Pressurised hot water and calorifier failure

[Peter]

Just reinstated calorifier after temp repair and when checking system noted ot water tank accumulator had failed, no pressure and some water coming out of valve, so assuming diaghram holed. In conjunction with NRV on calorifier cold feed, ie no room for expansion, might have been a contributory cause of the calorifier failing. Something to check on periodically, pressure in accumulator.
Anyway, my question is why do i need a NRV on the cold feed to the hot water tank?. If there isn't one then any expansion from hot water tank could be taken up in the water system and by the pump accumulator.
Another question how long should a accumulator last for?

 

[vyv_cox]

NRV on the cold water inlet to the calorifier is to prevent hot water from being delivered by the cold tap. Normally a second accumulator is then fitted in the hot water supply to take the expansion of thr calorifier.

I installed my accumulator in about 1997. I have never needed to repressurise it and it works perfectly.

 

[VicS]

Just reinstated calorifier after temp repair and when checking system noted ot water tank accumulator had failed, no pressure and some water coming out of valve, so assuming diaghram holed. In conjunction with NRV on calorifier cold feed, ie no room for expansion, might have been a contributory cause of the calorifier failing. Something to check on periodically, pressure in accumulator.
Anyway, my question is why do i need a NRV on the cold feed to the hot water tank?. If there isn't one then any expansion from hot water tank could be taken up in the water system and by the pump accumulator.
Another question how long should a accumulator last for?

If there is water coming out of the air valve on the accumulator tank ( or the hot water expansion tank) then little doubt that the diaphragm has failed The pressure relief valve on the calorifier should however prevent over pressurisation of the expansion tank.

The reason for having a NRV in the cold feed to the calorifier is to prevent hot water being pushed back into the cold water system ! The expansion should be taken up by the expansion tank.

This web-page explains how the whole cold and hot water systems should operate, how to size the accumulator and expansion tanks and how to determine the correct air pressures in them.

https://www.jabscoshop.com/files/Accumulator and Expansion Tank Instructions ZPWL4 doc595.pdf

There is also a troubleshooting guide