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Flat-plate heat exchanger installation.


canute

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Hi boating folks,

I would like to install a Flat-plate heat exchanger, heated via my calorifiers (Surecal) engine coil return pipe (primary heat), to transfer heat (secondary heat) into the vessels central heating (C/H) system. My query is “can I utilise the pump (ie run the pump only) of my Eberspacher Hydronic 10 (2009 model) to circulate the C/H system?” 
There have been various discussion in past issues of boating magazines, questioning why boat builders don’t install this sort of system, which could heat a boats (Narrowboats) accommodation in winter using residual heat from the engine that would otherwise be wasted through the exhaust system, obviously it goes without saying that the pump would only be switched on when cruising in colder weather, heat the calorifier as normal and essential heating the radiators for free! Well almost for free!

Any help will be appreciated, incidentally on pages 17 & 18 of the installation manual there is an additional relay “(2.5.18) Switch-over relay for water circulation system, to be fitted by customer if required” could this be what is required, unfortunately no other information is provided?

regards,

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Can’t help with the question about the Eber, except to say that if you circulate hot water through the Eber’s own heat exchanger, some heat may be lost to the air. And if the Eber is on maybe it will circulate your expensive diesel fired hot water into the engine coolant. Probably not very much, but it isn’t an ideal solution.
I have such a system (Mikuni heater) but I bought a small cheap 12v pump from Solarproject along with a couple of low opening pressure 1-way valves, so if the Mikuni is on it doesn’t circulate through the Plate heat exchanger, and if the plate heat exchanger pump is on it doesn’t circulate through the Mikuni.

 

Finally I will say that IMO it is better to use water from the skin tank loop to heat the plate exchanger, not the calorifier loop. That way there is no interruption in the operation of the calorifier heating engine loop, and no risk of over cooling the engine (because the skin tank loop is controlled by the thermostat, the calorifier loop isn’t.

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Nicknorman,

Many thanks for replying to my post, perhaps I should have elaborated, we rarely use the diesel heating (Eberspacher) on our boat, even in winter, the boats main source of heating is via a solid fuel stove.

My plan was to try and limit burning solid fuel on days that we were cruising and/or running our engine (Beta 43) to charge batteries by using wasted heat from the engine to space-heat the cabin. 
I may stand corrected, but I was of the understanding that, until the engines thermostat opens (ie engine at running temperature) water does not circulate through the skin-tank, and that at the point the thermostat does open, l am metaphorical speaking, dumping my hard earned £££‘s into the canal via the skin-tank and onto towpath via the exhaust, although I didn’t think about any heat-losses into the Eberspacher this will be negligible given that currently, all residual heat is dissipate overboard anyway.

I understand that the opening of the engines thermostat will be delayed initially if the flat-plate heat exchanger is transferring heat into the C/H loop, however I should have made it clear, that my intention is to switch on the C/H pump at the point the temperature gauge reached its nominal engine running temperature.

Is running an engine cooler detrimental?

Also to clarify the Eberspacher Does Not have an engine heating loop as in a ‘truck’ installation, it is stand-alone C/H only (space heating radiators and a second calorifier loop).

Further comments most welcome.

Regards,

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Fair enough regarding the Eber.

 

Your point about the skin tank loop is correct, hence my advice to add the exchanger in that loop. It will start working when the engine is up to temperature and not work if the engine is running below optimum temperature.

 

Ok it would be possible to manage all that manually as you propose, but why not just use the thermostat to do the same job? With our installation I find that whilst the rads get quite hot when cruising, when mostly idling eg on a lock flight, the heat transfer is much less (rads are cooler) because much less heat is being sent to the skin tank. The converse would be to try to maintain the heat transfer to the rads at the expense of the engine dipping below its optimal temperature.

 

And to answer your last question, yes it is bad for an engine to run for long periods below optimum temperature. It results in cylinder wall temperature below optimum and thus a propensity for deposits to form on the cylinder walls which ultimately cause bore glazing and a smoky exhaust.

 

My final thought is dont under spec the plate exchanger. The heat transfer of Plate exchangers are often glibly quoted in terms of kw. But the kw transferred depends on the temperature difference between the two sides, and this figure is often not mentioned. It seems to be based on a Combi boiler DHW concept where one side is at 5C (incoming cold water) and the other at 70C or whatever. Once the temperature difference decreases (hopefully the rads are warmer than 5C!) the heat transfer proportionally decreases.

 

I got a nominal 24kw exchanger with the hope of transferring 4kw to keep the rads hot at say 60C, but in reality it isn’t really big enough and I wish I’d got bigger. One has to remember that the Beta 43 thermostat is only 72C or so, and so the temperature difference (which drives heat transfer) would only be 12C for 60C radiators.

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1 hour ago, canute said:

 Snip

 

I understand that the opening of the engines thermostat will be delayed initially if the flat-plate heat exchanger is transferring heat into the C/H loop, however I should have made it clear, that my intention is to switch on the C/H pump at the point the temperature gauge reached its nominal engine running temperature.

Is running an engine cooler detrimental?

 

 

Some (a few) engines have a thermostat on the calorifier loop but not that many. I can only think of Barrus Shire.

 

I think the answer to the cool running temperature is "it all depends". Many industrial and automotive engines run with an 82 or 88 degree thermostat in their native form, but when marinised may run with stats some 20 degrees cooler with no apparent ill effects.

 

The problem with using a non-thermostaticly controlled supply from the engine for central heating is that the heat absorbed inside the boat could well be enough to run a lot cooler than the above, and then condensation might cause problems. However, the calorifier coil has the potential to short out the skin tank, but the resistance to flow ensures that it does not. I suspect putting the exchanger after the calorifier would not reduce the running temperature to an extent that could cause problems, but it's very much try it and see. Then be prepared to do it Nick's way if needed.

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Thanks gentleman,

 

Good point about size of exchanger, I was also assuming that the common 24kw would be more than sufficient, if lagged.

 

My inspiration for considering the reduction of wasted engine heat came from an article some years ago, published in one of the waterways magazines, whilst I can’t remember the article verbatim I’m sure that the exchanger was an Alde model installed in the calorifier return, thus ensuring that no heat was dissipate through the skin tank, because until the closed calorifier loop had done it’s work heating up the DHW and the newly installed exchanger, the thermostat would remain closed. My assumption was, that transferring heat from this loop would just prolong the opening of the engines thermostat, thus avoiding any heat losses through the skin tank until such time that the calorifier and heating were running at a temperature higher than the thermostat opening temperature.

 

I take your point about engine running temperature, so thank you for that.

 

The information so far is very informative “you can never have to much information”.

 

If there’s anyone who can help me with the switching of an Eberspacher, water circulation pump, without the unit calling for heat, I will be most grateful.

regards,

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6 minutes ago, canute said:

Thanks gentleman,

 

Good point about size of exchanger, I was also assuming that the common 24kw would be more than sufficient, if lagged.

 

My inspiration for considering the reduction of wasted engine heat came from an article some years ago, published in one of the waterways magazines, whilst I can’t remember the article verbatim I’m sure that the exchanger was an Alde model installed in the calorifier return, thus ensuring that no heat was dissipate through the skin tank, because until the closed calorifier loop had done it’s work heating up the DHW and the newly installed exchanger, the thermostat would remain closed. My assumption was, that transferring heat from this loop would just prolong the opening of the engines thermostat, thus avoiding any heat losses through the skin tank until such time that the calorifier and heating were running at a temperature higher than the thermostat opening temperature.

 

I take your point about engine running temperature, so thank you for that.

 

The information so far is very informative “you can never have to much information”.

 

If there’s anyone who can help me with the switching of an Eberspacher, water circulation pump, without the unit calling for heat, I will be most grateful.

regards,

Just as a general point, since I installed the “free heat” system it gives me a warm feeling every time we use it. Both literally and metaphorically! So I would definitely recommend it. Whilst it isn’t a substitute for a stove in winter, it is great for those intermediate days when it’s just a bit chilly, wet and miserable etc but not justifying lighting the stove.
 

As I said my only regret is not fitting a bigger exchanger because whilst the radiators get reasonably hot, I wish they got hotter!

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Once the thermostat opens, most of the coolant passes (or should pass) via the skin tank, rather than the calorifier, so putting the heat exchanger in the skin tank loop should result in the maximum heat extraction from the system, and hence the most effective heating of the boat.

 

Some boats have a single bathroom radiator or towel rail plumbed into the calorifier loop, after the calorifier, to provide a level of background heating to dry towels whenever the boat is under way. But then you can't turn this off on hot days!

Edited by David Mack
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9 minutes ago, David Mack said:

Once the thermostat opens, most of the coolant passes (or should pass) via the skin tank, rather than the calorifier, so putting the heat exchanger in the skin tank loop should result in the maximum heat extraction from the system, and hence the most effective heating of the boat.

 

Exactly!

 

Just to add that one concern I had was that the exchanger might restrict the flow and thus impede engine cooling under heavy load. So I incorporated a “short circuit” in 28mm pipe to bypass the exchanger, with a gate valve - normally closed to divert the coolant via the exchanger, or could be opened for maximum coolant flow. But I’ve never needed to open it, including prolonged high revs on the tidal trent.

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Just for balance, I have the same system installed in the calorifier return, essentially because it was a neater installation given my engine bay layout and I was worried about restricting the main cooling flow. If i leave the rad valves fully open then yes it over cools the engine, but that also cooks the cabin. To keep the temperature down, after balancing the rads, I then wound them down more, to reduce the flow to keeps the rads at a sensible continuous background temp. Even in mid winter sat at idle on lock landings it doesn't over cool a beta38 - once the engine and calorifier are up to temp. However Nick's solution is better and more automated.

 

I couldn't boat with our it, especially in winter, keeps everything so dry.

 

You need to think carefully how you control your eber heated calorifier loop, otherwise you are cooling you calorifier, use valves like Nick says with two pumps and keep the 2nd calorifier loop in the eber zone. Draw it out. Alternativly Webastos have a relay that operates at +40 degrees that can be used to open a 12v valve, don't know if ebers have the same.

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Thanks Cas446,

Putting the magazine article aside, the ease of installation is also a significant factor, cutting the exchanger into calorifier return loop and the C/H flow is all at hand and simple to undertake, not least because it's also 16mm and 22mm diameter pipe respectively, as opposed to 28mm from the skin tank, which would also be difficult to route given other services and restrictions (modern engine in a trad stern). 

 

If there is the ability to run the Eberspacher pump 'stand alone' then all this should entail is a switch to start and stop the flow, this could even be controlled via the engine ignition circuit, with an isolator for the summer months. Configured like this there is no need to install any IV's, NRV's or bypasses, in the unlikely event of the exchanger becoming blocked the engine thermostat would open sooner and sooner, water heating would take longer and longer, alerting one to the occurrence. Of course in the summer months the exchanger will be sitting there HOT, but without circulation of the C/H loop, lagged this should not represent any significant heat loss.

 

Being a trad stern and having the hatch 'open' when at the helm, would I presume prevent being cooked by the heating system, (most of us are pretty well toasted anyway with our solid fuel stoves!) in any event simply switching off the pump or opening a side hatch would soon remedy the situation.

 

I have emailed the pump question to Eberspachers technical team, but they are yet to respond!

 

After sleeping on it, the skin-tank approach I mean, I can't help thinking that the flat-plate heat exchanger will be competing for heat, against the vastly superior size of the skin tank heat exchanger, assuming that once the engine thermostat opens at it's (hottest) set point, the temperature would then have to drop XX number of degrees before closing at the (coolest) set point, however before reaching the closing temperature and now circulating the engine cooling water at the lowest running temperature, all the time losing heat through surfaces other than the flat-plate exchanger which is where it's required?

 

I'm no thermodynamicist, but my simple installation only involves an Exchanger and a Switch (assuming I can run the Eberspacher pump 'stand alone') that is.

 

Always open to debate and others views, fore or against.

 

Regards,

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1 hour ago, canute said:

… the ease of installation is also a significant factor, cutting the exchanger into calorifier return loop and the C/H flow is all at hand and simple to undertake, not least because it's also 16mm and 22mm diameter pipe respectively, as opposed to 28mm from the skin tank, which would also be difficult to route given other services and restrictions (modern engine in a trad stern).

 

 

After sleeping on it, the skin-tank approach I mean, I can't help thinking that the flat-plate heat exchanger will be competing for heat, against the vastly superior size of the skin tank heat exchanger, assuming that once the engine thermostat opens at it's (hottest) set point, the temperature would then have to drop XX number of degrees before closing at the (coolest) set point, however before reaching the closing temperature and now circulating the engine cooling water at the lowest running temperature, all the time losing heat through surfaces other than the flat-plate exchanger which is where it's required?

 

Yes it is certainly physically easier to insert the exchanger in the calorifier loop. But we too have a Beta 43 at the back of a trad stern and it wasn’t that hard! I seem to recall I removed the main run of 28mm pipe from the U bend near the engine (the outlet points to the stern, but the skin tank is a bit nearer the bow) and at a compression fitting where the pipe turned up to the top of the tank. I then cut out the appropriate chunk to fit (in my case ) the T fittings for the (actually unnecessary) bypass circuit and the reduction to 22mm for the exchanger. Then reinstalled it all.

….

 

no the second bit is a misconception. They are in series and the exchanger comes before the skin tank so the net result is that the skin tank inlet is a bit cooler than it might be. So what! The thermostat isn’t an on-off switch and it will settle at an appropriate amount of opening such that flow though the combination of the plate exchanger and skin tank dumps sufficient heat to keep the engine at the right temperature.

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20 hours ago, David Mack said:

Some boats have a single bathroom radiator or towel rail plumbed into the calorifier loop, after the calorifier, to provide a level of background heating to dry towels whenever the boat is under way. But then you can't turn this off on hot days!

When I added my bathroom radiator after the calorifier I fitted a bypass pipe and valve from the radiator inlet to the outlet so on those odd infrequent 25degC summer days I could open the bypass around the radiator and close the radiator valve.

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Thanks again, at least It would appear that there are two options I can try.
 

I won’t name the boat builder for obvious reasons but my boat, specifically the engine bay is absolutely jam packed, to the extent that the engine starter battery sits on the baseplate between the engine and the skin tank, goodness only knows how I’ll change it when the time arises.

 

Either way I will probably opt for installing in the calorifier return to begin with (easiest option) and if that doesn’t work it will be quite simple to either re-join or replace the cut hose and have another go with the more involved skin tank route.

 

I can’t thank everyone enough for the comments, it’s only my second post. The first post was either to technical or fell on deaf ears.

 

If any one can solve the Eberspacher enquiry I will be most appreciative.

 

Regards,

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On 13/07/2021 at 00:28, David Mack said:

Some boats have a single bathroom radiator or towel rail plumbed into the calorifier loop, after the calorifier, to provide a level of background heating to dry towels whenever the boat is under way. But then you can't turn this off on hot days!

I have added a second towel rail in my bathroom supplied in this way David. I fitted it in parallel with the calorifier return line, adding 2 full bore valves from tees so I could isolate it leaving the circuit "as was" and a full bore bypass valve between the tees so I could force some flow through the towel rad. As it turns out, it works perfectly with all 3 valves wide open!  I could easily turn it off in summer, but with the porthole open I've never felt the need. Works a treat. :)

 

It would be good to also be able to dump waste engine heat through the Eberspacher rads when cruising though.

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  • 4 weeks later...

Well the flat plate heat exchanger is now installed (into the calorifier return loop), I must say that I was pretty amazed at how hot the radiators get, the exchanger is rated at 45Kw with 3/4" ports. Unfortunately due to space limitations I was unable to install a 1" three port valve purchased specifically to enable full-bore flow through, or to bypass the exchanger on the C/H loop, however given that the exchanger ports are 3/4" I'll assume that the space between plates must at least equal this area. The circulation pump can now be controlled while at the helm, giving the pilot the ability to operate if or when the engine temperature drops off to much.

I still can't believe that the radiators get just as piping hot as they do when the Eberspacher is suppling the heat, at best I was only expecting very warm, exceeding all my expectations, I'll just need to keep an eye on that engine running temperature gauge to see if there's any issue!

 

Thanks for everyone's input.

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10 hours ago, canute said:

Well the flat plate heat exchanger is now installed (into the calorifier return loop), I must say that I was pretty amazed at how hot the radiators get, the exchanger is rated at 45Kw with 3/4" ports. Unfortunately due to space limitations I was unable to install a 1" three port valve purchased specifically to enable full-bore flow through, or to bypass the exchanger on the C/H loop, however given that the exchanger ports are 3/4" I'll assume that the space between plates must at least equal this area. The circulation pump can now be controlled while at the helm, giving the pilot the ability to operate if or when the engine temperature drops off to much.

I still can't believe that the radiators get just as piping hot as they do when the Eberspacher is suppling the heat, at best I was only expecting very warm, exceeding all my expectations, I'll just need to keep an eye on that engine running temperature gauge to see if there's any issue!

 

Thanks for everyone's input.

Jolly good. I definitely wish I’d gone for a bigger exchanger, ours was 24kw and the radiators get more than warm, but less than piping hot!

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Nicknorman

A special thanks to you, because I upped the exchanger size based on your input. Having thought about it though, I suppose you could spec even a greater output, my logic being that the exchange will naturally top-out when it's heat transfer equals that of the input (nearly equals that of the input, you don't get more out than you put in) I guess the output (radiator temperature) must be just below that of the engine temperature before the thermostat operates.

 

These exchanges are pretty good pieces of kit the whole thing can't be much bigger than a small loaf of bread, even including the solid insulation jacket. I'd recommend that every continuous or winter cruiser install one, free heat, it's a no brainer.

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  • 2 months later...

Hi Motters79,

 

I purchased a "Nordic Tech Ba 12-20 3/4'' 45kW  WITH insulation" from eBay £86.99.

 

Very impressed with the extremely small size, the amount of heat transfer and the quality of build.

 

I do have one piece of advise, because these are parallel threads; make sure you obtain 3/4" BSP compatible irons, I hunted high and low for 3/4" BSP flat seat irons with fibre washer to 22mm Compression, WITHOUT luck, (standard 3/4"BSP irons or 3/4" tap connectors do not fit), in the end I used three copper compression washers dabbed in Loctite thread sealant fluid, within a standard 3/4" BSP to 22mm compression iron.

 

If on the other hand you can get away with using 3/4"BSP to Hose Barb, these are readily available from "Advanced Fluid Solutions" with the requisite flat seating washer.

 

Remember what ever you use upstream air vent/s will be required to purge any air from the system.

 

I have attached a pdf of the panel that I had made, this was installed by the helm.

 

If you require any further information do not hesitate in asking.

 

Probable the best thing that I've done to the boat. Should have done it years ago.

 

Boat heating panel.pdf

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Thanks Cannute, thats very helpful! Id been looking at those on ebay and wondered if it was the same type that you used. Screw fix sell a 3/4 inch to 15mm compression tap connector. Id be surprised if that didnt do it as it has a flat washer in the tap connector part. Did you try one of these?

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A 3/4” Tap connector from anywhere will NOT fit, believe me I’m an x pipe installation supervisor, as said before after many trip to multiple outlets, DIY and trade I could not find a suitable flat seat adapter, the flat seat of the heat exchanger is a larger flat than a tap connector.

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8 minutes ago, canute said:

A 3/4” Tap connector from anywhere will NOT fit, believe me I’m an x pipe installation supervisor, as said before after many trip to multiple outlets, DIY and trade I could not find a suitable flat seat adapter, the flat seat of the heat exchanger is a larger flat than a tap connector.

 

So where did you get the connectors you needed?

 

We're looking at doing this on Mintball this winter.

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26 minutes ago, canute said:

A 3/4” Tap connector from anywhere will NOT fit, believe me I’m an x pipe installation supervisor, as said before after many trip to multiple outlets, DIY and trade I could not find a suitable flat seat adapter, the flat seat of the heat exchanger is a larger flat than a tap connector.

If the 3/4" bsp tap connector nut will go over the flat seat and onto the threaded stub then I don't understand the problem. On most tap connectors the OD of the fibre washer only just fits within the nut threads so must end up bearing on the end of the male threaded stub.

Edited by David Mack
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27 minutes ago, David Mack said:

If the 3/4" bsp tap connector nut will go over the flat seat and onto the threaded stub then I don't understand the problem. On most tap connectors the OD of the fibre washer only just fits within the nut threads so must end up bearing on the end of the male threaded stub.

Or put 2 washers on to clear the raised inner lip on the tap connector. 

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