Central heating not working

[Jonnyhjazz]

Hi, Hot water is fine but no heating except for 1 rad upstairs. I don't have a combi boiler.....A new mid position valve was fitted 3 months ago, (Drayton MA1) the lever on the side is moving as it should dpending on what programme is selected. I replaced the pump last night (Grundfoss 15-50) but still no heat into rads. Boiler and pump are firing up on demand. There ois no air lock in the pump, all rads have been bled and i am now at a loss of what to do. Any help would be great

 

[Dickie1]

You may have an air lock or sh.t in the heating pipes mate? Is there any heat getting past the mid-poss valve on the CH side?? Does the boiler fire up when the system is cold & you select Heating only??

If you can establish that all the controls are working correctly, then it's down to circulation.

 

[Jonnyhjazz]

Thanks for the reply. There is heat getting past the mid poss valve on the CH side. On my central heating i can either select just hot water or hot water and central heating, i can't have central heating without hot water. If i turn it all off, turn the water stat down to zero, turn the CH room stat up and switch it on, the boiler fires up as does the pump

 

[Dickie1]

You may just have an air lock, did you drain the system to fit the new circulation pump??

 

[Jonnyhjazz]

Hi,

Only partially drained the system past the shut off valve near the pump.

Changed the pump, bled all radiators, undone brass screw on pump to make sure no air lock.

I will say that I kept the heating on overnight and 2 radiators downstairs have heated up, but there are still 4 that are freezing cold.

 

[HERTS P&D]

Normally with a stubborn air lock what I do is, turn on the heating only and turn the pump speed up and down constantly leaving a 1 second between settings.

You can normally hear the air moving around and hopefully coming out.

Andy

 

[Dickie1]

Jonny, you can take heart from the fact that if you have an air lock, you'll clear it. 40 years in the trade & never not cleared an air lock. If you're system is manky, well that's another matter.

Is you're system open vented with a F&E tank?

 

[Jonnyhjazz]

Ok, it is an F&E system..will try the switching the pump speed up and down and see if that helps. So if it's an air lock problem,would that cause random radiators to not work? (Or does it look random to a non plumber person but there is actually a reason for it?)

 

[Jonnyhjazz]

After doing various things with the pump, swithching off and on again, powering the boiler down and back on, all but 1 radiator is now working, don't know how or why the rest have decided to work. Thanks for all your hep and suggestions, very much appreciated

 

[HERTS P&D]

Now with the heating off, go round and bleed everything to remove any more air.

If you want you can close down the working rads to force the heating to remove any air from the non-working rad.

Make sure you just close the TRVs, it will be easy to adjust back up again, or count the turns on the rad valves so that you know how they were set.

After 24-48 hrs go round and bleed again.

Keep Warm

Andy