I've Been Experimenting

[Biggles]

It occurred to me a while back that my hot water in my calorifier made by the engine coil is insanely hot and that in the calorifier there is another coil from the CH. All that's needed is the CH pump running to use the water in the calorifier to transfer heat to the radiators when the engine is running.

 

So I rigged up a temporary power supply to the the CH pump independent of the CH control and run the engine to charge the batteries and low and behold the radiators got very, very warm. Not as hot as the water in the calorifier as the hot water from the tap was still insanely hot from the tap but there was defiantly significant heat being put into the boat CH from the engine.

 

I assume given time the radiators would get as hot as the water but think the heat in the radiators is limited to the absorption capacity of the CH coil from the surrounding water.

 

However given that a few hours a day of cruising in winter could dump some significant free heat into a CH system, I think why have I never heard anyone doing this?

 

Am I missing something?

 

Oh and FYI my CH is by Mikuni not a back boiler not that I can see this would change the basic principle if the fire was out as the Mikuni is when the experiment was conducted.

 

Discuss?

[David Schweizer]

It occurred to me a while back that my hot water in my calorifier made by the engine coil is insanely hot and that in the calorifier there is another coil from the CH. All that's needed is the CH pump running to use the water in the calorifier to transfer heat to the radiators when the engine is running.

 

So I rigged up a temporary power supply to the the CH pump independent of the CH control and run the engine to charge the batteries and low and behold the radiators got very, very warm. Not as hot as the water in the calorifier as the hot water from the tap was still insanely hot from the tap but there was defiantly significant heat being put into the boat CH from the engine.

 

I assume given time the radiators would get as hot as the water but think the heat in the radiators is limited to the absorption capacity of the CH coil from the surrounding water.

 

However given that a few hours a day of cruising in winter could dump some significant free heat into a CH system, I think why have I never heard anyone doing this?

Am I missing something?

 

Oh and FYI my CH is by Mikuni not a back boiler not that I can see this would change the basic principle if the fire was out as the Mikuni is when the experiment was conducted.

 

Discuss?

I have no idea why you haven't thought of it, lots of boats (ours included ) have that system.

[Biggles]

I have no idea why you haven't thought of it, lots of boats (ours included ) have that system.

 

I've ne'er heard it discussed but guessed it must be out there.

[David Schweizer]

I've ne'er heard it discussed but guessed it must be out there.

It was late and I mis-read your post, the system you are describing is different from that on our boat. We do not have a ciculation pump, instead the circuation relies upon convection assisted directly by the engine coolant pump, there is only one coil in the calorifier, which is teed off to feed the radiators with valves to isolate the CH during the summer.

 

The system on your boat appears to be a fairly standard twin coil system, but if there is no circulation round the CH system using only engine heat, there is something wrong with the system. The engine coolant on your boat clearly feeds the calorifier and heats the domestic water, the second coil in the calorifier should then distribute water round the CH system using convection, have you checked that the header tank is full, or that you do not have any airlocks, sometimes bleeding the radiator at the end furthest away from the calorifier will encourage flow to start.

 

It also occurs to me that the pipes feding the radiators may not be of sufficient size for convectuion to work properly. Ideally they should be 28mm, at one time a fairly easily sourced size, but given how much it costs these days your builder may have fitted a smaller size which will be fine for a pumped system, but possibly inadequate for the twin coil system to work effectively. The only way to find out would be to replace the existing CH system supply pipes which could be quite disruptive (and expensive) Or you could try and instakl a more permanent version of your experiment by sourcing a second circulation pump and fitting that into the system after the calorifier. In home systems the pump is normally fitted into the return flow pipes to avoid water being pumped into the header tank and out through the overflow pipe, I assume the same principal would apply to boats.

 

I would add that I am not a qualified heating enineer, and there could be flaws in my suggestions. I have successfuly installed two domestic central heating systems in my house, and I have introduced significant modifctions to the system on our boat, but this has been based upon reasoned assumption and a lot of book reading, rather than any formal training. There are people out there who are qualified, who will be able to give you better and more informed advice.

Edited October 29, 2012 by David Schweizer

[bottle]

The system on your boat appears to be a fairly standard twin coil system, but if there is no circulation round the CH system using only engine heat, there is something wrong with the system.

 

Sorry David

 

No there is not.

 

I have twin coils and the radiators are only supplied from the Erbaspacher at no time does the engine supply heat to the radiators.

 

I am sure though that, if I was to run the central heating pump, a certain amount of heat could be transferred from the calorifier, using it as a heat exchanger, to the radiators.

[PaulJ]

You have about summed it up in your first post biggles. I would have expected a small amount of heat to be transferred to rads using your set up. The coils in your calorifier are obviously very efficient to achieve the results you got. I would imagine it is more down to the build quality of the calorifier to how successful this would be on oher boats.

[Keeping Up]

We've always switched on the CH pump to transfer some warmth to the radiators, to get some background warmth when cruising in weather that doesn't quite justify lighting either the solid fuel stove or the gas-hungry boiler. I'd assumed that everybody did this. The radiators get moderately warm but definitely not hot.

[dor]

I've mentioned this a few times on here over the years.

I fit a switch so I can turn the pump on without running the boiler so that the calorifier is used as a heat exchanger.

On my last boat it worked very well, with the rads getting nearly as hot as I would expect if the boiler was running. On my present boat it is a little more tricky. I need to balance the flow between the rads and the calorifier carefully to get the heating to work, otherwise the flow just seems to go through one circuit or the other. However when I get it right it works well. The water temperature in the calorifer stays pretty hot too when cruising.

[johnmck]

I've mentioned this a few times on here over the years.

I fit a switch so I can turn the pump on without running the boiler so that the calorifier is used as a heat exchanger.

On my last boat it worked very well, with the rads getting nearly as hot as I would expect if the boiler was running. On my present boat it is a little more tricky. I need to balance the flow between the rads and the calorifier carefully to get the heating to work, otherwise the flow just seems to go through one circuit or the other. However when I get it right it works well. The water temperature in the calorifer stays pretty hot too when cruising.

 

 

Hi. We have a similar system but using a dedicated heat exchanger rather than the calorifer. I believe the heat exchanger was sourced from Alde. This year, with the loveley weather we have had, the system has been more than handy. Toasty boat at the end of a cruise with no reduction in hot water in the calorifer. The rad's get as hot as when the Webasto is used.

 

Forum member Ally ( Beacon boats), will be able to give the full spec as she built the boat!

 

Brilliant bit of kit.

 

http://www.alde.co.uk/itemdetails.php?itemId=58

Edited October 29, 2012 by johnmck

[David Schweizer]

Sorry David

 

No there is not.

 

I have twin coils and the radiators are only supplied from the Erbaspacher at no time does the engine supply heat to the radiators.

 

I am sure though that, if I was to run the central heating pump, a certain amount of heat could be transferred from the calorifier, using it as a heat exchanger, to the radiators.

I must admit I am confused, are you saying that the calorifier has two coils one connected to the engine water coolant system, and the other one unused? If that is the case I agree that my observation is irrelevant.

 

I am also confused about the function of the Mikuni, does it heat the calorifier and radiators or just the radiatiors, if it heats both, and the engine also heats the calorifier, what is preventing the hot water from the engine heating the radiators?

 

I must admit I have never come across a system with a twin coil system which did not take advantage of surplus heat from the calorifier, and my immediate inclination would be to connect the CH system to the second coil, but if the pipework is small it may not work very well without a circulation pump in line,

Edited October 29, 2012 by David Schweizer

[Biggles]

David. My system is sealed pressurised so. No header tank. The Mikuni does the rads and the calorifier. The engine coil just heats the calorifier. The transfer from the engine heat to the CH system is done by the calorifier water acting as a big heat exchanger. My calorifier is 120L

[David Schweizer]

David. My system is sealed pressurised so. No header tank. The Mikuni does the rads and the calorifier. The engine coil just heats the calorifier. The transfer from the engine heat to the CH system is done by the calorifier water acting as a big heat exchanger. My calorifier is 120L

Ah, now I understand, but let me assure you it can still be done with a pressurized system, but you only use one coil. The system on our boat takes hot water from the engine to the calorifier coil, T connections in the supply take the pipework to the Ellis heatmaster gas boiler, with a second pair of T connections after the boiler, taking the water to the radiators. Just before it enters the forward raditor, there is a small pressurized header tank, again teed into the supply pipe, which absorbs expansion when the water get to the design pressure (4lbs in our case) the expansion tank is a standard automobile one with a standard vehicle pressure cap.

 

Whether such a system would work with a Mikuni rather than a boiler, in line I do not know, and small pipework could inhibit the flow, but it works on our boat and has done so for thirty years, several gate valves and a non return valve allows any part of the system to be closed down and not over pressurise the system.

Edited October 30, 2012 by David Schweizer

[bottle]

My system is as Biggles.

 

I have not tried running the CH pump and using the calorifier as a heat exchanger because I have found no need to do so.

[ditchcrawler]

It occurred to me a while back that my hot water in my calorifier made by the engine coil is insanely hot and that in the calorifier there is another coil from the CH. All that's needed is the CH pump running to use the water in the calorifier to transfer heat to the radiators when the engine is running.

 

So I rigged up a temporary power supply to the the CH pump independent of the CH control and run the engine to charge the batteries and low and behold the radiators got very, very warm. Not as hot as the water in the calorifier as the hot water from the tap was still insanely hot from the tap but there was defiantly significant heat being put into the boat CH from the engine.

 

 

That's what we do using a Johnson low voltage pump, I also fitted a thermostat to the tank to start the pump if the tank gets very hot. As well as the engine it is heated by the Dickinson cooker. I have a manual switch in parallel with the stat so can bring it on manually.

[Tacet]

Biggles radiators will never achieve the same temp as the hot water; the rate of transfer from the cylinder through the coil will be less than that which can be dissipated by the rads when hot, so the system will find a lower equilibrium. The solution is to fit a better heat exchanger - for example a plate exchanger (mine was about £30 on ebay) and plumb one side into the engine coolant. On a conventional layout, this is easy enough as all the relevant pipes can be found at the calorifier.

 

Upside is a warm boat when cruising (and whilst the solid fuel stove gets going), useful washing-drying capabilities and boost to engine cooling if required; all for zero running cost. Downside is uselessness in the early morning, potential to rob the hot water and possible overcooling of the engine - depending on take-off position with respect to thermostat(s).

[BlueStringPudding]

It occurred to me a while back that my hot water in my calorifier made by the engine coil is insanely hot and that in the calorifier there is another coil from the CH. All that's needed is the CH pump running to use the water in the calorifier to transfer heat to the radiators when the engine is running.

 

So I rigged up a temporary power supply to the the CH pump independent of the CH control and run the engine to charge the batteries and low and behold the radiators got very, very warm. Not as hot as the water in the calorifier as the hot water from the tap was still insanely hot from the tap but there was defiantly significant heat being put into the boat CH from the engine.

 

I assume given time the radiators would get as hot as the water but think the heat in the radiators is limited to the absorption capacity of the CH coil from the surrounding water.

 

However given that a few hours a day of cruising in winter could dump some significant free heat into a CH system, I think why have I never heard anyone doing this?

 

Am I missing something?

 

Oh and FYI my CH is by Mikuni not a back boiler not that I can see this would change the basic principle if the fire was out as the Mikuni is when the experiment was conducted.

 

Discuss?

 

Sounds ingenious to me, Biggy!

 

My system sounds like yours except I have a header tank (engine feeds calorifier hot water coil, Eber feeds calorifier coil and the second coil which feeds the radiators)

 

I'm trying to picture where the pump would go if I did something like that with my system? Being very much a layperson in these matters. Between the engine and the calorifier? Or between the calorifier and the rads? If the pump was switched off I assume the water would flow as it needed to but just not feed hot into the rads?

 

This "over cooling of the engine" malarkey sounds scary

Edited October 29, 2012 by BlueStringPudding

[Biggles]

Sounds ingenious to me, Biggy!

 

My system sounds like yours except I have a header tank (engine feeds calorififer hot water coil, Eber feeds calorifier coil and the second coil which feeds the radiators)

 

I'm trying to picture where the pump would go if I did something like that with my system? Being very much a layperson in these matters. Between the engine and the calorifier? Or between the calorifier and the rads? If the pump was switched off I assume the water would flow as it needed to but just not feed hot into the rads?

 

This "over cooling of the engine" malarkey sounds scary

 

Why not use the pump already in your CH system? Just feed it independently with your voltage. I am going to use a relay to disconnect it from the main control box on the Mikuni just in case it upsets the electrical box with some back feed.

[BlueStringPudding]

I have an eber that doesn't work. How do you make that pump?

 

Does that mean if I buy a cheap and cheerful eBay pump it can go in where the eber currently is in the system? The electrics are there as are the pipes...

Edited October 29, 2012 by BlueStringPudding

[BlueStringPudding]

So what sort of pump would be needed?

[Biggles]

I don't know what the pump arrangement is in the ebby, someone will be along shortly who does. But somewhere in the ebby or close by there will already be a pump. Before spending out on a pump which are not cheep I would see if the one in the ebby an be used. Also the pump in the ebby might be restrictive on the flow .. There is a name for non restrictive pumps.

Edited October 29, 2012 by Biggles

[BlueStringPudding]

As I would quite like to bludgeon the eber with the splitting maul, maybe I should see if the pump can be doctored and function as a standalone piece of kit, then.

 

And then bludgeon the rest of the eber

Edited October 29, 2012 by BlueStringPudding

[mickspangle]

This is an interesting thread. I hadn't realised heat exchangers were so cheap. Would I be right in thinking that I just connect it across the return to the engine from the calorifier and connect across the CH pipe run? I'm already able to run the CH pump independently (and tend to do this when cruising, using the calorifier as a kind of heat exchanger already). If the heat exchanger goes in between the calorifier outlet and the skin tank inlet is it likely to make much difference to engine temps?

 

Would any old heat exchanger with the right connections do? Am I likely to get radiator temps in the region of the engine coolant temp as a consequence? For 30-40 quid it sounds good to me.

[Biggles]

As I would quite like to bludgeon the eber with the splitting maul, maybe I should see if the pump can be doctored and function as a standalone piece of kit, then.

 

And then bludgeon the rest of the eber

 

Maybe he ebby is still viable. I'm sure someone would give it the once ove for you. There's plenty of people with them that know how to "manage" them. The pump should be easy to test, just disconnect it from the main power supply and put your own in with fusing to protect everything.

 

I am liking the idea of the heat exchanger too.

 

 

BSP I don't think there is any chance of over cooling the engine unless the thermostat is faulty.

[colin stone]

I have my engine calorifier connections supplying a Bowman tubular heat exchanger, which is installed in the "out/hot/supply" pipe from the boiler. Bowman £40 at boat jumble is is actually an oil heat exchanger. A boiler heat exchanger would probably do just as well.

 

www.luxe-motor-kei.co.uk/internal/page/image179.html

 

The CH pump switches on 15 mins after engine start - a delay on relay - so that the engine is up to temp. The result is piping hot water all round the boat to 2 calorifiers and 14 radiators. With a few hours run, the temp inside is a toasty 28C. System also works for engine cooling - had an airlock in the keel cooling system and used rads for engine cooling for a few days until I could fix issue. It was August, so very hot inside!

 

Written about system several times over the years!

[PaulJ]

As I would quite like to bludgeon the eber with the splitting maul, maybe I should see if the pump can be doctored and function as a standalone piece of kit, then.

 

And then bludgeon the rest of the eber

Can you put this on you tube if you do please :-D