Household radiator problem

[Bobby Dazzler]

The radiators in our kitchen and downstairs toilet stopped working at some point in recent months. We didn't notice until the cold snap, and I haven't got round to sorting it yet.

They're the two radiators closest to the central heating boiler. The downstairs toilet is fine now I've bled the air from it, but the kitchen is still a problem - when I tried to bleed it water came straight out, no air.

If I feel the pipes coming from the wall they're cold too. We don't use the adjustable 1-5 valves that are fitted, so I don't think it's that.

Any ideas?

 

[Will]

I know you say you're not using it - but maybe the thermostatic valve is stuck or blocked?

As a test - could you try closing off the lockshield valve (the other radiator valve that isn't the thermostatic one) and carefully open the bleed screw on the top - maybe with a suitable pot underneath or an old towel etc.

Will

 

[Rory]

Thermostatic valves sometimes stick - take the head off and tap the valve body.

 

[Darrell]

Try balancing the system.

 

[grober]

If you have the older Danfoss thermostatic valves fitted the actuating pin can jam shut. Remove the thermostatic/control part by slackening off the circular securing bracket after noting its position+setting relative to the radiator/valve body. You will see a small pin sticking out. Grasp it firmly with a large pliers and see if its free to move in and out- there's not a lot of movement but it should be obvious if its free. If its jammed free it with a strong push/pull--- in/out movement of the pliers but don't bend it. After its free replace the thermostatic actuator and radiator should now work.

 

[Merc Owner 2B]

I know you say you're not using it - but maybe the thermostatic valve is stuck or blocked?

As a test - could you try closing off the lockshield valve (the other radiator valve that isn't the thermostatic one) and carefully open the bleed screw on the top - maybe with a suitable pot underneath or an old towel etc.

Will

Hi Bobby. I'm an experienced plumber and encounter this all the time. The above advice is where I would start. You need to ensure there is a clear passage through each valve independently.

Do you have a pressurised or combi system?

 

[x332race]

Trvs can stick and your system may need flushing through to remove build up of gunge in it. Pressurised system may have lost pressure and need recharging.

 

[Bobby Dazzler]

Thanks for the suggestions so far - keep 'em coming.

Will try tinkering with the lockshield valve as suggested.

 

[Merc Owner 2B]

If you have the older Danfoss thermostatic valves fitted the actuating pin can jam shut. Remove the thermostatic/control part by slackening off the circular securing bracket after noting its position+setting relative to the radiator/valve body. You will see a small pin sticking out. Grasp it firmly with a large pliers and see if its free to move in and out- there's not a lot of movement but it should be obvious if its free. If its jammed free it with a strong push/pull--- in/out movement of the pliers but don't bend it. After its free replace the thermostatic actuator and radiator should now work.

This also applies to Honeywell valves. But be VERY CAREFUL not to bend or mark the pin. I prefer not to grip them with anything. I use the pliers flat, ontop, to depress the pin. But if it's bent, even slightly, it'll jam and is therefore a write off.

 

[Bobby Dazzler]

Hi Bobby. I'm an experienced plumber and encounter this all the time. The above advice is where I would start. You need to ensure there is a clear passage through each valve independently.

Do you have a pressurised or combi system?

Excellent - thanks will give this a go in the morning.

It's not a combi so I guess it's pressurised.

 

[Merc Owner 2B]

Excellent - thanks will give this a go in the morning.

It's not a combi so I guess it's pressurised.

No. You must have a small cistern (tank) in the loft or airing cupboard. This is in addition to the larger cold water storage cistern feeding the hot water cylinder. This is an open vented (conventional) system.

 

[Stratman]

It'll be the TRV.

They have spent all summer in the 'shut' position and have stuck there. It happens all the time.

 

[Rory]

Thanks for the suggestions so far - keep 'em coming.

Will try tinkering with the lockshield valve as suggested.

Not the lockshield - the other end (if as, as your 1-5 comment indicated, it's a thermostatic valve).

If you haven't touched the lockshield valve then you might want to close and open it a few times - sometimes balanced systems run with them barely open and they can bung up.

 

[A-AvantGarde]

Funnily enough, we had the exactly the same problem at our home too last week with the same radiators. I bled the air from the downstairs loo and that was then fine. Same problem as you with the kitchen, no air!

Plumber came out (it's a new build home and they cover all that stuff for the first two years), and said it's most likely the thermostatic valve 'they often jam'...

He removed the TRV and all is well, new TRV in the post - the type we have simply unscrew. With the valve removed it should just be in the open position so it should just warm up.

 

[stevesey]

Same here - freed two of our TRV's up last month when I noticed the rads were cold. Take the thermostatic head off and give the pin a tap.

 

[renault12ts]

Its absolutely the truth that one of the valves is stuck. Water will come out when you bleed it because the other valve is open, but because of lack of circulation no hot water can go through the rad.

Close both valves. Now open the bleed screw. Turn each valve on in turn...one will spurt water the other will not...that will be the blocked one. It could be a bit of sludge...try poking it with a pointed stick...or it is jammed...drain system, remove and replace.

By the way a lockshield valve is the same as anyother valve, except it has a cover fitted over instead of a tap. The lockshield, especially the one closest to the boiler will only be open very,very slightly, and so will (contrary to what may have been said previously) get blocked very easily because of the small opening.

 

[renault12ts]

Try balancing the system.

It'll not be a balancing problem because its the rads closest to the boiler.