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Calorifier pressure release valve


Dave .Morialta

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19 minutes ago, WotEver said:

I believe they all do these days. 

Ahh. Ok. Mines made by “Howden”....it must be getting on for 25 years old now...it’s outlasted 2 calorifiers! Last time it was being swapped over it looked like new! The manufacturer at the time made a thing of the twin stats as I guess it wasn’t common then. 

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You may recall I had issues with our nearly installed systems. I thought I had it fixed. I did have. But the last week or so the system started playing up a little. 
 

Yesterday, got my car tyre pump out and checked the pressures. Hat water was a couple of digits down. Pumped it up the cold side was well down by about ten-twelve digits. Pumped it up. The systems works perfectly now, better than before. Turn tap on, pumps switches on. Turn tap off, pumps turns off. Instantly. I’m well impressed.

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2 minutes ago, Nightwatch said:

You may recall I had issues with our nearly installed systems. I thought I had it fixed. I did have. But the last week or so the system started playing up a little. 
 

Yesterday, got my car tyre pump out and checked the pressures. Hat water was a couple of digits down. Pumped it up the cold side was well down by about ten-twelve digits. Pumped it up. The systems works perfectly now, better than before. Turn tap on, pumps switches on. Turn tap off, pumps turns off. Instantly. I’m well impressed.

Surely the accumulator should mean that the pump doesn’t start when the taps open...I’d expect at least a litre if not more of water out before the pump kicked in depending on the size of the accumulator. Likewise the pump should run on a bit to recharge it when the tap is closed. 

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4 minutes ago, frangar said:

Surely the accumulator should mean that the pump doesn’t start when the taps open...I’d expect at least a litre if not more of water out before the pump kicked in depending on the size of the accumulator. Likewise the pump should run on a bit to recharge it when the tap is closed. 

To be honest that what I’ve always thought. But now I’m confused. I’ll recheck the pressures later if I get the chance. Is there a sequence? ie. hot before cold or t’other way round?

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42 minutes ago, Nightwatch said:

To be honest that what I’ve always thought. But now I’m confused. I’ll recheck the pressures later if I get the chance. Is there a sequence? ie. hot before cold or t’other way round?

Personally I’ve set the accumulator to a couple of psi less than the pump cut in & the expansion to a couple of psi over the cut out. I’ve also fitted a separate square d switch as the one on the brand new jabsco par max was playing up...I’d already sent one back! 

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1 hour ago, Nightwatch said:

To be honest that what I’ve always thought. But now I’m confused. I’ll recheck the pressures later if I get the chance. Is there a sequence? ie. hot before cold or t’other way round?

Did you set it with pump off and taps open?

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Gone through it all again. Pump off. Taps on and left on. Pump is40psi, set air pressure to 38 psi ish.

 

Carried out on both accumulator and expansion tanks. Separately. Both hot and cold taps open with pump off.

 

Water pump comes on instantaneously when either hot or cold taps turned on. Pump goes off when each tap turned off. (As if there’s no pressure in the system. I am confused.

 

Any magical thoughts please. It all seems to work okay as described, but I know it’s not right, or should I say, I don’t think it’s right or correct.

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32 minutes ago, Tony Brooks said:

If the pump cut out pressure is 40psi then the ACCUMULATOR needs setting to around 20psi or pump CUT IN pressure (probably both near enough the same). The expansion vessel should be fine at 38psi

Thanks Tony. Once again I find myself in a tizwas. I shall give it another go!

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If you set the accumulator pressure as I advised you can easily find the pump's cut out pressure by measuring the air pressure in the accumulator soon after the pump cuts out.

 

I suspect what you referred to as the "hot" one is the expansion vessel and the "cold" one the accumulator. Both may look identical but do different jobs so need different internal air pressures. To recap set the pressures with the pump off and taps open otherwise the water pressure will give you a potentially wrong reading..

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1 hour ago, Nightwatch said:

Gone through it all again. Pump off. Taps on and left on. Pump is40psi, set air pressure to 38 psi ish.

 

Carried out on both accumulator and expansion tanks. Separately. Both hot and cold taps open with pump off.

 

Water pump comes on instantaneously when either hot or cold taps turned on. Pump goes off when each tap turned off. (As if there’s no pressure in the system. I am confused.

 

Any magical thoughts please. It all seems to work okay as described, but I know it’s not right, or should I say, I don’t think it’s right or correct.

Have you measured your pump cut in pressure?

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On 08/02/2020 at 10:13, Mike the Boilerman said:

 

Yes this is a legal requirement nowadays for immersion heaters in houses, since the death of two children about 20 years ago.

 

I remember that case. Immersion heater running continuously and the water in the hot water cylinder boiled, steam and boiling water vented over into the plastic cold water tank in the loft, until that too was near boiling, at which point the plastic tank softened and collapsed sending near boiling water down through the ceiling onto sleeping children below. Horrible.

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Right. Set the accumulator to 20psi. Took about15 seconds for pump to cutout after tap turned off. Made an executive decision to increase pressure to 30 psi. Pump now cuts out (turns off after) approx five seconds. 
 

With the tyre inflator still in situ it seems the pumps cuts out at 38 psi which is what the expansion tank is set at.

 

As the pressure in the systems reduces with the tap on, immediately prior to the pump cutting in, the flow of the water in the tap almost stops, as the pump cuts in the flow increases as you would expect. 
 

At the end of the pump, not accessible unless pump is moved, there is an adjustment screw. Does this increase/decrease the flow  of water? Is it worth mucking about with it. The flow is not as high as in previous years and someone , obviously not me chief, has fiddled with this screw.

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1 hour ago, Nightwatch said:

Right. Set the accumulator to 20psi. Took about15 seconds for pump to cutout after tap turned off. Made an executive decision to increase pressure to 30 psi. Pump now cuts out (turns off after) approx five seconds. 
 

With the tyre inflator still in situ it seems the pumps cuts out at 38 psi which is what the expansion tank is set at.

 

As the pressure in the systems reduces with the tap on, immediately prior to the pump cutting in, the flow of the water in the tap almost stops, as the pump cuts in the flow increases as you would expect. 
 

At the end of the pump, not accessible unless pump is moved, there is an adjustment screw. Does this increase/decrease the flow  of water? Is it worth mucking about with it. The flow is not as high as in previous years and someone , obviously not me chief, has fiddled with this screw.

It will adjust the pressure. If you have your air pressure gauge on the accumulator (cold) and watch it while someone tuns on a cold tap slowly you should be able to watch the pressure fall until the point where the pump cuts in

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2 hours ago, Nightwatch said:

Right. Set the accumulator to 20psi. Took about15 seconds for pump to cutout after tap turned off. Made an executive decision to increase pressure to 30 psi. Pump now cuts out (turns off after) approx five seconds. 
 

With the tyre inflator still in situ it seems the pumps cuts out at 38 psi which is what the expansion tank is set at.

 

As the pressure in the systems reduces with the tap on, immediately prior to the pump cutting in, the flow of the water in the tap almost stops, as the pump cuts in the flow increases as you would expect. 
 

At the end of the pump, not accessible unless pump is moved, there is an adjustment screw. Does this increase/decrease the flow  of water? Is it worth mucking about with it. The flow is not as high as in previous years and someone , obviously not me chief, has fiddled with this screw.

Of course it did, you reduced the volume for water in the accumulator. You really want the maximum volume of water in the accumulator to minimise pump running as the calorifer or water in hot pipes cool. Nothing wrong with 15 seconds of pump running while it filled the accumulator.

 

Although 20psi (half the cut out pressure) will not be exactly the cut in pressure it is normally near enough for typical systems.

 

What was the purpose of your executive decision?

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1 hour ago, Tony Brooks said:

Of course it did, you reduced the volume for water in the accumulator. You really want the maximum volume of water in the accumulator to minimise pump running as the calorifer or water in hot pipes cool. Nothing wrong with 15 seconds of pump running while it filled the accumulator.

 

Although 20psi (half the cut out pressure) will not be exactly the cut in pressure it is normally near enough for typical systems.

 

What was the purpose of your executive decision?

I raised the psi to reduce the pump running time. Obviously a wrong decision. I will reduce the psi to 20 tomorrow. It’s a bit annoying though. Will it harm the system?

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10 minutes ago, Nightwatch said:

I raised the psi to reduce the pump running time. Obviously a wrong decision. I will reduce the psi to 20 tomorrow. It’s a bit annoying though. Will it harm the system?

No, it won't harm the system, in fact in theory the shorter pump run time would  cause a shorter cycling period for the pump and than might do a degree of harm (but not much, if any). Also because the accumulator stores less water the pump will run sooner when you open a tap so its probably swings and roundabouts.

 

How long do you think the pump runs for when someone is taking a shower or has both taps open? Bet its longer then 15 seconds.

 

If you are happy leave it as it is, it is just more likely to run in the wee small hours as the calorifier cools unless you turn it off at night.

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1 minute ago, Tony Brooks said:

No, it won't harm the system, in fact in theory the shorter pump run time would  cause a shorter cycling period for the pump and than might do a degree of harm (but not much, if any). Also because the accumulator stores less water the pump will run sooner when you open a tap so its probably swings and roundabouts.

 

How long do you think the pump runs for when someone is taking a shower or has both taps open? Bet its longer then 15 seconds.

 

If you are happy leave it as it is, it is just more likely to run in the wee small hours as the calorifier cools unless you turn it off at night.

Points taken. I will do as suggested. It makes sense.

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