Problem with one Radiator

[PJB]

Hi All,

I have a problem with one of my radiators. It seems to keep getting a certain amount of air it. I have 7 radiators in the system which is a one pipe open traditional system. The boiler is a back boiler and the Water/heating is controlled via thermostats and a 3 way valve.

All the radiators work and apart from the one on the bathroom collect no air at all.

The Bathroom one however seems to need frequent bleeding. After bleeding the radiator gets hot again at the top and stays hot until the timer turns it off. Then when it comes on again the bottom is hot but the top is warm (NOT cold). Infact it seems to cool from one corner and spread down and across. It is always the TOP LEFT corner that cools first.

It seems air enters the radiator when the system / Radiator Cools.

I dont really know what else to do. The Pump is on 1 as it was higher and was overpumping, but that is now resolved and the remaining Rads are very hot with no air at all.

Any Suggestions welcome - I am contemplating buying a AutoBleed Valve?

Thanks
Paul

 

[Softus]

There's nothing strange about the way that the pattern of 'coolness' spreads across the rad in this situation.

Accumulation of air/gas in the system, plus the previous symptom of pumping over, together indicate that you have a corroding system that has sludge in it.

There are lots of posts on this, because it's so very common, but the usual answer is a complete drain down, flushing out the system, cleaning by including a cleaner in the re-fill, waiting, draining again, flushing again, and finally protecting by including an inhibitor in the re-fill.

Along the way you can encounter the delights of stuck valves, drain cocks that don't open, blockages in the cold feed, air locks, and, later on, pinhole leaks in the rads that have been corroding.

 

[PJB]

Thanks for the message, however that has all already been done, the system has been flushed through and emptied twice. Cleaned with chemicals and topped up with inhibitor. Like i said it is only the one radiator affected the others do not show any air at all since the overpumping was cured.

Thanks
Paul

 

[meldrew's_mate]

PJB, check the loft header tank is full and the level is at least 1" above the outlet pipe when the system is cold. Next tie up the ballcock and bleed air from all rads, then drain about half a gallon from anywhere on the system into a bucket - this proves the cold fill pipe is clear; you can put this water back into the header tank to save the chemical. If you have flushed as you said the water you drain should be relatively clear and free of black particles.

Check the ballcock works.

If speed 1 works, use it; speed 2 is therefore a waste of power!

Is the header tank at least 6 feet above the point at which the cold feed joins the system, or could it be "sucking down" on pump start-up?

 

[daffs]

Hi,
I've got a similar problem with one radiator.
About 6 weeks had the boiler & tank replaced with a condensing (system?) boiler and new tank, i.e. it's not presurrised. The system was power flushed then.

Now about every two weeks have to bleed one radiator, the one nearest the tank if that's a clue.
The TRV was replaced on this radiator at the same time.

I've rang the plumber, but has not returned my call (it's only been two days so i'll give him a chance) - but when searching i came accross this post.

I have been to look at the expansion tank - compared to how it was it's set a a much (much) lower level than it was - before it was just below the overflow now it's mm's above the outlet. Should i go and have a look when the pump starts up? Should I just raise the level?

Also I've noticed a green stain build up near where the TRV enters the radiator - does this indicate a leak? There's no water anywhere.

Thanks

 

[daffs]

ooops - double post - sorry

 

[Softus]

daffs, you should really create another topic for your problem; however...

I have been to look at the expansion tank - compared to how it was it's set a a much (much) lower level than it was - before it was just below the overflow now it's mm's above the outlet.

Should i go and have a look when the pump starts up?

Yes - ensure that the pump doesn't 'drag' the level down and draw in air.

Should I just raise the level?

Probably not - when cold, around 50mm above the outlet would be ok. Less is wrong, and more is wrong. As the system heats up the level will rise, but not so much that it reached the overflow outlet.

Also I've noticed a green stain build up near where the TRV enters the radiator - does this indicate a leak?

Yes.

There's no water anywhere.

Probably because the water evaporates from the heat of the rad and pipework before you see it.

 

[bengasman]

Typical case of heavily soiled system, not a great design either. Possibly vent pipe too low and in wrong position. One pipe system not particularly good for powerflushing so you may have to remove all rads, link the valves and blow it through that way. This would be a good time to modernise the system, one pipe is about as modern as a a steam train

 

[Softus]

Typical case of heavily soiled system, not a great design either. Possibly vent pipe too low and in wrong position.

That's some pretty impressive guesswork there.

One pipe system not particularly good for powerflushing so you may have to remove all rads, link the valves and blow it through that way.

I believe that to be wrong.

This would be a good time to modernise the system, one pipe is about as modern as a a steam train

There are plenty of one-pipers still running happily.

 

[Nige F]

way. This would be a good time to modernise the system, one pipe is about as modern as a a steam train

Thomas says you are a naughty man