Community Forums

rcrevolution · 12-27-2017, 11:23 AM

I'm thinking about installing a Webasto for heat and hot water and I'm wondering how the RV manufacturers set them up. I've done 2 bus conversions in the past and set up the Webasto differently in both.

On an older MCI, I installed the Webasto right in the main heater lines running from the engine to the front dash and cabin heat. I used baseboard heat radiators with zone pumps connected to thermostats. For hot water, I had a single heat exchanger. When the engine was running it provided heat and hot water. When the engine was not running, the Webasto kept hot water circulating with the added benefit that the engine was always worm and ready to go, even in the dead of winter. We used to go up to Canada to remote lakes and go kite skiing.

Fast forward a few years and I did a newer model Prevost. This time I installed the Webasto with a 10 gallon insulated holding tank. Zone pumps moved water from the holding tank to (2) forced air automotive type ducted heaters and a hot water heat exchanger at every point of use. There were two heat zones and 3 hot water zones. There was no connection to the bus coolant at all. Not a big deal since by that time, we had no interest in going north.

The current rig is a 2005 Revolution with 2 propane furnaces and a 10 gallon electric/propane water heater. My goal is to get away from propane entirely other than cooking. Diesel is way easier to find than propane. I don't want any critical systems on propane.

I'm inclined to set it up like the Prevost since we're done with the cold weather at this point. If I do need to start when it's cold, the Rev has an electric block heater.

Just wondering how the RV manufacturers set them up.

Thanks

Twomed · 12-28-2017, 09:08 AM

Google Espar various sizes, le$$ than Webasto and looks like easier to plumb into an existing system...maybe.

rcrevolution · 12-28-2017, 01:28 PM

Webasto is a little more money, but 3 times the BTU output.

bruceisla · 12-28-2017, 01:47 PM

Quote:

Originally Posted by rcrevolution

I'm thinking about installing a Webasto for heat and hot water and I'm wondering how the RV manufacturers set them up. I've done 2 bus conversions in the past and set up the Webasto differently in both.

On an older MCI, I installed the Webasto right in the main heater lines running from the engine to the front dash and cabin heat. I used baseboard heat radiators with zone pumps connected to thermostats. For hot water, I had a single heat exchanger. When the engine was running it provided heat and hot water. When the engine was not running, the Webasto kept hot water circulating with the added benefit that the engine was always worm and ready to go, even in the dead of winter. We used to go up to Canada to remote lakes and go kite skiing.

Fast forward a few years and I did a newer model Prevost. This time I installed the Webasto with a 10 gallon insulated holding tank. Zone pumps moved water from the holding tank to (2) forced air automotive type ducted heaters and a hot water heat exchanger at every point of use. There were two heat zones and 3 hot water zones. There was no connection to the bus coolant at all. Not a big deal since by that time, we had no interest in going north.

The current rig is a 2005 Revolution with 2 propane furnaces and a 10 gallon electric/propane water heater. My goal is to get away from propane entirely other than cooking. Diesel is way easier to find than propane. I don't want any critical systems on propane.

I'm inclined to set it up like the Prevost since we're done with the cold weather at this point. If I do need to start when it's cold, the Rev has an electric block heater.

Just wondering how the RV manufacturers set them up.

Thanks

Assuming you mean it, why bother?

Although I have HydroHot, I only use the electric element and heat is via the 3 heatpumps. We are in FL and don't go anywhere that is below 32 degrees.

rcrevolution · 12-29-2017, 10:22 AM

I don't like relying on propane. It's too hard to find while traveling. My heat is propane only. I don't think the roof air units have heat.

bruceisla · 12-29-2017, 12:14 PM

Quote:

Originally Posted by rcrevolution

I don't like relying on propane. It's too hard to find while traveling. My heat is propane only. I don't think the roof air units have heat.

I get the not relying on propane but I'm surprised the rooftops aren't heatpumps.

Twomed · 12-29-2017, 12:20 PM

Quote:

Originally Posted by rcrevolution

Webasto is a little more money, but 3 times the BTU output.

They are available up to 83k btu

rcrevolution · 12-31-2017, 04:54 PM

Quote:

Originally Posted by bruceisla

I get the not relying on propane but I'm surprised the rooftops aren't heatpumps.

Might be wrong. I'm still figuring it out, but when I switch the T-Stat to heat it says propane. I didn't fiddle with it to see if I could switch to electric heat.

rcrevolution · 12-31-2017, 06:18 PM

Turns out I do have heat pumps. I tried them out and the front one started blowing cold then eventually (15 minutes) started getting warmer. The rear one never blew warm air. Just cold like the AC was on. I left it on for 30 minutes or so. The thermostat is in the bedroom and has 2 zones. When I switch to heat, I have the option to choose gas or electric.

Based on the output of the front unit, I'm even more convinced that I need diesel heat. I wouldn't want to rely on the heat pump if I really needed heat.

rcrevolution · 12-31-2017, 07:28 PM

Forgot to mention that the rig is inside a heated shop fight now (60F), so heat pump efficiency shouldn’t be an issue. The front unit seemed to run cold for few minutes then shut off and restart. After restarting, it was blowing warmer.

The rear unit just started and never cycled. Just stayed on blowing cold air. I’m guessing there is an issue.

bruceisla · 01-01-2018, 05:40 AM

Quote:

Originally Posted by rcrevolution

Forgot to mention that the rig is inside a heated shop fight now (60F), so heat pump efficiency shouldn’t be an issue. The front unit seemed to run cold for few minutes then shut off and restart. After restarting, it was blowing warmer.

The rear unit just started and never cycled. Just stayed on blowing cold air. I’m guessing there is an issue.

Manufacturer and model numbers of topside units and thermostat ??

FWIW, my Dometic heatpumps are perfectly fine to heat the RV down to about 35 degrees outside temps. Although I have HydroHot, I seldom use it. It's currently 57 degrees outside and 1 (of 3) heatpumps occasionally cycled on during the night to maintain an inside temp of 71 (setpoint).

It's your money but I'd be spending mine ensuring the air conditioning/heatpumps were in perfect shape before I tackled a Webasto install. You'll probably be spending far more time trying to cool your RV than heating it.

rcrevolution · 01-01-2018, 01:48 PM

The heat pumps are RV Products 9000 Series and the thermostat is a RVComfort.ZC. Appears to be Coleman now.

Looks like the thermostat manages the gas and electric according to temp. If the set temp is 5 or more degrees higher then the room temp, the thermostat turns on the gas heat. If this happens more than 3 times in a row, the HP is locked out for 2 hours. Also appears that if the HP runs for more than 20 minutes steady and doesn't reach set temp, the gas heat comes on.

The problem I see with this is that while the HP may not be adequate to keep you comfortable, it may be adequate to keep you from freezing. So imaging you are below freezing outside and you run out of gas. The HP tries to keep up but it can't and switches to gas...but there is no gas. You cycle the thermostat and try to get the HP going again, but again it can't keep up. You try one more time and the HP is locked out for 2 hours and you have no gas and no heat.

That's what's going on now. After three tries with the HP, it locked out. Going to wait 2 hours and have another look at it. I'm not sure what to do about this other than replace the unit...probably replace both since they are both 12 years old. AC works great on both units. I'm thinking the rear unit has a stuck or bad reversing valve, but I can't think of anyone other than myself that I trust to fix it right. Assuming the system has to be opened up to replace the reversing valve, I don't have the equipment or the HVAC license to buy refrigerant.

bruceisla · 01-01-2018, 02:39 PM

Quote:

Originally Posted by rcrevolution

The heat pumps are RV Products 9000 Series and the thermostat is a RVComfort.ZC. Appears to be Coleman now.

Looks like the thermostat manages the gas and electric according to temp. If the set temp is 5 or more degrees higher then the room temp, the thermostat turns on the gas heat. If this happens more than 3 times in a row, the HP is locked out for 2 hours. Also appears that if the HP runs for more than 20 minutes steady and doesn't reach set temp, the gas heat comes on.

The problem I see with this is that while the HP may not be adequate to keep you comfortable, it may be adequate to keep you from freezing. So imaging you are below freezing outside and you run out of gas. The HP tries to keep up but it can't and switches to gas...but there is no gas. You cycle the thermostat and try to get the HP going again, but again it can't keep up. You try one more time and the HP is locked out for 2 hours and you have no gas and no heat.

That's what's going on now. After three tries with the HP, it locked out. Going to wait 2 hours and have another look at it. I'm not sure what to do about this other than replace the unit...probably replace both since they are both 12 years old. AC works great on both units. I'm thinking the rear unit has a stuck or bad reversing valve, but I can't think of anyone other than myself that I trust to fix it right. Assuming the system has to be opened up to replace the reversing valve, I don't have the equipment or the HVAC license to buy refrigerant.

For comparison purposes, here's how my Dometic system with HydroHot works:

Select HP (heatpump) for Zones 1, 2 ,3 (any combination).
Select separate Setpoint for each Zone.

Each Zone will control it's associated heatpump. Each Zone will attempt to reach the Setpoint unless the outside temperature is 35 degrees or less. If outside is less than 35, Zone 1 will shut down it's HP and trigger the HydroHot (Zones 2 and 3 will shut down their HPs). Our bus is all electric so we don't have a propane furnace. The HydroHot can be operated independently if desired.

The output temp of each HP is 20-24 degrees above the input temp ... for instance, if the RV inside air temp is 60, the HP temp will be at least 80. As the inside temp rises, the HP will follow (keeps a 20 degree differential).

rcrevolution · 01-01-2018, 03:28 PM

That's basically how mine is working, except the rear heat pump isn't pumping heat. It's operating in AC mode regardless of which mode the thermostat is in.