No, it's not impossible. If the bladder is ruptured, the gas volume becomes displaced to water. Then the compressibility of the system changes radically, and you can see things like you describe.
Is there a valve you can top up the gas pressure with? If you poke it, does gas or water come out?
If you get any water, then the accumulator is goosed.
i'd check it anyway - the "continuous hunting" you describe could be what my similar setup does when there's no/not enough air in the pressure vessel to slow the pump hysteresis. the pump will still pressurize the tank with water .... (to pump air in easily, remember to switch off the pump and open a tap
- so as you pump air in the water has somewhere to go)
Jim K
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...
The pressure even without gas in the accumulator would drop to the pump start pressure before cutting in. As I said previously and subject to the checks I listed I would be looking at the pressure switch being damaged by the frost. The available cushion volume will be very much reduced at the high pressures quoted simply because it is compressed. Reduced cushion volume - reduced hysteresis and hunting results.
your theory assumes the pump is capable of those high pressures - seems a bit "over spec" to say the least?
Jim K
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Jim K saying something like:
Those pumps will reach that, no problem.
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This group is free.UK.DIY.Home - it is free, it's aimed at the UK, it covers DIY, specifically in the home. There's a competing (and usually better) group called uk.d-i-y; this is also for the UK, but has at least one regular from New Zealand...
Andy
That's very interesting and I agree that it is possible ! I do have a valve on the accumulator and I will check Thanks Blair
I have already cheeked the pressure and it is correct but Ron pointed out that the bladder may be ruptured and the accumulator may be filled with water! Blair
The pressure even without gas in the accumulator would drop to the pump start pressure before cutting in. As I said previously and subject to the checks I listed I would be looking at the pressure switch being damaged by the frost. The available cushion volume will be very much reduced at the high pressures quoted simply because it is compressed. Reduced cushion volume - reduced hysteresis and hunting results.
Thanks for your comment. Yes it is possible the pressure switch has been damaged as well as the pressure gauge. I'm not sure how I can check the operation of the pressure switch? Blair
which pump are we talking about again?
Jim K
or simply have no air on the "air side" as I and others have postulated...
maybe the severe cold temporarily messed with the accumulator sealing (contraction/expansion?) and allowed your air out? easily tested......
[on mine the EPDM "bladder" is moulded to a shape a bit like a rugby ball but with one end opened out and moulded to mate with a 6 bolt flange where the pump output gubbins, pressure switch etc are located- at the other end on the *outside* of the pressure vessel is a schrader valve where one tops up the air pressure. The air normally
*surrounds* the inner bladder (NB water on the inside of the bladder) and provides the desired hysteresis - if it's low/gone as mine does for some reason once a year I get instantaneous on/off pumping when taps are opened /closed (albeit without any wacky pressure readings)]Jim K
Confirm the pressure gauge is ok. If it is watch it when the pump turns on and off. The operating pressures should match the switch setting
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Jim K saying something like:
Fuck knows, I haven't clapped eyes on the OP's pump. I've occasionally seen pumps of this pump-above-accumulator type at more than 6bar, which is too high for the house pipework, caused by the owner fiddling or the settings drifting.
The pressure even without gas in the accumulator would drop to the pump start pressure before cutting in. As I said previously and subject to the checks I listed I would be looking at the pressure switch being damaged by the frost. The available cushion volume will be very much reduced at the high pressures quoted simply because it is compressed. Reduced cushion volume - reduced hysteresis and hunting results.
The firm who supplied my system has now returned from holiday and I asked the manager to comment. Fortunately he was paying a visit near me and said he would call in. His conclusion was the pressure switch and pressure gauge were Ok and the likely cause was the non return valve on the inlet to the pump was leaking due to particles preventing complete closure. I will check this as soon as the weather improves I have always found him to be very reliable in his answers Hope he is right. Watch this space! Blair
yes...
it's not really the volume that reduces hysteresis, it's the pressure that volume is under.
When you said in your OP:-
"> The pressure in the pressure vessel is at 1.38bar"
was that one of your measurements or not?
but shurely that would mean pressures inside are lower than they should be not higher?
that's not logical - if it's leaking pressure back out why does the
will do - it's getting rather difficult to keep track of what's fact and what's expectation here! ;>)
Jim K
The pressure gauge had been affected by the freezing and he simple removed the over and wound the pointer back to its correct pressure saying at the time that pressure gauges are unreliable. In other words the original starting and stopping pressures were the same as before Blair
strewth ;>))))) that doesn't sound like a "gauge" that actually measures anything then!
so have you checked that there *is* air and the pressure of it (with pump switched off and a tap open) yet? or are you leaving it all to "the professionals"?
Jim K
I must thank you for making me check the pressure again and I found that the pressure is 2.0 lbs?sq ins and not 20 as I had previously read. The hunting is obviously caused by this. What a mistake! Will report back when I pump up Blair
I am happy to say that now that I have brought the pressure tank up to the correct pressure my system is back to normal The only thing wrong is the pressure gauge which is reading high. I could replace it but at present there is no need as the pressure switch is still set as before If ever I needed to reset the pressure switch I would need an accurate reading gauge Many thanks to all who helped Blair
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