Air circulating after 40 minutes

[Diyplumb]

The T goes to a bathroom radiator which is always on and acts as a bypass. There are no other valves. The pipework starts with 28mm from the boiler, then down to 22mm as per the photo and then down to 15mm nearer the radiators.

 

[Last Plumber]

My advice is to get a heating engineer or Plumber, ( unless you're competent enough of course), to get rid of that air separator and re pipe that section / area of your system, ( cold feed, vent and the bypass).
Then it needs balancing.
Presuming the system is wired correctly and there are no restrictions or blockages / partial blockages, it should be fine.

The other option is to convert to a sealed system.

 

[Diyplumb]

Thanks for the thought. Yes, I can make any plumbing changes. Are you suggesting replacing the separator by just using two Ts to take the vent and feed off to the t/e tank? Could you help me understand why you think the air separator should be removed. I have tried to see if air is entering via the vent pipe by putting a thin plastic bag over it (it could blow off it overheating) but this also does nothing.

 

[Last Plumber]

I just never used them and never liked them.

This is obviously only my opinion of course, some do rate them !

In my part of the world they were used a lot on housing estates and the problems you describe are plentiful.

That said, the plumbers left a lot to be desired in all areas, not just heating, so it could just be, that when I see one, I am reminded of past encounters !

I will see if I can find a good example of how I think it should be done !

Bare with me and I will try to post a diagram.

 

[Last Plumber]

Hello again.
Read the above and see if it makes sense to you.
Pay attention to the comment about the pump manufacturer instructions too.

The above is how I tend to pipe things up and have done for a very long time without any issues. I can only tell you my thoughts and I obviously haven't seen your system in the flesh, so to speak.

The bypass is a different thing to this of course.
You could leave the rad as a bypass but I, ( if installing this from new), would have the bathroom rad as part of the Heating circuit and fit an Auto bypass from where yours is now ( after pump/before valves) into the boiler return, in 22mm !
It would be best to have at least 3 meters of that bypass.

This is the type I would use.

 

[Diyplumb]

Many thanks for the diagram. Would you know what the explanation is for the inverted piped cold feed entry? I thought it was to stop hot water rising into the f/e tank however due to water expansion i think this will still happen. I also have a problem that due to the positioning of the boiler in relation to the f/e tank in the loft, I can't take the vent and cold feed off to the loft until after 3 metres of sideways (slight incline) flow pipework. I presume this is not ideal but is this a show stopper?

 

[Last Plumber]

The flow off your Boiler MUST go directly to vent and rise all the way. It can travel off to the side of course, some go all the way across the house. There must be no restriction and even when it is in the horizontal it should still have a slight rise to it so any air or gases will naturally purge over the vent. Does that make sense?

 

[Diyplumb]

After much investigation, I have decided to get the system converted to a pressurized one. Thanks for all of the comments and suggestions.

 

[Last Plumber]

Good decision!

 

[Harvest Fields]

Just remember that sealing a system that has not been pressurised before can also cause a few small leaks. It does not happen often, but does happen sometimes. Also make sure the system is flushed properly.