Central Heating - Flushing or Cleaning

[smudgersmiffy]

My mother has recently decorated her bedroom and decided that she wanted a new radiator (one of the new convector types), so I drained down the system, removed the old rad, fitted the new one (including a new thermostatic valve and lockshield).

I then re-filled the system (expansion tank in the loft), then tried to bleed the new rad.

However, there's nothing coming out of the new rad (when you first open the bleed screw, you can hear a very slight hiss, but this stops after after a couple of seconds), or indeed any of the rads upstairs. All the rads downstairs bleed without any problems whatsoever.

Now, I don't think the system's had any Fernox or similar in for a number of years, so the chances are, it's full of sludge, (although the water wasn't too bad when I drained the system down).

Not sure what brand of boiler she's got, but it's a back boiler, behind the lounge fire (pretty sure it's a Potterton off the top of my head).

Should I pour a container of Fernox in and hope that clears any blockage that may be present. If so, do I need to turn the termperature right up on the boiler to get the Fernox to work.

Any help would be much appreciated.

 

[GasMan1965]

If there is water in the tank then its a blocked feed where it joins the heating !!

 

[JohnD]

get yourself a small strong magnet and hold it to the copper pipe where the Feed & Expansion joind the main circulating pipes.

What mud did you find in the F&E tank, and when you drained out?

 

[Whitespirit66]

Do the upstairs rads. heat up properly?

Did you bleed the pump after refilling the system?

You may have an air lock. 8 times out of 10, if I get an air lock its with a back boiler system for some reason.

 

[GasMan1965]

He's got no water coming out of upstairs rads when he bleeds !!

 

[Whitespirit66]

Why is there water in the downstairs rads if its a feed problem?

 

[smudgersmiffy]

Yes, I can confirm the downstairs rads fill up with no problem. I didn't bleed the pump, but can confirm the downstairs rads warm up without any problems

 

[GasMan1965]

Coz when he refilled he sucked in some rubbish which blocked an already gunked fitting , IMO of course

 

[simond]

There is water in the downstairs rads because water flows downhill.

Hope that question wasn't asked by someone in the trade

 

[smudgersmiffy]

So if I have sucked some gunk into the system, what can I do to clear it?

 

[GasMan1965]

Can you see the feed pipe in the airing cupboard where it joins the heating pipes??
That Tee is where the blockage is!!!
Sometimes there is a fitting above you can undo as the problems probably been there b4,, and clear the blockage ,, if not then you have to cut above the tee ,, the pipe has water in it so have a bucket ready and make sure the ball valve is shut off or tied up ..

 

[Whitespirit66]

To find out whether its a blocked feed or an air lock try this;

Isolate mains cold water to feed and expansion tank, or tie up its float valve to stop it refilling. Drain down the system. Turn water back on to tank, or untie valve.

If
A) the system refills itself, bleed the pump. Turn heating on. You may be lucky and the upstairs rads work. If they don't, then you have another air lock.
OR
B) The system doesn't fill at all, you have a blocked feed.

 

[smudgersmiffy]

I know the answer to some of this, as when the problem first appeared, I thought I'd re-fill the system with fresh water.

I isolated the expansion tank in the loft.

I then drained the system down.

And then re-filled the system.

Same problem.

Upstairs rads didn't fill - the downstairs ones did without any problems.

When you bleed the upstairs ones, you hear a tiny hiss, but then nothing.

 

[GasMan1965]

So if you drain again and refill it does the same ??

 

[smudgersmiffy]

Yes

Bottom rads fill.

Top rads remain empty.

On the new rad I installed. I could remove the rad - leave the valves open, and nothing would come out!!!!!!!!!!!!!