Open vent downstairs rads cold

[zooankski]

HI all

My brother and his young family moved in to their first home last week and it has been a complete mare!
Everything from the front door multi point lock jamming, total re skim needed upstairs after removing 4 layers of wall paper, to the heating problem.
I am trying to help out here as funds are exhausted now and the kids need some warmth.
I will try and explain the issue and what i have tried so far to get the 3 rads down stairs to work.
2 of these are on the same run which drops down from the ceiling in the living room and the third is on a separate drop from the ceiling in the hall way.

I think the pump is on the return and attached to the round chamber in the picture which also has the feed and vent going in to it. I assume this is just a common connection point as i have not seen one before?
I think it's the return as it is cooler than the flow although don't think it really matters as it has obviously worked before.
If i run the heating for an hour then the flow pipework that i can see ( i have some access under floors upstairs) is damn hot but the return appears almost cold so i am guessing a blockage judging by some of the crud i drained in to the bath?
I have tried blanking off the vent and using mains pressure connected to the feed pipe to flush through with the y valve open. We did manage to get loads of crud out but rads still seem cold.
Am i missing something here with my flushing technique? What is the round chamber with the feed / vent and flow and return on?
Any advice would be great as i only have tomorrow left to help before i am back on shift.

 

[D_Hailsham]

The round chamber with four pipes connected is an Aerjec air separator. Unfortunately they have a tendency to block up. Use a magnet to check the copper pipes near the device (not the device itself). If it sticks, the pipe is blocked.

 

[terryplumb]

How did all that crud get into the bath ?
As DH says above you may have a blockage .
Do all upstairs rads get to full temperature ?
Besides what you described doing in your post ,what else have you established or done?

 

[zooankski]

The round chamber with four pipes connected is an Aerjec air separator. Unfortunately they have a tendency to block up. Use a magnet to check the copper pipes near the device (not the device itself). If it sticks, the pipe is blocked.

Great, that puts me out of my misery regarding what it is then - thanks!
The rads upstairs take a long time to get hot but they do and the flow pipe is damn hot.
I am home now but will check with a magnet in the morning. I did check a lot of pipework with a magnet but no joy as yet.
I think upstairs rads may have crud in too as they are hot at the top and get cooler on the way down so they will all come off tomorrow for a hose pipe flush.
Is it worth pulling off ALL the rads, closing lock shields and TRV's and then using the mains pressure to check and clear pipes only? I am assuming if i do that then i will need to tap in to the return or should it do flow and return with my main feed connection in to the aerjec feed connection only (22mm vent capped off).
The other option is making an adapter and hooking a mains hose to flow and then return on a removed radiator with the associated valve open obviously through to a drain point, or sticking with the existing feed mains supply but flushing out of each open rad valve in turn using an adapter and hose?
All the crap in the bath is from draining the header tank and my hose was not long enough to reach the lav
If the aerjec is blocked then is it worth replacing? I could fit a tower type i guess if feed and vent can be tied in together?
Thanks for the help chaps! much appreciated as i don't think my younger brother can take much more . I would pay for a plumber but we all gave towards the house deposit so all skint myself now too.
I just need a plan of attack for the morning!

 

[terryplumb]

As you have limited time before your own work commitments ,you should give priority to certain things.
1. Establish if pipework around air separator is blocked ,cut out and replace.
2. Check the pump is not clogged up and is actually working.
3. Remove the downstairs rads and flush them .just close both their valves
4. With the system filled with water open one valve at a time on each downstairs rad and ensure water flow's out. That will at least establish that all their pipes are not blocked.
5 .If any time left do the upstairs rads.

 

[zooankski]

Thanks Terryplumb. If the pipework around the separator is blocked then can i fit a tower vent? Only difference is there is no separate cold feed connection. I assume i could T in the feed to the 22mm vent as soon as possible after the air separator connection which is pretty much what i had in my first house many moons ago?
I know Toolstation do one and they are close by if needed.