Atwood furnace

[fldunes2003]

I just had to replace 2005 Penquin 13.5BTU ac/heat pump unit with a new 15K btu Dometic ac/heatpump with new thermostat and I'm having problems with the furnace. It was professionally installed and the ac/heat pump works great. but went to use the furnace and it is not putting out sufficient heated forced air to keep the trailer at 68 degrees when it is 35 degrees outside. The air coming out of the vents is luke warm and before was very hot. Never had a problem with the furnaces hot air before, was always too hot, now can't keep trailer warm enough, any thoughts as to what might be wrong?

[Protagonist]

Originally Posted by fldunes2003

I just had to replace 2005 Penquin 13.5BTU ac/heat pump unit with a new 15K btu Dometic ac/heatpump with new thermostat and I'm having problems with the furnace. It was professionally installed and the ac/heat pump works great. but went to use the furnace and it is not putting out sufficient heated forced air to keep the trailer at 68 degrees when it is 35 degrees outside. The air coming out of the vents is luke warm and before was very hot. Never had a problem with the furnaces hot air before, was always too hot, now can't keep trailer warm enough, any thoughts as to what might be wrong?

Does the problem occur only when you're running heat pump and furnace together, or does it also happen when you're running the furnace by itself?

If it's doing it only when you're running both, then the new heat pump could be putting out enough heat to fool the furnace thermostat. The thermostat is mounted on the wall a bit below eye level, so extra heat coming down from above can tell the thermostat it's warm, even though air down at floor level is still cold.

That's a basic drawback of a roof-mounted heat pump. Hot air rises, so if you pump in warm air at the ceiling, the heat never reaches floor level. Furnaces are mounted at floor level, and heat the air from the bottom up, not the top down.

But if the problem also occurs when you're running the furnace by itself, without the heat pump, then there is a malfunction in either the furnace or the thermostat.

[fldunes2003]

thank you for your response.

No, I don not run both the heat pump and the furnace together. This is happening when the furnace is running on its own with no other source. There has to be something going on for the furnace not the heat the air to a reasonable temperature in order to keep the trailer warm and no one can figure out what or why. This furnace was working perfectly until we installed the new 15000BTU AC/Heatpump unit in august. So I'm wondering if the Dometic is not compatible with the Atwood furnace which has not been changed out, it is the original that came with the trailer.

[Protagonist]

Originally Posted by fldunes2003

thank you for your response.

No, I don not run both the heat pump and the furnace together. This is happening when the furnace is running on its own with no other source. There has to be something going on for the furnace not the heat the air to a reasonable temperature in order to keep the trailer warm and no one can figure out what or why. This furnace was working perfectly until we installed the new 15000BTU AC/Heatpump unit in august. So I'm wondering if the Dometic is not compatible with the Atwood furnace which has not been changed out, it is the original that came with the trailer.

The only place where the heat pump and the furnace are connected— where one could interfere with the other— is at the thermostat. They are otherwise completely independent systems. If the heat pump is affecting the furnace, it's at the thermostat. Was the thermostat changed out as well?

[Greg@AirLA]

There is a DIP switch panel in the upper unit, it may have to be changed to recognize the furnace, the settings should be in the installation instructions.
Greg

[fldunes2003]

Ok, everyone is missing the problem. The furnace is recognized on the new thermostat, the dip switch has been checked. what is happening is that when the furnace comes on there is no REAL heat coming from the vents. the air is luke warm and that is not sufficient to heat the trailer up when it is 35 degrees outside. And before the new AC unit was put in the furnace would drive you out of the trailer because it was so hot.
I just don't know what to look for because everything is working except the temp of the air. The furnace was also cleaned and a new burner was installed 2 weeks ago, because of the problem stated above.

[Protagonist]

Originally Posted by fldunes2003

Ok, everyone is missing the problem. The furnace is recognized on the new thermostat, the dip switch has been checked. what is happening is that when the furnace comes on there is no REAL heat coming from the vents. the air is luke warm and that is not sufficient to heat the trailer up when it is 35 degrees outside. And before the new AC unit was put in the furnace would drive you out of the trailer because it was so hot.
I just don't know what to look for because everything is working except the temp of the air. The furnace was also cleaned and a new burner was installed 2 weeks ago, because of the problem stated above.

And you're missing our point. The heat pump cannot make the furnace blow lukewarm air just by being installed. If the thermostat isn't acting up, then there is no way at all that the heat pump can have anything to do with the furnace blowing lukewarm air.

Based on what you've said, it's pure coincidence that the furnace problem occurred just after you installed the heat pump. Forget the heat pump, and look for a cause elsewhere.

[n2916s]

What Protagonist said! The furnace is a dumb appliance. It is either "on" or "off", no middle ground. If the fan is coming on, then the thermostat has asked for heat. If the heat is not forthcoming prodigiously, then the problem is in the furnace, not on the roof.

When you hear hoof beats, think horses, not zebras...

Mike

[dznf0g]

Sounds to me like a gas supply problem. Like solenoid not opening all the way or an obstruction in the line or bad regulator. Does the stove work normally?

Sent from my XT907 using Airstream Forums mobile app

[TG Twinkie]

I would remove the thermostat. Disconnect the 2 wires going to the furnace. Jumper them together and see if the furnace fires up and puts out heat.
If it does not. The problem is in the furnace.
If it does. I would be getting hold of the guy who installed the A/C unit. You said it worked correctly before.

[dznf0g]

As stated above. The furnace is either on or off ....no in between. All the thermostat does is act as an on/off switch. If the blower runs, the thermostat is doing its job.

Sent from my XT907 using Airstream Forums mobile app

[fldunes2003]

Thank you. Yes the stovetop and oven are working properly. So it looks like I will getting ahold of the guy to put in the new AC unit and have him trace back the gas lines and check the solenoid.

[fldunes2003]

thank you all for helping me. I have contacted the RV guy who installed the new unit and he will be out on Monday to trouble shoot this problem.

MERRY CHRISTMAS TO ALL OF YOU AND HAVE A GREAT AND SAFE HOLIDAY!!!

[mjayjensen]

Let us know what he finds,
Jay

[fldunes2003]

Originally Posted by dznf0g

Sounds to me like a gas supply problem. Like solenoid not opening all the way or an obstruction in the line or bad regulator. Does the stove work normally?

Sent from my XT907 using Airstream Forums mobile app

that is exactly what happened. there was gunk in the gas supply line and when the rv tech came out he was already to replace the solenoid but he first recleaned everything and that's all it took. we are very warm now and thank you to everyone here at AIRFORUMS for the support and advice/suggestions!!!