Calorifier Pressure relief Valve

Chris_Robb

Chris_Robb

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Does anyone know what pressure the valves run at? I have just replaced mine, at 3.5 bar, and it keeps blowing off. The next one up the scale is 6 bar, which sound quite a high pressure.

The old one that came out was 4.5 bar and I cannot find another at that setting.
 
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Standard relief valve on Hotpot is 3.5 bars...have you too small an expansion tank or has it lost its air cushion?

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Agreed, if the 3.5v/v is ok there must be a pressure system fault. A slight weep is normal according to the distructions for mine, though it has never leaked.
 
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Standard relief valve on Hotpot is 3.5 bars...have you too small an expansion tank or has it lost its air cushion?

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Yep, 3.5bar is more or less the standard now and I'd think 6.0 way too high. It does sound as if there is another 'weak' spot somewhere, perhaps a connection that weeps when the water temperature rises.

As someone has already asked, what make is the calorifier? Is there a pump? Is the water definitely 'blowing off' via the pressure valve? Is there an accumulator?
 
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Yep, 3.5bar is more or less the standard now and I'd think 6.0 way too high. It does sound as if there is another 'weak' spot somewhere, perhaps a connection that weeps when the water temperature rises.

As someone has already asked, what make is the calorifier? Is there a pump? Is the water definitely 'blowing off' via the pressure valve? Is there an accumulator?


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Its on a westerly oceanlord. It is blowing off as soon as the pressure pump is turned on when it is stone cold, in a series of spurts which then pumps up to pressure again, pauses then spurts again - the bilge is getting water in - I had asssumed it was from this valve - beter check wider, by taking the hose off it. I don't know the make of the tank but it is vintage 91. It has an accumulator - I take it this should be full of air? It has a bleed valve on the top, so if I bleed it off surely it will then be full of water.
 
Water pressure pumps typically have pressure switches set at 2.5 to 3 bar. It's possible that your pressure pump has a switch with a higher setting, sufficient to cause the new 3.5bar relief valve to operate. With most pumps, the pressure switch can easily be replaced, so it would be worth your while looking at the pump first (the pressure switch rating is usually clearly marked on it).

As for the accumulator/expansion tank, the valve on the top is for adjusting the internal pressure, using a bicycle pump. It's a bit of a black art, because you can't see what's happening to the rubber diaphragm inside the tank, but generally they should be pressurised to about 0.5bar less than the pressure switch setting.
 
>> As for the accumulator/expansion tank, the valve on the top is for adjusting the internal pressure, using a bicycle pump. It's a bit of a black art, because you can't see what's happening to the rubber diaphragm inside the tank, but generally they should be pressurised to about 0.5bar less than the pressure switch setting. <<

Yes, that's true if it's the type with a flexible diaphram, but if it's the sort I have (the VERY basic one or two litre type made, I think, by PAR) you have to drain down the water to below the bottom of the accumulator after opening/removing the plug at the top. Once the accumulator is empty, replace the plug, turn on the pump and bleed the sysytem starting from the tap farthest from the accumulator.

When that's flowing smoothly, shut it off and bleed the next one etc.

Once all the air is out, that's it. Over a season, or more often if you live aboard or use it a great deal, the air is absorbed and you have to repeat the operation.

Draining down the accumulator is made very simple by putting a draincock in the hose immediately after it leaves the accumulator. A temporary bit of hose on this into a bucket/container and bingo, a few minutes and it's done.
 
You're right - that is a very basic accumulator. Also sounds quite old, all of Jabsco's accumulator tanks have had internal diaphragms for a long time.
 
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Yes, that's true if it's the type with a flexible diaphram, but if it's the sort I have (the VERY basic one or two litre type made, I think, by PAR) you have to drain down the water to below the bottom of the accumulator after opening/removing the plug at the top. Once the accumulator is empty, replace the plug, turn on the pump and bleed the sysytem starting from the tap farthest from the accumulator.

When that's flowing smoothly, shut it off and bleed the next one etc.

Once all the air is out, that's it. Over a season, or more often if you live aboard or use it a great deal, the air is absorbed and you have to repeat the operation.

Draining down the accumulator is made very simple by putting a draincock in the hose immediately after it leaves the accumulator. A temporary bit of hose on this into a bucket/container and bingo, a few minutes and it's done.

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Thats the one I have too. Works perfectly with the calorifier, I had a pump up job and chucked it out, pain in the b##. Bill.
 
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You're right - that is a very basic accumulator. Also sounds quite old, all of Jabsco's accumulator tanks have had internal diaphragms for a long time.

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Ah! An oldie but goodie!! Westerly fitted it from new (1984) and it's performed, as has KBT's, perfectly ever since. No point in changing it even though they are still available (and still without a diaphragm!) from any chandler.

It's the effective simplicity I like.
 
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If its not the valve nthen the accumulator probably needs re-charging with air.

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But that would not account for the pump pressure valve not cutting out surely? The pump would just cycle more often. I think it would be interesting to know what pressure the pump is producing. i.e. not cutting out at the correct pressure, I had a brand new Whale pump switch gave up after a few cycles, (btw, I have always found them brilliant for A S Service). Bill.
 
I think it is the basic type - so I will drain it down as described. Also will look more closely at the pump and see if I can see what pressure it says. But I would like to replace the releif vale with a 4.5Bar as that is what came off, but only 2.5, 3.5 and 6 seem to exist.

Thanks all -
 
If it's the 'basic' type it has a plastic butterfly type grip on the plug, the other has a bicycle tyre inflator connection. Bill.
 
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