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Andrew Rolland

First post....newbie so please excuse any errors and not using correct terminology!

Conventional boiler at head height on ground floor. F&E tank in loft. Pump under ground floor as are zone valves. All rads are fitted with TRVs. 6 radiators upstairs. 7 radaitors downstairs.

We are in the process of decorating a couple of rooms so I took an old radiator off the wall and plan to re-fit a new one in a slightly different place which obviously means moving around a bit of pipe work. No problem with that have done that several times before.

Removed radiator and blanked off pipe work. Because I knew I would need to drain the system again to move the pipework I thought I would try giving it a clean with X400.

On refilling the system I poured in two litres of X400 Sentinel into my F&E tank in the loft and filled the system as usual to allow it to do its work before draining down to do the necessary moving of pipework in a few weeks time after blanking off the pipes to the radiator I have just removed. First time I have used X400. System has had X100 in it before.

It's now been about 4 weeks since I drained the system to remove the rad and blank off the pipes.

One of the two radaitors in the lounge (downstairs) is now cold. Both inlet and outlet pipes are cold. I don't know when this first occurred. Checked that both the valves were open. Shut and opened them a couple times to make sure they weren't stuck but then they have not been touched for months so ther was no reason as to why they would have been shut

Last night I switched system off and bled offending radiator. Clear water came out. Wound out the bleed key too much and big jet of water accross the living room so I know there is flow into the radaitor. The outlet pipe from the rad was now slightly warm but the inlet pipe was cold. Again indicating flow into the radiator is happening but wrong way round.

Turned down the trvs on the majority of other radiators to try and see if that radiator would get hot after 10 mins.

Radiator still cold. Oh bother or words to smilar effect but not for forum use.

Get up this morning to discover another downstairs radiator is stone cold. Oh bother, again. Away to work so couldn't bleed it, joined up on here!

Questions.

Have I managed to free up the sludge using the X400 which has now decided to deposit itself in locations in the pipework which means I've got two cold radiators?

Or have I pulled in a bit of sludge from the F&E tank when refilling the system. I noticed it looked bad on puring in the X400, but to me it was no worse than before and it is always very soft sludge that easily breaks up when water enters via the cistern/ball valve to my mind not sufficient to cause a block somewhere.......?

Or have I just got an air lock in the system which I have partially moved around which is now affecting two radiators?

A wee bit of info on my system....

My system is a pig to drain.

System all off, I either shut the service valve on the inlet to my F&E tank or sometimes I shut the service valve on the outlet of my F&E tank before opening the drain.

The drain is located under the ground floor level so it is at the lowest point in the system. I open this and water comes out and quite quickly stops. When working on upstairs rads this is fine. This is how I drained it when I did the recent work. However when working on downstairs rads (which are above the level of the drain) there is still water in them. I had to fit a draw off valve to one of the downstairs radiators to allow me to drain the downstairs rads. This takes quite a while via a length of hose out the front door! The central heating drain can be lying open under the floor yet there is water in the radaitors above it and their bleed vents open!


My system is a pig to fill.

System off. It gets all sorts of air locks in the pipes. I can have a full F&E tank in the loft above my head then remove the upstairs bathroom towel rail bleed valve and peer into the radaitor and see it half full of water.

To allow me to re-fill the system with out problems I fill the system via the F&E tank and then bleed the radiators starting from downstairs working up. I then switch on the system but turn the boiler off so that the pump runs but the system is not heated. I then switch off the system and bleed. Do this twice and generally I get all the air out the system.

The plan when I get home is to do a full drain via the draw off valve and using the central heating drain point. Then re-fill.

If that doesn't work the plan is to remove one of the offending rads and flush the rad outside.

Both the offending rads are old ones and have original trvs fitted.

Boiler fine, other radiators fine so it's not the pump/boiler/zone valves.

Any thoughts? Please let me know if you need any other info.

Many thanks

Andrew
 
hi andrew welcome to the forums. did you manually open and latch the zone valves before draining down?
 
Hi Steve

No and that is another reason why the system is a pig, the zone valve for the heating is under the floor, next to the pump. Means lifting carpet and floor boards. It is not well installed at all as you can't easily get to bits that need servicing.

When I get to renovating the downstairs room that has the pump and the zone valve in it I'll put another drain point on the other side of the zone valve. Then I could connect the two together outside the house with a hose and bypass the zone valve on filling.

I figured that was part of the problem which is why I set the system on but with no heat to allow it to fill, the zone valve opens to allow water to flow.

I'll mibbies try that but on draining next time.

Cheers

Andrew
 
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I would shoot the system up with mains pressure.

1. Connect a hose from outside tap to drain off point (with jubilee clip)
2. open up drain off
3. Give it plenty of mains pressure -in bursts
4. bleed rads
5. Watch out if you over pressure it as water will come out of F&E o/flow
6. give the pump a few bursts of action - ie on off on timer

dis-connect

centralheatking
 
Thanks for that centralheatking, I'll try that tomorrow. I spent this evening cleaning out and flushing the F&E tank, soft sludge in my mind not enough to cause a block but some of it was black at the bottom. Will keep you posted. Andrew
 
Right, drained the system yesterday and switched the system on so that the zone valve opened and sure enough the system drained correctly. Connected up mains hose to the main drain and gave it a few blasts, and again connected up the to draw off point. On removing the hose from each point when the water drained out, no sludge was observed. Put it all back together and commenced filling, got to the two offending radiators and got plenty air out of them. Then decided to check that the valves on each radiator could be opened and closed to hold the flow, checked by air coming out as the system filled. It was at this point that I realised that I couldn't stem the flow into one of them. Decided to give the valve a light tam with an Engineers adjustment and re-set tool (a hammer!). It was at this point that the valve stem popped out of the valve and a corresponding huge gurgle in the radiator! It was only the sodding valve stem had jammed shut closed. I had checked this previously, I could move the valve stem in a couple of mm or so but this moved about 4 mm back out of the valve. Gave the other offending radiator valve stem a tap and sure enough out it popped and so far all has been well! Just shows you that it a simple thing like a valve sticking that was my problem and here was me thinking something else.....all is well, just wish I had checked it more thoroughly the night before. Thanks for the help guys. Apologies for the layout of this text, my windows 7 laptop won't take a new line on hitting return. How do I fix that? Andrew
 
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well done, it just goes to show how useful the old Engineers adjustment and re-set tool is.
 
a RESULT - well done - and thanks for letting us know CHK
 
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