DIY Doctor UK DIY Forums

Hello,

I've got an Ariston combi that's worked brilliantly for about 4 years but recently, I've had a problem with the pressure rising to between 3 and 4 bar (I'm constantly having to drain some water to stop it tripping the safety shut down). The dhw is flowing hot for about 5 secs then cold for about the same time.

Any ideas much appreciated.

Turn off cold water and run the heating - if it still rises and the combi fill is disconnected then it's probably the expansion vessel needs recharging or replacing.

If the pressure doesn't rise with the cold water turned off - then it'll be the cold water mixing with the heating water, through the plate heat-ex or combi fill etc/

Hope this helps

Rising pressure could be due to filling loop valve either not being closed fully or not sealing when closed, allowing pressure to gradually increase.

Lack of hot water could be due to faulty diaphragm.

ALDA and htg engineer,
Thanks for the replies. I recharged the expansion vessel the pressure is now ok - but my dhw still runs cold. The burner kicks in but shuts down after a couple of secs before kicking in again.
Anymore thoughts please.

could be a faulty or limescale build up on DHW sensor.