Heat pump blowing cold air

[togue]

I have a 2019 Winnebago Forza 34T. Last night the heat pump started blowing cold air (All settings are correct). The gas furnace works, but we're flying home for the next ten days and Xmas eve forcast calls for a low of mid 20's. Any suggestions?

[dougrainer]

LouLawrence wrote:
This IS NOT an Aqua Hot. The bus uses a Webasto system (50,000 BTU) for baseboard heat. It keeps us toasty warm in Temps well below zero. We have NO 120V heat other than the heat pumps and heat straps in the roof A/C units. Most Prevosts have basement air units called Cruiseairs and not roof mounted units. The newer ones are all going to roof air due to the PIA issues of the Cruiseairs. The bus is very air tight and we just use a couple portable heaters for most of the Winter. When it gets cold enough to be concerned about the bays getting to cold we turn on the diesel heat. Since we carry 160 gallons of fuel it will keep us warm for a Very long time.

Sorry, I stated Aqua Hot TYPE systems. I realized you had a Webasto powered system and NOT an Aqua Hot after you posted a clarifying update. Doug

[LouLawrence]

This IS NOT an Aqua Hot. The bus uses a Webasto system (50,000 BTU) for baseboard heat. It keeps us toasty warm in Temps well below zero. We have NO 120V heat other than the heat pumps and heat straps in the roof A/C units. Most Prevosts have basement air units called Cruiseairs and not roof mounted units. The newer ones are all going to roof air due to the PIA issues of the Cruiseairs. The bus is very air tight and we just use a couple portable heaters for most of the Winter. When it gets cold enough to be concerned about the bays getting to cold we turn on the diesel heat. Since we carry 160 gallons of fuel it will keep us warm for a Very long time.

[dougrainer]

grldst wrote:
Are you sure about that Doug……I’ve had two motor homes with Aqua hot and neither would heat an RV in 40 degree temps with just the 120 Element. The diesel burner will need to be used at them temps.

1998. I ASSUMED you had the standard Aqua Hot system that has both 120 and Diesel. So, if you do NOT have the 120 option on your webasto system, then you have to use the Diesel burner. In the almost 30 years I have been servicing Aqua Hot type systems, I have never come across a Aqua Hot type system that did NOT have the 120/240 options. BUT, I rarely work on Prevost buses. I have worked on Hi line Monaco Signature motorhomes from the early 90's and up and they while not up to the standard of a Prevost, use 120/240 and Diesel combo systems. BUT, your RV should be able to handle outside temps to HEAT the RV down to about 20 degrees. IF NOT, you either did not operate it correctly or you had malfunctions.The manual states down to 50 degrees for 120 Heat. BUT, I have heated customers coaches down to 25 degrees when in for service on 120 only. The problem with NOT using the diesel option when running the system for heat is, when you use ANY hot water on 120 only the Furnace system shuts down to allow the Water heater function to supply hot water. Hence, you need to leave both the 120 and Diesel burner ON when in temps below 50 degrees. This will allow no disruption of either furnace function or lack of continuous hot water AND enough heat for the furnace system. If you have the larger Aqua Hot (600 series) it has 240 for 2 elements that WILL heat for furnace below 50 degrees. Doug

[LouLawrence]

No, Doug is not correct. Ours uses a Webasto heater and there is no electric option. If you turn it on in any form you will be burning diesel. For hot water there are 2 - 10 gallon water heater each with their own electric element so we have nearly continuous hot water whenever we are plugged in. When the Webasto is running it also heats the water (and the engine and the basement and the interior).

[grldst]

Are you sure about that Doug……I’ve had two motor homes with Aqua hot and neither would heat an RV in 40 degree temps with just the 120 Element. The diesel burner will need to be used at them temps.

[dougrainer]

LouLawrence wrote:
I have the 5 button. I have 2 different units that have heat pumps and 1 unit that has a heat strip (wish I had thought it out as I would now have 2 with heats strips as the heat pumps appears to be just somewhat above useless!). We full time so cold is a normal part of our life and that means electric heaters and Webasto diesel heat is about all that works much of the Winter.
We replaced the existing old unit with an exact replacement new unit so the installer swapped the old control board with the new control board so it would still work with the old style thermostat.
Yes this is all on our 1998 Country Coach Prevost.

Sorry, you did NOT replace with an exact. They(Penguin HP) are updated units so as I stated, you CANNOT move the control board from the old to the new. That P/n I listed is the correct control board for your 5 button. The NEW HP had a 12 button control board and the hardware on the new HP will not respond correctly to the original old style control board. Heat Strips are NOT the answer. They are 5200 BTU heat strips and all they do is take the chill out of the air. They are NOT designed to HEAT an RV. Besides, since you have the Aqua Hot(webasto) there is no reason to run the roof HP's below 40 degrees. The Aqua Hot 120 element is enough to heat your RV without running the Diesel burner. You only need the Diesel burner when you require continuous HOT water. Doug

[LouLawrence]

I have the 5 button. I have 2 different units that have heat pumps and 1 unit that has a heat strip (wish I had thought it out as I would now have 2 with heats strips as the heat pumps appears to be just somewhat above useless!). We full time so cold is a normal part of our life and that means electric heaters and Webasto diesel heat is about all that works much of the Winter.
We replaced the existing old unit with an exact replacement new unit so the installer swapped the old control board with the new control board so it would still work with the old style thermostat.
Yes this is all on our 1998 Country Coach Prevost.

[dougrainer]

LouLawrence wrote:
New, Dometic. Older 3 zone thermostat. Had to replace New style control board with old style from previous unit.

You show a 1998 Prevost. Still have it? You have 3 HP's? Now it gets interesting. How many of the HP's have you had replaced? There were 3 Tstats from 1998 to now.
1. Was the original one control 4 button? NO Zone button?
2. The next was the 5 button Zone control(released 2001 and the 4 button discontinued). HAS Zone button
3. The LAST is a 12 button Zone control released about 10 years ago.
Now, you CANNOT mix the various HP's up with the wall tstats. YOU CANNOT TAKE THE NEW HP CONTROL BOARD OFF THE NEW HP AND INSTALL THE OLDER CONTROL BOARD IN ITS PLACE. You will get malfunctions. Possibly like you have now. You have to purchase this Dometic control board kit ( 3313107.107) and install it on the NEW HP you have. Which allows the NEW HP to interface with your wall tstat. Since you state you had to remove the NEW HP control, that means you have a PENGUIN lo profile model. You really need to post the Model numbers of all 3 HP's. Doug

[LouLawrence]

New, Dometic. Older 3 zone thermostat. Had to replace New style control board with old style from previous unit.

[dougrainer]

LouLawrence wrote:
That makes sense but it's freezing in the coach by the time the heat kicks in again. You would think the fan should quit running.

Year and Brand of HP. Doug

[LouLawrence]

That makes sense but it's freezing in the coach by the time the heat kicks in again. You would think the fan should quit running.

[dougrainer]

LouLawrence wrote:
I had to replace my current Dometic A/C heat pump last Summer. Had never use the heat output option until this fall. As mentioned, it needed to be around 40+ degrees to do anything. What's weird is that it blows nice and warm for awhile and then when it reaches the right temp if does not shut off but rather blows cold air for a while and finally shuts down. Then, just a minute or so later it starts back up and blows warm again.....repeat over and over.

Should be the defrost cycle causing that. Doug

[LouLawrence]

I had to replace my current Dometic A/C heat pump last Summer. Had never use the heat output option until this fall. As mentioned, it needed to be around 40+ degrees to do anything. What's weird is that it blows nice and warm for awhile and then when it reaches the right temp if does not shut off but rather blows cold air for a while and finally shuts down. Then, just a minute or so later it starts back up and blows warm again.....repeat over and over.

[LMHS]

My suggestion for an easy fix is to turn the heat pump off and leave your gas furnace on a low setting and hope the power doesn't go out while you are gone. Alternatively, place some small electric space heaters near the plumbing, turn them on at a low setting and hope the power doesn't go out while you are gone.