How do I stop Air being sucked into pump of Vaillant heat only boiler?

[raidac]

Vaillant ecoTEC Plus 400 15kW Heat Only Boiler
I've got air in the pump and one gas engineer has said I need to move the pipes as they are configured incorrectly. Another said all I need to do is add an AAV as high as possible. Another said I should seal the system. Boiler was installed in November. The fitter didn't complete the electrics so the pump (old one now broken) controlled the boiler. He's advanced Vaillant approved and signed off the boiler as fully commissioned. Another installed the new pump which has air leaking in. The boiler is in a Studio flat (1 large room, kitchen and bathroom). There are 2 radiators in the large room, 1 small in bathroom and 1 small in hallway. What should I do?
I don't have a combi because its on 4th floor of a Victorian conversion with 22mm pipes into the building. There is a high risk rust combi wouldn't work and even if it did the boiler might not pass gas safety checks. About 90% of gas engineers I met tried to push me to get a combi but didn't have the skills to check and measure if the pressure would be an issue

 

[raidac]

Photos of system which hopefully help understand the problem a bit more

 

[EvilDrPorkChop]

What pump speed has new pump been left on? and is there an Automatic Bypass

 

[ShaunCorbs]

Seal it

 

[raidac]

What pump speed has new pump been left on? and is there an Automatic Bypass

It was on 3 for a few weeks but is now at 2. There is an automatic bypass

 

[John.g]

Assuming a UPS3?, 2 is still too high IMO as it will pump up to 1.2m3/hr (20LPM) at > a 5M head. Suggest PP2 and if you find this a bit on the weak side then go to CP1 which is a constant 3M and shouldn't cause pump over, & air ingress. ABV may then require re calibrating.
Can you post a photo of the vent & cold feed arrangement?. Pump pumpimg in correct direction??.

 

[raidac]

Assuming a UPS3?, 2 is still too high IMO as it will pump up to 1.2m3/hr (20LPM) at > a 5M head. Suggest PP2 and if you find this a bit on the weak side then go to CP1 which is a constant 3M and shouldn't cause pump over, & air ingress. ABV may then require re calibrating.
Can you post a photo of the vent & cold feed arrangement?. Pump pumpimg in correct direction??.

 

[raidac]

These are the only pics I have as I'm not there at the moment. The first pic in the original posting shows the overall system and the other 2 show the pipe work. It is a PS3 pump.

 

[John.g]

If the old pump wasn't causing any air ingress problems then very unlikely IMO that the UPS3 will cause any BUT it must be run in either PP2 mode or CP1 mode IMO.

 

[Timmy D]

Pump/feed/expansion are piped/in wrong positions.

Can’t see pipework above pump but it looks like cold feed tees in to return and pump is teed in to vent pipe.

This means the pump is pulling down the vent.

Need all 3 on the flow (as below/manufactures instructions), vent, then feed, then pump.

Won’t take long to repipe.

And at least one engineer was correct, 4th floor, you’ll never get a combi in there without a gas pipe upgrade.