Webasto auxiliary heater campervan /hot tub project

Pinkythelabrat

A2OC Donor
I have sourced a couple of spare Webasto units with the intention of repurposing these. This isn’t strictly A2 related but hopefully anything that I may learn might help others with their own car-based equipment.

The first project is to use this little diesel powered Lovely to heat an inflatable hot tub. I scored this beauty for 200 quid with all chemicals needed to use it and it is a lovely thing to be able to sit in the garden and watch the stars. On the down side electricity is ruinous to heat them (a 2kw electric heater and 1000L of water) and it is designed for occasional use so only runs for 3 day’s without input and cannot be set below 30C. That second is a problem because I want to keep it out all winter (best time for bathing) and the PVC doesn’t like temps below 6C (it can crack) and the pump/heater/filter cannot freeze without damage. It also takes a fair while to heat up from cold - about 1-2C per hour - so spontaneous bathing is a challenge.

My plan is to use a thermostatic controller to turn on and off the Webasto and maintain the temperature of the tub above freezing (or 6C) and also to use it to heat up to operational temps (40C) when I want to use it. 5kw should give about 4C an hour.

I’ll come back with plans and designs in a later post.

The second project will hopefully use my learning from the first to retrofit a Webasto heater onto my VW T25 campervan to provide heating and possibly hot water depending on how ambitious I get.

Previous chat and research on this subject has revealed that this heating role is actually the much more normal purpose for Webasto units and they are used in campervans, caravans and yachts worldwide.

It would be mounted externally, have its own fuel container externally and will probably heat a liquid circuit and radiator/heat exchanger to give warm air within the van. The heat exchanger may also give hot water depending on what I go for plumbing wise. This will need to work overnight as well so it can’t be hooked into the vehicle coolant circuit and will need to be thermostatically controlled.

As an aside, I may look at retrofitting a circulation pump into my TDi75 and putting in a remote controller to allow the Webasto to be remotely activated to heat the coolant system and engine block on frosty mornings. This is something which can be done by professionals and should only, theoretically, require a pump to move the coolant around, a thermostatic controller and a remote activator. This might be something which is well beyond me but I’ll see how I get on with the other stuff.

If anyone has any knowledge of the Webasto and fuel pump system they wish to share please do feel free. I’m particularly interested in the wiring and electrical controls.

Here goes!
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Alex



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I picked up a lay-z-spa from mfi(shutting down) some years ago for £150 though struggled justifying the cost of electricity to heat it. It was lovely to sit out on a cold night admiring the stars that were visible past the orange glow. ;) I've since toyed with building a log burner heat exchanger though it's very low on a long list.
Best of luck, if I can help, you know where I am.
 
Thanks bud. It might happen.
I have a chiminea modification design I made about a year ago to do just that. You run a copper coil around the inside of the chimney, move the baffle to the top and add on a couple of brass hose fittings at either end. It could run on just thermosiphoning as well which was an attraction but I decided a controllable and contained heat source that could prevent freezing would be better for me.

If you want a hand with your wood fired heater let me know and I’ll happily drink a beer while you do all the work.


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I also insulated mine to make it retain the heat better. Foil bubble wrap around the inside of the shell. An XPS foam and rubberised mat to go underneath. On the top I made an XPS lid which floats on the water top and goes underneath the inflatable lid that came with it. Really reduced the amount of Watts used to maintain the heat when I checked - about a third reduction I think.


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The testing rig! Now if I can only get the heater to talk to the PC!

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Ps. I learned last week that antifreeze really is essential! Froze SOLID!


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