Getting hot water but no heat to radiators.

[Mark1992]

Hi,
I am abit stuck and cant really find a solution anywhere..
So, i have an F&E gravity system. The central heating pump needed replacing as the shaft had seized, changed it all well and good pump working lovely.
I am getting only hot water
The mid position valve is on the middle setting , if hot water only its on water only and heating is on the heating setting. So the actuator works fine..
Just nothing is passing through the radiator circuit from that valve.
Ive drained the system twice and bled the system..
Ive bled the boiler aswell. Ive ran out of ideas, if no solution i guess its a call to the local plumber!
Thankyou

 

[king of pipes]

Did you bleed the pump these can become air locked loosen the screw on the front of the pump ? With a suitable container under there and an old towel run the system on heating only to start with gravity systems are notorious for air locking.

 

[Mark1992]

Its a self bleeding pump i replaced with the old one like for like the old one had a screw but this one is just a blanked cap and cant be undone?
Dosnt sound like an airlock the pump is running really quiet?

 

[Deleted member 120897]

So the pump runs and 3port valve moves to heating, doesn’t the boiler fire up for heating alone?

 

[Mark1992]

Thats correct, the pipes around the pump are hot but the one that goes to the radiator circuit are cold.
The boiler fires up no problem

 

[Deleted member 120897]

Well if it’s not an air lock, although the 3 port valve is moving position, it might not be moving on the spindle? do you know if the head is detachable? Starting from cold, if you select just heating does the boiler fire up and the pump and pies get hot?

 

[Mark1992]

Well if it’s not an air lock, although the 3 port valve is moving position, it might not be moving on the spindle? do you know if the head is detachable? Starting from cold, if you select just heating does the boiler fire up and the pump and pies get hot?

It is detachable if i turn heating on/off you can see the spindle turn and on the body of the valve you can freely move it with your fingers . Yeah just heating the pump and pipes get hot it is just the radiator pipes not hot
So in the picture the pipe going to the right is really cold

 

[John.g]

Looks as if it could be some pump "problem".
Check that the pump is orientated correctly (same way as last one) arrow on pump body should be pointing at the mid position valve. Pointing UPWARDS (just saw a bit of the pump)
Check pump mode and setting, some have a auto setting mode which is completely useless on most. Can you post or photo the actual pump make, model and mode, and setting, may be able to assist.

 

[Deleted member 120897]

Well I’d say either a pump issue (valves don’t look fully open), or could be rad valves. Did you close any off?

 

[Mark1992]

Thanks everyone, i did put the pump upside down whst a doughnut to be honest been scratching my head for like 12 hours. Had to bleed everything on the system including the hot water tank in airing cupboard... 30 minutes later radiators come on nice and hot.

Thanks for your help, this was my last resort before calling someone

 

[John.g]

It could happen to a Bishop!. As a matter of interest what make is your replacement pump and what mode are you running it on.

 

[Mark1992]

It could happen to a Bishop!. As a matter of interest what make is your replacement pump and what mode are you running it on.

Its a grundfos alpha 2 auto adapt, i was running it at the max power setting to start with as it suggests in the manual but now its in automode and radiators are all good

 

[John.g]

Very good. At last, good to hear that the Auto Adapt is working well.
I think that pump also displays the power output in watts (W), if so, when you get a chance, you might post the power outputs in CH only, HW only, and CH+HW.
Thanks.