New build hot water issue

Hi All,
Recently moved into a new build over the weekend but having issues with the hot water. Posting here in case it’s a stupid error before getting the builder out. I have a unvented hot water cylinder but it doesn’t appear to work unless I also switch on the immersion heater which I’m told costs a fortune to run. The program timer has been set fine but even after a few hours it’s only like warm. There is a thermostat on the tank and I can hear it click off around 30 but never gets above that - it’s set at 65. Iv attempted to reset the thermostat but it’s not had any impact .

Thanks

You need a G3 qualified plumber, not a builder.
When you say cyl stat clicks at 30° do you mean when you rotate it manually?
That would be normal as it will click when you go below and above the temperature it is currently at!

Do you have a gas heat source (boiler)
Is it a heat only or a system boiler?

Try your central heating at the same time as your DHW.

Michaelmholden said:

Posting here in case it’s a stupid error before getting the builder out

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It probably is something simple but if you don't know you don't know. Give the builder a call.