Cold Radiators

[Deryck Tintagel]

I had previously posted about this a year ago but did not get to the bottom of it due to other things happening and then the COVID outbreak.

Previous thread here:

https://www.diynot.com/diy/posts/4509406/

I did manage to get one radiator hot again but this has now gone lukewarm to cold. So before I call in a heating engineer I thoug t I would try a couple of things. I thought that it may be an airlock so tried this

• Locking off both valves on the radiator
• Releasing the pressure
• Remove bleed valve
• Connecting a hose to the bleed nipple
• Opening TRV
• Opening lockshield

I get a moderate flow from the lockshield which I think is the return but very little from the TRV. TRV seems OK. I repeated on another radiator with the same result.

Water is in the header tank, but cannot say if there is a blockage.

Any thoughts would be great!

 

[Hugh Jaleak]

First thing I'd do is shut down all the other Radiators, and see if that does anything. If there is an air lock or balancing issue, then forcing the flow to the affected rads may force the air lock through. If they then begin to work, switch the other rads back on. If these 2 go cold again suspect a balancing issue, see FAQ's for further advice.

If this doesn't work come back and we can look deeper.

 

[Deryck Tintagel]

Update

Thanks for the reply. I tried a few things with shutting of rads but nothing helped so I called in the heating guys.

I know the 3-port valve was faulty and the pump wasn't quite right so these have been changed whilst I had some rads changed. Engineer thought it was a big airlock but couldn't shift it. Thoughts turned to a couple of blockages as some rads worked in groups but others didn't. Some dubious pipework was altered (not well plumbed apparently) but tht wasn't the cause. Turns out the 10mm drops to the rads and some 15mm feeds were blocked. Blockages cleared and all is well. Just waiting for a system clean and filter to be added.

I suppose the lesson learnt form this is get the system cleaned when rads start to go a little be cooler as it will save a lot of trouble and is easier to fix

 

[Hugh Jaleak]

If the system is flushed properly, then correctly dosed with Inhibitor, doesn't need frequent topping up, and with a Magnaclean fitted, (and cleaned out as required), it should remain clean for the foreseeable future. Inhibitor will prevent the internal corrosion that causes sludge and/or blockages.

 

[Deryck Tintagel]

The piping is run in plastic but I was shown some build up of sludge around the reducing T and elbows. They did say that the overall standard wasn't wonderful and they would have brought all rad piping back to a manifold somewhere that is accessible. Seeing what I saw (and I am no expert) it did look messy. However,I wonder if this is because the house was replumbed at just 2 years old because the original plumbers contracated by the developer did not flush the system of flux. With the house being 2000 build all the upper floors are sheet rather than the traditional floor board so not easy to get to all locations without major work to make a neater job.

I expect the full system flush and Magnaclean filter will keep it going for quite some time yet.

 

[Hugh Jaleak]

Plastic piping would reduce the formation of sludge slightly I would think, but there are still steel radiators, brass valves, and whatever the boiler HEX is made from, all of which can react with the water as the electrolyte. If flux was left in that probably wouldn't help matters...