10mm Microbore - suspected blockage or airlock on C/H return

[Wildeman]

I have a weird issue with my C/H which has been happening for a while now but I am now in a position to drain the system (fitment of a new 3 port valve body and TRV's on the rad's) that I want to see if I can cure this issue once and for all so I would welcome any opinions:

I know that there is sludge in the system due to it being run by previous owners without any inhibitor in it and the 3 port valve is also jammed as when the H/W is on it's own the radiators come on but this valve is being swapped as I mention.

The main issue I have is the H/W works fine and then it works fine when the H/W cylinder is calling for heat and so too is the room stat for the C/H. The issue I have is when the H/W cylinder stat reaches it's temp but the room stat for the C/H is still calling for heat the valve moves fine, the wiring and voltages are what is expected but there is a whooshing sound of water and the heating pipes around the valve and pump go cold. The radiators will eventually go cold too.

I have noticed that the boiler fires but not for long, the pumps runs as expected. Now my thoughts are that there maybe a blockage or even an airlock in the return from the heating to the boiler (the boiler is a Glow Worm System boiler - non condensing about 20 yrs old and has 1 feed and 1 return on it) and this is stopping the flow causing the boiler to cut out due to the water not moving through it. I am also thinking this because when the valve is in the mid position the return flow to the boiler is through the hot water cylinder taking the path or least resistance. I also think this as I get water from the overflow loop on the F&E tank when the valve is in the C/H only position.

I have sludge in my F&E tank so the plan is to clean that out and then drain the system and flush with mains water from a hose pipe on just the C/H circuit but wondering if I may need to back flush it (assistance on how to do this would be appreciated - there are pictures on my profile of the parts of the system). Once I have flushed I was going to run the system with X400 in it (maybe double dosed) for a while to further clean the system.

Are my thoughts (and they are only thoughts) valid - any assistance would be appreciated.

 

[Agile]

Why use X400 when you can use X800 ?

Tony

 

[Wildeman]

Is X800 not just for powerflush machines or can it be used in the system and circulated via the pump?

 

[Agile]

Its stronger than X400 and works in a couple of hours!

X400 is weaker and takes 4-5 weeks!

 

[Wildeman]

Thanks Tony

I have 11 rad's - would you double dose the system (2ltrs) or just use one litre and am I right in thinking circulate it for a couple of hours at normal running temperature?

Andy

 

[Terry7556]

I used some x800 last week on a 10 mm system in a bungalow. Before 3 of 6 rads worked , after ,2 of 6 rads worked . God knows how it was worse.thats life
What worked on this system was a combination of things , mostly elbow grease and a tip I read on here last week. Rod the pipework with curtain wire.
Went to wilkos, bought a 8 foot length for 85p and when I took a rad off and opened the valves each side to check for flow, if water did not flow I took the valve off and rodded the pipework with the curtain wire.had a clear h /duty bag (Plumbcentre bags perfect, clear ones, see what's going on) ready to collect water, crap whatever
I know this sounds crazy but it worked. Also realise with a bungalow it's easier as there is only so much water over your head in the loft area to come down. That's why a clear bag helps, you can see what's going on as you try to reconnect the valve to the pipework after rodding it and water flows again
So a combination of rodding and changing manifolds worked in this case
Good luck with it

 

[Agile]

Thanks Tony

I have 11 rad's - would you double dose the system (2ltrs) or just use one litre and am I right in thinking circulate it for a couple of hours at normal running temperature?

Andy

Why would you double the dose?

Particularly with microbore when there is less system volume.

I would leave it running for at least four hours.

Its OK to drain it the next day but don't leave for more than one day.

Tony

 

[Wildeman]

Thanks Tony

I have 11 rad's - would you double dose the system (2ltrs) or just use one litre and am I right in thinking circulate it for a couple of hours at normal running temperature?

Andy

Why would you double the dose?

Particularly with microbore when there is less system volume.

I would leave it running for at least four hours.

Its OK to drain it the next day but don't leave for more than one day.

Tony

Thanks Tony

Just been reading an article about Y-Plan systems and the fact that if they do not have a by-pass fitted (which mine doesn't appear to have as there would be a T piece in the pipe work near the pump) then normally one of the rad's acts as a by-pass. It says if this is the case then that by-pass rad either has no valves on it or two lockshield valves.

I am wondering if one of the rad's on my system is a by-pass rad, but if this is the case all of them has a lockshield valve and a hand wheel valve. I have got the hand wheel valve and lock shield valves on all the rad's almost closed to get he heat to all rad's and wondering if I have messed with the by-pass rad without knowing it!!!!

How could I tell which rad is a by-pass if this is the setup - the kitchen rad was removed 4 yrs ago and the pipe tails capped and buried in the wall.

 

[Wildeman]

I drained the system down fully yesterday to fit TRV's to all but 2 rad's (11 rad's in total and 9 with TRV's) the water and F&E tank were sludgy so I removed the F&E tank and fully cleaned it out and then once I brought the system back up and filled with water and used X800 and ran the system for 5 hours with all the valves on the rad's fully open and pump on it's fastest seting. I then flushed the system under mains pressure from all the downstairs rad's drain off points and also from the drain on the return to the boiler.

The water was very dirty at first from all points and then eventually ran clear and on a couple of them and the boiler the flow was small and then surged and was increased.

The system is now fully running with inhibitor in it and all rad's bleed.

Now can you tell me if the next steps I have taken are correct in your opinion:

1. I have all the lockshield valves on all rad's (not just those with TRV's fully open)
2. I have the TRV's set to the desired room temp
3. I have a new 3-port mid position valve (the head appears to be working ok from the old valve but I have a new one just in case)
4. The hand wheel on the pipe to the H/W tank from the valve is fully open
5. Room stat set to desired house temp

I have noticed that I am getting a better flow with heat now when only C/H is being called for and the pump seems a lot quieter. Would you adjust that handwheel to the H/W tank at all to create more circulation on the heating side? Would you adjust any of the lock shield valves to balance the system?

Thanks

Andy