Modifying Webasto Scholastic heater controls?

[Deadman06271]

Hey, new to the skoolie life and i have the interesting situation of having to live in my bus while I complete my conversion.

I have a 2010 international 36ft bus, with a webasto scholastic heater that does work (i have tested it and it runs and ignites no problem)

The issue i have is my bus has 0 insulation right now and i want to run the webasto at night because its winter here and about 20-36 degrees on most nights. But the controller maxes out at 2 hours of run time.

Does anyone know of a plug and play controller that will let it run longer and maintain a more comfortable temperature overnight?

The two attached images are all ive found regarding the controllers for these heaters, mine is the rectangular one.

Would the round controller work more like a thermostat for the cabin temperature if anyone who has used it knows

[aswallie]

I'll see if anyone else can give you a better answer than me but i have a bunch of information on how to wire the scholastic.

While we were gutting our bus i accentually trashed our 7 day timer which looked like your first picture. We have a rocker switch that controls our circulation pump so i hot wired the relay lead into the pump switch. Pump comes on, relay gets power, webasto run until i turn the switch off. There are temperature switches within the webasto that regulate it's run time but off the top of my head i forget the numbers. An example is it would kick off at 150°f and back on at 120°f so I'm my case my unit isn't actually burning the whole time, it just has the power turned on.

I hope someone else can offer a better solution then mine but I can confirm mine works.

[Deadman06271]

Originally Posted by aswallie

I'll see if anyone else can give you a better answer than me but i have a bunch of information on how to wire the scholastic.

While we were gutting our bus i accentually trashed our 7 day timer which looked like your first picture. We have a rocker switch that controls our circulation pump so i hot wired the relay lead into the pump switch. Pump comes on, relay gets power, webasto run until i turn the switch off. There are temperature switches within the webasto that regulate it's run time but off the top of my head i forget the numbers. An example is it would kick off at 150°f and back on at 120°f so I'm my case my unit isn't actually burning the whole time, it just has the power turned on.

I hope someone else can offer a better solution then mine but I can confirm mine works.

Thanks! Didn’t realize it was that simple, now its piped in as a block heater too, which would be a huge heat loss if i kept heating the engine, do you know if ill run into over pressure issues if i install valves to isolate the engine and just run the cabin heater cores? Or would ii need a sort of expansion tank too

[Sehnsucht]

The engine heater function shouldn't cause any heat loss in the cabin, it simply circulates and warms the engine coolant at the same time as it warms the cabin so that your engine block isn't frozen solid.

I'm pretty sure the 2 hour limit is just that thermostat because it's essentially the same setup in semi trucks but those can either be set for 10 hours or no limit which basically means when the batteries give out. The only thing I'm not sure of though is how effectively it'll maintain a comfortable cabin temperature all night in a space the size of a bus. It's designed to take the chill off but not be the sole heat source in the bus because once the engine warms up you'd have the traditional heater cores to bring the interior up to temperature. Plus buses have so little insulation it pretty much relies on those heaters to overcome the massive heat loss. If it came down to necessity I think I'd build myself a smaller room inside the bus interior, insulate it, and pipe my Wabesto into that for the time being but it'll definitely be roughing it to spend all winter in that situation.

[aswallie]

Yup, pretty easy fix. The grey wire is the pump control, the black is the power relay,c the other capped wires go to the timer harness.

Our heater is plumbed in as a block heater also. We did a heater delete and ran new coolant lines from the back all the way to the defrost with one line passing through the heater on the way (we have a pusher).

Initially i was thinking about running out radiant heat floor off the webasto but our pump and burner are so loud! We park the bus about 15 feet behind the house and i can hear it running from inside.

Had i flowered through with my plan to use the heater i was going to link the two lines between the heater and the engine, just beside the heater. I was going to plum in three shut off valves. One on the flow to the engine, one coming back, and one in the link between the lines so i could cut off flow to the engine and open it in the connection or close the connection and open flow to the engine. I even toyed with the idea of making them electronically controlled valves so i could open flow to the engine with a press of the button from inside the cab. In this layout i would have had a reservoir for the heat exchangers to the floor.

In the process of figuring out how to bi-pass my 7 day timer i actually spoke with a Webasto rep and he said the pump with the scholastic has a really high flow rate and when i told him about my heat exchanger idea he encouraged a couple gallon reservoir to have fluid on demand to meet the pumps pull.

[aswallie]

Originally Posted by Sehnsucht

The engine heater function shouldn't cause any heat loss in the cabin, it simply circulates and warms the engine coolant at the same time as it warms the cabin so that your engine block isn't frozen solid.

The thought process is you're wasting fuel heating the engine block when you don't need to. The scholastic is a 45,000btu heater that, when on full burn, takes up to half a gallon of fuel an hour. If you're only heating the cab then you'd hopefully be doing less full burn time.

We have both rear heaters out, just the dash heat exchanger, and when our heater is on, the engine is off, and we're not moving it actually gets close to comfortable in the bus. Once we start moving and we get a draft, because we currently have no insulation, the heater doesn't do too great keeping up, but just sitting parked is kinda nice.

[Deadman06271]

Originally Posted by Sehnsucht

The engine heater function shouldn't cause any heat loss in the cabin, it simply circulates and warms the engine coolant at the same time as it warms the cabin so that your engine block isn't frozen solid.

I'm pretty sure the 2 hour limit is just that thermostat because it's essentially the same setup in semi trucks but those can either be set for 10 hours or no limit which basically means when the batteries give out. The only thing I'm not sure of though is how effectively it'll maintain a comfortable cabin temperature all night in a space the size of a bus. It's designed to take the chill off but not be the sole heat source in the bus because once the engine warms up you'd have the traditional heater cores to bring the interior up to temperature. Plus buses have so little insulation it pretty much relies on those heaters to overcome the massive heat loss. If it came down to necessity I think I'd build myself a smaller room inside the bus interior, insulate it, and pipe my Wabesto into that for the time being but it'll definitely be roughing it to spend all winter in that situation.

The block and main radiator, for lack of a better term would radiate a lot of heat if still piped into the circuit for the inside heater cores. The same principle that allows the engine to cool down when its off and the coolant isn’t circulating still applies and doubly so right now in winter.

Takes about 45 minutes to go from full operating temp to about 90F right now for the engine coolant.


You aren’t wrong about the roughing it comment! Right now ive got a heated blanket under my sheets keeping me warm at night, the air inside measured 28F this morning, not ideal but with the electric blanket not unlivable.

[Deadman06271]

You’re awesome man! Thanks a ton, i tried to run the heat last night with a battery charger hooked up and it didn’t fire! I checked my connections and found that one came loose, got it to fire up today after work luckily. Gonna try it out tonight and see how well i can heat the interior.

[cadillackid]

+1 on needing plenty of fluid.. my VVKB heater has a pretty powerful pump.. I also installed a second pump to keep the flow going a bit down the line.. and an expansion reservoire in the cabin loops.. this way I can shut off the engine altogether if i want and only heat the cabin loops.. (my bus is used as a mobile office and dining-room during covid so i want lots of heat while I hang out but have no need to lose heat into the engine as it will stay warm enough to start up easioly after sitting for a few hours while I work)..



I did do soem testing with Johan's ideao f leaving one heater valve open on the suction side of my pumps so that there is always the ability to pull fluid when it needs to however with only one valve open the heater cant move much fluid through the engine, thus far that seems to be the best situation for me to heat the cabin without heating the engine. when I want to heat both I turn on the electric valves both so the fluid can circulate through the whole system.. (and along with it if I desire i can run the OEM bus coolant booster pump)..


my VVKB heats the water and sends it directly to the rear heater which is pointed forward and blows warm air under the seats and right at my work space. so it warms me first with the hottest water.. the front system is secondary when the coolant heater is on. as need for defrosters and front heat is really only necessar ywhen driving. or having some aux heat to temper the cold from the bus door.. of course when my VVKB is off the coolant comking fro,m the engine first hits my right front and driver heater cores, then the mid heater and finally the rear.. (all my cores are in parallel flow).. thus far with the meager cold snaps we have had its worked great other than some issues with coolant deficiency that seem solved with leaving a single valve open.