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tojohnson
tojohnson

Posted: Wed Jun 15, 2011 2:46pm

Post Subject: Leaking PRV on Calorifier

I have recently replaced what I thought was a leaking PRV only to discover that the new one is also leaking! So there must be another problem. The leak only happens when water is actually being heated either by the engine cooling system or by the Eberspacher heater. It's not just a few drips but a good litre after four hours cruising (I have learned to place a bowl under the valve outlet!). The calorifier water does not appear to be overheated and certainly nowhere near to boiling. The PRV is rated at 3bar as per the original, and I'm loath to fit a higher rated valve in case of possible major damage to the hot water tank. Have you any suggestions as to the reason for the continued leaking. Could the water system be over-pressurised? I have not made any changes to the fresh water pump or the pressure vessel, so cannot see how this could happen. Your comments would be most welcome to point me in the right direction of a cure. Many thanks, Tony J

Tony-B
Tony-B

Posted: Wed Jun 15, 2011 3:39pm

Post Subject: Leaking PRV on Calorifier

Pity you did not ask before assuming the valve was faulty - it would have saved you the cost of a valve because this is normal and to be expected. It's what is meant to happen. If you go to (http://www.plumbset.co.uk/waterexpansion.asp)(a ll on one line) and enter the volume of your calorifier and a final water temperature (which will be about 85C unless you have a low temperature engine thermostat fitted) you will fins that a 65 litre calorifier will need to vent about 2 litres of water. This will be less if you have an accumulator suitably positioned in the system or an expansion vessel. In the latter case the valve would probably not vent at all. If the water in the boat worries you pipe it over the side. Tony Brooks

tojohnson
tojohnson

Posted: Thu Jun 16, 2011 9:44am

Post Subject: Leaking PRV on Calorifier

Thanks for your reply as always Tony. I'm a little surprised that this is usual because it didn't seem to be happening last year, but I will fit an expansion vessel or arrange to vent overboard via a skin fitting. Should the expansion vessel be fitted to the inlet or outlet of the calorifier?

Tony-B
Tony-B

Posted: Thu Jun 16, 2011 10:08am

Post Subject: Leaking PRV on Calorifier

An expansion vessel has to be fitted to the calorifier side of any non-return valve and needs pressurising to the pump cut out pressure or above. You may already have an accumulator and it it has lost pressure the valve will vent more water. Its pressure shoddily be set to about the pump cut in pressure but half the cut out pressure will do (its easier to measure). If you had air in the system last year it would act as an expansion vessel. Tony Brooks

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