Air in rads

[DaveSteveBob]

Whats the best way to remove trapped air from rads as the bleed screws don't do the job. I recently fitted another rad in the hall. I drained and then flushed the system but now I can't get rid of some air pockets that seem to stay in 2 of the rads. The system is a sealed system with all the main flow and return pipes in the loft so the rads are all lower. How does the auto vent on the boiler work (baxi duo tec), are you supposed to open it or something?

 

[JohnD]

the bleed screws don't do the job.

Do you mean (a) it doesn't come out, or do you mean (b) it fills up again?

If (a) turn off the system so the pump isn't running while you bleed, and check the pressure on the boiler gauge.

If (b) please read //www.diynot.com/forums/viewtopic.php?t=257346&highlight= to save me typing it again.

 

[DaveSteveBob]

The bleed screws are fine, no air comes out when you open them!
I will read the faq, thank you.
Is there a correct procedure for filling to minimize this problem?

 

[misterdubya]

Re-pressurise it and start re-bleeding.

Mr. W.

 

[DaveSteveBob]

Done all that and still the same, what about the boiler vent, should that be opened?

 

[xr4x4]

a auto vent is just that, auto.

have you bled the pump?

or is the system working.

 

[JohnD]

The bleed screws are fine, no air comes out when you open them!

does water come out, or nothing?

what makes you say they are fine?

what is the pressure?

was the pump off?

 

[DaveSteveBob]

Pump was off.
Water comes out all rads
Pressure is correct 1.5 Bar
Bled when cold

Why does the auto vent have a screw on the top to open when commisioning?

 

[DaveSteveBob]

Just to add to this. The rads that have the problem make a loud clonk noise as if some water has just disloged the air at times. When you put your ear to the top of the rad you can hear water dripping inside from a void onto a hot part of the metal and then fizzing. There are no cold spots on the rads however!
Could it be debris?

 

[JohnD]

Water comes out all rads

Then why do you say they have air in them?

 

[joe-90]

Cold at the top?

 

[JohnD]

There are no cold spots on the rads however!

 

[joe-90]

I saw that and read it to mean down the sides rather than the top.

 

[DaveSteveBob]

An update on the situation, I am now sure that the noise is not air after extensive efforts at the weekend. When the system first comes up to temp I get a noise that could only be described as bacon frying in a pan, the noise can be heard from some of the rads and also the boiler but seems to move about. The system was fine until I had some of the rads changed, the installers had major problems soldering the joints as they never had the right equipment to drain the system properly and tried to solder while water was dripping into the joints from inside. Eventually they used compression joints. Could the noise be clumps of flux boiling. They never flushed after doing the work by the way.

 

[joe-90]

Did the heating work properly before you messed around with it?