Webato Startup Procedure

[richard5933]

The current system uses a small tank mounted next to the unit on one side. It only holds a few gallons and is capped with a radiator cap. One the other side of the unit is a heater core, mounted in a steel box, with a squirrel fan below it. The heat from the Webasto is fed from this heater core to the interior of the coach as hot air.

There are two circulation pumps. The first is mounted immediately next to the Webasto heat exchanger and circulates the water between the small tank, the Webasto, and the heater core. This pump appears to run the entire time the Webasto has power, whether or not the thermostat is calling for heat

The second pump is used to circulate the hot water from the Webasto to the bus engine for pre-heat. There are two heater hoses that loop from the Webasto tank/heater core setup into the bus coolant lines. This circulation pump has a separate on-off switch so that the cold engine doesn't draw away heat from the inside of the coach when it's not necessary to heat the engine.

I'm not sure how things were originally set up on this system, but two parts of it are puzzling me right now. First, there is apparently not a way to totally disconnect the Webasto from power. The on-off switch is wired in series with the thermostat, and they only determine whether or not the burner fires. There is still power to the Webasto control box and to the main circulation pump. I'll remedy that easily by adding a continuous duty relay with a toggle switch inside the coach so that I can cut power to the Webasto when it's not needed.

The second thing that puzzles me is it seems the main circulation pump is set up to run continuously when the Webasto is powered up. The thermostat controls the burn, and the air circulation fan only moves air when the water in the pipes is up to temp. But, the water continues to circulate. I suppose that it is not any different from the boiler at my shop - its circulation pump runs 24/7. My concern is about drawing down my battery bank when dry camping. I could wire the circulation pump to shut down after the burn by tying into the circuit that powers the main blower. The main blower runs for a couple of minutes before firing, and then stays on for a few minutes after the burn. My fear is that if i don't have the circulation pump running enough I stand the chance of an overheat situation or of not cooling down the unit after it fires.

This last puzzlement is what I'm looking for assistance with. Is it okay for the main water circulation pump to run all the while that the Webasto is powered on? If not, how would I best control it coming on and off?

Richard

[opus]

You would surely draw down your batteries what with the Webasto motor and circulation pump.  The pump runs all the time, as you noticed.

Personally, me....just me, not anyone else, I would never run a Webasto on batteries.  I run mine with a 110v power supply which delivers about 13v DC.

Years ago I had a unit running on batteries, voltage got low.  I think they power down at 10v maybe, I forget.  Volts were low and the fuel wasnt atomizing as well as it does with good voltage.  This caused "dribbling" of the fuel, which in turn cause the flame to splash back, etc, etc.  Burnt up the whole inside plate with the wires and eye on it.

[richard5933]

Opus - That certainly something to consider. Don't want to cause a fire or damage the unit. Lloyd warned me about running with low voltage.

We've got an alarm on the battery bank that screams at us at about 12.1 volts.

Our battery bank is about 550 Ah. I'd hope that with nothing running besides the Webasto, the fridge, and a couple of LED lights we'd be able to go a good way through the night. Not sure though. Anyone have an idea how much current the Webasto takes? I've read 60 watts, but that was by no means definitive.

We've got a 13kw generator that can be powered up to run things, but it's noisy and of course has a pretty good appetite for fuel. Running on batteries would give us at least a few hours of quiet.

Richard

[richard5933]

Happy ending to the story.

Got the Webasto back from Lloyd. Looked better than it probably has since it was first installed. Got the unit re-installed. It would now fire if I jumped the contact as Lloyd instructed, but would not work otherwise. Here's what I had to do to get things working:

-Replaced thermostat inside coach.
-Replaced main water circulation pump & secondary pump which bypasses the heater core and sends all the heat to the engine for pre-heat.
-Replaced the fan-control thermostat which senses hot water before turning on the air circulation fan.
-Removed exhaust pipe to clean out mouse debris and nests.
-Added master power relay to eliminate any possibility of phantom current draw when not using the Webasto.

My only task left is to investigate all the various places the hot air is supposed to be blowing inside the coach to make sure that they are all open and sending heat.

Thanks to all who offered advice.
Richard

[Oonrahnjay]

... My only task left is to investigate all the various places the hot air is supposed to be blowing inside the coach ...

     Not quite -- there's the finding an old shoe box so you can cut some rectangles of cardboard to pad your wallet out a little bit so it won't fall out of your pocket.   $$Ouch$$  (but worth it, IMO).   Glad you got it done.

[richard5933]

Yeah - it cost a few shekels. About $550 for the initial rehab on the unit itself including a new fuel pump. Another $300 or so for the main water pump and its fittings, and about $75 for the secondary pump and fittings.

Given the options for replacing it with something else, I think that I'm still ahead of the game.

The only thing that still puzzles me is getting the heated air inside the coach. So far I've only found three vents connected to the air circulating fan - two of them in the center of the coach near the unit and one more further down the same side of the coach. I've got a theory that the air is also being pushed into the main air chamber for the OTR HVAC system, but since the squirrel fan doesn't move that much air to begin with it's hard to tell. Probably on a day when it's not in the mid-80s I'll get a better idea of where the warm air is going/not going..

The original setup for the Webasto in this coach is to heat water in a heater core, and then push air through that heater core to heat the air inside the coach. I was told by Lloyd that I can add additional heat to the inside by adding a couple of baseboard heat registers to the loop with the heater core. The Webasto puts out more than enough BTUs to do this, but I'd have to find somewhere to run the heater hose from the middle bay all the way to the bedroom in the rear of the coach. I'm certain that will be the cold spot.

Anyone else add hot water baseboard registers after the fact?

Richard

[sledhead]

http://www.parts.rvhydronicheaterrepair.com/Heat-Exchangers_c13.htm;jsessionid=14AEDCE3DA6321D09D08907CEA4269C6.p3plqscsfapp005

this might work

dave

[opus]

Not after the fact but this is 3 of my 6 heaters, maybe one of these would work:

[richard5933]

Wow - that's one bright yellow floor...

After I got done wrapping up work on the bus today and after putting away all the tools, I realized that perhaps I know why there is no heat coming from the back of the coach. When I redid the bedroom area I stuffed lots of insulation into lots of empty spaces, including around the (I thought) unused vents. Perhaps those empty spaces were actually designed to route the heated air to the vents. I'll reopen the decking under the mattresses tomorrow and see what I find. Hopefully I'll be able to get the heated air flowing to the bedroom again. Sure wish I knew how the original converter set this thing up. Right now I feel like I'm putting together a jigsaw puzzle without the picture on the top of the box.

Richard