Radiator questions..

[WaterTight]

1) If a radiator no longer gets hot at all (whole rad, valves and pipework all remain cold) can it still be a faulty valve rather than a blockage? Say for reasons (including but not limited to) like the rad had been added to the original system and the feed and return pipes go off at quite a tangent? Or if they travel away from the main circuit for quite a distance - maybe to an extension or annex? In these circumstances, if the TRV fails, is it possible that hot water may not circulate as far as faulty TRV and therefore all pipework remains cold? Or would you be thinking blockage or air lock. Rad is bled.

2) If the pin on a TRV can be pushed down and pushes itself back up quite freely can it still be faulty and not allowing rad the get hot?

3) If you remove the head from a functioning TRV does it become a valve that is just fully open?

4) If a rad doesn't get very hot, it's valves are a wheelhead and a lockshield, the customer mentions the rad had been removed for work by decorators and replaced and she thinks it might have been after that that it stopped working, both valves are turned to where they at least feel fully open and when the heating is on the pipework and valve get hot as far as the lockshield, the rad gets lukewarm all over but the wheelhead valve and attatched pipework remains cold would you be relatively confident that changing the wheelhead valve would sort it or would you suspect there may be a blockage (presuming there was no drain down and so unlikely non-multi-directional valve replaced on return by accident - can wheelehead valves be directional?..)?

5) If you think there might be a blockage, would you go straight to a full drain-down or would you try and run a valve into a bucket via a hose for a bit?


6) If both valves on a rad, tried individually, allow water to pass through, can there still be a reduction in flow - caused by blockage or air - significant enough that you may not perceive it but can prevent rad from getting hot? Or if they allow water through at a decent rate does that eliminate the possibility of a blockage or air?

 

[dontknowitall]

In my experience/opinion:

1. Yes - would look first at faulty trv (easiest), then lockshield. Then remove radiator and open/close valves. If water coming through quite well then I'd try changing trv.
2. Yes - had one of these before and the plastic inside the head was not moving up or down even though the head could be swivelled.
3. Yes (as long as the valve is open/pin not stuck down
4. Yes/no/don't know. Quite often some radiators still remain cold after heating is satisfied. Then after another 20 minutes or so the cold ones become warm. Then after an hour or so most become hot. Could be too small a pump (not pushing water around system properly), could be pump not running at 100% efficiency and quite often it's because the one way trv and lockshield are on the wrong ends.
5. Definitely start by removing radiator and opening/closing valves. Much easier, quicker and cheaper for customer. If it doesn't work then adjust pipework or whatever and try again before fitting radiator.
6. Usually eliminates possibility of air but more usually a blockage.

As I said at beginning, these are in my experience.

Also, I think too much is made of airlocks. If a system is new then there might be airlocks and customer won't be happy until they're sorted. Because of this when a system is older you can assume that any airlock issues would have been solved in the past (e.g. fitting bleed points).

 

[kirkgas]

if you remove the rad and open each valve one a t a time and get water out it doesnt really prove you havea flowing circuit you will get water coming out from the other side of the circuit from another rad, to confirm you are getting flow through the valves, i have taken the rad off the joined the 2 valves together with a piece of pipe and some fitting, plastic pipe or whatever you have then open the valves turn the heating on and close all other rads, and see if you get flow through them, ie temp pipe heats up, this proves the valves and circuit are ok or not, if you get hot flowing then the prob is with the rad or balancing, so sort the rad then re balance the system, if the system was balanced before the rad was removed when it was put back on and fully opened it will upset the balance and will need sorted, if you dont get any heat at the temp pipe then you have a circuit problem stoppping circulation, then you want to connect a hose to one end at a time and see if you can drag hot water through or the flow will stop showing what side the blockage is just takes a wee bit of time to sort therough the options, cause you aint gonna pick the right one first time are you?

 

[WaterTight]

Lots of good advice, thanks chaps.

Just one thought though kirkgas, when you say "if the system was balanced before the rad was removed when it was put back on and fully opened it will upset the balance and will need sorted" - if it was only the rad in question that was removed and replaced for decorating I understand that if it were opened fully this might upset balancing but just to be clear there's no way that could make that particular rad not get hot is there? It would at worst guarantee it gets hot at the expense of other rads?

But it sounds like you both agree you start with the simplest things to attempt first i.e. change valves.

 

[dontknowitall]

"Simplest things to attempt first" - definitely and the customer will then see how you can justify your bill if there is much more work involved.