Shop heater won't fire when its below 20

[JUNK-MAN]

So I installed this Goodman furnace in my garage this year and for some reason it will not future when its below 20 out. Every once in a while it will fire if I put a small space heater on a ladder aimed at the back (circled area). What's the matter with it and what can I do to fix it? Thanks

Sent from my SM-G930V using Tapatalk

 

[Showkey]

Is the building temperature also low as in freezing ?

That appears to be a condensing furnace and should no be allowed to freeze.
What are you doing with the drain water ?

 

[JUNK-MAN]

The garage is an unheated pole bard, here's a pic of the condensation drain.

Sent from my SM-G930V using Tapatalk

 

[aandpdan]

Is it natural gas or propane? If propane, how big is the tank?

 

[JUNK-MAN]

It is propane and have it set to run off the size tank a gas grill uses. As I said, i have had no problems until it gets really cold.

Sent from my SM-G930V using Tapatalk

 

[58Yeoman]

I'm going to go out on a limb here and say one problem is your tank is too small.

 

[American Locomotive]

It is propane and have it set to run off the size tank a gas grill uses. As I said, i have had no problems until it gets really cold.

Sent from my SM-G930V using Tapatalk

The problem is almost certainly your propane tank. Those propane grill tanks cannot evaporate enough gas fast enough when it gets extremely cold out.

 

[epmills]

https://www.amazon.com/dp/B06WGX4V91/?tag=atomicindus08-20

 

[Adk Mike]

You can not run a furnace like that in cold weather on a 20 pound propane tank. A propane tank vaporizes the gas much like boiling water on a stove. You are burning the vapor. When it’s cold the pressure in the tank goes way down. 28 pounds at 0. On a hot summer day it 190 or so. You need to get what the industry calls a 420 or 100 gallon tank and you’ll be fine. Mike

 

[bob from indiana]

You could warm the tank up and see it if works until it cools. I agree that you need a larger tank for this to work reliably. How long would it run from the grill tank?

 

[Adk Mike]

A 20 pound grill tank holds 4.5 gallons at 91,400 btu’s per gallon.the tank has 411,300 BTU’s In it . If it’s a 100,000 btu furnace you can run it 4 hours. But if the tank won’t vaporize it doesn’t really matter.

 

[Showkey]

Agree tank size problem for furnace size........

http://www.tarantin.com/blog/propane-101/propane-tank-sizing

 

[yeldogt]

Also -- You can't allow a high efficiency furnace to freeze ... they have water in them?

If you read the specifications ... most heaters are not designed for continuous cold weather operation. Some need return air almost 60 degrees.

 

[DenisG]

Check the water trap in the supply line (1st picture).

 

[Showkey]

Likely two or more issues .........water freezing internally and small propane supply.

 

[Bretny]

I really dont know to much about condensate heaters but i can tell you that a BBQ tank will only output 13kbtu per hr at 20*F.
Take a look at this propanr vaporization chart.
https://www.google.com/search?clien...10i30k1.175.Dxs9TQLMzh4#imgrc=cvWGX61KvprmeM:
I think the 100lb tanks are good for a 74kbtu heater. What size is yours?