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Tring Man

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Having problems with water pump pulsing and pressure release valve "releasing" water. 

 

What is the correct relationship between the pressure settings for the water pump, the accumulator and the pressure relief valve?

 

The water pump is rated at 40 psi (2.8 bar). 

 

The pressure relief valve is 5 bar. 

 

Is this the correct rating for the PRV considering the pump? 

 

What pressure should I pump the accumulator up to in this system? 

 

Regards 

Alan 

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8 minutes ago, Tring Man said:

Having problems with water pump pulsing and pressure release valve "releasing" water. 

 

What is the correct relationship between the pressure settings for the water pump, the accumulator and the pressure relief valve?

 

The water pump is rated at 40 psi (2.8 bar). 

 

The pressure relief valve is 5 bar. 

 

Is this the correct rating for the PRV considering the pump? 

 

What pressure should I pump the accumulator up to in this system? 

 

Regards 

Alan 

Somewhere between the two figure - say about 3.5 bar

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If a 5 bar PRV is lifting either the PRV is faulty or the pump pressure is higher than it should be,  i.e. over 5 bar.

 As long as the accumulator pressure is over the pump pressure by a few psi it should be fine but measure the actual  pump pressure. It sounds wrong.

 

5 bar is not a common PRV, what's the calorifier?

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Changed (like for like) the PRV a few months ago. Used 5 bar as that is what was fitted. 

 

Sorry, no idea on what calorifier is fitted. 

 

Not sure that I set the accumulator pressure above 40 psi though, recall setting it in mid 30's. 

 

So sounds like that needs resetting. 

 

What pressure PRV would you expect to see with a 40 psi (2.8 bar) pump? 

 

Pump was replaced just over 2 years ago, it is a Jabsco. Water pressure from taps does not seem any different over that time. 

Edited by Tring Man
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I set the accumulator to a few psi below the water pump cut in pressure with pump switched off and a couple of taps open.

 

Edit: If you have a hot water expansion vessel plumbed into your hot water system somewhere near the calorifier, it should be set at or a few psi above the pump's cut out pressure, again with the pump switched off and taps open.

 

Can this be pinned somewhere please as it comes up again and again?

Edited by blackrose
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No idea what pressure is being produced by the pump, have no way to measure. As I mentioned earlier, it is certainly seems no higher pressure than when I originally installed a couple of years ago, if anything it is lower. So if it is higher than rated, it has always been that way, and problem has only occurred over the last few months. 

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3 hours ago, Tring Man said:

What is the correct relationship between the pressure settings for the water pump, the accumulator and the pressure relief valve?

 

 

The pressure setting for the accumulator should be a little lower than the cut-off pressure of the water pump. I'd suggest 20% lower than the measured cutting-off pressure.

 

If you have a calorifier with a non-return valve in the supply pipe or built into the connector on the calorifier, you'll also need an expansion vessel on the outlet of the calorifier. (This is an identical device to the accumulator, but serves a different purpose.) This needs setting slightly higher than the pump cutting off pressure, say 10% higher.

 

So as you will see, determining and knowing the actual pump cutting off pressure is crucial to setting pressures.

 

Pressures need setting with the pump turned OFF and a hot tap OPEN. 

 

24 minutes ago, Tring Man said:

No idea what pressure is being produced by the pump, have no way to measure.

 

In which case, installing a way to measure is the first step. Fit a pressure gauge in the outlet pipe from the pump, I suggest. They don't cost much on eBay.

 

 

Edited by Mike the Boilerman
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Tony, sounds interesting, So to be clear, I would connect the car tyre pump to the accumulator (exactly what I used to pressurise it originally when I set it a few PSI below water pumps 40 psi a few months ago when I changed PRV), open a tap to get pump going, then close tap to check what pressure registers on tyre pump pressure gauge as pump turns off a few seconds later. Have I got that right? 

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11 minutes ago, Tony Brooks said:

As long as the accumulator pressure is less than the pump cut out pressure then a car type pressure gauge on the accumulator valve with the taps closed and pump turned on will show the actual cut out pressure.

 

Not necessarily Tony!

 

If the resting accumulator pressure happens to be higher than the pump cutout pressure, the value measured at the Schrader valve will never change. Best to reduce accumulator pressure to say 1.0 bar or less before using the Schrader valve for this purpose, in my opinion. Or zero, even. 

 

 

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The reason I said about the pump going high was I had it happen so fitted an external pressure switch and a pressure gauge. It popped my RV as well which was what alerted me to it.

1 minute ago, Mike the Boilerman said:

 

Not necessarily Tony!

 

If the resting accumulator pressure happens to be higher than the pump cutout pressure, the value measured at the Schrader valve will never change. Best to reduce accumulator pressure to say 1.0 bar or less before using the Schrader valve for this purpose, in my opinion. Or zero, even. 

 

 

Thats what he said "As long as the accumulator pressure is less than the pump cut out pressure "

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Not really covered so far, I think, but I doubt many calorifiers are actually designed to be used at 5 bar, so I'm not sure the 5 bar PRV fitted will be offering enough protection from calorifier damage.

 

I'd say a PRV rated at over 4 bar is unusual, and I'd be hestitant to have a system relying on a 5 bar one.

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I think there is some manufacturing tolerance in PRVs. We changed out  a seat scoured 4bar PRV with another of the same rating and encountered the pulsing problem with avengence. There is no adjustment on the PRV but under the end cap of flo jet and sure flo pumps is an adjustment screw. Turning it one way will replace the pulsing with continual flow, bur turning it the other way will decrease the pulsing and finally eliminate it. Job done.

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If we are talking about an accumulator vessel on the cold water side, the pressure in it should be set to just over the CUT IN pressure of the pump, not the CUT OUT pressure.

If we are looking at an expansion vessel on the hot side, ( after a non return valve on the calorifier cold feed in or a hot pipe ) then the pressure in it should be the pump CUT OFF pressure.

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Just to let you know I will not have time to look at this today, but will hopefully get back to you tomorrow. 

 

One problem is that the responses appear to fall into two distinct categories, setting accumulator pressure either above or below pump pressure. Which is correct? I assume the answer is related to whether accumulator is on cold or hot water side. It is physically located next to calorifier rather than anywhere near cold water tank, so it may well be hot water side. I will check the pipes! 

 

Very interested in DandV comment about an adjustment on the pump itself, it is a flow jet (Jabsco) but I have not noticed any adjustment screw to date. Will have a look at that too. 

 

Thanks for all the responses/help. 

 

Regards 

Alan 

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2 minutes ago, Tring Man said:

I assume the answer is related to whether accumulator is on cold or hot water side. It is physically located next to calorifier rather than anywhere near cold water tank, so it may well be hot water side. I will check the pipes! 

 

Very interested in DandV comment about an adjustment on the pump itself, it is a flow jet (Jabsco) but I have not noticed any adjustment screw to date. Will have a look at that too. 

 

Thanks for all the responses/help. 

 

Regards 

Alan 

If it is hot side it is an expansion vessel, not an accumulator and should be charged to the same cut off pressure as the pump.

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7 hours ago, Boater Sam said:

If we are talking about an accumulator vessel on the cold water side, the pressure in it should be set to just over the CUT IN pressure of the pump, not the CUT OUT pressure.

 

 

I agree that the cold water accumulator setting is related to the pump's cut in pressure, and I may have got it wrong but I thought it was meant to be set to a few psi below the pump's cut in pressure as I mentioned in post 5 ? 

Edited by blackrose
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2 hours ago, Tring Man said:

Just to let you know I will not have time to look at this today, but will hopefully get back to you tomorrow. 

 

One problem is that the responses appear to fall into two distinct categories, setting accumulator pressure either above or below pump pressure. Which is correct? I assume the answer is related to whether accumulator is on cold or hot water side. It is physically located next to calorifier rather than anywhere near cold water tank, so it may well be hot water side. I will check the pipes! 

 

Very interested in DandV comment about an adjustment on the pump itself, it is a flow jet (Jabsco) but I have not noticed any adjustment screw to date. Will have a look at that too. 

 

Thanks for all the responses/help. 

 

Regards 

Alan 

 

Also note what Brian said about fitting and external  pressure switch. Once fitted they will outlast  several/many pumps and both the cut in and cut out pressures can be adjusted (D Square type switch). It sounds to em as if your system is over-pressurising and if so I would definately advise an external switch.

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On 29/12/2019 at 15:49, blackrose said:

I set the accumulator to a few psi below the water pump cut in pressure with pump switched off and a couple of taps open.

 

23 hours ago, Mike the Boilerman said:

The pressure setting for the accumulator should be a little lower than the cut-off pressure of the water pump. I'd suggest 20% lower than the measured cutting-off pressure.

 

12 hours ago, Boater Sam said:

If we are talking about an accumulator vessel on the cold water side, the pressure in it should be set to just over the CUT IN pressure of the pump

Well that’s cleared that up then. 

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22 minutes ago, WotEver said:

 

 

Well that’s cleared that up then. 

Mike and Sam are both in the same ballpark and Blackrose is not a mile away, All 3 will work well its just a matter of how well. The OP probably wouldn't notice much difference between any of them unless he was measuring how much water came out between pump cut off and pum cut on. Its when people say its the pump cut off pressure or above its a waste of time.

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