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iansutton
iansutton

Posted: Fri Jan 22, 2016 4:16pm

Post Subject: Weeping PVR

Hi Tony The Pressure Relief Valve on my calorifier seems to constantly weep when the water is being heated via the immersion heater when I am connected to my shoreline power. I am guessing but am not sure that the PVR is probably doing the same with the engine running whilst I am cruising. I don't get any hammering noises from it whilst operating any of the taps, it just weeps. It is just a little frustrating, and I need to remember to keep emptying the bilge every day to prevent it flooding the engine tray. I am not sure if the PVR is faulty, so I thought I would check with you before purchasing a new one. The setup I have is a standard setup, with water pump, then an accumulator, and then the hot water tank. The water pump is a Jabsco 31395-0292 with a pressure cut in of 1.0 bar and a cut out of 1.7 bar. I am not sure on the make of the Accumulator but I believe it to be the diaphragm type with the car tyre valve. I have set the pressure on this as recommended and also tried increasing and decreasing the pressure, but this has had no effect. The Calorifier is a 30 litre SurCal with a factory fitted 3 bar PVR. The immersion is pre-set to 80 deg C, but I think I remember lowering this to 70 deg C. I have tried turning the red knob on the PVR several times to try to clear any potential dirt/limescale on the valve seat, but this didn't have any effect. I have NOT removed the PVR yet and manually inspected it. The PVR as stated is 3 bar, although I thought the calorifier is normally supplied with a 4 bar PVR.

Tony-B
Tony-B

Posted: Fri Jan 22, 2016 4:38pm

Post Subject: Weeping PVR

The one thing missing is exactly what pressure have you put in the accumulator. It needs to be between 0.8 and 1 bar for it to do its job. If the air side of the diaphragm has a lot of water in it then the unit is faulty and needs changing. Calorifiers use the PRV as recommended by a particular maker. 4 bar or 60psi sounds very high to me, 3 bar seems more likely. When ever cooler water is heated by whatever means it expands. The accumulator should take care of most of that by providing a space for the water to expand into without raising the pressure to a significant degree. If there is no air space (air is compressible, water is all but not) in the system and you have closed taps the pressure in the system will rise very quickly and cause the PRV to dribble, this is normal for a boat with no accumulator or expansion tank. You could try fitting another accumulator pressurised to 1.7 bar so it acts as an expansion vessel. If you fit a PRV of a higher pressure than that recommend you stand a fair chance of splitting the calorifier by pressure from the expanding water. Once you are sure the accumulator is pressurised as I indicate I think the next thing to do is to ft a new PRV set to whatever pressure Surecal recommend. Some have a rubber washer like a tap washer and this can go hard.

iansutton
iansutton

Posted: Mon Jan 25, 2016 5:57pm

Post Subject: Weeping PRV

Hi Tony Thanks for the reply and advice. I seem to remember trying the accumulator pressure at 1.0 and 1.3 bar, both set with the pump switched off and any excess pressure drained of by opening the tap. Neither pressure had any affect. With regards to the 4 bar PRV, I got this information from the description on the Midland Chandler website for the Calorifier, but as I said in my previous post, it has a 3 bar PRV fitted. I will check the accumulator next time the diagphram has not ruptured, I guess this can be done by turning the accumulator so the tyre valve is underneath, then releasing any pressure, and see if any water comes out of the tyre valve. If all is well, I guess I will need to replace the PRV.

Tony-B
Tony-B

Posted: Mon Jan 25, 2016 6:10pm

Post Subject: Weeping PVR

I would suggest that you double check what Surecal has to say about the PRV for your particular calorifier. If they say 4 bar is OK then it will be but check for their piping diagram. I have a horrible feeling the say you need an expansion tank as well as an accumulator. I would not put over much faith in a chandlers information when the manufacturer has a half decent website. Rather than swivelling the accumulator just leave the pump turned on and take out/push down the valve. IF no water comes out the diaphragm is serviceable.

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