Potterton Promax 15 HE

[MethodPH]

Been called out to an issue with a Potterton Promax 15 HE. Boiler fires up and runs for 30 seconds, no heat leaves the boiler, then you get loads of clunking which sounds like air/crap. Then flow and return get red hot and it cuts out. Have disconnected flow and returns from boiler and and checked that water passes through the boiler without obstruction, which it does. Have checked where cold feed and vent enter the system no blockage there. Pumps working. Have tried draining down and refilling, fills fine but still get the same issue. Any ideas would be appreciated. I’m gas safe registered

 

[RBG]

Sorry to ask a stupid question...have spoken to Baxi technical to see if they have any pointers?

 

[MethodPH]

Sorry to ask a stupid question...have spoken to Baxi technical to see if they have any pointers?

No mate haven’t yet as I’m not sure if it’s a boiler issue or system issue

 

[oz-plumber]

Sounds like a pump issue.
Not enough flow through boiler.
Could be a faulty capacitor on pump.
Unscrew bleed screw on pump and see if you can stop the spindle with a screwdriver.
If you can stop it quite easy, replace capacitor or pump.
If you can't stop pump with screwdriver , check for any other items that may cause flow restrictions.

Boiler fires up, overheats / kettles - no flow of water or over gassed