Water issue

[ditchy]

This just doesn't add up.

There aren't many conditions. So when I have the washing machine running, the hot water tank pressure relive valve begins to offload the water. Sometimes this sorts itself out. Sometimes I have to turn the system water electrics off. The reason i do this is because the relive valve stays open and wastes all the hot water and continues through the cold water replacing it. The water pump keeps running, topping the water up that's leaving.

I would a appreciate any ideas why this could be happening. The relief valve has been replaced a month or so ago for a like for like. Thanks in advance

[by'eck]

PRV faulty or insufficient difference between water pump cut-off and PRV release pressure.

[Tony Brooks]

My first instinct would be to measure the pressure the water pump pressure switch is cutting out at. If you have an accumulator make sure you have some air pressure in it with the pump off and tap open. Then close the tap, turn the pump on and measure the pressure in the accumulator with a car type pressure gauge. If you do not have an accumulator then I fear you need to fit a pressure gauge. I suspect the pump's switch is set to too heigh a pressure or the PRV is not like for like pressure wise. I note that you do nt give us a PRV pressure.

[ditchy]

Thanks the PRV is 3 bar.. I don't seem to have any issue when running the boat without washing machine on.

[Paul C]

Do you have an accumulator, and is it working properly?

[Tony Brooks]

I do not see how a washing machine can create any pressure in the system but I suppose it may cause water hammer or a pressure pulse when the fill solenoid turns off but that should only make the PRV jump off its eat once or twice and almost instantly reseat. However when the pump cut out pressure and PRV settings are close I have heard of PRVs staying off their seat. (As By'eck has intimated).

 

Try turning the pup cut out pressure down a bit or if you have an accumulator make sure it has air pressure init. For an accumulator (not an expansion vessel that looks the same) set to the pump cut in pressure or about half the cut out pressure.

[Paul C]

I was going to suggest water hammer too - that's why I asked about the accumulator, this (if working) should minimise it. I imagine a washing machine's valves are able to open and close much quicker than the average tap, thus it occurs only with the washing machine. But also, PRV opening pressure being too close to the max pump pressure can be a factor, along with a poorly calibrated/worn PRV.

 

Given the limited info so far (no pressure readings): an easy first step to fixing might be to check the accumulator is working properly; fix this if it isn't; and replace the PRV with one with a pressure gauge.

[ditchy]

Just got the pressure gauge on. O psi/ bar. Shall I pump it up to 2.5 bar?

Edited October 31, 2015 by ditchy

[Tony Brooks]

No, whatever the pump cut in pressure is or half the pump cut out pressure. I would guess about 1 to 1.5 bar

[ditchy]

Ive pumped the accumulator upto 1 bar with the pump switched off and with the taps closed. All seems to be well now, but I assume the test will be when i put a wash on again. My pump is a jabsco 2.9 with pressure of 1.7bar and accumulator has a 4 bar max(now 1bar). It's always difficult when there's no problem.

[bottle]

Ive pumped the accumulator upto 1 bar with the pump switched off and with the taps closed. All seems to be well now, but I assume the test will be when i put a wash on again. My pump is a jabsco 2.9 with pressure of 1.7bar and accumulator has a 4 bar max(now 1bar). It's always difficult when there's no problem.

 

Ooops. should be pressurised with, pump OFF tap OPEN.

 

Then if you SHUT tap and turn pump ON then take another reading (when the pump stops) it will read the pump cut-out pressure

[ditchy]

Ok. Tried what you just said bottle. 0.9 bar tap open, pump off... After the pump comes back on the pump cuts off at 1.5 bar.. Do this sound better and do I need to do anything else?

[blackrose]

I would have thought this was more of an issue about whether there is a hot water expansion tank in the system, not just accumulator settings?

 

Is there a non-return valve in the cold water feed pipe to your calorifer?

Edited November 1, 2015 by blackrose

[valrene9600]

Thanks the PRV is 3 bar.. I don't seem to have any issue when running the boat without washing machine on.[/quote

 

 

Were you able to use w/machine OK before you put in new prv.

If yes then suspect new prv is faulty or not same bar as old one.

[bottle]

Ok. Tried what you just said bottle. 0.9 bar tap open, pump off... After the pump comes back on the pump cuts off at 1.5 bar.. Do this sound better and do I need to do anything else?

 

Sorry Ditchy

 

Just got back on-line.

 

That all sounds fine, maybe a little tweaking, it's not an exact science, see Tony's post #9, so with a cut off of 1.5 bar the setting for the pressure would be 0.75 bar but at the moment the difference between 0.75 and 0.9 is not a problem, I do not think your problem is the pressure setting of the accumulator.

 

PRV, do you know what that is set at, it should be marked in some way.

 

If it is wrong, then I cannot understand why it is not doing it all the time.