New 3 port valve -> air in system

[guinness22]

Hi,
I have been having problems with my heating for a little while (downstairs rads not getting warm / all a bit noisy ect) but with the help of this forum, I managed to get it all working fairly OK.

Only problem I had left was that the control system was very naff so bought a new Danfoss heatshare pack (OK not the best, but as three port valve was Danfoss, thought it should be easiest to fit)

Changed the electrical side on Saturday and all fine, changed the 3 port valve Sunday, and all fine for about 8 hours. After that all the radiators have gone cold. Tried bleeding at the bleed valve next to the cylinder (on a 1 ½ foot vertical bit of pipe) loads of air.

Ran the pump for ~5 seconds I could feel this pipe get cold again. Stopped the pump and tried the bleed, and sure enough full of air again. Repeated this until I got bored.

As I see it, the pump must be sucking in air somewhere, but does anyone know how I would tell where. Will probably change the three port valve back for my old one tonight and try that – old one was stiff to turn – how stiff should it be? Don’t want to damage the actuator. (Never been able to have HW on without getting CH also in past so could live with sitting actuator on floor and turning valve manually)

Any help / advice would be gratefully appreciated.

J

 

[MANDATE]

Will probably change the three port valve back for my old one tonight and try that – old one was stiff to turn – how stiff should it be?

Any help / advice would be gratefully appreciated.

The spindle on a 3 port valve should turn very easily using finger and thumb. The motor in the valve has to turn the quadrant against a strong return spring and a stiff spindle maybe too much for it.
You can't fully operate the valve manually. You can use the lever which engages with the quadrant to move the valve from HW position to just past mid position, but not fully across to CH position.
The purpose of the lever is to latch the valve in mid position when refilling the system, so both HW and CH ports are partially open.
If you don't do this, then the CH port remains closed off and prevents the system from filling correctly and you most likely get 'air locks'

 

[guinness22]

Hi, thanks for this, was wondering the point for the manual lever on the actuator. Had removed the actuator and turning valve with pliers previously. Not put old valve back in as I think it is too stiff, and I can't see what could be wrong with the new one.

Only thing I see that I may have got wrong is I have put the valve the wrong way around - I.E. A side towards HW rather than CH, not sure whether this would make a difference as the valve (without actuator appears symmetrical) – please correct me if there is a difference.

From looking at other threads, the only place that air could usually come into the system this quickly would be through the overflow in the loft - anyone know under what conditions this occurs?

Thanks

J

 

[MANDATE]

It will make a difference if you put valve wrong way round.
If you select CH only you want valve to move fully across to the CH position and send heated water to radiators and not to the cylinder.
If you feel at the pipes leaving valve, one will be hotter than the other.
So is the right pipe the hottest.
Not only that if you put CH on and water goes to cylinder how can the cylinder stat or room stat control anything. The cylinder stat is not providing the power to light boiler and the room stat will never get satified