Central Heating - Blocked 22mm return pipe?

[VinMK73]

So if you turn all upstairs off no flow to downstairs?

Yep, no heat to downstairs with all upstairs off. But plenty of flow through all rads, both sides/valves when flushed.

 

[ShaunCorbs]

When you tested / flushed did you turn all the other rads off and then see if water came out of both sides ?

 

[Ric2013]

I'll leave you and Shaun to discuss flow as you seem to be getting somewhere and I don't want to interfere when it's going well.

Re the tees on the return mystery, I've thought about that. Obviously the return from the cylinder and the radiators will join up at some point before they reach the boiler so quite possible that the tees into the return from the cylinder are from radiators or from a bypass valve.

 

[ShaunCorbs]

I'll leave you and Shaun to discuss flow as you seem to be getting somewhere and I don't want to interfere when it's going well.

Re the tees on the return mystery, I've thought about that. Obviously the return from the cylinder and the radiators will join up at some point before they reach the boiler so quite possible that the tees into the return from the cylinder are from radiators or from a bypass valve.

Tee for the rads left side after the lever valve coming out of the floor

 

[VinMK73]

When you tested / flushed did you turn all the other rads off and then see if water came out of both sides ?

Yes, as I flushed each radiator, from each side of the rad I was working on at that time, ALL other rads were off, both valves closed.

I repeated this as I moved around each of the rads in the house. Only the one I was working on, had valves opened then closed as I flushed from each side, alternating each side until water was crystal clear.

 

[VinMK73]

Hello again.

Just an update - So no progress for this issue for me.

This week I fully drained down again, water wasnt too bad, pretty clear during the drain down. Refilled and added 2 litres of CalMag, its been in there 3 days now. I gradually added the Calmag as the system filled to distribute it as evenly as possible.

Exactly the same issue, all upstairs rads warm to hot, with the exception of 1. Downstairs rads cold. Boiler comes on for about 1minute 20 seconds every 5-6 minutes.

Took these pictures of the old 3 way valve that was replaced a couple of months ago now. The clear side was to the hot water, the heavily contaminated side, was to the central heating / rads.

I am completely out of ideas and options, other than try Powderflush, but the quote for that was very high (considering that I seem to have good flow and to / from the actual rads. Or strip them all out and put in electric rads. But electricity prices are a real issue on that front.

If anyone can give me any further ideas to get this system working, it would be appreciated. Im sure its not the boiler itself, unless the heat exchanger is also partially blocked with that crud in it.

Cheers.

 

[Ric2013]

In fairness, that does look to be heavily contaminated. Unfortunately, I am out of ideas as if you are actually getting a reasonable flow to the radiators it follows that this should be accompanied by a flow of heated water and that the radiators should therefore heat up.

Last ditch attempt if you want to avoid an expensive powerflush would be to try flushing through the pipe runs (not the boiler itself) using your water mains as the source of flow. May not work, but shouldn't really cost you anything to speak of except your time.

 

[VinMK73]

Thanks again for the response. Yes it seems to have too much crud in the system. Why I am not sure, as it was only a very small old rad that appeared to be rusting, all the rads are now new and the water flows through when I forced it through each rad, alternating on the flow and return on each of those rads. Im stumped but Im no expert on this.

Only way I can think of doing that is cutting the pipe in the airing cupboard and creating some sort of attachment. I'd also have to cut the return pipe above the boiler.

Im now pretty certain it is the return pipe, main return from the airing cupboard to the boiler as its remaining too cool compared to feed. The returns from rads are too cool too in comparison to feed.

In between a rock and hard place with it right now, as Im getting just about enough heat upstairs to stay warm and using elec rads downstairs to heat the rooms in use, only 2.

Im at the point Id happily just strip out the water rads and boiler and go full electric, but that becomes a running cost issue!

 

[Knappers]

Nowhere here can I see any mention of removing pump head and checking/cleaning veins.
That would have been first on my list.

 

[VinMK73]

Nowhere here can I see any mention of removing pump head and checking/cleaning veins.
That would have been first on my list.

The pump was new at the time of the power flush and after the rads were all replaced. I dont think it's the pump at this stage, though have considered swapping it out again.

The CH feed pipe in the airing cupboards, some 7-8 meters from the pump and boiler is very hot. The return pipe below it for the CH and hot water cylinder is cool/cold to touch. As is the section of the return pipe at the boiler (as expected if its cold elsewhere.

Im now almost certain its a blockage between the airing cupboard and the boiler 7-8meters away. If I could clear that pipe I think it will start working significantly better. But there may be minor build up and restricted flow elsewhere in the system. If I can get the main flow and return working correctly, given how I've flushed all the radiators I think Im in with a chance of fixing it, but how can I clear a blockage on the return?