Vaillant 424 open vent ,pump over run.

[bob1956]

Have just installed my boiler with the nest thermostat,the pump is connected directly into the boiler,
My problem is the pump is running after the default setting on the boiler,ie;pump is running almost constantly,has anyone had this problem.

 

[CBW]

Do you mean you’ve fitted a nest to your boiler, or a nest with a new boiler?

 

[bob1956]

New boiler

 

[CBW]

Something is keeping the pump overrun on. How was the nest connected at the boiler end? 240 or 24v?

 

[Johnmdc]

Have you removed the 24v link on the boiler circuit board?

 

[bob1956]

240v I have not removed the 24v link on the board

 

[CBW]

240v I have not removed the 24v link on the board

Likely cause, this need to be removed, otherwise it’s trying to keep the heating on with the link in.

 

[bob1956]

I previously removed the link,with what I thought no change,I must have been too impatient doh,
I have removed the link now all seems ok
Thanks both for your input

 

[CBW]

Your pump will overrun at a set time period (usually by the boiler) to dissipate any heat from a hot water or heating demand. So it could have been coincidence at the time of removing the link?

 

[bob1956]

Your pump will overrun at a set time period (usually by the boiler) to dissipate any heat from a hot water or heating demand. So it could have been coincidence at the time of removing the link?

Yes I think you are right ,I was too impatient,at the time I was having problems with the nest ,im on my 3rd nest and this one works yeh

 

[bob1956]

Ok, hot water timed for 17hr this evening,boiler didn't fire nest room stat set at 30deg,to force boiler to fire,boiler didn't fire ,S30 indicated (no call for heat ,)
This is with the 24v link removed,
Pump connected directly to X14 on boiler.
Am I missing something hear

 

[picasso]

Have you connected the switched live from the zone valve/s to the 240v RT connection ?

 

[bob1956]

Have you connected the switched live from the zone valve/s to the 240v RT connection ?

Is this the connection you mean

 

[picasso]

Yes that's the one .

 

[bob1956]

No the pump is connected to x14 on the board.
Should the pump be connected as per diagram