Hot water won’t turn on by Thermostat unless the heating is on

[Honeymazey]

I’m on my second Nest because the first one went wrong, I have the same issue again, the controls won’t schedule any Hot water and won’t be en work in boost mode…

I can only heat my mega flow when the boiler is off…

[Frustratedddd]

Where are you? UK?

Are you saying the first Nest thermostat could not heat the water as well? You have exactly the same problem with this thermostat?

Who installed the thermostat and when? ie: Nest pro, plumber, yourself?

[Honeymazey]

hi , I have 2 thermostats 1 upstairs and 1 downstairs, the downstairs thermostat has been replaced because of a fault.

for no reason at all the Hot water schedule stopped working and the Boost , if the heating is on I can get my mega flow to heat up.

i have factory reset the thermostat which use to control the hot water and that’s not worked.

ThIs morning I turned the heating on then managed to turn on boost on the App…..

This system has been in for 3 years without any issues other than replacing the first Nest.

Combi and system regularly serviced by B/Gas.

[Frustratedddd]

Are you in the UK?

Do you have motorised valves in the system?

[Honeymazey]

Hi , I have a Logic combi which feeds into a mega Flow system.

it worked perfectly till a week ago no issues at all.

Combi boiler was making a noise so British Gas changed the heat exchanger….

today the boost worked ok but didn’t come on with the schedule.

thanks.