Adding a Webasto for hot water....

[mattnj]

I've got hold of a Webasto hot water heater (proper marine one).... planning on adding to the existing calorifier (single coil).....I did search and there seems to be various options...what's the way to plumb this in to a exist md2020 engine circuit? Series or parallel? Can it even just go into existing circuit? (Expansion tank big enough?)

Seems like short cycling is a potential issue, what can be done to reduce that?

 

[pvb]

It's generally best to use a twin-coil calorifier. If you plumb it into the existing engine circuit, you may end up heating the engine unnecessarily.

 

[mattnj]

It's generally best to use a twin-coil calorifier. If you plumb it into the existing engine circuit, you may end up heating the engine unnecessarily.

I get that....but it's not going to happen.... heating engine will be happening...

 

[Moodysailor]

Parallel, always - with isolation valves for each part of the system. You want to be able to isolate the engine from the calorifier & Webasto, and the Webasto from the calorifier & engine if not using a twin coil calorifier. This is so that in the event of a leak in either, they can be isolated from the circuit and you still have the remaining parts functioning.

This is, ultimately the point of a twin coil system, so it can be achieved with a few ball valves and T-pieces.

One other thing to consider is that you may want a non-return valve in the engine out (to calorifier) to ensure that the water from the Webasto is directed to the calorifier primarily.