 500 gal tank when temps drop to 0*F or below?

im concerned that my furnace isnt putting out max heat due to reduced input pressure from the tank due to the cold weather.

ps tank lvl at 67%

Do you in fact have reduced pressure or is it an assumption ,your pressure should be 10" WC when it is running,if it's below that I would look for a partly closed valve ,regulator not set right,regulator safety discharge port plugged,faulty regulator.
If the pressure is OK I would look at the quality of the flame air /fuel mix all work should be done by a gas technician.

 

[charlz]

Propane pressure definitely drops with temperature. At low pressure the size of your delivery pipe likely comes into play as you need a certain cubic ft/min supplied to your furnace. You either do that with small pipe/high pressure or large pipe/low pressure.

I agree though that the most likely answer is your house is simply losing more heat.

 

[bigtiller]

anyone have experience running a house on a 500 gal tank when temps drop to 0*F or below?

im concerned that my furnace isnt putting out max heat due to reduced input pressure from the tank due to the cold weather.

ps tank lvl at 67%

You won't have any gas problems. If your tank was down to 25% and it was -20 degrees outside, the tank can still produce 68,900 BTU at a continuous withdrawl rate. But your furnace runs intermittently so you can draw quite a few more BTU's.

The line from your tank to the house has 10 pounds of pressure and the regulator on the house cuts that down to 11 water column inches, which is about half a pound or so. So as long as you have a few gallons in the tank the furnace will make "max" heat.

 

[Patriotic Stabilist]

Maybe just a filter replacement is in order? My furnace guy also told me to go to the cheaper ones, can you imagine? I was using those pleasted ones to take the dirt out and he said they cut the air flow to much. I had called on a couple of my rental furnaces and that's all it was.

 

[schmism]

filter issues is usually a air flow issue (like not enough)

the issue im wondering about was the overall temp of the air felt cooler than normal when feeling the 2 closest vents.

 

[Egon]

We had propane fired furnace heating for a number of years. No problems with propane flowing even the few times it went down to -40C. [Actually it may have -45C for a short period]

Sometimes people will put a light bulb under the tank cover.

Some have even built fires under the 500 gallon tanks in the extremely cold weather.

 

[SPYDERLK]

0* F will get you about 23-24 PSI

Pressure - Temperature Chart for HC-290 (Propane)

[As long as there's liquid in the tank, it'll be the same pressure be it 80% or 10% full.]

You won't have any gas problems. If your tank was down to 25% and it was -20 degrees outside, the tank can still produce 68,900 BTU at a continuous withdrawl rate. But your furnace runs intermittently so you can draw quite a few more BTU's.

The line from your tank to the house has 10 pounds of pressure and the regulator on the house cuts that down to 11 water column inches, which is about half a pound or so. [So as long as you have a few gallons in the tank the furnace will make "max" heat.]

Not exactly. The liquid gets colder as you draw from the tank because the liquid is evaporating giving its latent heat of vaporization to the gas. It you draw too fast at cold temps the liquid will get much colder than the [already low] air temp. If the liquid gets down to -40 there is no pressure. The reduced delivery to the furnace will be notable well before that.
larry

 

[schmism]

Not exactly. The liquid gets colder as you draw from the tank because the liquid is evaporating giving its latent heat of vaporization to the gas. It you draw too fast at cold temps the liquid will get much colder than the [already low] air temp. If the liquid gets down to -40 there is no pressure. The reduced delivery to the furnace will be notable well before that.
larry

This is what i was talking about.

I found this very educational link that explains my concerns nicely for the next guy whos wondering.

Chapter 5 - Vaporization of Propane

note the table that lists the available BTU/hr vs temp for various size tank and how 1) the available btu drops as temp drops and 2) the larger the tank the more BTU/hr are available.

also note the assumptions (that the tank is half full) which is why i posted a tank lvl at the beginning of my question (i already knew that the available output depends on wetted surface area of the tank which changes as the gas lvl decrease)

the point is at 0 deg f on a half full 500gal tank you can pull 300K BTU/hr off the tank and still have it work fine. Well within the range of most furnace requirements (certainly mine)

 

[schmism]

on a related note this same issue will crop up when trying to run to large an item (btu/hr requirement) off to small a tank. such as a large propane generator (continuous draw) or some other larger burner. for instance our 4'x6' 3 burner fish fryer we use at the FD that will frost up a 100lb tank durring a fish fry on a 70deg day. (we can always tell our gas lvl about half way through the event)

 

[Willl]

The liquid gets colder as you draw from the tank because the liquid is evaporating giving its latent heat of vaporization to the gas.

Which would happen regardless of tank level.

 

[schmism]

Which would happen regardless of tank level.

to some point. if the surface area of the liquid is unable to absorb enough heat to replace that which it gave off to evaporate the gas, then the tank is running at a negative heat ballance. The lower the tank lvl the less surface area there is to absorb heat. When there is insufficient surface area (or outside ambient temp to warm the side of the tank) then the temp of the liquid cools which then cools the side of the tank. If that keeps up you eventually frost the side of a tank which acts as an insulator which prevents heat transfer thus makeing the problem worse = the term "to freeze up the tank"

so the tank lvl does play an important role in determing how many BTU/hr you can pull off the tank. (as the chart indicates)

 

[Willl]

to some point.

Oh brother,,,,OK, would you agree that 'static' pressure would be the same ?

And by "static" I mean NOT being drawn down. As-in main outlet valve shut, 0 flow.

 

[SPYDERLK]

This is what i was talking about.

I found this very educational link that explains my concerns nicely for the next guy whos wondering.

[Chapter 5 - Vaporization of Propane]

Interesting link. It gives a good idea about what is happening. There are some anomalies in the data in tables that raise some questions - the trends shown are quite lumpy. I think it may be that they are giving empirical data, but not accounting for the dewpoint.
larry