Vokera unica HE combi- hot water activates when cold water tap is turned off

[JOHNNIE7]

hi Guys
i have hust had this new unit installed...and any time the cold tap or washing machine or dishwater takes cold water and stops ...the hot water side of the boiler starts up...it stays on for about 30 secs then switches off

im worried because with the dishwater and washer on at the same time the boiler is on and off many many times

is this a simple problem that can be fixed easy?

my old gravity feed boiler never had this problem

any help much appriechated

best wishes
john

 

[bert large]

Try getting a check valve fitted in the cold pipe to the boiler. Sounds like the pressure drop when the tap is turned on is triggering the boiler.

 

[Billy Bob Bob]

you have a dead leg on the hot call your plumber back to vent it or cut it out