Heat output just dropped to lukewarm

[rogerkathy]

Switched to a full propane tank in 38 degree temps. Furnace output now is lukewarm instead of hot. Also blower now runs fine (good air output) but I hear the flames shut on and off. Propane is fine in water heater and stove. Not convinced it’s the propane and furnace now shuts off way below my set thermostat temperature. Ideas?

[SeaDog]

Have you tired switching back to the original tank to see if the normal operation returns if it does the that would indicate a problem with the regulator.

[cavie]

turn off the tank valve. wait 1 minute. Open the valve slowly. Turn on the stove top to remove any air.

[rogerkathy]

Other tank is empty but stove and water heater work fine so don’t think it’s the regulator. Good to consider for future “issues”.

[TitanMike]

If you can hear the flame being shut off and turned on even though the t-stat is saying it needs more heat this is usually caused by restricted air flow through the furnace heat exhanger. That or a bad limit switch in the furnace that's erroneously telling the control board the furnace is too hot.

I had a similar problem and merely re-working the ductwork to eliminate excessive bends and kinks cured it for me. One may feel "flow" but the question is is it enough to keep the heat exchanger cool enough during operation, moving as much heat as possible into the RV?

One more possibility is that the outside temp is cold enough to reduce flow from the tank. Vertical tanks are vulnerable to this due to the reduced evaporation surface of the LPG in the tank and the cold slowing the rate of evaporation.

Last item, if your regulator has AUTOMATICALLY switched to the full tank and the lever has been left in it's original position, the flow from the fresh tank is restricted. The lever/knob/"switch" needs to be moved to the fresh tank position to restore full flow from the tank.

[Bob Maager]

Originally Posted by rogerkathy

Switched to a full propane tank in 38 degree temps. Furnace output now is lukewarm instead of hot. Also blower now runs fine (good air output) but I hear the flames shut on and off. Propane is fine in water heater and stove. Not convinced it’s the propane and furnace now shuts off way below my set thermostat temperature. Ideas?

Had a simulator problem on my heater, it was the over heat sensor. It senses an overheat condition and shuts the gas off till it cools off and then relights. Replaced it ops check ok.

[NJKris]

Tanks themselves have a built in gas flow reduction safety, which can cause restricted gas flow. If the tank valve is opened too quickly, and there is room for the gas to rush out quickly, like gas lines that are not purged and full, the safety will kick in, and I believe the tank needs be completely shut off for several minutes before safety valve begins working properly again. This reduced gas flow may be more obvious in furnace than water heater. Light a range burner or two and see if the flame is noticeably less than usual.

[ross0547]

WE had the same problem, but I had inadvertently changed the Thermostat.
It has to be on "Auto" instead of fan low or fan high. If the latter, the blower will work for awhile, but isn't calling for heat!!

[TimVWulp]

Lite all 3 stove top burners on hi. Now start the furnace and watch the flame on the stove burners. If the flames for the stove top drop to a lower flame level the regulator change over position may need to be changed or the regulator may have a probelem. If it stays the same the furnace has a problem.
Hope this helps tim.

[dbledan]

Originally Posted by TimVWulp

Lite all 3 stove top burners on hi. Now start the furnace and watch the flame on the stove burners. If the flames for the stove top drop to a lower flame level the regulator change over position may need to be changed or the regulator may have a probelem. If it stays the same the furnace has a problem.
Hope this helps tim.

Good test. This will tell you if you have a furnace or a propane problem.

For me I had a problem with the regulator when it auto switched AND I had a bad pigtail on one tank...took me a month to find all the issues. I had to keep moving the second tank over to get things going actually changing tanks.

Best of luck!

[rogerkathy]

Found the problem (I think). Had one of my registers blocked. When I removed the obstruction instant cure! Furnace now runs smoothly. Waited till now to see if the problem was solved or if I needed to explore all the other ideas that were offered. It seems furnace was just overheating due to blocked air flow and hence, shut down till it was cooled. Just glad it was a simple solution.

[GoneSouth10]

Originally Posted by rogerkathy

Just glad it was a simple solution.

I love it when those happen - it's like getting a 100% off coupon for the repair shop!!

[NJKris]

How come I never get that lucky???