circulation problems

[darksta]

hi all. am pulling my hair out with a c /heating fault i have at the moment. i'm an ex-bt building services engineer, and spent many years working on boilers & heating systems industrial & domestic, large & small, did corgi when it first came out in late 80's and so should kinda know my way around a boiler etc.

this is a vaillant turbomax combi, that used to work fine. rented the flat out a couple of years ago, but since ive been back its not right.

boiler seems fine, i.e. no error codes, pump's running (impellor spinning) but we dont have any hot water at rads.

a few days ago we had hot water at rad stems, but only luke warm rads, with one not hot at all (furthest) so i balanced them up, the farthest heated up a little, so decided it needed a flushing, which i did, and then used fernox system restorer.

however, since refilling, boiler fires up, runs for 20 secs or so, flow temp is showing 82C, so obviously it shuts down.

but the flow pipe away from boiler is cold, and so, obviously are the rads now. have bled rads, drained and refilled system, vented boiler (on pressure overflow) and refilled again.. ..most confused. I cant get my head round why the pump impellor is spinning, but the flow pipe is cold.

can the boiler be airlocked? theyre supposed to be automatic venting arent they? the installation manual says so.

any suggestions anyone please?

thanks in advance.

 

[Gasguru]

If its a Turbomax Plus the diverter valves give trouble.

Turn off boiler.

Unscrew knurled ring holding on the motorised actuator.

Use long nose pliers to grip the pin inside the brass valve body. It should move freely backwards and forwards - design fault means they are often jammed.

 

[darksta]

you are spot on my knowledgable friend. i cracked it myself last night after i posted this

it did take me a good while messing about with it though, what i should have done is had another cup of tea first, waited ten minutes or so for your reply, then gone back to it

top marks!