Lukewarm top floor radiators - but with red hot return pipes

[Oakwood]

Hi,

We have a four storey house, including a basement - which is where the boiler and the hot water cylinder are both located, which from my very limited plumbing knowledge (obtained from reading posts in this forum) is a sealed system.

We only bought the house earlier this year. It is quite old, but the boiler and certainly the cylinder system are all quite new.

Initially, after moving in during Spring, all the radiators which we turned on (using either the TRV, where fitted, or just a simple flow valve) seemed to work ok. However, when the weather started to get a little cooler a couple of months ago, I noticed that the top floor rads were cooler, and the heat was 'patchy'.

So I tried to bleed them (when the heating was on). This seemed to work OK for one, thankfully that in my daughters bedroom, as air and then water bubbled out (but not free flowing), and this rad is now working reasonably well.

However, only a very small amount of air came out of the others and then no more, nor any water - nothing happens at all now when I open the bleed valve, no air or water. If anything the radiators are now even cooler after my first attempt to bleed them, but not sure if thats coincedental given the onset of Winter - thats what I'm telling my wife who thinks my basic DIY effort to sort the problem has made it worse..!

All the upstair rads have TRVs and I have checked the pin - all move OK.

The flow pipes coming up out of the floor to each are lukewarm at best, whilst the return pipes on each are red hot.

In addition, after leaving the CH on for a while, these upstairs rads will eventually get lukewarm - but typically one side is hotter (eg that closer to the wall) and similarly one half is also a little hotter (that on the same side as the return pipe).

Any thoughts from the experts would be very much appreciated - as we have a houseful of guests coming shortly for christmas and I dont want to freeze them...!!

Many thanks in advance.

 

[45yearsagasman]

First of all do not bleed a system with it running.As you have a sealed system have you recharged it after bleeding the rads? Look for a filling loop and when the system is cool pressurise it to approx 1bar.You may have to bleed rads again and refill system a couple of times untill all air is out.Look in FAQ's on how to refill a sealed system.

 

[Oakwood]

Dear 45yearsagasman,

Many thanks for your swift response. Immediately after posting earlier, and before reading your response, by chance I gave bleeding one of the top floor radiators another go - but this time the CH was off.

A lot of air started to come out and the the rad made a very audible gurgling, glugging sound - quite like water was pouring into it (although, strangely, as if from the top - a bit like it were dripping and dropping).

Nervous that it was about to blow a leak, I shut the bleed valve, and then had to pop out for the rest of the afternoon.

Just home and before logging on and reading your message, I tried bleeding the same rad again - unlike any other time, air came hissing out again, and then water dribbled out and the rad now feels very hot all other.

Thought I had cracked it! But unfortunately, when moving on to the next rad, it was the same old story - still lukewarm (inc the flow pipe, but with a red-hot return pipe), and nothing would happen when trying to bleed (no air or water).

Have now logged on and read your post (forgive me - should have done this before meddling any further).

Will try bleeding again with the system off, as this does seem to have worked on one of the rads, as well as having a look at the guide on refilling/re-charging the system, so many thanks for this instruction.

However, do you think the fact that one of the top floor rads always worked and that a second one now works, but only after a large amount of gurgling - do you think there could be a partial blockage, that was initially between the two rads that now work, but which has now been pushed further along the system, thus preventing the next one from warming up (including its flow-pipe)?

In which case, would a 'power-flush' clean-up the whole system and help sort this problem out? Or is there anything else you would recommend - happy to get a professional around to undertake any necessary serious work.

Many many thanks again for your help!!!

Best regards

 

[Oakwood]

Dear 45yearsagasman, just to let you know that i took your advice, read up on re-charging our sealed CH system - and that seems to have done the trick!

Pressure gauge (which was tucked right out of the way and not positioned to be obvious) was very low. So re-charged system and the top floor rads are now all toasty hot again!!

System has lost a bit of pressure again since, but not to the point of being a problem. However, at this rate, we may have to re-fill after in another month or so.

Is this normal - especially as we are running our CH system quite hard at the moment, given the weather? Hope so, and not a sign of a bigger issue....?

 

[45yearsagasman]

Sounds like a bigger than average system and may still have air trapped and may require a further bleeding followed by a top up.I would not consider that to be a problem and would persevere through the Winter and if there is still pressure loss get it checked in the Spring.
Don't forget....Refill system when off and cool.Merry Christmas.

 

[Oakwood]

Thanks 45yearsagasman - will do, and have a merry christmas too (my family hopefully will now - as opposed to freezing to death...!)