Running out of Ideas

All radiators are cold, pump is ok, boiler is firing, hot water works, bi directional valve working. Pipes leading from the pump are good and hot but absolutely nothing at the radiators. Struggling as to what to do next

 

What system configuration do you have? Is the DHW circuit stealing all of the flow?

The energy is going somewhere...

 

Gets a little stranger, if I turn the heating off and the water on, all the radiators all begin to warm up

 

The radiators "appear" to get warm until the hot water is up to temperature and then cool off

 

You forgot to mention what you did prior to having the problem

 

It's entirely possible that this has happened (been happening) for a while, given that in the past the HW & CH have been on together. Have recently put in a Nest thermostat so had tried Heating Only, only to find that it didn't work. So quite possible that have thought heating was working when not.

 

Did the central heating work independently before the smart thermostat was fitted,its should be an easy answer.
ie,No
yes
I never tested it before fitting

 

I can't be sure as previously I hadn't ever run it independently. CH & HW were programmed together

 

If I was guessing (and I am) I'd say it wasn't working prior.

 

STEM will be along soon.

Andy

 

Despite being asked, the op hasn't deemed it necessary to tell us what system he has.

Chances are though that the wiring has been fecked.

 

Hasn't said please or Thank you either.
My crystal ball is in for a service!

 

You are unsure if it worked properly before Nest because you had both heating and hot water on.
If the fault was there before you fitted Nest, the radiators would only have been on for about a hour because once the hot water cylinder reached temp the boiler would have switched off and the radiators would have cooled down.
If the heating was working fine before, then you’ve probably done something wrong during fitted Nest

 

First of all, thanks for all the questions and suggestions, regarding the system, it's a conventional viessman boiler (not a combi).
And to summarise from the comments so far, there's a good chance the wiring is fecked.
Once again I thank you!

 

What happens if you turn on DHW only, but then operate the lever on your valve to CH?

Nozzle