Diesel hot water heaters

[wizard]

I have on my 31' yacht a Webasto hot air heater for cabin heating but need to find some way of heating water without running the engine.

Would one of the small units used on cars/vans work? Has anyone done this and could give me some advice.

 

[bendyone]

Yes, I have one (Webasto) from a Landrover Freelander, runs two fan-coil units but could do hot-water as well.

 

[David2452]

Over the top for just the hot water, even the smallest would coke up early because of low usage and cycling too much. If you fitted one and loaded it with something like a decent sized matrix or a towel rad in the heads as well as the calorifier it would perform better. Also be very careful when sourcing a vehicle unit, some (not all) have a different ECU which is controlled from the vehicle BUS.

 

[Gordonmc]

I installed a system with an old Eberspacher D5W at its heart. The unit came off Ebay and I set up the whole system in my garage before deciding the best location.
I am glad I did because the height of the header tank in relation to the rest of the system is critical.
The system comprises the D5W and, in order that the hot water flows, a three-vent fan matrix, a 22 litre calorifier, the 11 litre header tank and back to the D5W. I used 5/8 inch vehicle heater hose bought on the roll from a local truck factor insulated with foam pipe lagging.
I discovered the water pump on the D5W is not self-priming after installing the system and had to raise the header tank. It was tight as I had put the header in a hanging locker, but it worked.
The fan matrix had three outlets, of which I used two; one to the aft cabin and the second into the heads. I may use the third with a longer run of duct to the saloon, but for the time being I am happy.
The system seems to work well and its handy to have a heating system independent of the engine.

 

[David2452]

I installed a system with an old Eberspacher D5W at its heart. The unit came off Ebay and I set up the whole system in my garage before deciding the best location.
I am glad I did because the height of the header tank in relation to the rest of the system is critical.
The system comprises the D5W and, in order that the hot water flows, a three-vent fan matrix, a 22 litre calorifier, the 11 litre header tank and back to the D5W. I used 5/8 inch vehicle heater hose bought on the roll from a local truck factor insulated with foam pipe lagging.
I discovered the water pump on the D5W is not self-priming after installing the system and had to raise the header tank. It was tight as I had put the header in a hanging locker, but it worked.
The fan matrix had three outlets, of which I used two; one to the aft cabin and the second into the heads. I may use the third with a longer run of duct to the saloon, but for the time being I am happy.
The system seems to work well and its handy to have a heating system independent of the engine.

Get rid of the header tank and put a small 3 bar pressure vessel in line, then fill via a pressure loop to 1 bar from your water system (after inhibiting) we use that system most of the time now and have far fewer issues like air locks, frequent bleeding, over heat cut outs etc. than with the old header tank, if you do use a header, make sure it is of the swirl pot vareity and not just a single line.

 

[wizard]

Over the top for just the hot water, even the smallest would coke up early because of low usage and cycling too much. If you fitted one and loaded it with something like a decent sized matrix or a towel rad in the heads as well as the calorifier it would perform better. Also be very careful when sourcing a vehicle unit, some (not all) have a different ECU which is controlled from the vehicle BUS.

Sorry, forgot to mention that I have 22l calorifier!

So with a towel rail in circuit as well would this be OK?

 

[wizard]

Also be very careful when sourcing a vehicle unit, some (not all) have a different ECU which is controlled from the vehicle BUS.

Any rules to help me decide from the many advertised on eBay which to choose?

 

[bendyone]

Sorry, forgot to mention that I have 22l calorifier!

So with a towel rail in circuit as well would this be OK?

These unit push out 5KW so you need to use most of this energy. I have 2 fanciols both around 3 KW max output. Works well for me. I guess the tank might take 2 Kw Handrail who knows but probably around 1KW

 

[David2452]

Sorry, forgot to mention that I have 22l calorifier!

So with a towel rail in circuit as well would this be OK?

Should be fine then, you could always bung in a buffer tank if you find it is not loaded enough, instead of a standard header tank in the return line to the heater, in at the top and out at the bottom. Make sure it is the highest point in the system that way it will get rid of most of the air as well as buffer the heat, 2 or 3l size will do it, an Aladdin auto bleeder on the top of the towel rail is usually a good idea too. Steer clear of ones on ebay from modern vehicles, particularly passanger cars and you should be OK. If you PM me a proper email address I can send you a PDF of the marine specific install manual for the Thermo top range which covers plumbing and cabling too, much more useful than the generic one, assuming it is followed that is..
Edit to add, on a lightly loaded unit it is even more important that the burn rate is set correctly, if you know somebody with a flue anayliser you can check it against spec, if it is not to spec you will need a Webo guy with a thermo test interface to adjust a Thermo top C though.

 

[wizard]

Should be fine then, you could always bung in a buffer tank if you find it is not loaded enough, instead of a standard header tank in the return line to the heater, in at the top and out at the bottom. Make sure it is the highest point in the system that way it will get rid of most of the air as well as buffer the heat, 2 or 3l size will do it, an Aladdin auto bleeder on the top of the towel rail is usually a good idea too. Steer clear of ones on ebay from modern vehicles, particularly passanger cars and you should be OK. If you PM me a proper email address I can send you a PDF of the marine specific install manual for the Thermo top range which covers plumbing and cabling too, much more useful than the generic one, assuming it is followed that is..
Edit to add, on a lightly loaded unit it is even more important that the burn rate is set correctly, if you know somebody with a flue anayliser you can check it against spec, if it is not to spec you will need a Webo guy with a thermo test interface to adjust a Thermo top C though.

Many thanks for your help email address on its way

 

[Heckler]

Any rules to help me decide from the many advertised on eBay which to choose?

The rover 75 unit is good for our use, simple self contained, two wires for the on off switch and two for the power, thats it, the tick tick pump is under the rear offside arch! I bought one from our local scrappy the other week for £40
Stu