Pressure Valves

[sidon]

I have recently noticed that when running under engine my Jeanneau SO 37 dumps an alarming amount of hot water in the bilge from the cleghorn waring pressure release valve, this does not happen when using the immersion heater on shorepower. This point me to the conclusion that the water coming via the engine is hotter than the release valve is set at. On further enquiries I have found out that nearly all the SO37's sold in our area do the same. On confronting the dealer the explanation was, that due to global warming the sea temperature in the U.K had rissen by approx 1.5 degrees causing this problem. Also because my boat was 16months old she was out of warranty, but the dealer would supply a new valve at trade cost. What worries me is why is this valve going to be any better than the old one, as it is exactly the same valve. I would be gratefull for any advice on how to rectify this problem ie which valve to use etc.
P.s. If the dealers theory is right I bet there is no such thing as a SO37 in the med with hot water! due to the higher sea temperature. Thanks in anticipation.

 

[alanporter]

I believe your problem is due to the engine cooling water being too hot. Two ways to correct it would be 1: take the water to the calorifier from a different part of the engine cooling system, or if this is not possible, 2: fit a new thermostat with a lower opening temperature. I doubt if a new valve would help, unless the original one is definitely faulty. Good luck.

Alan Porter

 

[andyball]

An inventive explanation from the dealer......


Dunno if cleghorn waring valves are super-dooper, but asap sell pressure relief valves for calorifiers for £11 + vat- they do 2 Bar and 3 bar ones. I'll bet a plumbers merchants will be cheaper still.

However...the current range of c-warm(cleghorn) calorifiers are either 2.5 or 3.5 bar working pressure. (they do a high pressure , & "standard" range.

May be worth checking what's actually fitted, to be sure that Jeanneau used the right valve, and at the price, trying a replacement won't break the bank; otherwise the previous suggestion re. thermostat etc may help.

 

[AndrewB]

I solved a similar problem ...

... with my Cleghorn-Waring calorifier. The engine runs at 70degC, and this appeared to heat the water above the point at which the pressure/temperature release valve in the calorifier triggered. I suspect this was due to corrosion in the thermostat part of the valve, which was showing rust in places, rather than by design.

My solution was to replace the combined pressure/temperature release valve with the simpler and more robust pressure only valve. We've had no problems since. It should be good enough (I hope) if the water should reach close to boiling in the calorifier. Mind you, if my engine does that, it will be cooked.

 

[Robin]

This is a really common problem, we have it on our Jeanneau Sun Legende too, measured ours by putting the overflow pipe in a tonic bottle just to see how much was involved. I suspect a higher pressure valve might work but only if the calorifier tank was designed for that pressure, otherwise you could create other problems. Changing the engine thermostat setting is not a good idea, the engine manufacturer knows best what this should be. In our case I will simply lead the overflow overboard via a suitable skin fitting this winter. Our last boat took it to a plastic car radiator overflow tank with pressure cap (there was no relief valve) and presumably some was sucked back into the hot tank as it cooled, it too caused problems from time to time.

 

[Sinbad1]

B&Q do pressure relief valves that you set to the pressure you require. I bought one after discarding my old non operational relief valve but have never fitted it.

If we work our way through your system it probably works like this. Hot water from engine runs to calorifier. Inside calorifier it runs through enclosed tubes like a heating coil and then exits back to the engine where it continues to circulate as part of the engine freshwater cooling.

At the calorifier you have a hotwater take off tube which runs to your domestic hotwater taps/showers. (Is the pressure/temp valve on this tube/pipe) You also have a cold water inlet tube/pipe which runs into the calorifier from your freshwater tank, usually via a demand pump which is followed by an expansion tank which keeps the domestic system pressurised without requiring the pump to cut in.

So, in simple terms we have a heating coil within a calorifier tank. As the water in the calorifier heats up and expands it will exert pressure on the walls of the calorifier and upon the open system, ie on the pipework relating to domestic hot water and on the pipework relating to the domestic cold water supply from the boats freshwater tank.

So, if you have an expansion tank in the cold water supply, the increased pressure caused by the expanding water in the calorifier will simply be absorbed by the expansion tank on the cold/fresh water supply.

To me the worst thing that could happen is that you may find that on occasions you get some slightly warmish water coming out of the cold tap for a few moments.

Of course if your relief valve is on the hot water discharge line you will find that it probably only reacting to temperature. So if you don't want to just throw it away like I did, then remove it and place it in the freshwater inlet line into the calorifier. The pressures on both the inlet and outlet will be the same and theoretically the temp on the inlet will be cooler, preventing the relief valve from activating.

Hope this helps. Try and draw a pic of your system which will give you an understanding of how it all works.

 

[andy_wilson]

Due to global warming....

....your dealer is full o' 5h1t !

Ask him if it will be ok in the spring when the sea temp has dropped a few degrees, or if they specify different valves for the Baltic, North Sea, English Chanel, Med...........

The pressure is set by the accumulator tank. When warming the water a little expansion takes place so a little water may be lost. Does it still happen if for instance you draw a little water off as full temperature is reached? Probably will.

Try reducing the pressure setting on the accumulator pump/tank/device and see what happens.

However first of all have a close look at the hot water itself. A possibility is an internal leak on the heating coil, forcing hot engine coolant into the domestic hot water circuit whilst engine on, the accumulator tank sending water back into the engine cooling circuit when the engine is off.

Is your hot water clean and fresh, or salty (raw water cooling) or coloured by antifreeze (sealed cooling).

 

[COG]

Re: Pressure Valves ( possible cheap solution)

I had the same problem if I left the pump running while motoring, the pump seemed to hold the pressure as normal but as the water was heated in the calorifier it expanded and added extra pressure activating on occaision the relief valve.

I tend to keep the pump off when motoring and release the pressure a bit by running a tap before starting, as the water is heated it expends and gives enough pressure at taps for casual use. Not had any problems since adopting this ( it is also a cheap Solution

COG

What do you mean...... It was working when I left

 

[Sinbad1]

Re: Due to global warming....

Andy, had this problem once. Whenever I stopped the engine the header tank would slowly fill up and drain out through the radiator/ header tank cap releif hose and into the engine sump. As I keep my engine sump spotless I was mystified as to where it was coming from until I heard the tell tale brrrrrr of the domestic water pump repressurising the system even water wasn't being used..

The cause was as you state, a leak in the calorifier heating coil and it was only with the engine stopped that the domestic pump pressure was greater than the fresh water cooled engine pressure.