Calorifier overflow

[AJR]

Hi all, noticed slight leak from overflow coming out of the hull. Not obviously different when engine is on compared to off. There’s a red plastic ‘bottle cap’ which opens the valve fine but which doesn’t seem to be closing it completely no matter how hard you do it by hand. Between this and the metal valve assembly this there’s a plastic nut. There’s also a metal nut on the intake side of the valve. Before I start trial & error adjustments - anyone got a more informed suggestion of what to try? Many thanks, Alan 

[cuthound]

The leak is coming from your PRV (Pressure Relif Valve). It is designed to open as the water in the calorifier gets hot and expands. If it didnt the calorifier would eventually split open from continually expanding and contracting as the water got hot a d then cooled again.

 

Try rotating the red knob vigorously. This should clear the timescale who h has probably built up, preventing the PRV from closing. If that doesn't work, the PRV needs replacing.

Edited August 27, 2019 by cuthound
Spillung

[Tony Brooks]

and if you have an expansion vessel on the hot water system check it has air pressure in it  with the pump off and a tap open. If you don't then consider fitting one.

 

The problem may also be caused by the water pump turning off at too high a pressure so if you have an accumulator check the pressure in that with the pump turned on and stopped running and the taps off. That will tell you the pressure the pump turned off at, then see if you can see an opening pressure (usually in bars) on the PRV

[MtB]

3 hours ago, cuthound said:

If that doesn't work, the PRV needs replacing.

 

I'd say that will never work as the symptoms described are those of a non-working (or non existent) expansion vessel.

 

 

[cuthound]

10 minutes ago, Mike the Boilerman said:

 

I'd say that will never work as the symptoms described are those of a non-working (or non existent) expansion vessel.

 

 

 

Yes, re-reading the OP,  I now notice he ssys the leak is "not obviously different when the engine is on compared to off".

[Tony Brooks]

15 hours ago, cuthound said:

 

Yes, re-reading the OP,  I now notice he ssys the leak is "not obviously different when the engine is on compared to off".

Apart from the fact that on a non-expansion vessel system the main discharge will be during warm up and then much less each time hot water is drawn off so admitting cold for expansion doing it continually with the engine off suggest to me its more likely a water pump pressure issue so the OP needs to check pressures or get it leaking, turn the pump off, draw a few drops of water and see if it continues leaking with the pump off. If yes then its most likely a scaled up valve or a faulty valve seat. If no then its likely to be overpressure from the pump. If it has an expansion vessel or accumulator with an air valve I explained how to use that to check the pressure before in this topic.

Edited August 28, 2019 by Tony Brooks

[Laurie Booth]

On 27/08/2019 at 12:23, AJR said:

Hi all, noticed slight leak from overflow coming out of the hull. Not obviously different when engine is on compared to off. There’s a red plastic ‘bottle cap’ which opens the valve fine but which doesn’t seem to be closing it completely no matter how hard you do it by hand. Between this and the metal valve assembly this there’s a plastic nut. There’s also a metal nut on the intake side of the valve. Before I start trial & error adjustments - anyone got a more informed suggestion of what to try? Many thanks, Alan 

Leave the hot tap on with the pump off. The water will then go down the sink.

[AJR]

Thanks for the suggestions. I’m off the boat for a few days but repeatedly opened & shut the valve before I left so will see if the leaks still there when I go back on. If so I’ll look into the water pump pressure . Very helpful!

Alan