Furnace out of propane, fan continues to run blowing cold air.

[Wesley Trainer]

I have an Atwood furnace in my jayco popup.

One of the most annoying things is running out of propane in the middle of the night and the blower fan continues to run blowing cold air into the trailer. Why they did not make provision for this seems weird. If at 3 am the propane runs out, the furnace seems to be designed to freeze out the occupants.

In the manual, "Sequence of Operation" step 4, it states  ""if the system does not ignite and the thermostat remains closed, the blower will remain on until the thermostat is reset manually"

On a very cold night, this is not a good thing. Our first reaction is to curse the heating engineers who designed this thing as well as their ancestors. By the time we wake up and realize what is happening, the cold air has been blowing in for quite some time and the temperature is already very cold, so there is no chance of conservation of heat.

I have gone through this manual several times and have not yet found where it says how to reset my thermostat. It the middle of the night, I thought maybe turning down my thermostat to the lowest setting would help. But not if it is colder in the trailer, than the thermostats lowest settings. In the middle of the night, our solution was to unplug the trailer. Later we realized we could just turn off the converter. 

Any help with resetting the thermostat will help. Or if someone has a better solution, I would appreciate it.

 

[Gary RV_Wizard]

It doesn't actually blow cold air - it merely recirculates the inside air, which of course gets colder and colder.  I suppose they could shut off the fan after the flame goes out (there would have to be a safety delay to purge the burner), but it's an extra cost function for what surely is a relatively rare event?  Plus, they would have to add a second function to restart the furnace once the gas supply was replenished.  And you are going to be cold whether the fan is running or not, right?


You didn't tell us your thermostat brand & model, so we can only guess.  However, doesn't your thermostat have an OFF position? That should be sufficient to stop the call for heat.    Note that the fan will still run for 30-45 seconds after the thermostat shuts off - that's a required safety feature for gas furnaces.

 

[Gizmo100]

My thermostat has a switch that shuts everything down. But Our fan does shutdown if the burner doesn't ignite.

Just a thought...

A Very small electric heater may be a option. I know your only on a 15/20 amp connection so it would have to be a small heater.

 

[Wesley Trainer]

I attached a picture of my thermostat. 

It seems quite basic. Bottom needle shows the current temperature and the top needle is the temperature adjustment. I have run my fingers along the sides and there is no other switches or levers that I can feel. As soon as I turn on the power, that fan will run continuously even though there is no propane. The tank is currently not attached.

In the instructions it does say, that to turn off the fan, when the furnace fails to ignite, you have to reset the thermostat.

There is no instructions as to how to reset it.

 

[Gizmo100]

On the top of the thermostat is something white...I'm guessing that's where you set the desired temp.

At the bottom it looks as though you have something brown hanging down. It maybe a power shutoff.

The cover of the thermostat should come off to give a better view...DON'T Break it trying to get it off. Ours is a pull out and lift at the same time.

 

[Wesley Trainer]

Ok you got me on the right trail.  I didn't take off that thermostat cover because it was very stiff. As you suggested, I was afraid to break it, so I gave up. However, I decided to take the risk and try harder. (See attached)
And I made an incorrect assumption, the brown lever you mentioned I thought was part of the temperature gauge indicator, is separate. It is the on off, reset switch as you suggested. However, it was corroded stiff and would not move. A little lubricant solved the problem. Keep in mind the blower will run for a couple of minutes even after the switch is turned off. I suppose to cool the heat exchanger down.

Under the grill of the furnace there us another rocker switch. (See attached) It turns off the starter or the igniter. It also cuts the fire to the furnace. It does not turn off the blower.  I thought it was the whole furnace shut off. Apparently not.

If you turn off that rocker switch, the furnace will not restart until the thermostat switch, as mentioned before, is reset.

 

[Wesley Trainer]

No where in the instructions does it show the thermostat controls. There is no marker for off and on, on the thermostat. And the rocker switch under the grill also has no markings. So this has been very time consuming and frustrating. We had this trailer for a couple years and missed all of this.

Thank you so much for the help. I hope this thread is helpful to anyone else who finds it.

 

[NY_Dutch]

Dinosaur Electronics makes a "Fan 50 Plus Pins" replacement board that shuts down the fan on ignition failure:

"The FAN 50 Plus Pins is designed to replace the new Suburban? and Atwood? / HydroFlame? Fan Control boards as well as maintain backward compatibility with the Fan 50 Plus, and UIB Fan Control boards which have been available since 1994. This board can also be used to upgrade older furnaces to add the Fan Control feature."

"The basic purpose of a Fan Control Ignitor Board is to shut the fan motor off if the board fails to sense a flame after
the third ignition try. Thus, battery drain is reduced and the needless blowing of cold air is eliminated."

"The FAN 50 Plus Pins , after shutting the fan motor off, will wait for 1 hour and repeat the whole sequence again before
permanent shut down."

https://www.dinosaurelectronics.com/Fan_50_PIN.html

https://www.amazon.com/Dinosaur-Electronics-PLUS-Ignitor-Board/dp/B0031NNFLY

 

[Gary RV_Wizard]

This is one of many common knowledge gaps that the RV industry simply doesn't bother to fill in many cases. The furnace and the thermostat are separate components, both installed by the RV manufacturer.  The documentation for one or both may be missing, and typically nobody creates the documentation that explains how the two work together. A comprehensive owner manual covering all facets of the vehicle/house is rarely provided and only in the more expensive models.

I suspect, though, that many of you have no better info about your home heating or cooling systems and associated thermostats.

 

[Wesley Trainer]

Yes I can see how that happens.  Our new furnace is a Trane and Thermostat is Honeywell. I don't even think Honey well makes Furnaces or vise versa.
For our RV, the instructions on the furnace is in a Book from Atwood. But in the unit itself is Hydro Flame name brand., which is also the name on the Thermostat in the picture. It is likely made by another company with the Hydro Flame name on it.

Thanks again for your help.

 

[John From Detroit]

Interesting about the Dino Fan-50 Plus.. I have the Fan-50. it does NOT (near as I can tell) shut the blower off on ignition failure.. the OEM (Atwood)( board did... Not a problem for me in any case.

 

[NY_Dutch]

Yes I can see how that happens.  Our new furnace is a Trane and Thermostat is Honeywell. I don't even think Honey well makes Furnaces or vise versa.
For our RV, the instructions on the furnace is in a Book from Atwood. But in the unit itself is Hydro Flame name brand., which is also the name on the Thermostat in the picture. It is likely made by another company with the Hydro Flame name on it.

Thanks again for your help.

Atwood bought Hydroflame in 1993 and Dometic bought Atwood in 2014.

https://www.dometic.com/en-us/us/rebranded/atwood

 

[NY_Dutch]

Interesting about the Dino Fan-50 Plus.. I have the Fan-50. it does NOT (near as I can tell) shut the blower off on ignition failure.. the OEM (Atwood)( board did... Not a problem for me in any case.

Some furnaces require minor rewiring to use the fan shutdown feature. Instructions are included with the board.

 

[Gary RV_Wizard]

Ignition failure isn't the same as burner flame-out.  I don't know about the Fan 50 Plus, but most furnace boards don't check the flame sensor again once the burner successfully lights. Only the High Limit switch and the Heat Demand (thermostat) get continuously monitored.  If the furnace is running (burner operating) and then runs out of fuel, the board literally doesn't know the flame went out.

 

[NY_Dutch]

When we run out of propane while our Hydroflame furnaces are running, I can hear them trying to relight until they lock out, so the flame sensor circuit is still active.