LOFT CONVERSION done BUT 2 out of 3 loft rads not heating

[justlead1]

I do not know how handy you are, but you may be able to try.
Topping up the pressure
Turning off all rads.
On the last on circuit (One that not working) turn off both lock shield and hand wheel valves and remove 1/2" BSP plug or air valve at top of rad. Screw some thing 1/2" Bsp that you can connect a short length of hose to. Once the hose end is in a bucket turn on one of the rad valves, this should pull a lot of water and air through. ( you will see it, in terms of a splutter.) Turn off valve and try the other, same deal as above.
Put the plug back and turn rads on again.
(once a system has been drained and filled there will be pockets of air all over the system. Which will rise to the third floor, which means you may need to repeat.
Good Luck

 

[RJD68]

Thanks Justlead1, that sounds very much like what the plumber did the first time the 2 loft rads stopped working. I'm just surprised that so much air can find itself back into the system such that 2 rads go cold again after just 7 days or so. Maybe that's to be expected?? If the plumber can't come back right away then I'll follow your advice and give it a go myself. Thanks.

 

[Ric2013]

To answer latest question, the air shouldn't be getting in, but it might just have shifted within the system.
By inverted U, I meant that if the pipe runs uphill and then down again (like a U upside down where we thought it ran over a steel) air will tend to collect at the top of the upside-down U, or at the highest point. It is at this point that an air vent might be needed. Air vents elsewhere may be useful, but I meant specifically at the highest point where the pipe goes up and then back down. I meant this or this:

End Feed Air Vent Cap 15mm x
Bottle Air Vent 15mm

That said, I once (before I was a plumber) installed a system where pipework ran up from a manifold on the ground floor into pipework under the first floor boards and then dropped to radiators. One pipe run up and down again for each of 3 radiators (inverted Us). Once the initial airlock was cleared in commissioning, they did not ever airlock again.

Sometimes a system simply does airlock several times before it settles into reliable service. You can sometimes turn off every radiator other than the offending one and you'll hear the bubbles force themselves into the top of the radiator from where they will now be easy to bleed out and then it will get hot. Works best where there is a pump separate to the boiler that you can temporarily set to maximum while you do this.

But should not be a regular occurence and most installers would be happy to solve such teething problems for you, I think.

 

[RJD68]

Thats very helpful. Much appreciated Ric2013

 

[RJD68]

Had the installer back yesterday. He balanced the whole system from ground floor to loft and that has solved the problem. It wasn't another airlock after all which was a relief. Thanks all for helping sort this.

 

[RJD68]

2 weeks on from the balancing and the same 2 rads in the loft are cold again. So balancing didn’t do it. Any suggestions as to the best course of action, is it:

a) better to try to remove the airlock one more time.
Is it reasonable to expect air to lock a few times before all the it’s all finally purged?

or

b) as the air been removed once already and the problem persists might it be better to install an automatic air valve and be done with it?

If b) as we can’t now get access to the top of pipe run (it’s concealed in loft) we can only get access to the pipes that run up to loft from a cupboard below anyone have any suggestions as to how to get an air valve installed at the top of the pipe run? Is getting the valve ‘near’ the top of the pipe run OK and better than having no valve at all?

 

[king of pipes]

Fit some of these they will keep you system vented , check a good quality inhibitor has been added and raise your working pressure to 1.5 bar cold and around 2bar working pressure when hot . cheers kop

 

[RJD68]

Thanks kop, I’ll show this valve to the installer when he comes on Monday.

 

[Ric2013]

If the rads were filling with air, an autovent would be great, though wouldn't address the underlying defect. But, if the pipework itself is airlocking, I can't really see how it helps. KOP - can you please explain your logic, out of interest?

 

[king of pipes]

My theory is, this is a add on to the existing system so it would have been drained and refilled hopefully with a good quality inhibitor added to avoid hydrogen gas forming, when refilling the system via the filling loop there will always be air introduced into the system through oxygenated water it will take several days or even weeks to release this the heating process will cause the trapped air to rise collecting in the highest points of the system forming a air type plug in the pipework which the heating pump will struggle to overcome if you can realese this trapped air and balance the system correctly then you stand a better chance of the system working the Aladdin auto airvent will aid this process i usually still fit a manual vent in the other side of the rad , and also run the system at a higher operating pressure 2bar when fully heated , the op has not said if his boiler is a combi , or system boiler but i would guess it is one or the other so the pump will be internal to the boiler so you are stuck with what you have there are are methods of improving this but i would try the above first . regards kop