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Hi There,

 

My eberspacher is playing up again and I would like to use the heat from the engine to heat the radiators and the calorifier instead and bin the eberspacher.

 

My current setup is

 

beta 38 engine - calorifier

immersion - calorifier

eberspacher - calorifier - radiators

 

I would like to use a heat exchanger and a simple pump I can switch on when I want to use the radiators. I don't want the radiators on all the time when the engine is running just a simple system where i can direct heat to them

 

Thanks

 

Mark

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Hi There,

 

My eberspacher is playing up again and I would like to use the heat from the engine to heat the radiators and the calorifier instead and bin the eberspacher.

 

My current setup is

 

beta 38 engine - calorifier

immersion - calorifier

eberspacher - calorifier - radiators

 

I would like to use a heat exchanger and a simple pump I can switch on when I want to use the radiators. I don't want the radiators on all the time when the engine is running just a simple system where i can direct heat to them

 

Thanks

 

Mark

 

Hi Mark

 

I am no heating expert but doubt very much if the engine would produce enough heat for such a task. I have one rad plumbed in to my engine cooling system which is great for a bit of heat at the back of the cabin but doubt anything like enough more useable heat could be extracted for your wishes.

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This question has been asked previously - If I remember correctly some 'expert' did all of the thermal calculations and determined that a calorifier full of hot water would heat 2 or 3 radiators for about 10 minutes - as the water cooled and circulated back into the calorifier, it would not be reheated, and after a few minutes it would circulating warm - cooler - cooler - cold water.

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I brought into use the heat exchanger on my Mitubishi (designed for use with a raw water indirect cooling system) a couple of years ago. See photo below (the grey and white pipes, and also the small pump, and the pipe going up to the header tank).

 

It feeds two rads in the cabin and generates a reasonable amount of heat - obviously only when the engine is running). It was quite an expensive project. I have a thing about not running the primary cooling circuit through radiators: if all that extra pipework springs a leak as you approach a large weir you could be in trouble. Hence the use (as you are proposing) of a heat exchanger.

 

So it can work, it makes the bathroom toasty (in the middle of the boat) but does not really heat the rear bedroom that effectively.

 

dscf3154.jpg

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It feeds two rads in the cabin and generates a reasonable amount of heat - obviously only when the engine is running). ......................

 

 

 

But as I read it, the OP states he wants it to work when the engine is NOT running.

 

That's the problem.

 

Presumably, like most of us, he wants the heating on in the evening when moored up and has 'settled down' for the night.

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I read it as heating the roads only when the engine is on, but it's not clear. If the OP expects to heatnthe rads from stored heat in the calorifier, forget it.

 

But if the desire is to run the rads only when the engine is running, then fine.

 

We have such a system, a plate heat exchanger on the skin tank loop (so there is no risk of over-cooling), and a small Solarproject pump. It works fairly well but you have to bear in mind that the heat transfer across the exchanger is proportional to the temperature difference and, since the thermostat on Betas ismnirmally only 70C you are starting out "not that hot" and so you can't expect the rads to be much over 60C even with a large heat exchanger. Normal rad temp is around 80C with an Eber so you will get less heat out of the system.

 

I perhaps undersized our exchanger and pump a bit and I thus find the radiators only get "hot", not "piping hot". It does depend a bit on the engine load, there's quite a bit less heat when idling / locking than when cruising. It is certainly great to get free heat but it is only enough to warm the boat spring and autumn, not enough to be the sole source of heat in mid winter (and of course it stops when the engine stops). It is useful to keep the bedroom warm when cruising with the back doors open (trad stern).

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But as I read it, the OP states he wants it to work when the engine is NOT running.

 

That's the problem.

 

Presumably, like most of us, he wants the heating on in the evening when moored up and has 'settled down' for the night.

 

 

Correct only when the engine is running...the stove is fine for the evening but would like to use the radiators some how since they are there!

Edited by markcuk2016
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This question has been asked previously - If I remember correctly some 'expert' did all of the thermal calculations and determined that a calorifier full of hot water would heat 2 or 3 radiators for about 10 minutes - as the water cooled and circulated back into the calorifier, it would not be reheated, and after a few minutes it would circulating warm - cooler - cooler - cold water.

I've never tried it, but if you only run the rad pump via the calorifer when the engine is running it will heat the rads.

The next question though is the amount of heat available from the engine. Looking at the power curve for your engine I conclude that -

If just idling to gently charge the batteries the engine is probably creating a couple of kilowatts of waste heat, say 25% of which is put into the calorifier, which would be say 500W. If your rads are sized for your diesel boiler, then they are probably needing about 4Kw of heat, which is going to be mainly from your hot water tank. Which is not what you want. To get enough heat from the engine to heat the rads without cooling the calorifier too much will require you to be cruising up river at about 2000rpm. This will burn about 2 litres per hour of fuel, so not a cheap form of heating.

 

The above is very much a guess and will be far from accurate, but does show it basically is not a good idea, which is what everybody else is telling you.

  • Greenie 1
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I've never tried it, but if you only run the rad pump via the calorifer when the engine is running it will heat the rads.

The next question though is the amount of heat available from the engine. Looking at the power curve for your engine I conclude that -

If just idling to gently charge the batteries the engine is probably creating a couple of kilowatts of waste heat, say 25% of which is put into the calorifier, which would be say 500W. If your rads are sized for your diesel boiler, then they are probably needing about 4Kw of heat, which is going to be mainly from your hot water tank. Which is not what you want. To get enough heat from the engine to heat the rads without cooling the calorifier too much will require you to be cruising up river at about 2000rpm. This will burn about 2 litres per hour of fuel, so not a cheap form of heating.

 

The above is very much a guess and will be far from accurate, but does show it basically is not a good idea, which is what everybody else is telling you.

Thanks for your help

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On my boat the calorifier is used as a crude heat exchanger, by the simple expediant of putting a small DC pump into the heating circuit.

 

It works moderately well, the radiators get warm, rather than hot, and saves the cost of a plate heat exchanger.

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I've never tried it, but if you only run the rad pump via the calorifer when the engine is running it will heat the rads.

The next question though is the amount of heat available from the engine. Looking at the power curve for your engine I conclude that -

If just idling to gently charge the batteries the engine is probably creating a couple of kilowatts of waste heat, say 25% of which is put into the calorifier, which would be say 500W. If your rads are sized for your diesel boiler, then they are probably needing about 4Kw of heat, which is going to be mainly from your hot water tank. Which is not what you want. To get enough heat from the engine to heat the rads without cooling the calorifier too much will require you to be cruising up river at about 2000rpm. This will burn about 2 litres per hour of fuel, so not a cheap form of heating.

 

The above is very much a guess and will be far from accurate, but does show it basically is not a good idea, which is what everybody else is telling you.

Have a Green Thingy,you say that you are making a guess but your post is informative and Exactly what the OP needs to be aware of

 

CT

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Will rethink this over the summer... as we are looking to fit a morso 1410 for next winter but may look at the back boiler option and loose a radiator in the lounge (we only have 3)

 

thanks all again

 

Morso is the way to go. I retro fitted a back boiler to one of my boats stoves also a morso and fitted three rads on the thermo syphon system and it worked well.

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I don't think using the calorifier as a heat exchanger is a good way to do it since it isn't a good way to transfer heat effectively. I doubt you'd get much more than 1kw out of it on a good day!

 

Plate heat exchangers are not expensive, the main criteria being to select one that you can connect to easily, rather than one purpose designed to plug into a boiler with O rings etc. Something like this should be OK and not extortionate:

 

http://www.ebay.co.uk/itm/Stainless-steel-plates-PLATE-HEAT-EXCHANGER-brazed-NORDIC-TEC-25-65kW-Ba-12-/252585246336?var=&hash=item3acf40fe80:m:muNjpp1TLp_kGszJDdjttaw

 

Note that whilst the kw rating seem large, they are specified at quite a large temperature differential and so you need a higher rated one than you think to transfer the heat with minimal temperature drop. Thus I'd go for the 45kw one (I originally went for a 24kw one but wish I'd gone bigger as not that much pricier nor physically bigger.)

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I don't think using the calorifier as a heat exchanger is a good way to do it since it isn't a good way to transfer heat effectively. I doubt you'd get much more than 1kw out of it on a good day!

Plate heat exchangers are not expensive, the main criteria being to select one that you can connect to easily, rather than one purpose designed to plug into a boiler with O rings etc. Something like this should be OK and not extortionate:

http://www.ebay.co.uk/itm/Stainless-steel-plates-PLATE-HEAT-EXCHANGER-brazed-NORDIC-TEC-25-65kW-Ba-12-/252585246336?var=&hash=item3acf40fe80:m:muNjpp1TLp_kGszJDdjttaw

Note that whilst the kw rating seem large, they are specified at quite a large temperature differential and so you need a higher rated one than you think to transfer the heat with minimal temperature drop. Thus I'd go for the 45kw one (I originally went for a 24kw one but wish I'd gone bigger as not that much pricier nor physically bigger.)

I agree that a PHE is a better solution, indeed I am surprised at the relative effectiveness of using the calorifier on my boat. Radiator temperatures are around 50°C with the engine and pump running, enough to keep the chill off but not to heat the boat.

 

Given the really low price of the PME in your link I might look into installing one.

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We did much the same as Nick with a plate heat exchanger (BSP fittings) and a 12v pump; it worked well. The eberspacher was retained in the circuit in our case. With a twin coil calorifier all the necessary pipework is in close proximity.

 

A towel radiator was also plumbed in parallel with the calrorifier (on the engine circuit) which was good too.

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Hi Mark

 

I am no heating expert but doubt very much if the engine would produce enough heat for such a task. I have one rad plumbed in to my engine cooling system which is great for a bit of heat at the back of the cabin but doubt anything like enough more useable heat could be extracted for your wishes.

Mine does. The hot water in the engine is 85c into the heat exchanger. This gets all 5 radiators and a big towel rail to 56c.

 

I would say that works. Makes the boat very toasty.

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Mine does. The hot water in the engine is 85c into the heat exchanger. This gets all 5 radiators and a big towel rail to 56c.

 

I would say that works. Makes the boat very toasty.

Thanks for this...exactly what i wanted to do....

 

If i put a temp gauge on the engine and once it hits the highest temp I could then manually turn on a pump to the radiators?

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It's very easy to automate. You need a 12v motorised valve (I have some of these over) a double pole double through relay and a heat switch to the temperature you need. I think mine are 55c all powered through the ignition switch so it closes when stop the engine. Simples

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Rather than the complexity of motorised valves, I used low pressure non-return valves from Solarproject. So if I turn on the Mikuni it powers the radiators but doesn't circulate through the heat exchanger, and if I run the engine and turn on the pump it circulates through the heat exchanger but not through the Mikuni. Ie it just works seamlessly without any human intervention other than turning on the circulating pump.

 

As I think I mentioned, my heat exchanger is in the skin tank loop ie after the thermostat, so there is no risk of over-cooling the engine.

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I took the 12v supply from the engine panel so there was no chance of leaving it on when the engine was not running. It circulates through the eberspacher which has a centrifugal pump offering little resistance.

 

The exchanger is supplied from the return from the calorifier - but no risk of overcooling (too extremes) as the engine has a twin thermostat set-up.

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