Calorifier pressure valve

[peter2407]

Fairly certain rhat I have a dripping pressure valvo on my Howden AA 078 calorifier, anyone know where i can get a replacement and whether they are standard, ie not have to be bought from Howden but somewhere more mass market?

 

[oldvarnish]

Been quite a few threads recently on PRVs. Have a search. I seem to remember they're pretty much off the shelf at any plumber's store.

 

[Deleted member 36384]

Try this place http://www.cleghorn.co.uk and in particular http://www.cleghorn.co.uk/pressure-systems/c-warm-heaters/c-warm-heater-accessories/

 

[VicS]

asap supplies http://www.asap-supplies.com/search/prv

 

[peter2407]

Thank you all.

 

[Jean]

If you have an expansion vessel fitted in the HW, check pressure is set correctly, it may simply be that you are exceeding the PRV setting as the HW expands.

 

[SimonD]

I think you'll find that any plumbers merchants will be cheaper than Cleghorn or ASAP. Standard 3 bar PRV; should be aroung £10.

 

[mikegunn]

I have an Isotemp calorifier, but I guess the principles the same. In their installation manual Isotemp infer that leakage from the PRV can happen. Quote "A small quantity of water may be expended via the safety valve during the heating up period. This water can be led to the bilge or collected in a small plastic bottle.". If one thinks about it, they're correct. The chamber of water in the calorifier is effectively a sealed chamber. There's usually a non-return valve on the cold water inlet to the calorifier, to prevent back feed of heat into the cold side of the system. Unless there is a demand for water , ie, a tap is opened, there is nowhere for the water in the calorifier to go as it is being heated. That's when the PRV earns its keep.
How do I know this? I had reason, when all else had failed, to go back and read the manual!

Mike

 

[VicS]

I have an Isotemp calorifier, but I guess the principles the same. In their installation manual Isotemp infer that leakage from the PRV can happen. Quote "A small quantity of water may be expended via the safety valve during the heating up period. This water can be led to the bilge or collected in a small plastic bottle.". If one thinks about it, they're correct. The chamber of water in the calorifier is effectively a sealed chamber. There's usually a non-return valve on the cold water inlet to the calorifier, to prevent back feed of heat into the cold side of the system. Unless there is a demand for water , ie, a tap is opened, there is nowhere for the water in the calorifier to go as it is being heated. That's when the PRV earns its keep.
How do I know this? I had reason, when all else had failed, to go back and read the manual!

Mike

an expansion tank ( same thing as an accumulator tank) fitted, after the NRV, to the feed to the calorifier will prevent this happening! Its a better engineering solution than simply having the PRV open every time the calorifier heats up

 

[charles_reed]

an expansion tank ( same thing as an accumulator tank) fitted, after the NRV, to the feed to the calorifier will prevent this happening! Its a better engineering solution than simply having the PRV open every time the calorifier heats up

Or, alternatively, run a little water out of the hot tap to reduce the calorifier pressure, with the FW pump turned off, after about the 1st 20' of engine running - a rather simpler and more cost-effective solution which has worked well for me for the last 6 years.

 

[mikegunn]

an expansion tank ( same thing as an accumulator tank) fitted, after the NRV, to the feed to the calorifier will prevent this happening! Its a better engineering solution than simply having the PRV open every time the calorifier heats up

Forgive me, but being a bear of verY little brain, I'm not sure why the introduction of an expansion tank will actually reduce the pressure sensed by the PRV.

 

[peter2407]

NRV??

 

[Danny]

Forgive me, but being a bear of verY little brain, I'm not sure why the introduction of an expansion tank will actually reduce the pressure sensed by the PRV.

The increased pressure is due to the water expanding in volume at a faster rate than the volume of the vessel it's contained in. The accumulator helps by providing a chamber for the water to expand into. The accumulator is pressurised by a diaphragm. So long as the pressure of the accumulator is below the pressure at which the PRV opens, and so long as there's still room for the water to expand into the accumulator, then the PRV won't need to open.

 

[Danny]

NRV??

Non Return Valve.

 

[mikegunn]

NRV??

Non-return valve. Allows flow on one direction only.

 

[VicS]

an expansion tank ( same thing as an accumulator tank) fitted, after the NRV, to the feed to the calorifier will prevent this happening! Its a better engineering solution than simply having the PRV open every time the calorifier heats up

 

[mikegunn]

Thanks Danny, thanks VicS. I can feel an expansion tank coming on! Another job on my list of to do's.

 

[VicS]

Thanks Danny, thanks VicS. I can feel an expansion tank coming on! Another job on my list of to do's.

There is a lot of info on one of the websites on correctly sizing it if you do decide to fit one. Cannot off hand remember which one though

 

[prv]

Or, alternatively, run a little water out of the hot tap to reduce the calorifier pressure, with the FW pump turned off, after about the 1st 20' of engine running - a rather simpler and more cost-effective solution which has worked well for me for the last 6 years.

Ok, that saves the £20 for an expansion bottle, but if you think such a palaver every time you start the engine is "simpler" you're f'ing mental!

(Or possibly you write for the Top Tips page in Viz )

Pete

 

[VicS]

you're f'ing mental!

Pete

You trying to get the thread pulled ?