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Circulation Pump for Calorifier

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Hi all,

Back in July 2011, I posted a question regarding connecting the Calorifier to my Cumminns Mercruiser Diesel Engine (Isuzu 1.7 TD) which was originally connected to the 4.3L petrol lump that used to be in there.

Antares suggested, that it may need a ciculation pump inline with it.

Well, i have recently done this, but due to the way this has to be connected, the Calorifier connection is in parallel with the heat exchanger and therfore does not have a direct flow from the circulation pump that is fitted to the engine. So, it looks like it will need a pump. (Antares, well spotted)

There are quite a few to choose from and all have various flow rates and vary from around £26 for a cheap chinese import to well over £100 for a very good quality one.

I have been doing some digging on the net and have found something that might do the job very well.

Although i shall be speaking to the company, to see what they have to say about using it for this type of installation.

From what i have read on the net, this type of pump is a copy of the pump that is used in the higher performance versions of the Lotus elises and exiges as a coolant re circulation pump.

Lotus apparently used a Bosch PAA EWP pump, but the Davies Craig EBP pump operates at the same spec, apart from the fact that the Bosch is 20 L/pm & the Davies Craig is 13 L/pm.

At the end of the day, i only want to circulate the water / antifreeze mix through the coil in the tank and don't want to be doing this too quickly, so this may do the trick.

The could also be fitted on the return line, as the water temperature will lower there. (Although the spec says up to 120 deg C)

There is also a plus side to having a circulation pump in line, in that i could thermostatically control the pump, so that it doesn't circulate the water through the Calorifier until the engine has reached its normal working temperature, thus preventing a slow warm up of the engine from cold.

Just out of interest, has anybody else had to fit a pump configuration like this, as i have seen installations on the net that have to different marinised diesel engines and wondered what results people have had and what problems they have encountered.

Many thanks

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I’m not very happy even thinking about calorifiers at the moment as I’ve just had the devil’s own job drilling out and re taping a stubborn take off bung for one on a nearly new Beta, I put it off as long as I could but it worked out well in the end, however yours sounds like a plan Grant and I have seen such installations working to good effect, your point on the thermo switch is a good one, why not go one further and have it switch off when the calorifier reaches temperature thus extending the pump life. You are right to steer clear of the cheap imports, I have replaced too much of that kind of stuff to remember, false economy and whilst in this case the component is not mission critical it would still be a pain if it failed, most circulation pumps are rated for constant running and the materials used and tolerances in some (not all) Far Eastern products are not so good. If you can find something with a brushless motor that would be the best, that said even some of the real cheapo ones have brushless motors, just not very good ones.

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It will be interesting to see what gets the best results. I thought we might need a pump after the new calofifier was fitted as it is paralell with the engine. The yard didn't fit one so maybe it does work okay but to date, we have only used the immersion to heat water.

Might well need to go down the same route as you Grant :wave

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I'm glad that it worked out in the end after you had to drill & tap yours David.

Jim, it would be interesting to know how yours performs when the engine is heating your domestic water, instead of 240vac.

I will post the answer to the result that i get once it is completed. Initially, i will just connect a pump via a switch & a relay to test the performance of it.

Once this is successful, i will look into controlling the pump automatically with a thermostat & relay.

Thanks for your replies Guys, nice to chat with you again.

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I'm glad that it worked out in the end after you had to drill & tap yours David.

The sweat was because it was a customer's almost new motor I was drilling into Grant, would have been less of a worry if it were my own. :oops:

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Oh yes, when it's not your own and almost new, then yes the sweating part is totally understandable. Lol

By the way, I rang the company that is selling this particular pump that i was looking at and they informed me that it was actually made by Bosch.

They also have it in stock for immeadiate dispatch should i choose to order one.

Check out the spec -


12-volt brushless

Operating Voltage

9 - 15 volts dc

Maximum Current

1.3 amps

Pump Design




Magnetic - no seals

Operating Temperature

-40 to +120 deg C

Burst Pressure

36 psi

Flow Rate

15 litres/minute @ 1.4 psi


245 grammes

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Hi Grant,

As a matter of interest, where is your calorifier fitted? I wonder if it is in the engine bay on Starboard side. Falcon's are a bit limited on space and they installed ours on the Starboard battery tray. You may have seen the "ballast" thread and now we need 69Kg of weight to level Topaz up again :lol:

Must get SWMBO to stock up on pies :naughty:

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Hi Grant,

Different layout from ours. We have both batts on port shelf and new calorifier on sboard shelf. Holding tank was fitted on sboard side in the heads back in 2004. She has always had a slight list to starboard after the holding tank was put in but, add a 37.5 litre calorifier to starboard as well.... trouble!

I was the only place it could go to be fair.

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Just had a look at one of my photo's that i took of the engine bay 2 years ago.

On the starboard side of the boat is a really long glassed in wooden shelf that supports the Calorifier & the Aux battery.

(This looks original)

On the Port side, is a glassed in wooden shelf that looks like it may have been added at some point that supports the holding tank and between the holding tank and the engine is another shelf which supports the Start battery.

The main domestic water tank is located midships (under the rear berth)

We certainely don't have any listing problems, even when the holding tank is empty and the calorifier is full.

So, i am quite happy with the layout of it.

I have ordered the pump / kit today, so should turn up in a few days.

I am hoping this will work for us, as it would be quite novel to have some hot water on tap. Lol.

Also, we might be heading up your way in August Jim, I will let you know if and when it happens.

All the Best

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  • 3 weeks later...

Hi Grant,

We did get up to Horning on Sunday and then spent two days just washing and polishing the topsides so never left the mooring. So, I am still none the wiser as to how efficient the new cali is via engine heating only!

During the clean up process, one thing occured to me which will be a bugbear to all Falcon 22 and 23 owners and that is how to effectively clean the channel inside the cabin at the bottom of the front screens. We've tried long handled brushes, hosepipes, and never seem to be able to get the channel nice and squeaky clean. The worst bit has to be in front of the helm position where you almost have to lie on your front and try and reach beyond the map tray to get a good scrub going. Worst of all, you can't actually see what you are aiming at dirt wise.

Any fancy/better solutions will be welcomed!



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Hi Jim,

On the Laptop now....... couldn't write much with the Desk Top PC. I think i need to format & start again with it.

I know exactly what you mean regarding the dirty channel under the windows. To be honest, i haven't touched that area since ive owned our boat.

However, the thought of cleaning it had crossed my mind, as we bought a really long pipe cleaning type brush to do the job a while back, its about 2 & half foot long and has stiff bristles, but just haven't used it yet.

The other method that i was going to try, was to mask the area off with clear platic sheet & then make a curtain across the window section with the same stuff.

Then, blast it with the pressure washer. I reckon that would shift most of it.

The area could even be compounded & waxed afterwoods if you wanted, by attaching a pad to the end of a a long piece of wood & then changing it over for each application.

Maybe i will get around to doing mine at some point. You never know...............

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I know what you mean Grant as it shows through the screens when viewed from outside and looks awful. I will try the long pipe cleaning brush you mentioned and see if it works. I did want it compounded back in 2006 when the yard re-glazed our port and starboard windows (replacing the old acrylic) as they have to remove the whole top section to do that. If I thought that was easy enough to do I'd have a go but I'm sure it is heavy and has to be lifted very carefully.

Next time we are up I will make a point of trying to heat the water from the engine only and see what happens.

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I didn't know that you had your windows replaced. I did mine over the winter as well.

Although, i didn't remove the whole lot to replace the sides on mine. I removed the top section that runs all the way around, then unscrewed the sides near the radar arch, then the sides just slid upwards.

I had to make wooden supports for the front windows, mainly whilst the top part was off, as they rely on the that plus the sides to keep them up.

Once the top part was back in, the supports wouldn't really be needed at the front until the sides went back in, although, i left them there anyway.

But one each side was needed near the middle of where each side window was for supporting the top part.

This was to support the canopy and frame weight that was on it, otherwise it would have bent slightly.

I have fitted a slightly darker tint than what was originally there. Made a massive difference to the look of the boat.

The old ones were scratched and had uv damage. (which was the same with the foredeck hatch as well, as i replaced that also)

Did you change to clear, or did you stick with a tinted one.

Not that we are in competition here, Lol, but i think we should really meet up and compare boats.

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  • 1 month later...

Hi Grant,

Finally got to check the new calorifier this weekend and after running the engine for over an hour, the water was barely luke warm and in fact, no better than the old system we had. I checked the top hose afterwards and although it was hot where it sits near the engine block, it was distinctly cold before it arrives at the calorifier although the bottom hose was very hot. Poss airlock maybe? The yard are going to look at it this week so I will let you know the results later.

Looks like there is little or no circulation but I did notice that instead of the engine maintaining a steady 80 degrees as always, the temp was 90 for 45 mins??

Watch this space!



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yep most likely air lock, if the pump you added will not self prime then you have changed nothing until you draw the water around the pipe work, disconnecting the return side with engine running may pull it through then push hose back and tighten.

If your like me your not afraid of using your mouth to draw it round before starting the engine, or you can use a pump to pull it. sometimes a good rev up of the engine does the trick as this spins the engine water pump faster at tick over its often not enough to get the water to flow the extra distance.

This said 'im sure the yard your using will do this for you.

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I haven't got a pump .....just straight direct connections. It was Grant (the starter of this thread) that was looking at installing a helper pump.

Air lock looks very likely but I will leave it to the yard who fitted it all to find out :wave:wave

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