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b0atman

Heat from engine

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Present set up is a Webasto feeding radiators own pump. Stove feeds same radiators with a temperature controlled pump Common Antifreeze system with Header tank high up.

Question could engine hot water system be commoned into this ? 

 

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1 minute ago, b0atman said:

Present set up is a Webasto feeding radiators own pump. Stove feeds same radiators with a temperature controlled pump Common Antifreeze system with Header tank high up.

Question could engine hot water system be commoned into this ? 

The "best" way to do this is to put a plate heat exchanger on the engine cooling system to keep the two systems separate.  I think @nicknorman did this.

  • Greenie 1

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A direct connection would increase the volume of the engine cooling water to an unacceptable degree. you would problems coping with the expansion I think.

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Expansion ? i have a good size header tank with plenty of room for expansion. Heat exchanger ? sounds good bot would need to trigger pump to run or another pump.

 

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1 minute ago, b0atman said:

Heat exchanger ? sounds good but would need to trigger pump to run or another pump.

You said you already had two pumps on the heating circuit ...

 

Something like this type, but I don't know which size you would require - hopefully someone who uses one will add more details.

https://www.manomano.co.uk/heat-exchanger-for-boiler-3391

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Note, put the exchanger after the webasto so your not feeding it hot water.   Have the heat exchanger higher than the engine so you don’t transfer heat back to the engine when it’s switched off.  If you want to pre heat the engine from the webasto you can add a small pump on the engine side as well.

Edited by Robbo

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2 minutes ago, b0atman said:

Expansion ? i have a good size header tank with plenty of room for expansion. Heat exchanger ? sounds good bot would need to trigger pump to run or another pump.

 

I use a heat exchanger to heat my calorifier via the back boiler. So similar but different. Advantage is by using a thermo switch controlling the pump it only heats the calorifier when the stove boiler is up to temperature and has cured the problem of the stove cooling the calorifier when its on tickover. 

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Now i have ideas to consider i will need someone to do the pipework on the South Oxford. I think my system would be a  manual switch for fire circulation pump and a heat exchanger .Cheers all.

 

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Another argument against putting engine coolant is that if your system springs a leak your  engine will overheat and conk out. This may not be convenient. 

 

Another argument for a heat exchanger. 

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on my boat it is set up so that the engine heats the calorifier using it's first coil and heating in the boat is done by an alde gas boiler (which also heats the calorifier using it's second coil)

while cruising in cooler weather we turn the thermostat for the alde boiler up but don't light the boiler, this means that the alde is pushing water through the radiators and the calorifier but is not heating it.

the calorifier acts as a heat exchanger and we get a toasty boat from engine heat but do suffer from slightly cooler hot water (still too hot to keep your hand under)

admittedly this is not a proper way to do it but it heats a 45 foot boat quite effectively and in our case involved no messing around changing plumbing.

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Jess clever idea well done you great solution for others. I do not have a calorifier .

 

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12 hours ago, Jess-- said:

on my boat it is set up so that the engine heats the calorifier using it's first coil and heating in the boat is done by an alde gas boiler (which also heats the calorifier using it's second coil)

while cruising in cooler weather we turn the thermostat for the alde boiler up but don't light the boiler, this means that the alde is pushing water through the radiators and the calorifier but is not heating it.

the calorifier acts as a heat exchanger and we get a toasty boat from engine heat but do suffer from slightly cooler hot water (still too hot to keep your hand under)

admittedly this is not a proper way to do it but it heats a 45 foot boat quite effectively and in our case involved no messing around changing plumbing.

This is what I did on my last boat and it worked really well (I described it on here about ten year ago).  I've done the same on my current boat but it doesn't seem to get the radiators as warm for some reason, but still enough to keep the back of the boat warm.  I've also got two short (~30cm) finrads in a cupboard at the stern, one of which is on the return from the calorifier.

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3 hours ago, dor said:

This is what I did on my last boat and it worked really well (I described it on here about ten year ago).  I've done the same on my current boat but it doesn't seem to get the radiators as warm for some reason, but still enough to keep the back of the boat warm.  I've also got two short (~30cm) finrads in a cupboard at the stern, one of which is on the return from the calorifier.

Perhaps the heat from the engine is only a little more than than that needed to heat your water and those little rads so there's insufficient capacity once you also add your other heating?  Interesting idea though - I wonder of anyone has done it successfully with an Eberspacher or Webasto system?  Running just the pump is the key, I suppose. 

 

Incidentally, I also have a small bathroom towel radiator in my calorifier return line which works a treat.

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23 hours ago, Jess-- said:

on my boat it is set up so that the engine heats the calorifier using it's first coil and heating in the boat is done by an alde gas boiler (which also heats the calorifier using it's second coil)

while cruising in cooler weather we turn the thermostat for the alde boiler up but don't light the boiler, this means that the alde is pushing water through the radiators and the calorifier but is not heating it.

the calorifier acts as a heat exchanger and we get a toasty boat from engine heat but do suffer from slightly cooler hot water (still too hot to keep your hand under)

admittedly this is not a proper way to do it but it heats a 45 foot boat quite effectively and in our case involved no messing around changing plumbing.

I have the same set up and sometimes put the pump on when cruising. Although the radiators get just warm at best, it's free heat nonetheless.  

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Best thing I've done on our boat, plate heat exchanger fitted into the engine-calorifier circuit, boiler radiators connected to the plate heat exchanger, via a 12volt pump, powered from the engine electrics.

Once the engine has warmed up, and  the calorifier heated, the pump is switched on, 3 large radiators, piping hot!!

The secret is I think the extra pump, engine water pump doesn't have the power for the length of pipe to the furthest rad, and the boiler pump again not powerful enough for the heat exchanger.

The way it's wired, is that once the engine is off, the pump cannot run.  A valve stops the boiler trying to heat the engine.

 

Bod

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5 minutes ago, Bod said:

Best thing I've done on our boat, plate heat exchanger fitted into the engine-calorifier circuit, boiler radiators connected to the plate heat exchanger, via a 12volt pump, powered from the engine electrics.

Once the engine has warmed up, and  the calorifier heated, the pump is switched on, 3 large radiators, piping hot!!

The secret is I think the extra pump, engine water pump doesn't have the power for the length of pipe to the furthest rad, and the boiler pump again not powerful enough for the heat exchanger.

The way it's wired, is that once the engine is off, the pump cannot run.  A valve stops the boiler trying to heat the engine.

 

Bod

Does having it in the calorifier circuit not risk overcooling the engine?  @nicknorman has his heat exchanger in the skintank piping so it only uses waste heat which seems a better idea to me.

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44 minutes ago, TheBiscuits said:

Does having it in the calorifier circuit not risk overcooling the engine?  @nicknorman has his heat exchanger in the skintank piping so it only uses waste heat which seems a better idea to me.

I have plate heat exchanger setup, 12v pump, pressurised and it's superb. In the calorifier circuit on the return, I wait till engine up to temp then switch pump on, at tick over the engine temp drops 5 degrees over about 3 minutes but the temp is back to normal after about 10 minutes. When underway the engine temp gauge shows no change. No overcooling on my Beta38, 3x single large radiators and a towel rail.

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Hasn't been a problem so far.

The exchanger is not 100% efficient, and only the smallest one I could find.  It could delay the thermostat opening, but with no engine temp gauge it's difficult to know.

I'm plumbed into the return from the calorifier, so once the tank is up to heat, any extra heat not used is dumped into the skin tank.

These systems do rely on working thermostats, heat exchangers that do not use all the donor heat, and correctly sized radiators.

Nicknorman may have a too big exchanger for the heat source, or too lower rated thermostat, either would cause overcooling, one by taking to much, the other by not allowing enough heat to be created.

 

Bod

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2 hours ago, Cas446 said:

I have plate heat exchanger setup, 12v pump, pressurised and it's superb. In the calorifier circuit on the return, I wait till engine up to temp then switch pump on, at tick over the engine temp drops 5 degrees over about 3 minutes but the temp is back to normal after about 10 minutes. When underway the engine temp gauge shows no change. No overcooling on my Beta38, 3x single large radiators and a towel rail.

 

2 hours ago, Bod said:

Hasn't been a problem so far.

The exchanger is not 100% efficient, and only the smallest one I could find.  It could delay the thermostat opening, but with no engine temp gauge it's difficult to know.

I'm plumbed into the return from the calorifier, so once the tank is up to heat, any extra heat not used is dumped into the skin tank.

These systems do rely on working thermostats, heat exchangers that do not use all the donor heat, and correctly sized radiators.

Nicknorman may have a too big exchanger for the heat source, or too lower rated thermostat, either would cause overcooling, one by taking to much, the other by not allowing enough heat to be created.

 

Bod

Thanks both for the info.

 

I like @Cas446's approach of waiting until everything is warm enough before startting the pump - especially because I have a beta 38 & only 2 radiators ...

 

... but I think @Bod's approach of deliberately undersizing the heat exchanger is a good technique.  A bit difficult to exactly judge without a temperature gauge I would think.

 

For overall safety I do like @nicknorman's trick of having as big an exchanger as you fancy in the skin tank circuit - it is always waste heat as far as your engine is concerned, so you have the option of warming either the canal or the radiators.

 

I don't think nick has an overcooling problem with his, he just deliberately engineered for extra safety/redundancy because he is a pilot, so has to be a bit sensible!

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On 16/09/2018 at 01:23, TheBiscuits said:

 

Thanks both for the info.

 

I like @Cas446's approach of waiting until everything is warm enough before startting the pump - especially because I have a beta 38 & only 2 radiators ...

 

... but I think @Bod's approach of deliberately undersizing the heat exchanger is a good technique.  A bit difficult to exactly judge without a temperature gauge I would think.

 

For overall safety I do like @nicknorman's trick of having as big an exchanger as you fancy in the skin tank circuit - it is always waste heat as far as your engine is concerned, so you have the option of warming either the canal or the radiators.

 

I don't think nick has an overcooling problem with his, he just deliberately engineered for extra safety/redundancy because he is a pilot, so has to be a bit sensible!

 

If the plate heat exchanger (PHE) is fitted in the skin tank circuit you will not overcool the engine, because the engine thermostat will open and close as necessary to keep the engine at the required temperature.

 

Undersizing the PHE is a bad idea. They are rated in kW's, at a specified temperature differential across the two sides. Because of the relatively small heat load imposed by the boats radiators, there will not be much heat lost once the radiators are up to temperature. Therefore it is better to oversize the PHE as it will give better performance with a low temperature differential.

 

When I bought my boat it had just had a new calorifier fitted. The numpty who fitted it got the connections wrong, so the engine and central heating (CH) coils were in series. This gave lovely warm engine heated radiators (in June!), one of which couldn't be switched off. However I was concerned that the engine water pump wasn't designed to pump water around a 120 foot plus circuit, so reconnected the coils in parallel at the first opportunity.

 

I added a dc pump to the CH circuit, which allows the calorifier to act as a crude heat exchanger, but the engine only gets the rads warm, rather than hot, so next year I will fit a PHE instead.

Edited by cuthound
Spillung

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21 minutes ago, cuthound said:

 

If the plate heat exchanger (PHE) is fitted in the skin tank circuit you will not overcool the engine, because the engine thermostat will open and close as necessary to keep the engine at the required temperature.

 

Undersizing the PHE is a bad idea. They are rated in kW's, at a specified temperature differential across the two sides. Because of the relatively small heat load imposed by the boats radiators, there will not be much heat lost once the radiators are up to temperature. Therefore it is better to oversize the PHE as it will give better performance with a low temperature differential.

 

When I bought my boat it had just had a new calorifier fitted. The numpty who fitted it got the connections wrong, so the engine and central heating (CH) coils were in series. This gave lovely warm engine heated radiators (in June!), one of which couldn't be switched off. However I was concerned that the engine water pump wasn't designed to pump water around a 120 foot plus circuit, so reconnected the coils in parallel at the first opportunity.

 

I added a dc pump to the CH circuit, which allows the calorifier to act as a crude heat exchanger, but the engine only gets the roads warm, rather than hot, so next year I will fit a PHE instead.

and the other problem with 120 foot circuit is that it gives lots of failure points on a pressurised system, any of which would cause your engine to stop pretty quickly...  I use the heat exchanger in my bowman exhaust manifold for the rads, only comes into use when the thermostat opens so no risk of overcooling.

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