Nest turns off boiler when calling for hot water?

[Billy Fish73]

Recently had a nest thermostat 3rd Gen fitted when I had a Worcester Bosch boiler installed (Regular system with tank in loft and immersion heating in cupboard)
Everything worked fine for a few weeks but then a couple of weeks ago noticed the boiler had gone off and wasn't resetting. After a bit of investigation I've now got it so that it can run the heating system no problem working to the nest scheduler but if I turn on the hot water using the boost it turns the boiler off and it won't restart until the HW was set to off, this also happens when the HW is called using the scheduler on the nest.
The system worked fine for a few weeks on CH and HW but it may have happened when I first used the boost function on the thermostat.
Both the plumber and electrician have been back, plumber says there's nothing wrong with the boiler (fair enough it's still running the CH so appears OK) the electrician says there's nothing wrong with the Nest. I called Nest and they're saying it's a wiring problem but I can't understand how it would have worked for a few weeks if it hadn't been wired correctly.

I'm confused and stuck in limbo with everyone saying it's not their problem and no logical explanation. The only thing I can think is the boost function has turned a relay which has now affected the HW scheduling circuits causing the glitch.
Anyone any ideas on what the cause is and a solution for it?

 

[omega015]

I would initially agreed with nest that its a wiring issue. Can you post some pictures of the wiring to each component involved? What model boiler do you have? Have you or the electrician/plumber tried to run the HW without the nest?

 

[Billy Fish73]

I would initially agreed with nest that its a wiring issue. Can you post some pictures of the wiring to each component involved? What model boiler do you have? Have you or the electrician/plumber tried to run the HW without the nest?

At work now but will try and get some photo's tonight.
The hot water works by using the immersion heater but not sure how to work it without the Nest. If the CH is off it doesn't work just on HW via the Nest.

Logic says it's a wiring issue but I can't fathom out how it worked OK for a few weeks initially

 

[dang32]

your issue maybe the 3 port/2 port valves if the nest is working ok

 

[Billy Fish73]

your issue maybe the 3 port/2 port valves if the nest is working ok

The plumber has checked/ replaced the 3 port valve so it doesn't appear to be that.

 

[mcmoby69]

Read your posts a couple of times now, no please or thank you anywhere.
I'm out!

 

[Billy Fish73]

Read your posts a couple of times now, no please or thank you anywhere.
I'm out!

Thanks