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Engine to calorifier connections


Emz798

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We recently connected our Vetus engine to our calorifier and it turned out the plastic connectors (from engine to pipes) were not adequate for the heat and vibrations resulting in water+coolant leaks. We are now about to redo the connections using high heat rubber hose and jubilee clips instead instead (going from engine to water pipes for calorifier). The system was already all set up to be connected before we bought the boat, the pipes are plastic but rated for high temperature (I think-the pipes say central heating and 7BAR/82DEG  12BAR/20DEG)-hopefully this should be ok. 

Before we redo the connections I wanted to check if there is anything else that we might need to change or add to the system? Currently we are directly connected from engine to calorifier with two stop valves at engine exit and entry. There is no non-return valve anywhere (I wasn't sure if this might be necessary to protect the engine?). We also have a small pump on the calorifier return to engine pipe but this proved to be unnecessary as we get hot water without it (which we assume means the water is flowing as it should). The engine coolant system also has what appears to be a small plastic expansion tank connected as well.

Any advice would be appreciated! 

 

Thanks,

 

Emeline

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Did it work OK with the the previous connections? Does the hot water in the calorifier keep the engine warm overnight?

If yes to the first then you should have no problems provided the rubber pipes are as big inside as the previous plastic ones.

If yes to the second you will need a NRV  of the swing type.

The pipe markings are working pressure limits at the given temperature. While the engine outlet temp should be about 80C the pressure should be nowhere  near 7 Bar so I expect they will be OK but prone to sagging unless well supported.

I would leave the pump in the return pipe.  It will be handy for bleeding the cauliflower circuit after a full drain down and may be handy if/whenl the heating coil ever gets scaled up.  Run it occasionally for its own good. Five minutes once a month will be plenty.

Piccies of the header tank might elicit some more comments.

N

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Can't work out what the pump on the return pipe from calorifier to engine was for, unless it was being used to warm up the engine from the calorifier. has it always been there ?

Anyway, it seems like your removing it.

Don't forget to top up the cooling system with pre mixed water/antifreeze mix. Do you know what the correct water level should be and where to check ?

Hope this helps

 

Bazza

 

Edited by Bazza954
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Usually on plastic plumbing fittings there are inserts that go into the ends of the pipes to support these against the compression of fittings or jubilee clips. The fact that the original fittings failed might just be down to these having been left out.

These are the gizmos I'm talking about:

https://www.screwfix.com/p/jg-speedfit-sts22p-superseal-inserts-22mm-5-pack/92312

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Surprised that a pump is fitted in the circuit, as my Vetus 4.17 pushed the water through the calorifier hoses with a fair bit of force.  Might be needed if the calorifier was some distance from the engine.  My calorifier is on the swim next to the engine and has no need of a NRV, but my previous boat with a vertical calorfier inside the cabin did - more a problem with horizontal calorifers on the floor.

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Thank you all for your rapid and detailed responses! When we initially connected everything the hot water wasn't flowing to the calorifier which why we put in a pump (a tiny £15 one) to help the water go through and get air out. It worked because after that the engine water was heating the calorifier water very well. However after a couple days it started leaking. We spoke to another boater who thought the leak was caused by our plastic piping being very stiff and the engine vibrations. Rubber piping should do the trick hopefully.

Our engine is a M4.15 and actually does seem powerful enough to push water to calorifier without a pump. Our calorifier is at least 3 metres away from the engine and the piping doesn't go straight there so I think it just needed a bit of help initially. We've decided to keep the pump for the reasons suggested in the 1st post above (it doesn't obstruct the flow, we can just use it occasionally). 

I will check the engine temperature over night and see if we might need a NRV (thanks for the tip!).

We have noticed the water (+coolant) level in the expansion tank goes up and down but when the engine is on it's usually between Min and Max so should be ok. We generally top up when needed directly in the expansion tank as that's what previous owner told us to do. 

I've attached a photo of the engine coolant expansion tank to explain my earlier message better- we weren't sure if it releases pressure at the top. It connects to the engine coolant tank directly and the keel. 

 

IMG_0971.JPG.6ae6db9f6681e682eb6d6f48ca8f31cf.JPG

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If it releases pressure from the top I would expect the cap to be marked with the pressure release value, probably 0.9 0r 1.1 bar.  If no marking it may still release from the original filling cap on top of the engine.  You could totally fill the cooling system with coolant and as it gets hot and expands it will expel the excess and you can see from where. 

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It can be dangerous to completely fill the system without knowing if a pressure release cap is fitted. At the moment an air space will allow the water pressure to rise without doing to much damage. Excess pressure will probably burst something or damage the engine pump seal.

Use vehicle type heater hose (5/8 or 3/4" bore) from suitable brass hose adapters on the engine. It is best to terminate these at some sort of fixed ' bulkhead' type fitting not to  far from the engine, then use whatever pipe suits you with the correct sleeves fitted internally. Plastic pipe is best cut with the proper tool to make sure you do not damage the O ring seal on assembly. If the hoses can rub on anything use cable spiral wrap for protection. 

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THat type of expansion vessel is quite commonly used and is the same as mine.  With coolant at the correct level it will be empty when the engine is cold, and be about one third to half full when engine is at full temperature.   When cold, you can add water to the heat exchanger filler to the correct level, if you overfill it will be pushed out of the expansion cap.  The heat exchanger filler has a cap that looks like a conventional radiator cap, but it has no sprung seal inside.

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11 hours ago, adrianh said:

It can be dangerous to completely fill the system without knowing if a pressure release cap is fitted. At the moment an air space will allow the water pressure to rise without doing to much damage. Excess pressure will probably burst something or damage the engine pump seal.

Use vehicle type heater hose (5/8 or 3/4" bore) from suitable brass hose adapters on the engine. It is best to terminate these at some sort of fixed ' bulkhead' type fitting not to  far from the engine, then use whatever pipe suits you with the correct sleeves fitted internally. Plastic pipe is best cut with the proper tool to make sure you do not damage the O ring seal on assembly. If the hoses can rub on anything use cable spiral wrap for protection. 

If there is no pressure release cap then the op needs to know this urgently as it's better to have a burst as the water is expanding but still cooler than boiling than one day have an overheat problem which would lead to a burst and the 'explosive' release of boiling water and steam.  That said, I don't believe anyone would be stupid enough to design a cooling system without a pressure release.

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I did use some Speedfit plastic pipe and fittings in my boats calorifier installation, connecting to the engine rubber hose with hose tails. You need to check the maximum temperature rating for each fitting used. Some are good for 80C continuous, if I remember correctly, which should be fine for the calorifier circuit, others only for 60C. I am guessing that the 80C parts would be designed for domestic central heating and the 60C only for domestic hot water. I ended up using brass fittings for some parts as I couldn't find an 80C rated plastic version. For this I would also want to use name brand parts with stated temperature ratings, rather than no-name DIY shed, or Ebay fittings.

I fitted a couple of valves so I could isolate the calorifier from the engine, but when isolated would still allow coolant to loop from the hot outlet back to the engine water pump. These valves had to be brass as the Speedfit ones were only 60C.

Jen

Edited by Jen-in-Wellies
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  • 2 weeks later...

We've finally finished connecting everything using rubber hose and brass connectors to plastic piping. So far it's worked great and no more leaks. Our header tank does appear to have a lid with a spring in it so I assume that would release the pressure if it built up too much. Thank you everyone for your advice with this, it's great to finally have hot water on the boat!

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