Coach Hydronic Heat

[Jim Magowan]

We have been trying, ever since we bought the coach in 02, to get the hydronic heat working properly. So far without success.

We installed a Webasto Scholastic which works great when we are parked. We had to disconnect the power fromt he Sporlan valve because the Webasto circuit furnishes power to the Sporlan. The only time we were able to use the hydronic heaters is when we were parked with ignition off.

Now with the Sporlan disconnected from power it stays open and we get heat as long as the engine is not running. Once the engine gets to temp and the thermostat opens we stop getting heat. Thinking hte problem might be an airlock we spent the better part of two days bleeding the system and got good heat until we drove the coach.

In tracing out the water lines we found that the water goes from the engine to the frame mounted circulation pump. From the pump the water goes to a Y fitting. From the Y the water goes through the hot water heat exchanger and from the heat exchanger it goes to a Y on the return line. I assume the reason for running the water back into the return line instead of back into the supply line was so the water would be heated when the Sporlan is closed.

At this point the most likely reason for the lack of heat seems to be that then the engine is up to heat the coolant is simply following the path of least resistance, going through the loop to the hot water heater and back to the engine. The simple solution seems to be to install a circulating pump in place of the Sporlan valve (after the Y to the hot water heater) to force the water to go through through the heater loop as well as the hot water loop.

I would be interested to know if any other SP owners have had any problems with the hydronic heat, particularly with how much heat the hydronic heaters put out. The way I see it, with the Sporlan valve wide open and engine coolant temperature above 190 the heaters should blow very hot air. As it is, using the Webasto when parked puts out pretty good heat and the Webasto heats the coolant to 140 so 200 degree coolant should really put out some heat.

[Randy Dupree]

Jim,i have been following your problem with the heat on your coach for a few years now.
I have to think its an easy fix,too bad your so far away!
its also a strange thing that the guy that needs the heat most,can't get it!
what i would do first is drawa diagram of the entir heating system (i'm sure you have) and study it,then replumb the coach as needed to make it all work together.
see,i fixed it!
too bad its not that easy,i replaced the engine in an 84pt40 i had a long time ago,while the engine was out i replaced all the hoses etc,my conclusion was that BB must have gotton a deal on the 1'' heater hose,i deleted at least 50' of extra hose that went around and back and over and who knows where or why.
point i'm making is that theres almost no way to map that system.
good luck,keep us informed.
Randy

[NH Bill]

Hello,

I am planning to install a Webasto in our 83 FC.

I contacted tech support at Webasto. They have been very helpful. I sent them the coach heat diagrams from the manual. After reviewing them they responded in short order with a specific installation recommendation.

The contact at Webasto was Erich Kopp <Erich.Kopp@webasto-us.com>

He also suggested

"For additional information on RV heating and accessories, our dealer Aqua Hot Heating Systems, Inc. has an excellent site. Their specialized RV heating systems utilize Webasto burners. They supply the high end conversion companies (Blue Bird Wanderlodge, Country Coach, Monarch etc.), and are probably the best in the country at doing these type of systems.

www.hydro-hot.com"

NH - Bill

[Randy Dupree]

Bill,i have a hydro-hot with 3 hours on the hour meter,it came out of a burned monaco,the fire was above the floor and this unit was below the floor and did not get damaged.
its for sale if your interested.
Randy

[NH Bill]

Randy,

I already have the Webasto...I just need the time to install it.

Thanks - Bill

[Randy Dupree]

darn the luck!
hey,keep us advised on the install,take some pics if you can,we would love to see it happening!
Randy

[RAGster]

Randy,

Can you give me the details on the hydro-hot? Does it include the circulation pump? What else would need to be purchased? How much do to want for me to take it off of your hands?

Thanks,

Glenn

[NH Bill]

Originally Posted by Randy Dupree

darn the luck!
hey,keep us advised on the install,take some pics if you can,we would love to see it happening!
Randy

Randy,

From what I have read, this is not going to be a typical hydronic install.

I want to install this Webasto because we intend to do a fair amount of boon-docking and we are not crazy about the the FHA furnaces for heat or running the 12.5 Kohler or 3208 to make hot water when we are off the grid. This unit will provide additional redundancy and its very efficient. Here are some of the specs

Heat output Maximum 31,000 Btu/hr
Control range 6,800 - 26,000 Btu/hr

Fuel consumption Maximum 0.28 gal/hr
Control range 0.06 - 0.26 gal/hr 0.05 - 0.24 gal/hr

Rated power consumption Maximum 90 W
with circulation pump Control range 37 - 83 W

At 31,000 BTU, this is may not be large enough to heat the coach in really cold weather. For this, we can fire up one or more of the Suburban units as needed to supplement. We are thinking it will do well to extend the season in early spring and well into late fall in the north, and handle southern winters comfortably.

Initially, I was going to install it in the front passenger basement compartment. However, after bantering this around with others including the techs at Webasto, the rear drivers side compartment is a better choice.

The plan is to tap into the aux. pump outlet line, to connect the Thermo 90 in series with the aux pump. The Webasto techs recommended this location to optimize domestic water heating and coach heat.

See photo of aux pump location at rear driver's side corner adjacent to the rear basement compartment.

Question:

What I have not figured out is the best way to tap the fuel source. My initial plan was to tap it at the genset. However, the unit cannot take fuel under pressure. I don't know if the fuel to the genset comes from the facet pump that also feeds the Racor or is it a separate and static line. I would like to avoid taping the tank directly.

I also will need to bypass the ignition switch and provide power directly to the aux pump switch.

Any thoughts and recommendations?

Thanks, Bill

[Randy Dupree]

Glenn,
theres 3 pumps inside the "box" that house's the burner and all of that.
the only thing thats needed will be the thermostats in each zone,they would have been on the walls in the bedroom,living area etc.
of course they burned up in the fire.


Bill,i would talk to Mike H. hes got A webasto unit in his FC,its mounted in the front compartment i believe.
maybe he will speak up.
Randy

[NH Bill]

Randy,

I did communicate with Mike H about this a while back. What I understand based on my discussions with Mike and others is the front location is well suited for to optimize for engine block heating and it will also take care of hot water and coach heat and I think this works well with larger heaters.

Most retro installations I am aware of use the Webasto 2010, Scolastic or Pro-Heat. I think these units are larger (45,000 BTUs) and do not have a variable range like the Thermo 90. They also appear to consume significantly more fuel.

The Thermo 90 is smaller and to optimize for what I am trying to do the Webasto folks suggested keeping it close to the water heater and the aux pump to circulate directly to the coach heat exchangers and hitting the engine last. I do not expect to be using this in extremely cold weather.

Any thoughts on the fuel tap and aux switch issues?

Thanks- Bill