Repeated Air in Central Heating System - Help appreciated

[John.g]

CP1 on that pump is a excellent mode on that pump as it maintains a 3M head between 0 LPM and 48LPM, CC1 rises to 4.2M at 0 LPM and the head falls below 3M from a flow rate of 23LPM.

 

[Limecc]

I had this problem and it was caused by a leaking coil in the hot water cylinder leading to fresh water constantly entering the radiator circuit. Fresh water is aerated and was released when it heated up. Changing the cylinder and fitting a vortex type air separator (don't know the proper name) fixed the problem.

I think I diagnosed it by tying up the ball cock and emptying the cylinder via a hot tap. Water never actually stopped, now entering via the system circuit header tank.

 

[John.g]

A very good point. My F&E tank is higher than the CWST and I keep the mains supply to it (F&E) shut permanently via a 1/2 ins gate valve, I can't look into the tank but open the isol valve a few times/year so will hear any make up via the ball cock. Ideally the water level in the CWST should be higher than the F&E tank to avoid contamination if the coil fails, if so then both levels will equalize or the F&E might start overflowing so worth checking out in the OP's case but easy to overlook.

 

[Limecc]

Ideally the water level in the CWST should be higher than the F&E tank to avoid contamination if the coil fails

I'm in a bungalow so have them both at the highest possible point, but I think it's a moot point as there was contamination every time somebody ran a bath or shower. With all that air and no inhibitor I must have had some serious rad corrosion going on.

I fitted an Adey Magnaclean filter before the boiler at the coolest point and it's pulled out an incredible amount of crud. The back boiler no longer pops and bangs, I'd attributed that to limescale. Must get rid of the latter, will start a separate thread.

I placed the air separator/vent pipe just before the pump suction, the pump is fitted horizontally tilted about 30 deg. System is more or less self bleeding since.

 

[Vessy_1]

I had this problem and it was caused by a leaking coil in the hot water cylinder leading to fresh water constantly entering the radiator circuit. Fresh water is aerated and was released when it heated up. Changing the cylinder and fitting a vortex type air separator (don't know the proper name) fixed the problem.

I think I diagnosed it by tying up the ball cock and emptying the cylinder via a hot tap. Water never actually stopped, now entering via the system circuit header tank.

Hi, I’ve already considered this and ruled it out, the CWST level is probably 2ft higher than the F&E level, I have had no increase in height of the water level in the F&E. Heating been on all day today and I’ve had very minimal air, putting that down to the fresh water taken in yesterday to bleed the air out, time will tell!

 

[John.g]

I'm in a bungalow so have them both at the highest possible point, but I think it's a moot point as there was contamination every time somebody ran a bath or shower. With all that air and no inhibitor I must have had some serious rad corrosion going on.

I fitted an Adey Magnaclean filter before the boiler at the coolest point and it's pulled out an incredible amount of crud. The back boiler no longer pops and bangs, I'd attributed that to limescale. Must get rid of the latter, will start a separate thread.

I placed the air separator/vent pipe just before the pump suction, the pump is fitted horizontally tilted about 30 deg. System is more or less self bleeding since.

A lot of problem systems have the pump pumping downwards which doesn't help, also helps a lot if the pump head can be limited to 3M or less. My OV system with a combined cold feed and vent does have the pump pumping downwards but its installed downstairs and outside on the boiler return. I run the pump on a PP setting of ~ 4.3M which results in a effective head of ~ 3M and less as the TRVs throttle in.