Plumb engine cooling circuit into Webasto circuit?

[Tim Good]

I have a Thermo 90 webasto heater that heats water and pumps it round the boat to heater matrix units that then blow hot air and also heater the calorifier.

At the same time the engine cooling loop goes to the calorifier as with many boats.

Is there any reason I couldn't rig the webasto water pulmbing in parallel with the engine cooling plumbing (as it goes to the calorifier) so that i could run the heating whilst the engine is on and without running the webasto. i.e. hot water would run around the system but the webasto would just be turned off.

 

[NormanS]

The only problem that I see is that the coolant pump on the engine, which is designed merely to circulate the coolant around the engine, may not be able to cope with all the extra length of plumbing.

 

[ianj99]

I have a Thermo 90 webasto heater that heats water and pumps it round the boat to heater matrix units that then blow hot air and also heater the calorifier.

At the same time the engine cooling loop goes to the calorifier as with many boats.

From what you've said, it already does that but Webastos are used on many upmarket vehicles where the engine coolant does circulate through the unit so it pre heats the engine.

So you can plumb it into the loop from the engine to the calorifier, but of course, when the engine is not running, the Webasto will also be heating the engine as well as the domestic hot water and drastically reducing the heat available for the heater matrices.

 

[David2452]

Issues would be, as already said, circulation and the requirement for the whole circuit to have 50/50 antifreeze, the temperature the engine runs at would be fine and heat the system well once up to temperature. The T90 on the other hand runs at a much lower temperature and as glycol is a poor heat conductor will be far less efficient. As an example, I went to a new DIY install before Christmas to investigate the radiators not getting hot enough, his mate knew better than the Webasto instructions and my advice and insisted on filling with 50/50. I drained it down an diluted to 25%, refilled and Bob was his uncle.

 

[lw395]

From what you've said, it already does that but Webastos are used on many upmarket vehicles where the engine coolant does circulate through the unit so it pre heats the engine.

So you can plumb it into the loop from the engine to the calorifier, but of course, when the engine is not running, the Webasto will also be heating the engine as well as the domestic hot water and drastically reducing the heat available for the heater matrices.

The engine will be heated by the eberbasto. Where does the heat go from the engine? In most boats, it dissipates through the accommodation, so the engine acts as a storage heater. If your engine compartment is very well ventillated, more of the heat may be lost.
In practice, I found that the engine seemed to heat up and not lose ever so much heat when not running, so once the engine had got hot, there was little reduction in the heat to the matrices and calorifier.
The 'thermal mass' of the engine also prevented the eber from short cycling which was a definite benefit.
Downside is obviously it takes longer to get the calorifier hot.
I plumbed mine in parallel with the engine, I believe others plumb them in series. I think I made it more complicated because I wanted to be able to isolate the heating plumbing in the event of a leak and still use the engine.
Maybe the ideal system might have valves or thermostats to direct the hot water, depending on what you wanted to achieve.
Mate of mine put one in a Land Rover, his priority was to demist the screen before he left his house. Warming the engine was a secondary benefit.

 

[ianj99]

Maybe the ideal system might have valves or thermostats to direct the hot water, depending on what you wanted to achieve.
Mate of mine put one in a Land Rover, his priority was to demist the screen before he left his house. Warming the engine was a secondary benefit.

A valve on the loop from the engine (with the Webto connected in parallel) would prevent it heating the engine.
The consensus is that there is no problem if the engine coolant flows through the T90 whether its in series or parallel but might it not need a non return valve in the T90 outlet if in parallel, to prevent it short circuiting the coolant flow from the engine?

 

[David2452]

The consensus is that there is no problem if the engine coolant flows through the T90

Did you not read my post?

 

[ianj99]

Did you not read my post?

The OP hasn't mentioned his engine or heating system antifreeze, so we don't know what type or dilution they are.
As far as the circulation goes, presumably there is a circulating pump in the heating system so this will assist the engine coolant pump if the T90 is connected in series or even in parallel if plumbed in correctly.
The flow to the calorifier can be reduced by a valve to prevent it short circuiting the heating circuit.