My heat sink radiator won't bleed - with pictures

[mcemily]

Hi

I have a towel rail radiator (one that looks like a ladder) in an upstairs bathroom which acts as a heat sink and, consequently, is permanently on. A week or so ago I noticed that the top 2 bars were only warmish, whereas the rest of the bars were very hot, so I bled the air out and the bars were instantly hot. I had to repeat this over the next few days, as the top 2 bars were going back to lukewarm. However, now the top 2 bars are almost cold (the rest of the radiator is very hot) but I can't get any air to come out of the bleed valve at all. I've turned the screw until it's all the way out but....nothing. I've had a look at the valves at the bottom of the radiator (didn't really know what else to do!) and found that one of them, on the right as I look at it, seems to be static although the white knob has + and - signs on. The other one, on the left, can be turned either way, so it's not fully open. Should it be? Even so, I don't understand why this radiator would bleed before and become hot all over and now it won't.

I'll give you what I know about the system (bear with me...I'm not a plumber and I'm only a girlie!!). The system is run by a Rayburn in the kitchen. It runs UFH downstairs and a radiator system upstairs (although no radiators are fitted at the moment, just pipes up out of the floor). The radiator system upstairs is turned off. Then there's this heat sink raditor I'm having trouble with. In the airing cupboard upstairs there are 2 round things; one white and one red. I don't know what they are but we've had differing advice on them. One person (a 'plumber'...I use the term loosely!!) told us that the white one needs bleeding every now and then as it will get air in. He was supposed to show us what to do but never came back!! Then we had a man from Eon here (due to a gas leak) and I picked his brains about this white round thing. He said that you can't bleed them and didn't know what the other guy was on about!!

Well, if you're still reading this and not bored to death by now, can you give me any advice? I'd be very grateful for any!! Thank you so much.

 

[ChrisR]

Your system needs repressurizing. WIll probably only take you a minute...
WHat boiler do you have?
Can you find a pressure gauge... reading zero...?

 

[mcemily]

YES!! I have one reading zero. It's under the red thing....which I now believe might be a pressure vessel from reading on t'internet (not sure what it does or how it works, though!!). My boiler is a Rayburn Nouvelle on mains gas. What do I need to do? I'm confident enough to have a go as long as I know exactly what to do and what to look out for. Thank you so much for your help with this

Here's a pic of my gauge.....

 

[gasbanni]

YES!! I have one reading zero. It's under the red thing....which I now believe might be a pressure vessel from reading on t'internet (not sure what it does or how it works, though!!). My boiler is a Rayburn Nouvelle on mains gas. What do I need to do? I'm confident enough to have a go as long as I know exactly what to do and what to look out for. Thank you so much for your help with this

Here's a pic of my gauge.....

see the little black lever in the background turn it so that its horizontal with the pipe, if there's two turn them both you should hear water running in to your heating system and the black needle should go up turn it off when it reaches 1.5bar bar, bleed the system and top up as necessary.

 

[mcemily]

Thank you so much. One of the levers is already horizontal. You can see it just to the right of the guage. The other one is very difficult to move, it's really stiff. I'm guessing it should turn left, towards the copper pipe. Is that right? If so, I can give it a bit more wellie!! I don't want to until I know I'm turning it in the right direction Also, do you have any idea how long it'll take for the pressure to build up? A couple of seconds? Half a minute? I just want to know how much on pins I should be

 

[mcemily]

Right......I've done it!!! I have a dinky adjustable wrench in my girlie tool bag and it's done the trick. Just enough leveredge to move the lever. Got the system up to 1.5, bled the radiator, topped back up to 1.5......amazing!!! Thank you so much for your help. The internet is a brilliant place. This has probably just saved me at least £40

So, now I have some questions.....

1. What does a lack of pressure do to the system (apart from not being able to push the water around)? Is it detrimental?
2. What causes a system to lose pressure?
3. How does air enter the system?

I'd just like to understand a bit more about what's going on

 

[Burnerman]

The red vessel that you see is called an expansion vessel - basically its a metal container with a rubber diaphragm in the middle, splitting it into two halves.
On the lower half there is water, and on the upper side there's air.
As the water heats up and expands, the air becomes compressed, but if this is overdone then water is allowed to escape through a pressure release valve. This system allows for normal hot water expansion without any water being lost or stored in a tank somewhere.
If the pressure drops then you have a slight leak somewhere - often not enough to even bother about - it depends how quickly the pressure drops!
Central heating systems often contain a black rust called magnetite. If this is excessive it produces its own hydrogen gas. A powerflush clean is used to expel all of this grot.
One wee point about the expansion vessel...ideally when your water pressure is at zero the air pressure in the tank is checked and if necessary pumped up to around 10 psi. There is a car tyre type valve on the top to allow this.
Pleased you got the pressure issue sorted - well done!
John

 

[mcemily]

Thanks for this, John. I have a reminder now to check the pressure once a month, just to monitor how it goes. I may be back if it's dropping too quickly!!

 

[xr4x4]

If the pressure is rising to high while the system is running, this maybe the reason why your losing pressure.

A test to check for this, is to run the heating for around an hr and check that gauge.

The needle should be no higher than around 2.5 bar.

At 3 bar the pressure reilef safety valve will 'pop' releasing the pressure in the system.

Just a thought and worth checking.

 

[mcemily]

Well, it's just over a month now since I had this problem. I'm happy to report that everything has remained as it should and the heating system is running brilliantly. Thank you so much again to everyone who helped