Garage furnace not working

[Grinder]

Its a Reznor furnace and it will light and run till it heats up then wont relight. I have changed thermistate and does the same. Changed thermocouple and it does the same. Changed gas valve now and still the same the pilot wont light. I manualy relight pilot and it will run for a while then cant relight. What am i missing? There is a box with white cover but i dont know what it is or does.

 

[rsaint]

That white box is a control transformer steps down 120v to 24v so it must be good if gas valve opens maybe adjust pilot lite to a stronger flame and make sure thermocuple is in the flame.

 

[Fun$]

I think there's limit switches in that thing somewhere hi and low

 

[Eagle]

Your hi limit switch is tripping. It is for hi temp. It is a small disk like device mounted inside the heater on the side. My 2 cents.

 

[team dirt]

Did you get this working. If not can you email me a picture of the wiring diagram. It should be on the unit somewhere. Also a picture of the gas valve showing the model number of you can. Sneu@pronghorn.ca

 

[hbar218]

Is the pilot light going out? If it is then it is gas supply, gas valve or thermocouple related. If it is staying lit then it is probably a rollout or limit switch tripping.

 

[Grinder]

The pilot is going out but isnt that a safety isomethings wrong?

 

[Grinder]

See i just lit pilot wait for flame to stay on turns switch to on then put thermestat at 20 and it runs. But it will shut down and im waiting to see if the pilot stays lit.
Is the thermalcouple too low?

 

[Grinder]

So funace just shut off pilot is still going...... for now.

 

[Ricki Bobby]

Give ATCO a call. They will come and check it for free!

 

[Audette13]

That unit is using a standing pilot(always on), so it should never go out unless you turn the gas off, the thermocouple fails or power head in the gas valve failed. If you have changed out all of those items and know for sure they are new and working correctly , sounds like you have a crack in the heat exchanger. When the unit fires up it will run heat for a short period of time before the fan comes on, once the fan comes on the pilot is most likely being blown out by the fan (hence the crack in the heat exchanger).

Thermocouple looks fine location wise, 3/8"-1/2" in pilot flame. Shut it down, using a flash light look in through the back of the unit at the base of the heat exchangers.

 

[Grinder]

Still going now will check in the morning

 

[Keith Brown]

Your Gas valve has a energy cut out its the two red wires just under the thermal couple connection on the gas valve. When the sensor connected to the two red wires opens it drops the thermal couple out of the loop. You can verify this by jumping out the two red wires. If this is right now the unit will not tip out but you have not solved the problem. It can be caused by a sensor that is thermal aged but most often it is caused by a flame disturbance. Which could be caused by a cracked heat exchanger. If the exchanger is cracked what happens is the crack opens up during the heating cycle and causes a flame disturbance that trips the energy cut off or another possibility is when the main burner shuts off the pilot could be blown out by air blowing thru the crack that has opened up by heating. The easiest way to check if this is the case is by bring the unit to operating temp and observing the difference in the flame between when the fan is on and off. There should be no flame disturbance when the fan starts Many reznors have a ridiculous long warranty on he heat exchanger. If the exchanger is good make sure your vent cap is on and in good shape and the venting and exchanger are clean. If it all look good change the energy cut off sensor. It go's with out saying make sure the gas pressure to the burners is 3.5" Water Colum

 

[YamaDad]

I think Audette13 is on the right track, which means the end of the line for that heater. One thing to try is check the pilot line and connections for a leak, it could rob gas pressure from the pilot burner when the gas valve is open. Not really likely but worth a look. By the way keep an eye on that stainless flex gas connector, or better yet replace it. They are know to develop leaks.

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[Grinder]

K thanks guys I will check it tomorrow and post what I find.

 

[Caper11]

Possible flakey hi limit switch?, its a little disk looking thing around your heat exchanger. I had a garage heater do that but it was a DSI, not a pilot.

Now the only thing im unsure of is the pilot Im thinking that if the high limit switch activated it would keep the pilot lit, but it may not. The only way to know is put a new one in. Thats how I fixed my heater.


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[Grinder]

Well it stayed lit. Dam thing is like a woman. Had to spend some money on her but the parts are still good. She would lite but not warm up. Tease. Then when Im pissed off she stays lit and be damed if I dont know how I did it or how to do it again.

 

[DaveB]

I had the same furnace at my last garage. It worked flawless for about 6 years (since new) then started eating thermocouples. I would keep 3 in the cabinet in the shop at all times. It went though about 2 a winter...randomly. It was real finicky about the routing of the line to the valve and don't over-tighten the end that goes in the gas valve.

 

[jayson]

if it's the reznor I am thinking of, it has an eco safety switch that if it trips it shuts off the pilot, it's prob those 2 red wires on the side of the gas valve that go to that switch, they fail a lot.

 

[E-Zmoke]

Woah woah woah boys anyone who did not say Hi limit switch is all wrong! I have the same heater and I've ran it for a very long time...you need a big big big fan to run this unit. Awesome heater but keep the switch cool or she will do everything you describe