Any ideas? Unreliable heating.

[garyevans]

Heating issues. Had new water pump fitted 3 weeks ago, new 3 port valve 18 months ago, boiler is 4 years old. I balanced radiators when new pump was installed and for 2 weeks or so the heating and hot water worked a treat. 3 days ago, woke up to find neither working properly. Timer comes on, boiler fires up but radiators downstairs not getting warm. Hot water not great. Balanced radiators again and all was fine but last two days every time I turn heating on nothing warm downstairs in spite of balanced radiators two days ago working fine. Pump does seem to work fine when it runs quietly but each time it starts there is a whirring noise and you know it won't work properly. Any ideas?

 

[ShaunCorbs]

What’s the make of the pump ?

 

[garyevans]

What’s the make of the pump ?

Grundfos

 

[ShaunCorbs]

Grundfos

Black one or red one ?

 

[garyevans]

Black one or red one ?

Black

 

[John.g]

Is it this one?, if so post a photo of the LEDs while running.

 

[ShaunCorbs]

Ups3 any red lights when running / having problems?

 

[garyevans]

Is it this one?, if so post a photo of the LEDs while running.
View attachment 79947

 

[garyevans]

View attachment 79949

Radiators are bled, upstairs all hot but nothing downstairs. Inlet valves are warm but nothing getting into rads. All balanced 2 days ago and working fine.

 

[John.g]

How many rad? and is it a sealed or open vent system with a Feed&Expansion (small) Tank in the attic.
If a sealed system ensure that the system pressure is 1.5bar cold.
If a OV system, present setting of CC3 at 6.4M is too high IMO and can cause air ingress.
Suggest, in either case, c/o to constant pressure setting 2, CP2 which is 4.5M.
Press the setting button for ~ 3 secs until the yellow LED illuminates at the far right, then briefly press the button until the green LED and the yelloe LED next to it are also illuminated, you are now on CP2 at a constant 4.5M head.

(Also, these pumps have had more than their "fair" share of failures.)