Plate heat exchanger to heat radiators from engine.

[jonesthenuke]

11 hours ago, nicknorman said:

Useful information. However I think your interpretation is wrong. It is all about temperature difference and in your cited example, the incoming water is at 10C. Big temperature difference compared to primary side, which equals lots of heat transferred! Whereas in a radiator system the returning radiator water should be about 10C less than the outgoing water, ie if the primary side is 70/50 the radiator side would be 60/50 and at that (40C greater return temperature) the heat transfer would be MUCH less so that in reality you would get nowhere near 60C. And really 60C is not particularly hot for a radiator system. The max is 80C and that is what diesel heaters generally give out (well, that is what our Mikuni does anyway). With an engine only at 75C you obviously can’t get 80C but the closer the better, and that is achieved by as big a HE as is reasonably feasible (on grounds of size and cost).

There are additional factors. The proposed 25kw heat exchanger has 12 plates not 10, so some gain there.

 

More to the point, there is no great benefit in a much bigger unit as the available heat source is not large. A narrowboat engine at normal cruising speed on a canal will not reject much heat. If it is assumed that consumption is 1 litre an hour then this equates to 45MJ per hour or 12.5 kW. If say the heat rejected to the cooling system is 30% then the available heating power is only circa 4 kW. Thus this is not going to heat several radiators to full output even if all the engine coolant flow passes through the heat exchanger. It is likely that the efficiency is  lower at the low load applied when cruising,  but I doubt that the more than 50% (6kW) could be extracted from the coolant.

[nicknorman]

7 hours ago, jonesthenuke said:

There are additional factors. The proposed 25kw heat exchanger has 12 plates not 10, so some gain there.

 

More to the point, there is no great benefit in a much bigger unit as the available heat source is not large. A narrowboat engine at normal cruising speed on a canal will not reject much heat. If it is assumed that consumption is 1 litre an hour then this equates to 45MJ per hour or 12.5 kW. If say the heat rejected to the cooling system is 30% then the available heating power is only circa 4 kW. Thus this is not going to heat several radiators to full output even if all the engine coolant flow passes through the heat exchanger. It is likely that the efficiency is  lower at the low load applied when cruising,  but I doubt that the more than 50% (6kW) could be extracted from the coolant.

Depends on the engine of course. Our Beta 43 uses about 1.5 litres /hr at narrow canal speeds (1300rpm) so considerably more than 6kw will be lost to heat. It’s certainly true for us that when idling in locks etc the radiators don’t get beyond “warm”, but they get reasonably hot but no more than about 45 to 50c when cruising. Once again I’ll say that there is no “right answer” but the larger the HE, the less temperature difference there will be between coolant and rads. With diminishing returns of course. So bearing in mind the cost and hassle of the whole thing, and the relatively small difference on cost of the larger HE, that is what I’d go for if I were doing it again. If you wanted to fit a 25kw HE you wouldn’t be wrong, but if I fitted a 50kw HE my radiators and hence my boat would be warmer.

 

[JoshS]

Thanks for all the comments with useful tips and advice so far! The heat exchanger has been delivered to my parents and I'm going to pick it up this week, and am starting to accumulate the fittings required as well. 

 

Since I'm replacing the hoses between the engine and skin tank, I thought I would also replace the ones that go to calorifier as well. These say 15.8mm on them and one side has a rather dodgy looking homemade copper tee which connects THIS  header tank, which I've recent been told is a central heating header and therefore not appropriate! 

 

I was told by the previous owner that this header was just for the calorifier engine coil and that he'd never needed to top it up. We recently had the calorifier replaced and the engineer pointed out that there was a closed ball valve under the tank (explaining why the levels never changed). Since opening this the tank has effectively become the engine header tank too - I can no longer open the one on the engine with the pressure cap without all the coolant coming out of the tank! 

 

This is fine, but I guess the appropriate solution is to replace the crappy grey box tank with something which is suitable for use as an engine header. I'm struggling to find something appropriate though, so does anyone have any recommendations? 

[Tracy D'arth]

20 hours ago, JoshS said:

Thanks for all the comments with useful tips and advice so far! The heat exchanger has been delivered to my parents and I'm going to pick it up this week, and am starting to accumulate the fittings required as well. 

 

Since I'm replacing the hoses between the engine and skin tank, I thought I would also replace the ones that go to calorifier as well. These say 15.8mm on them and one side has a rather dodgy looking homemade copper tee which connects THIS  header tank, which I've recent been told is a central heating header and therefore not appropriate! 

 

I was told by the previous owner that this header was just for the calorifier engine coil and that he'd never needed to top it up. We recently had the calorifier replaced and the engineer pointed out that there was a closed ball valve under the tank (explaining why the levels never changed). Since opening this the tank has effectively become the engine header tank too - I can no longer open the one on the engine with the pressure cap without all the coolant coming out of the tank! 

 

This is fine, but I guess the appropriate solution is to replace the crappy grey box tank with something which is suitable for use as an engine header. I'm struggling to find something appropriate though, so does anyone have any recommendations? 

I would ditch the tank completely, the engine obviously works without it if it has been closed off for so long. I fail to see any purpose in it.

[JoshS]

1 minute ago, Tracy D'arth said:

I would ditch the tank completely, the engine obviously works without it if it has been closed off for so long. I fail to see any purpose in it.

It seems strange to me that the calorifier coil ever worked though, since it is higher up than the engine. Surely all the coolant in the coil would just drain out into the header tank on the engine itself? 

[Tony Brooks]

4 minutes ago, JoshS said:

It seems strange to me that the calorifier coil ever worked though, since it is higher up than the engine. Surely all the coolant in the coil would just drain out into the header tank on the engine itself? 

 

Not if the header tank on the engine was fitted with a pressure cap. My guess is that the plastic tank was either a device to aid bleeding the calorifier engine circuit or a misunderstanding by whoever fitted it in the first place.

[JoshS]

2 minutes ago, Tony Brooks said:

 

Not if the header tank on the engine was fitted with a pressure cap. My guess is that the plastic tank was either a device to aid bleeding the calorifier engine circuit or a misunderstanding by whoever fitted it in the first place.

It does have a pressure cap. So if I was to remove the tank from the calorifier circuit when I replace the hoses, the calorifier coil will get filled by the water pump on the engine when it runs? Or will I have to somehow prime that circuit when I'm putting the hoses back on? 

[Tracy D'arth]

31 minutes ago, JoshS said:

It does have a pressure cap. So if I was to remove the tank from the calorifier circuit when I replace the hoses, the calorifier coil will get filled by the water pump on the engine when it runs? Or will I have to somehow prime that circuit when I'm putting the hoses back on? 

Once it is vented of air it will stay full as long as the engine is up to level, there will be nowhere for air to get in to let water drain out.

[Tony Brooks]

29 minutes ago, JoshS said:

It does have a pressure cap. So if I was to remove the tank from the calorifier circuit when I replace the hoses, the calorifier coil will get filled by the water pump on the engine when it runs? Or will I have to somehow prime that circuit when I'm putting the hoses back on? 

 

Assuming a normal centrifugal automotive water pump. That is the $65,000 question. It may or it may not, but it is easy enough to bleed if it does not, as long as you have assistance.

 

On a cold engine unless yours has a calorifier thermostat:

 

Fill watering can with some antifreeze mixture.

 

Loosen hose clip and free, but do not take off, the return hose where it joins the engine cooling circuit - usually in the return to the water pump pipe/hose.

 

Remove filler cap

 

Set engine to around 1200 rpm (a bit faster than a fast idle)

 

Get helper ready to top up the filler as required

 

Pull said hose off the engine and very quickly put your thumb over the hole in the engine side and watch the coolant issuing form the hose. After you see/hear a section of air leaving the hose put the hose back on and tighten the clip.

 

Top up as required and normally the job is done.

 

It takes longer to write than do,

 

 

 

 

[ditchcrawler]

3 hours ago, Tracy D'arth said:

I would ditch the tank completely, the engine obviously works without it if it has been closed off for so long. I fail to see any purpose in it.

Maybe its handy for refilling to get the calorifier loop air free.

 

Edit I see its already been done. 

On my engine I fill the coolant system full, start the engine and as it warms up open an air blead at the highest point, the coolant expanding pushes the air our.I then just close the blead point.

 

Edited December 28, 2022 by ditchcrawler

[JoshS]

17 minutes ago, ditchcrawler said:

Maybe its handy for refilling to get the calorifier loop air free.

 

Edit I see its already been done. 

On my engine I fill the coolant system full, start the engine and as it warms up open an air blead at the highest point, the coolant expanding pushes the air our.I then just close the blead point.

 

That sounds like a nice idea, I might look into that! 

[JoshS]

On 14/12/2022 at 22:31, nicknorman said:

You just have to be a bit careful  - bog standard plumbing non-return valves have a very high opening pressure such that a circulation pump won’t open it. Hence the specialised low opening pressure ones I got. Or maybe look into flap valves (sometimes called swing check valves) which also have low opening pressure. Flap/swing valves have to be mounted in the correct orientation I think.

Still collecting parts for this project! Just wanted to check (valve hur hur) that this was the right sort of valve I needed to be low pressure enough to not offend the eberspacher, whilst still preventing the extra central heating pump pushing the hot water back that way? 

 

https://www.ebay.co.uk/itm/294715298693?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=gHiU7mRwSvG&sssrc=2349624&ssuid=0DnBHlu5Si-&var=&widget_ver=artemis&media=COPY

 

[Tony Brooks]

3 minutes ago, JoshS said:

Still collecting parts for this project! Just wanted to check (valve hur hur) that this was the right sort of valve I needed to be low pressure enough to not offend the eberspacher, whilst still preventing the extra central heating pump pushing the hot water back that way? 

 

https://www.ebay.co.uk/itm/294715298693?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=gHiU7mRwSvG&sssrc=2349624&ssuid=0DnBHlu5Si-&var=&widget_ver=artemis&media=COPY

 

 

If you are worried about low pressure I would use a flap valve like this https://www.bes.co.uk/water-swing-check-valve-brass-3-8-bsp-7518/

 

It will needs adapters to fit it to pipe work.  If anyone has successfully used a sprung valve then that the one in your link should be OK.

[jonesthenuke]

I would not use that valve it's a spring loaded one with plastic

Internals(probably) look for a swing check valve, with a flap. I doubt you will find one with compression connections, they are usually screwed ends. Try BES ltd

[JoshS]

2 minutes ago, Tony Brooks said:

 

If you are worried about low pressure I would use a flap valve like this https://www.bes.co.uk/water-swing-check-valve-brass-3-8-bsp-7518/

 

It will needs adapters to fit it to pipe work.  If anyone has successfully used a sprung valve then that the one in your link should be OK.

2 minutes ago, jonesthenuke said:

I would not use that valve it's a spring loaded one with plastic

Internals(probably) look for a swing check valve, with a flap. I doubt you will find one with compression connections, they are usually screwed ends. Try BES ltd

Cheers both! Will look for a swing check valve and some bits to connect it to 22mm push fit then 😬

[Tony Brooks]

Just now, JoshS said:

Cheers both! Will look for a swing check valve and some bits to connect it to 22mm push fit then 😬

 

I think I saw a 22mm version when looking for the link, the bigger the more expensive.

[JoshS]

DN20 Female Thread Brass Non-Return Swing Check Valve 232PSI Prevent Water Backflow 1Pc https://amzn.eu/d/cn2nxzo

 

...and this...

 

UKDD® 22mm Compression by 3/4" BSP Brass Male Iron Coupler (Pair), 22mm x 3/4" Straight Adaptors https://amzn.eu/d/fNeGTZo

 

...might do the job? 

[Tony Brooks]

4 minutes ago, JoshS said:

DN20 Female Thread Brass Non-Return Swing Check Valve 232PSI Prevent Water Backflow 1Pc https://amzn.eu/d/cn2nxzo

 

...and this...

 

UKDD® 22mm Compression by 3/4" BSP Brass Male Iron Coupler (Pair), 22mm x 3/4" Straight Adaptors https://amzn.eu/d/fNeGTZo

 

...might do the job? 

 

Yes.

[JoshS]

Great cheers! 

[Tony Brooks]

Just make sure you mount it so the arrow on the casting points the right way and get it horizontal and the right way up, big hexagon at the top.

[JoshS]

2 minutes ago, Tony Brooks said:

Just make sure you mount it so the arrow on the casting points the right way and get it horizontal and the right way up, big hexagon at the top.

Good knowledge, cheers! 

 

Think I'll be ready to put this all together next weekend, so I'll post back with how it turns out! When I looked into the price of a heat exchanger I thought it was going to be a cheap project, but now here I am having spent 4x that with a bag of parts I can barely lift! Still, it's worth doing these things properly, just hoping I get even a little bit of heat to the radiators from it now! 😂

[JoshS]

On 15/01/2023 at 19:50, Tony Brooks said:

Just make sure you mount it so the arrow on the casting points the right way and get it horizontal and the right way up, big hexagon at the top.

Another question sorry. The brass compression fittings have come with copper rings which I believe are called olives. Since I'm using plastic barrier pipe (with inserts of course!), should I still use the olives too? They seem to fit over the plastic pipe ok.

[Tony Brooks]

42 minutes ago, JoshS said:

Another question sorry. The brass compression fittings have come with copper rings which I believe are called olives. Since I'm using plastic barrier pipe (with inserts of course!), should I still use the olives too? They seem to fit over the plastic pipe ok.

 

Yes, but for goodness’s sake fit metal inserts. The plastic ones you would use for push fit plastic pipe will tend to squash under the olive when hot. I would have thought you could get BSP male to push fit adaptors. (Assuming the common barrier plastic pipe.)

Edited January 18, 2023 by Tony Brooks

[ditchcrawler]

1 hour ago, JoshS said:

Another question sorry. The brass compression fittings have come with copper rings which I believe are called olives. Since I'm using plastic barrier pipe (with inserts of course!), should I still use the olives too? They seem to fit over the plastic pipe ok.

[nicknorman]

1 hour ago, JoshS said:

Another question sorry. The brass compression fittings have come with copper rings which I believe are called olives. Since I'm using plastic barrier pipe (with inserts of course!), should I still use the olives too? They seem to fit over the plastic pipe ok.

Yes, it is the olives that form the seal. Don’t overtighten though! Typically fittingly come with brass olives that are quite hard. Ideally get some copper olives (much softer) but it’s not critical.