Valliant ecotech 418 boiler

Hi we have a valliant ecotech 418 boiler and we have just added two new radiator and and two days later our boiler now cuts out after 20 seconds of been on, it has no flame on and either comes up with an error code f72 or a egg timer flashing

we have bled the radiators
We have opened up the return valve to drain water and air out

could anyone give us some advice on what this fault could be Thankyou

 

Could be you have air in the pump/system, try opening the big screw in the middle of the pump (with the heating off) and see if it helps.

 

Fault Code F72

Permanent Temperature Difference Between Heating Flow & Return NTC Thermistors (Thermistor Error)

• The Heating Flow NTC Thermistor Is Reading The Incorrect Resistance (Should Read 12Kohms @ 20C)
• Wiring Harness Fault Or Connection Error Between The Heating Flow NTC Thermistor And The Main PCB
• The Heating Return NTC Thermistor Is Reading The Incorrect Resistance (Should Read 12Kohms @ 20C)
• Wiring Harness Fault Or Connection Error Between The Heating Return NTC Thermistor And The Main PCB
• The Thermistors Have Been Reversed (Connected To The Wrong Pipes)

 

I’d suspect air in the system myself - can’t see how adding a couple of rads would cause a wiring/electrical fault unless it’s an unhappy coincidence.

 

Sounds like trapped air, suggest what Picasso has suggested with the pump bleed screw. The 2 radiators added, do they get hot? Do all the others get hot? Did you balance the system afterwards?

 

There should be an auto air vent inside the boiler - maybe stuck closed. On our old ecotec pro, its above / behind the pump.
We had air in the system causing pressure drop two days after radiators were changed as the air finds its way out although our air vent worked so we just had the pressure drop.

 

This is a heat only boiler and the circulating pump should be located externally on the system. Also we (as gas safe registered engineers) discourage removing a front case that may form part of the combustion circuit.

 

If the boiler is at a local high point - i.e flow and return come in underneath the boiler, better get a gasafe to come and check / replace the auto air vent.

 

It doesn't, please stop posting incorrect information, it adds nothing but confusion.
If you're not familiar with the boiler there's no sense in posting...twice you've mentioned an aav that isn't on this model and the flow and return are on top of the boiler on all the 418 variants.
Your ecotec pro is an entirely different boiler.