Gas shop heater coil temps

[CTC DEEZUL]

Heys guys,

I've got a shop heater that's from 2003 that heats my barn. Recently we had a cold snap and at the same time I had the tstat set to about 67°F which is the hottest I've set it to in its life. The shop is fairly insulated but I did have a cool draft coming in due to a leaky doggy door.

The high limit switch tripped (burned up, there is no reset) and shut her down. I jumped it and it works again but I wanted to figure out why. My thought is 20 year old parts that got ran and ran harder than ever. So it gave out.

I took a temp reading and this is what I got
Exhaust



I have a brand new unit in my other garage and this is the reading I got from it.


So I actually don't think I have an issue with my shop heater since the newer unit has more heat in the coils.

The high limit lives in the coil chamber right inbetween coils.

 

[PoorUB]

I did HVAC service for years. Many times I have seen heat exchangers barely glowing red on a perfectly working units. Steel glows around 800F.

I have walked into shops with the lights off and could see the heater barely glowing red.

 

[American Locomotive]

Those temperatures do not seem out of line at first glance. Replace the high limit switch, however. It's a critical safety device, and the temperature it trips out at will be stamped on it somewhere.

Also, the thermostat setting has no bearing on how hard the unit works. You could set the thermostat to 120°F, and the unit will work just as hard as it does if you set it to 60°F. The only thing that will change is how long it runs for.

 

[CTC DEEZUL]

Those temperatures do not seem out of line at first glance. Replace the high limit switch, however. It's a critical safety device, and the temperature it trips out at will be stamped on it somewhere.

Also, the thermostat setting has no bearing on how hard the unit works. You could set the thermostat to 120°F, and the unit will work just as hard as it does if you set it to 60°F. The only thing that will change is how long it runs for.

So with this, the unit is backed into a corner and right against the ceiling... Is there a chance that it was recirculating warmer air and the heat wasn't being extracted from the coils, causing an over temp?

 

[American Locomotive]

I mean it's possible, but like I said, the thermostat setting has no effect on how hard the unit works. If the unit has been working in that location for years, it should be fine.

Sometimes hi limits fail. Replace the hi limit and see if it goes out again.

 

[CTC DEEZUL]

I've got 2 en route. I've got the heater running with the wires bypassed but I'm home for the weekend so should be good.

 

[PoorUB]

I've got 2 en route. I've got the heater running with the wires bypassed but I'm home for the weekend so should be good.

I should add, there is probably nothing wrong with the heater other than the bad limit, but how dirty is the fan blade? A little bit of dirt on the fan blades will cut the air flow a lot. It might be time to clean the blades.

 

[CTC DEEZUL]

It needs a dusting now that I've been up close.

I'm also going to run a 4 inch pvc pipe to the rear of the unit and run it maybe 20 feet down the wall so it can **** some different air.

 

[The Cobbler]

I'm also going to run a 4 inch pvc pipe to the rear of the unit and run it maybe 20 feet down the wall so it can **** some different air.

thinking that's not going to help anything. possibly if you forced air thru it with another fan, but then you may end up with too much turbulence and cause other problems

 

[American Locomotive]

It needs a dusting now that I've been up close.

I'm also going to run a 4 inch pvc pipe to the rear of the unit and run it maybe 20 feet down the wall so it can **** some different air.

That won't do anything - don't even waste your time.