Calorifier Pressure relief valve

SpringFever

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I recently purchased a replacement calorifier from a boat jumble. The pressure relief valve was missing so I purchased a 3 bar one (the largest they had) along with some other fittings from ASAP. When I pressurised the system up initially all was ok. After stopping the subsequent leaks and re-pressurising the PRV spurted out water then stopped. This repeated itself several times before I removed it for inspection, where I discovered some minor debris (PTFE tape shreds).
My water pump is rated at 30 psi (2 bar).
My question is, will a 3bar (42 psi) PRV be man enough for the job?
If not does anyone know of a supplier of PRV’s rated at a larger pressure.
 

Bilgediver

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My question is, will a 3bar (42 psi) PRV be man enough for the job?
If not does anyone know of a supplier of PRV’s rated at a larger pressure
***************************************************

Before you kill yourself please check the calorifier and confirm what its working pressure is!!!!!! To stick a 3 bar PRV on it might be just the same as putting a blank plug if it is only designed for 2 bar and a little tired.

Ask yourself of you want the water to come out of the taps like the exhaust from a spaceshuttle solid rocket booster or at a sensible rate.

2 Bar is more than necessary and I expect there is provision on the pump pressure switch to adjust accordingly.
 

SpringFever

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Sorry, forgot to mention that!
From manual-
Tank pressure during running test is 8 bar
Maximum working pressure is 6 bar

This is one reason I went for the PRV I did so as not to over pressurise the cylinder.
 
S

Skyva_2

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Agree with above, 2 bar is adequate. If you get leaks from the PRV try turning it a few clicks, this may dislodge debris.
 

matelot

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you will get a leak from the prv when the water is first warmed up and pressure increases. way I would read it is that the operating pressure of your pump is 2 bar but thats not the same as saying that above 2 bar water can be forced backwards through the pump. so as the water warms up and pressure rises it gets to 3 bar and then lets a bit out to reduce things again. where else can the excess pressure go?

you should have some sort of bleed pipe to take this water out into the cockpit or even the bilge.
 

CET1

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Most calorifiers are fitted with non return valves so the water in the system can not back flow into the cold water system side. A 3 bar PRV is used so that the as the water in the caloifier warms up and expands it is contained within the hot water side of the system. If a 2bar PRV was used and the whole water system was maintained at 2 bar by your pump then when the cylinder was heated and the water expands then this excess of water pressure would be blown off into the bildges loosing some hot water.
 

SpringFever

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I have fitted a pipe to direct the water from the PRV into a container so I can keep check on the calorifier & I have got non return valves fitted so the pump/cold system does not receive any back pressure.
Am I correct in assuming then that the 3 bar PRV I have fitted will be sufficient so as I do not lose the majority of my hot water as it expands?
I have looked at other manufacturers of calorifiers and they tend to fit 4 bar PRV’s. I cannot find any information detailing what was originally fitted to the Quick BX 25 I have bought.
I am probably worrying over nothing but as boating season is fast approaching I want to get everything sorted.
 

matelot

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between ambient at (say) 15 deg and operating at 60 deg the water will expand by 1.6% (its doesnt compress much) so to relieve pressure back to 2 bar or less you will need to release maybe 1% of the volume contained or typically 10 cc for a 10 litre tank. rough figures cos it depends on how stretchy your tank is etc.

So you are in no danger of losing the majority of your hot water as it expands. what you have done sounds fine to me. in fact checking the volume of water lost on heating up will give you a good check on things working right. worry if there is no water or way too much.
 

Alyssa

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Have been having some problems (leakage from the immersion heater joint) with a Quick BX20 calorifier. Extract from an e-mail last November from one of the Quick technical guys in Italy ............

"Regarding pressure relief valve, I can inform you that for Quick models it has pressure of 6 bar "
 
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