Telfords Thermal Store Drop tight PRv

[DiyMarkJones]

Hi -

I have a Telford's Tristar Thermal store with a Caleffi 533..h PRV set to 3 bar.

The PRV doesn't appear to be drop tight, so static rises from 3 bar to 5.6 bar when no flow.

When I had the thermostat replaced on the cylinder recently the plumber doing the job suggested I should replace the PRV. When I had another plumber out (as the original wasn't available to do the job) to replace it they suggested that it didn't need replacing as it was fine for it to not be drop tight and for the pressure the creep back to mains. It's been like this since install, around 6 years ago.

My question is, who is right and if I do need a drop tight PRV, any recommendations on brand?

 

[John.g]

If it rises from 3 to 5.6bar very rapidy which is probably the mains press then the expansion relief valve will lift at 6bar every time the store heats up, it takes 7L to increase the pressure from 3 to 5.6bar with a 18L E.vessel and 9.5L with a 24L.
The Caleffi 533841H doesn't specifically state that it is drop tight other than saying that it conforms to EN1567
The Honeywell D04 is not stated in their brochure as being Drop Tight whereas their D05 is stated as being Drop Tight,

 

[ShaunCorbs]

If it rises from 3 to 5.6bar very rapidy which is probably the mains press then the expansion relief valve will lift at 6bar every time the store heats up, it takes 7L to increase the pressure from 3 to 5.6bar with a 18L E.vessel and 9.5L with a 24L.
The Caleffi 533841H doesn't specifically state that it is drop tight other than saying that it conforms to EN1567
The Honeywell D04 is not stated in their brochure as being Drop Tight whereas their D05 is stated as being Drop Tight,

They don’t have a expansion relief eg prv is only there to regulate the incoming coil pressure to under 10 bar