Webasto and Calorifier sizing

[IanD]

1 hour ago, Tacet said:

What does the temperature difference need to be to achieve a 5kW transfer? 

Not sure, I assume they're rated with a hot output from the boiler into a cold tank -- maybe 50C difference? (I expect there's a standard spec for this).

 

I do know the coil surface area is 0.6m2 per coil (including fins) which is a lot bigger than a standard one, also the coil pipes are bigger diameter (22mm?).

[ditchcrawler]

43 minutes ago, IanD said:

Not sure, I assume they're rated with a hot output from the boiler into a cold tank -- maybe 50C difference? (I expect there's a standard spec for this).

 

I do know the coil surface area is 0.6m2 per coil (including fins) which is a lot bigger than a standard one, also the coil pipes are bigger diameter (22mm?).

Mine is 22mm but I don't think its finned. I went for 22mm as I was going to thermosyphon the Dickinson through it, but changed that setup.

[Colin Brendan]

Does anyone put the calorifier in series? I know it's often ill advised, but if it's 22mm (and maybe with an optional bypass) - or are you just causing other convection problems doing that?

[Tony Brooks]

31 minutes ago, Colin Brendan said:

Does anyone put the calorifier in series? I know it's often ill advised, but if it's 22mm (and maybe with an optional bypass) - or are you just causing other convection problems doing that?

 

In series with what?

 

If you mean the rads then apart from a longer warm up I can't see why it would not work. I doubt it would be easy to get gravity circulation if you did that, but as you seem to have a pumped system it should work, but what you hope to achieve I don't know.

[IanD]

26 minutes ago, Tony Brooks said:

 

In series with what?

 

If you mean the rads then apart from a longer warm up I can't see why it would not work. I doubt it would be easy to get gravity circulation if you did that, but as you seem to have a pumped system it should work, but what you hope to achieve I don't know.

 

Mine will be in series -- calorifier first, rads second -- to give the fastest possible water warm-up time with shortest generator/boiler running time when the demand is for hot water only, when all the water goes through the calorifier.

 

For this to work without a bypass you need a big heat source as well as a big coil calorifier, otherwise it would take too long for the rads to heat up when you also want heating. My boat will have this, both diesel pressure-jet boiler and generator can push about 10kW of heat into the (pumped) system (with 5kW calorifier coils), but most boats don't so a bypass would be needed for when you want quick radiator heating, then some of the hot water goes straight to the rads and some through the calorifier.

 

This solution should work for me but most people will need something different, you need to design the system based on your particular requirements not "one-size-fits-all"... 😉