Heating with single coil calorifier with two sources

[laurence_penpol]

Hi everyone,

I have just quoted a 33ft Sailing boat and am in the process of putting in some heating to make cruising a little more comfortable in the winter months. I have a single coil calorifier on board which is in good condition which is currently heated by the engine for hot water. I want to add a Websasto diesel water heater into the system so I can get hot water and heating in the winter without switching the engine on, but I am struggling to think of the best approach. I know ideally I would have. a twin coil calorifier but there is only room for a small tank and most at that size dont come with two coils.

Where I have got to in my thinking (pic below) is that an additional heating circuit with the Websasto and Heater Matrix in but with a 12v solenoid valve (normally closed) would do the job in separating the heating from the engine when not using the Webasto heater but allowing both to heat the water. I am trying to minimise the water that the engine would have to pump around beyond the calorifier. The other option is just to disconnect the engine entirely and only use the Webasto on its own separate circuit for heating and hot water.

I was not too worried if the Webasto heated the engine block a little as it will help with short cycling of the heater and is a good overall heat sink, but equally, Im conscious about keeping the engine coolant paths as simple as possible to reduce risks of engine failure. Im also aware I would need a header tank on the Webasto circuit but didn't include that in the diagram.

Any thoughts about the best setup for a single coil calorifier most welcome!

 

[Tranona]

Not common to have water heating on your sort of boat - expensive, bulky and inefficient.

Better to install diesel hot air heating, now using one of the copy heaters available at a fraction of the cost of your proposal.

 

[laurence_penpol]

Not common to have water heating on your sort of boat - expensive, bulky and inefficient.

Better to install diesel hot air heating, now using one of the copy heaters available at a fraction of the cost of your proposal.

Thanks but that's not the issue. I used to have a hot water system on a 27 ft installed by the previous owner - it was great! My plan is similar but a different problem.

 

[Boater Sam]

Can you install a Willis heter in the pipework to the calorifier? Willis External Immersion Heater Complete With 3kW Element

 

[laurence_penpol]

Can you install a Willis heter in the pipework to the calorifier? Willis External Immersion Heater Complete With 3kW Element

Thanks. I think these are electrical immersion style? I’m on a swinging mooring on the river dart so don’t have power, so these wouldn’t be viable. The Calorifier I have got has an immersion fitted but I’m unlikely to use it because of the lack of power.

 

[geem]

There is no problem installing a hydronic system. You can connect the engine circuit in with the heating system, you just need antifreeze at 25%. Use a pressure vessel rather than a header tank if you go this route. The pressure can be set the pressure quite low on the pressure vessel. In the summer you can isolate the heating circuit and get nice hot water from the heater. Enjoy

 

[Neeves]

If all you want is hot water but don't want to run the engine, don't have electricity (or not enough) - and have gas.....

You can buy, relatively cheaply, instant, gas, hot water heaters - used in mobile homes, caravans (some are dual energy, gas and electric.. Go visit your local caravan retail outlet. I don't have experience of these units except that the flow rate (of the water) is not high (we used a normal domestic gas boiler, Bosch) as we had the same issues - but it was quite large and I suspect you would not have room - the versions for motor homes are much smaller.

Jonathan

 

[Plum]

Hi everyone,

I have just quoted a 33ft Sailing boat and am in the process of putting in some heating to make cruising a little more comfortable in the winter months. I have a single coil calorifier on board which is in good condition which is currently heated by the engine for hot water. I want to add a Websasto diesel water heater into the system so I can get hot water and heating in the winter without switching the engine on, but I am struggling to think of the best approach. I know ideally I would have. a twin coil calorifier but there is only room for a small tank and most at that size dont come with two coils.

Where I have got to in my thinking (pic below) is that an additional heating circuit with the Websasto and Heater Matrix in but with a 12v solenoid valve (normally closed) would do the job in separating the heating from the engine when not using the Webasto heater but allowing both to heat the water. I am trying to minimise the water that the engine would have to pump around beyond the calorifier. The other option is just to disconnect the engine entirely and only use the Webasto on its own separate circuit for heating and hot water.

I was not too worried if the Webasto heated the engine block a little as it will help with short cycling of the heater and is a good overall heat sink, but equally, Im conscious about keeping the engine coolant paths as simple as possible to reduce risks of engine failure. Im also aware I would need a header tank on the Webasto circuit but didn't include that in the diagram.

Any thoughts about the best setup for a single coil calorifier most welcome!

View attachment 183217

My thought would be to insert a 3-port 12v diverter valve between the engine hot water output and the calorifier with the webasto hot output feeding into the second port of the valve. The valve is then used to have either the engine OR the webasto sending hot water to the calorifier. The 12 v activation would come from the webasto when the webasto is stitched on with the valve defaulting to the engine supplying the hot water/coolant when the webasto is off. The return from the webasto/heater matrix is just T'd into the return hose between the calorifier coolant-output and engine. You would not need an extra header or expansion tank beyond what is already on the engine. The default would be the engine supplying the hot water to the calorifier and when you switch on the webasto that would then heat the calorifier. But, this assumes you only want hot air from the matrix heater when the engine is off, not unreasonable in my view.

 

[geem]

My thought would be to insert a 3-port 12v diverter valve between the engine hot water output and the calorifier with the webasto hot output feeding into the second port of the valve. The valve is then used to have either the engine OR the webasto sending hot water to the calorifier. The 12 v activation would come from the webasto when the webasto is stitched on with the valve defaulting to the engine supplying the hot water/coolant when the webasto is off. The return from the webasto/heater matrix is just T'd into the return hose between the calorifier coolant-output and engine. You would not need an extra header or expansion tank beyond what is already on the engine. The default would be the engine supplying the hot water to the calorifier and when you switch on the webasto that would then heat the calorifier. But, this assumes you only want hot air from the matrix heater when the engine is off, not unreasonable in my view.

You still need to deal with expansion in the heating circuit when not using the engine. This is why an expansion vessel is a good idea as it will work for both scenarios. You can't over size and expansion vessel

 

[Plum]

You still need to deal with expansion in the heating circuit when not using the engine. This is why an expansion vessel is a good idea as it will work for both scenarios. You can't over size and expansion vessel

But the Webasto circuit is open to the engine circuit on the return and the engine coolant circuit has expansion provision. There may be problems with airlocks if the webasto and calorifier are higher than the engine

 

[geem]

But the Webasto circuit is open to the engine circuit on the return and the engine coolant circuit has expansion provision. There may be problems with airlocks if the webasto and calorifier are higher than the engine

The expansion provision needs to be proportional to system volume. By adding the webasto system to the engine cooling circuit, you are dramatically increasing the system volume. The pressure cap on the engine is not designed to accommodate the large system volume. Webasto recommend a 5 litre pressure vessel. This approach resolves the problem of the large system volume.
To stop air locks you simply need a quick fill connection at the bottom of the system, and vent at the high spot. A small header tank helps to add the 25% glycol as well

 

[Plum]

The expansion provision needs to be proportional to system volume. By adding the webasto system to the engine cooling circuit, you are dramatically increasing the system volume. The pressure cap on the engine is not designed to accommodate the large system volume. Webasto recommend a 5 litre pressure vessel. This approach resolves the problem of the large system volume.
To stop air locks you simply need a quick fill connection at the bottom of the system, and vent at the high spot. A small header tank helps to add the 25% glycol as well

Aha, now I understand. Good point.

 

[Andrew_Fitton]

Fit a second coil to your calorifier. Search for solar calorifier coil.

 

[geem]

Fit a second coil to your calorifier. Search for solar calorifier coil.View attachment 183273

It's better with a second coil. That's the way I will be going as my calorifier is in need of replacement. However, you don't need to have two coils. A friend runs his as combined system on a single coil without issue. He uses a 5 litre pressure vessel as described in my previous posts. It works fine. My only concern is a leak in the heating system could disable the engine just when you don't want it