domestic hot water

[ccha]

does domestic hot water supplied by a combi boiler require any expansion vessel or safety valve ?
excessive pressure on system when tap closed due to latent heat in boiler causing expansion!?!
may have been like this for some time
boiler or system fault?

 

[bellairaphon]

what make/model? think there was a few out there with an expansion on the dhw side the vokera fm rs 80/20 had one. new ones no

 

[holty]

i know worcester covered there own ass by insisting on an expansion vessel on the dhw supply if there was some sort of check valve on the supply e.g water meter.seem to remember, think glowworm, had one with a 10 bar pressure relief valve on it on the dhw side.

 

[petit_pablo]

Can cause issues if a water meter fitted as they have NRV in them. Had a few GW cxi's leak intermittantly because of this

 

[ccha]

Ravenheat rsf84et
dhw pressure going over 10 bar when turned off
runs at 2 bar
4 bar static through prv (when cold)
no water meter

 

[ccha]

thinking faulty diverter valve, although burner goes off immediatly the hot tap turned off
possibly diaphram?
or possibly heat exchanger as static pressure rises with CH on
turning tap off very slow helps pressure
leaaving one tap very slightly open as a temporary relief as this reduces pressure without operating burner

any ideas?

 

[ccha]

exp vesel has calmed things down
max now about 2.7 bar

how many have this pressue without knowing?