No heat downstairs since Homeserve 'fixed' it

[Shcuble]

Prepare for a long story/process....
Open vented system no longer heats downstairs radiators.
No thermastatic valves just manual.
Boiler downstairs, BAXI, seems to work fine

I am a DIYer, Homeowner just over 1 year.
Moved in, heating was fine.
Then some blew up in the airing cupboard.
After 8 homeserver visits and a compensation cheque for their lack of skills..
The motor has been replaced twice
The diverter valve 3 times
HW tank stat twice
Room thermastat once
Whole system drained twice.
Eventually the electrical problem was fixed

Since then, we no longer get heating downstairs, their last visit "there must be a blockage caused by sludge". This is when i sacked them off and looked into this myself.

I've removed and flush out EVERY radiator in the house (Yes, they did have a fair amount of sludge in, now removed) I placed them back in and bled the air. Still no heat downstairs.

So i drained the system down as much as i could, every radiator open, doing this, i found that even though the water stopped coming out, if i went to another downstairs radiator, it was full of water?? This may be normal, or this might be part of the issue?

This is when i also added a Magiclean filter to the system, on the pipe between outlet of the pump and diverter valve. I bought 2m of pipe and ended up with 1.3m left, only used around 30cm but there was a lot of trial and error with fitting due to very tight space. This thing is working a treat, up to now it has cleaned a good amount (nothing compared to what i manually flushed out, it would have taken months of cleaning for the filter to do the same job if at all)

Once drained, i cleaned the header tank, added 2 liters of 800x cleaning solution (I have 9 radiators, most single but some double) so this should have been more than enough. Let everything fill up and bled the air, ran for 24 hours, mostly with heat, but at night i turned off the boiler and left pump running.
Next day i went around to each radiator at a time, attached hose to downstairs radiator, left the top tank filling ON, and left the pump on.
My idea was to keep adding fresh water to the system whilst draining each downstairs radiator, diluting the chemical in the system (Not letting the header tank get low) did this for around 2 hours.
Then drained the whole system. again, downstairs radiators still had water in them? so drained them manually as well.

Added neutralister to the header tank, let everything fill up, bled and ran for 1 week.

Still no heat downstairs!

So i learned about air locks.
Upstairs rads were fine and bled, so turned them all off at just 1 side as normal.

One at a time, isolated each radiator, bled out pressue, removed whole bleed nut(i think its called) attached a plastic nut to hose adapter.
Then i opened one side of the radiator fully for a few seconds, from what i can tell, a few bubles came out, turned that side off, did the other side.
Moved on to the next rad.

Every time i did this, hot water came through one side as expected, so the hot feed must be fine.
The cold side also generated high pressure as expected.

So this is where i am up to.
All upstairs radiators turned off, no heat downstairs.
Hot and cold feed seem to be fine to me.
pump seems to be working fine.

I have no idea what to do, the hot water is being pushed into the radiators, the cold water will flow backwards at force, so i assume the pipe isn't blocked.

Any ideas or questions extremely appriciated

 

[Shcuble]

So if you start from the front working to the back with the pipes along the wall you've got,

1) Return to boiler (The tee is the cylinder return)
2) Flow from boiler
3) Return from rads (22mm coming up from floor elbowing across)
4) Flow to rads (The one with the red arrow pointing down)

Ahh makes perfect sense, i assumed the return from the rads would be under the floor somewhere, spot on thanks

 

[Riley]

Is that an albeit thin air separator on the pipework too?? That could also be completely blocked

 

[Burger]

This is the heating plan as far as i am aware.
All upstairs rads off - 2 rads downstairs kinda warm, 3 main ones stone cold.

I am sure the pump is working, as i've opened drain valves on lower rads with and without the pump on and i'm confident it is producing pressure when on.

@Steve weightman before all the cleaning, a magnet would stick to the water/air seperator in the aircupboard, i've just tested and it still does

@Jones82 It's only one zone for the whole house
House built in 1997 so not that old!

Like i said, i can isolate a rad downstairs, take out the nut from the top, put on a house and open each valve on the rad, one will give me flow hot water, other will give me flowing colder water, so the pipes going to them seem fine..

If there was for some reason a non return valve on the heating system, where would i look?

View attachment 39018

I’m assuming it’s just your diagram, but according to that, on the ground floor, you have a flow in one side with no return, and a return with no flow or the flow and return from one rad at the same end?

 

[Steve weightman]

Still say somewhere in their there's a blockage it could also be pumping over

 

[Millsy 82]

Personally I would say remove gate valve under the 3 way valve as there is no need to have that there.

I would doubt that the pump would be running slow as it looks like a ups pump so not very old but there is a possibility.

Those air seperators are shocking and do block up but from experience they limit the amount of cold coming in so they suck loads of air in. But I wouldnt say that is your problem.

You will have a blockage somewhere shut off all rad valves throughout the house drain 1 of the culprit rads open flow then return see if water stops if water flows but slows down you have a partial blockage somewhere give the system a good powerflush to try and remove the blockage.

 

[Amos84]

I would personally cut that air jec out and replace with a traditional h block. Had exact same problem on a job a few years back and worked a treat. Cut it open and there wasn’t much in it but enough to cause issues. Well worth a try