Using engine for heating boat

[PeteS]

I am considering the using the engine coolant to heat the central heating radiators this will give heat to the boat when under way without having to worry about keeping the fire in/top up with wood.

 

Initial thoughts are to divert the return from the calorifier coil through a heat exchange, connect the radiators to the other side of the heat exchanger and use a 12v pump to push the water through them.

 

Has anybody done this, what components were used, were there any problems?

 

Thanks

[curzons246]

Hi Pete,

my central heating is set up as you describe apart from the engine does all the pumping needed to circulate the hot water

Cheers Bill

[by'eck]

Sounds like a good idea but have a look how your present engine/calorifier system is set up. If you have a single thermostat engine with the calorifier in the bypass circuit (before thermostat brings skin tank into circuit) then adding the boat heating may mean the engine is over-cooled & runs less efficiently, with the thermostat never operating.

 

If you have a twin thermostat engine setup then at least the engine will still have a quick warm up via direct bypass, before the first thermostat kicks in & brings your calorifier & boat heating circuit into play. You will still have the likelihood that the second thermostat will never kick in, & the possibility of engine over-cooling.

 

In either situation maybe a changeover valve so either the calorifier or the boat heat exchanger are brought into play, but not both, would allow the engine to run at a better temperature.

[Tacet]

Yes - I have done as you propose and it works very well. I used a plate exchanger (bought from ebay for about £30)which seems very effective at its job; it has male bsp fittings which makes it simple. You will need a pump that passes the flow adequately when it is not running in order to allow the existing system to operate

 

Someone suggested that the conventional heat source (eberspacher in my case) could grumble at being heated whilst not itself operating - maybe upset the electronics? If that's the case, it's not caused me any problems, yet.

 

The slight snag is, of course, that it only works when the engine is running - but still useful for those indoors, drying the washing and being warm as you tie up. If you only ran your engine for a short while, you could prejudice the temperature of the domestic hot water. One potential bonus is in providing additional cooling for the engine. I have not needed that capability, but as the engine is a twin thermostat model it can be seen that it makes a noticeable difference.

[Chalky]

I've done exactly the same as Ian. I've got an Isuzu engine and after talking with HM marine they said that the engine water pump was ok to pump the calorifier circuit, but not a heating circuit. I bought a plate heat exchanger off ebay for £10 - they're used in combi boilers to heat the domestic water. It's connected after the calorifier so the domestic water heats first, then the rads. I've got a car auxiliary coolant pump as the pump for the radiator circuit and the whole lot is plumbed in 22mm Hep2O. When I get hold of a webasto boiler I'll plumb it into the circuit before the heat exchanger.

The control gear consists of a domestic room stat that turns the pump on and off, the power to the whole system being provided by a relay that is switched on when the ignition is on. I'll probably change it to a microprocessor system so I can match the pump speed to the heat that the heat exchanger is producing and get it to heat up faster - the pump is seriously over rated! I'll also be able to let the micro decide which is the most cost efficient heat source and turn on as appropriate.

We used it quite a lot this summer. The main complaint was that it made the boat too hot!

 

The other / main advantage of the system is that more of the energy released when burning the fuel is going to heating rather than propulsion so it could mean that you could claim a different split and be able to justify the figures.

Edited November 8, 2011 by Chalky

[BlueStringPudding]

it has male bsp fittings which makes it simple.

 

[Chalky]

 

It means that you can get bits easily that allow you to attach rubber coolant hoses to it.

[Guest]

I've been doing this for years,but without heat exchanger or second pump. We have a Smith's fan assisted convector right at the back, connected to the calorifier circuits. This dumps an amazing amount of heat into the cabin when the engine is running.

 

If the Smiths' unit had not been available (skip find) I would have used one of those cabin blower heaters from Vehicle Wiring Products.

Edited November 8, 2011 by Guest

[The Pipe]

female BSP fittings fit also male BSP fittings if your confused...........

[Chalky]

I've been doing this for years,but without heat exchanger or second pump. We have a Smith's fan assisted convector right at the back, connected to the calorifier circuits. This dumps an amazing amount of heat into the cabin when the engine is running.

 

I considered that as an option. Since we've got a Liverpool hull we have a 4mm steel bulkhead between the engine room and the cabin and so it wasn't going to be easy / possible with that and our interior layout (40' boat sleeps 5). If you went that way there are a lot of car heaters with blowers that would suit. My parents house has myson fan assisted radiators that were exactly what you describe and they threw out amazing amounts of heat for their size.

[Guest]

I considered that as an option. Since we've got a Liverpool hull we have a 4mm steel bulkhead between the engine room and the cabin and so it wasn't going to be easy / possible with that and our interior layout (40' boat sleeps 5). If you went that way there are a lot of car heaters with blowers that would suit. My parents house has myson fan assisted radiators that were exactly what you describe and they threw out amazing amounts of heat for their size.

Yes the Smith's unit is almost identical to a Myson unit (we too have Mysons at home and agree they are amazing for their size.) The one I got had been slung out of a night club because they didn't like the colour. Matches our oak lining a treat and saved close to 300 quid. Down side is it needs 240Vfor the fan.

 

After our experience I am convinced that if engine heat is being recovered (and why not,we pay for it) then the best way is with some sort of blown system.

[AJLintern]

female BSP fittings fit also male BSP fittings if your confused...........

Ooh matron!

[Sir Nibble]

Also has the advantage of keeping the engine warm overnight so winter morning cold starts are a thing of the past and providing hot water independent of the engine. After all, while you're at it it makes sense to link everything. Got a back boiler?

[PeteS]

Thanks for the replies. I'll do some more investigation of the engine to see if it's a 2 thermostat job. It's an Isuzu 35, any ideas were I can look. I know car engines inside out but not too familiar with marines.

 

No back boiler

[Capt Ahab]

I've done exactly the same as Ian. I've got an Isuzu engine and after talking with HM marine they said that the engine water pump was ok to pump the calorifier circuit, but not a heating circuit. I bought a plate heat exchanger off ebay for £10 - they're used in combi boilers to heat the domestic water. It's connected after the calorifier so the domestic water heats first, then the rads. I've got a car auxiliary coolant pump as the pump for the radiator circuit and the whole lot is plumbed in 22mm Hep2O. When I get hold of a webasto boiler I'll plumb it into the circuit before the heat exchanger.

The control gear consists of a domestic room stat that turns the pump on and off, the power to the whole system being provided by a relay that is switched on when the ignition is on. I'll probably change it to a microprocessor system so I can match the pump speed to the heat that the heat exchanger is producing and get it to heat up faster - the pump is seriously over rated! I'll also be able to let the micro decide which is the most cost efficient heat source and turn on as appropriate.

We used it quite a lot this summer. The main complaint was that it made the boat too hot!

 

The other / main advantage of the system is that more of the energy released when burning the fuel is going to heating rather than propulsion so it could mean that you could claim a different split and be able to justify the figures.

I like this idea - and not a solution I had considered before. I guess that this means that the heating fluid is completely separate to the engine coolant and can therefore be drained off in the winter. Two questions: 1. How many rads do you run off it and 2. what pump would you suggest?

[aread2]

I've got a Beta 43 with a twin coil calorifier and a car interior heater. The calorifier is heated by the engine when it's running and via the second coil by the Eberspacher which then goes on to heat the rads. When the engine is running the heat is transferred to the central heating via the calorifier. The Eberspacher doesn't seems to mind a second heat source in the circuit. In addition to this we have a 2.5Kw car interior heater about where the range would be in a back cabin that blows onto the steerer's feet (advantage of a trad), using engine heat.

 

The central heating pump is the internal Eberspacher one. There are two towel rails and four two metre finrads in the CH circuit.

 

Edit : to add more detail.

Edited November 8, 2011 by aread2

[Chalky]

I like this idea - and not a solution I had considered before. I guess that this means that the heating fluid is completely separate to the engine coolant and can therefore be drained off in the winter. Two questions: 1. How many rads do you run off it and 2. what pump would you suggest?

 

Yes it's two completely separate circuits. Both have 50% antifreeze in them so they don't need to be drained.

 

I've got 2 rads, both relatively small, but that's due to the limited amount of wall space we've got available and the fact they were on clearance at Coventry plumbing centre @ £2.50 each.

 

The pump was one I happened to have in the garage. It's designed to pump coolant for large engine - I just used what I had to hand. The mod I would do is to fit a speed controller to it, however it does provide extra cooling for my engine.

If I was to add an extra rad I'd fit a towel rail in the bathroom however I'm going to have to solder one up and it's not a priority at the moment.

 

The advantage of the heat exchanger plumbed into the calorifier circuit after the calorifier is that unlike using the second calorifier circuit it doesn't rob heat from the hot water.

The disadvantage is a slower warm up time since it's got to heat the calorifier first. You also need to drain down part of the engine coolant circuit to fit it which you don't have to do if you use the spare calorifier coil. The heat exchanger however is considerably smaller and should be capable of transferring far more heat - it was suggested by a colleague who specialises in this technology that the one I've got could transfer 5kW.

Edited November 8, 2011 by Chalky

[blackrose]

I am considering the using the engine coolant to heat the central heating radiators this will give heat to the boat when under way without having to worry about keeping the fire in/top up with wood.

 

Initial thoughts are to divert the return from the calorifier coil through a heat exchange, connect the radiators to the other side of the heat exchanger and use a 12v pump to push the water through them.

 

Has anybody done this, what components were used, were there any problems?

 

Thanks

 

I've done exactly what you describe. My central heating system used to be heated from the eberspacher but once that packed up and was unserviceable I chucked it out and indirectly connected it to the engine with a tubular heat exchanger (can't remember the make but it isn't a Bowman). Anyway, the system works well. I'll post a picture...

 

Edit:

 

The hot water from the engine goes to the calorifier coil and comes back (grey plastic bulkhead connectors on the left), then it goes into the bottom of the heat exchanger (right) and out of the bottom of the heat exchanger (left) and back to the engine. It might actually flow the other way around I can't remember? Anyway, the other circuit goes through the 12v water pump, through the other side of the heat exchanger and on to the central heating circuit & second coil (white plastic bulkhead connectors on the right) and then back to the 12v pump. The pump is switched on/off with a switch on the boat's control pedestal.

 

You could plumb the engine directly into the central heating system, without the heat exchanger & 12v pump, but I was told that this may put undue strain on the engine's water pump. Also that would mean any leak in the central heating would drain the engine.

Edited November 10, 2011 by blackrose

[PeteS]

Thanks once again for the replies.

 

For those who have used a combi boiler heat exchanger - what type was it, there seems to be a plethora of them out there

[colin stone]

Yes - good idea. I have a Bowman tubular heat exchanger on the boiler out CH pipe and the normal CH pump does the circulation. The engine calorifer connections provide the heat to the exchanger. After the engine starts, there is a 15min delay before the CH pump kicks in - this gives the engine a chance to heat up first. 14 radiators, all piping hot, which makes winter cruising great.

 

CH Heat Exchanger

[Chalky]

Thanks once again for the replies.

 

For those who have used a combi boiler heat exchanger - what type was it, there seems to be a plethora of them out there

 

Cheapest I could find on ebay and fingers crossed that it was big enough.

[JerryP]

There's a full article on using your engines heat in the December issue of WW.

[Mike Jordan]

Hi Pete

By happy coincidence the December edition of Waterways World will have an article in Boat Projects, showing a simple method of keeping warm using waste engine heat. The heater shown is cheap and easy to construct and takes up very little space. It's ideal for retro-fitting in a completed boat.

Mike.

 

Sorry Jerry I missed your entry, must be early onset something or other.

Edited November 9, 2011 by Mike Jordan

[PeteS]

It's that deja vue feeling all over again

 

Thanks I'll pop into Smiggies and have a look

[Neil2]

Just wanted to say what a great thread and thanks to all who have contributed. I've wanted to do this for a while, especially since I don't think my engine is cooled sufficiently. Lots of great ideas/advice, just what the forum should be about.