Pressure release valve keeps "releasing"

[umpire111]

the pressure release valve on top of my calorifier keeps releasing and letting out water. This occurs every 2 or 3 minutes. Even occurs when the engine is not running and moored. I have a new water pump (30 psi) and the PR valve is for 3 bar. The water pump kicks in when the water is released, obviously. Have changed the valve but same problem re releasing. The calorifier seems to be pressurising to above 3 bar which is 43 psi but how can this be the case if the pump is only rated as 30 psi? Going mad at the moment- all advice or ideas welcomed

[Flyboy]

Most pumps have an adjusting screw on the pressure switch so you may be able to reduce the cut out pressure. It's possible the pressure switch is faulty of course. It's quite possible that the pump can exceed 30psi if the pressure switch is not adjusted properly or is faulty.

[deckhand]

We had exactly the same problem.. Our boat builder just kept fitting a new pump (3 new ones ) until we finally took a stand and said get someone who knows what they are doing. The engineer from Sawley finally identified that there has to be a slight difference in the pressures between the PRV and the pump and the calorifier and sorted the small but very annoying issue for us by making the relevant adjustments.

[mrsmelly]

the pressure release valve on top of my calorifier keeps releasing and letting out water. This occurs every 2 or 3 minutes. Even occurs when the engine is not running and moored. I have a new water pump (30 psi) and the PR valve is for 3 bar. The water pump kicks in when the water is released, obviously. Have changed the valve but same problem re releasing. The calorifier seems to be pressurising to above 3 bar which is 43 psi but how can this be the case if the pump is only rated as 30 psi? Going mad at the moment- all advice or ideas welcomed

 

Is it a Shurflo pump?

 

Tim

[umpire111]

It's a Whale Universal

[Paul C]

the pressure release valve on top of my calorifier keeps releasing and letting out water. This occurs every 2 or 3 minutes. Even occurs when the engine is not running and moored. I have a new water pump (30 psi) and the PR valve is for 3 bar. The water pump kicks in when the water is released, obviously. Have changed the valve but same problem re releasing. The calorifier seems to be pressurising to above 3 bar which is 43 psi but how can this be the case if the pump is only rated as 30 psi? Going mad at the moment- all advice or ideas welcomed

 

30psig or 30psia (gauge or absolute)? (I suspect its psig, since its a pressure difference that it generates, and this is what they'd indicate the pump achieves in the specs).

 

psia = psig + 14.7, by the way, in this instance.

 

That explains why the PRV is releasing, and why an initial look at the specs wouldn't explain it. Post #3 more succinctly says it.

[alan_fincher]

Nobody has yet asked if there is a non return valve (NRV) in the cold water feed, nor whether the calorifier has a separate expansion vessel (EV) on the hot water side.

 

If there is an NRV present, and there is no EV, then water coming out of the PRV is almost inevitable, and it actually has nothing to do with the cut out pressure of the hot water pump.

 

As cold water in the calorifier is heated either by engine, or any attached boiler, it will expand. It cannot expand backwards into the cold water system, because the NRV prevents it.

The excess hot water due to expansion to go somewhere, so it is pushed out the PRV. If there were no PRV, the calorifier might split.

 

If you have this set up (i.e. have an NRV, but no EV), then you need to add an EV.

 

Note, if you have a pre-plumbed calorifier, such as the popular Surejust/Surecal ones, with the shiny blue insulation, then it is not obvious that an NRV is incorporated into the pre-plumbing. It is small, and "hidden" in one of the other parts. Surejust say you must have an adequate EV fitted, if it is one of these.

 

If there is an NRV

[Guest]

Hope it ok to jump on this thread. Mrsmelly , why did you ask if the pump is a shurflo? I've have similar problem but with added prob of, when the hot pump is switched on 'not opening the taps' just the power the pumps pumps water gushed out of the PRV, I. Received a lot of advice on here BUT the problem still goes on & on driving me crazy. I have a shurflo 45psi & a new PRV 3 bar. Ran the engine today, water started to drip out past the PRV. I don't have a NRV or EV. So I continue to have to ask advice. Cheers anyone.

[bottle]

Hope it ok to jump on this thread. Mrsmelly , why did you ask if the pump is a shurflo? I've have similar problem but with added prob of, when the hot pump is switched on 'not opening the taps' just the power the pumps pumps water gushed out of the PRV, I. Received a lot of advice on here BUT the problem still goes on & on driving me crazy. I have a shurflo 45psi & a new PRV 3 bar. Ran the engine today, water started to drip out past the PRV. I don't have a NRV or EV. So I continue to have to ask advice. Cheers anyone.

 

3 bar is almost equal to 45 psi, so your PRV is at its limit, when the water is heated it expands (raises the pressure) PRV vents.

 

Solution change pump to lower pressure model ( the pressure switch on the existing pump may be adjustable) or change the PRV to a higher pressure one, be careful because the calorifier may not be able to withstand a pressure greater than 3 bar, check the specification.

[Flyboy]

I agree with Bottle, 45psi = 3.1 bar. Try reducing the pressure with the adjusting screw on the pump. I think using a 45psi pump is risking a split calorifier anyway. My own pump is a 20psi Shurflo Aquaking which is more than adequate.

[alan_fincher]

I think using a 45psi pump is risking a split calorifier anyway.

Though, not, of course if the PRV is working as it should.

 

Obviously not ideal, but the PRV will protect the calorifier, albeit only by dribbling.

[Guest]

Thanks guys will have another go at it 'IF' I manage to sort it I will post on here as it might help someone else. Cheers

[Flyboy]

Though, not, of course if the PRV is working as it should.

 

Obviously not ideal, but the PRV will protect the calorifier, albeit only by dribbling.

Agreed, but it's still a lot kinder to the calorifier if you can run it at a lower pressure.

Edited March 8, 2015 by Flyboy

[Neil Smith]

Don't want to open another thread as knowledgeable peeps on this one, I am fitting a new whale 2 bar pump so what prv should I get, and do I really need a nrv and expansion tank as I want to keep things simple, I think my tank is tested to 5 bar safe running pressure.

 

Neil.

[alan_fincher]

Don't want to open another thread as knowledgeable peeps on this one, I am fitting a new whale 2 bar pump so what prv should I get, and do I really need a nrv and expansion tank as I want to keep things simple, I think my tank is tested to 5 bar safe running pressure.

 

Neil.

 

A 3 bar PRV should be fine if the pump delivers circa 2 bar maximum pressure.

 

If you don't have an NRV and hot water EV, then you may well find expanded hot water from your calorifier gets pushed back through your cold supply. If that has an accumulator, it may to some degree act as an EV, and it is also possible that the expansion may try to push water right back into your fresh water tank. Theoretically hot water out of cold taps may occur along with all this.

 

If you have a Surecal/Surejust pre-plumbed calorifier, they come pre-equipped with an NRV, and Surejust state firmly now that these calorifiers should have an EV fitted to the hot water side.

 

Of course the downside of having both a cold water accumulator and a hot water EV (apart from cost!) is that space has to be found for both. However the resulting system is far more likely to operate smoothly and problem free.

[smileypete]

Thanks guys will have another go at it 'IF' I manage to sort it I will post on here as it might help someone else. Cheers

 

Ideally you're looking to adjust the pump cut-out pressure down to 28psi/2 bar.

 

As already said, it will also need a potable grade expansion vessel, at least 10% of calorifier volume, from Ebay or plumbing outlets.

 

If the pump can't be adjusted enough, a £15 pressure reducing valve from the likes of Ebay, between pump and calorifier should sort it.

.

 

cheers, Pete.

~smpt~

Edited March 9, 2015 by smileypete

[Neil Smith]

Thanks Alan,

 

Its not a pre plumbed job so I will try without a prv and expansion tank, its got a tank on the cold side which could help as you say, if I get hot water out of the cold taps I have room in the engine room next to the calorifier.

 

Neil.

[bottle]

Thanks Alan,

 

Its not a pre plumbed job so I will try without a prv and expansion tank, its got a tank on the cold side which could help as you say, if I get hot water out of the cold taps I have room in the engine room next to the calorifier.

 

Neil.

 

So you plan to have an open overflow pipe?

 

Problem, the pump will continuously run as the system will not pressurise.

[Paul G2]

Thanks Alan,

 

Its not a pre plumbed job so I will try without a prv and expansion tank, its got a tank on the cold side which could help as you say, if I get hot water out of the cold taps I have room in the engine room next to the calorifier.

 

Neil.

 

 

 

So you plan to have an open overflow pipe?

 

Problem, the pump will continuously run as the system will not pressurise.

 

Neil - I think you mean without an NRV, don't you? If not, you should.

[Neil Smith]

Sorry yes a nrv. It will have a prv to let it pressurise.

 

Neil.

[bottle]

No need to be sorry, we just needed to be sure.

[Paul C]

Nobody has yet asked if there is a non return valve (NRV) in the cold water feed, nor whether the calorifier has a separate expansion vessel (EV) on the hot water side.

 

If there is an NRV present, and there is no EV, then water coming out of the PRV is almost inevitable, and it actually has nothing to do with the cut out pressure of the hot water pump.

 

As cold water in the calorifier is heated either by engine, or any attached boiler, it will expand. It cannot expand backwards into the cold water system, because the NRV prevents it.

 

The excess hot water due to expansion to go somewhere, so it is pushed out the PRV. If there were no PRV, the calorifier might split.

 

If you have this set up (i.e. have an NRV, but no EV), then you need to add an EV.

 

Note, if you have a pre-plumbed calorifier, such as the popular Surejust/Surecal ones, with the shiny blue insulation, then it is not obvious that an NRV is incorporated into the pre-plumbing. It is small, and "hidden" in one of the other parts. Surejust say you must have an adequate EV fitted, if it is one of these.

 

If there is an NRV

 

I think this is a red herring. At the end of the day, the PRV (Pressure Release Valve) is required, and the additions you mentioned just alter the quantity of water lost through it during a heat cycle, which is insignificant with respect to the amount of water lost in the original post (PRV opening every 2-3 mins, even with engine not running). The fact that the fault started occuring with the replacement of the water pump, is convincing enough to suggest the slightly higher pressure of the water pump is the root cause of the issue.