yet Another Central Heating question

kenmc

Howdy,
for a long time now, the rad in the kitchen (nearest the boiler) is only heating up at the bottom quarter. I thought that it was a serious airlock, and bled it but I have never managed to get any water out of the bleed hole, only air. Everytime I bleed this rad, air comes out for a bit, then stops. I can repeat this again some time later, after the heating has been running for a while.
All the rads are on the ground floor (there's no heating or water upstairs - don't ask).
I do not know if this is a sealed system or not - how can I tell??
The hot water cylinder is in the kitchen, and the boiler is in the shed, so it's all spread out over a bit of a distance.

Any ideas of why I have to keep bleeding this rad, and indeed why I never seem to get it fully bled would be a start I guess. I read the "Another C.Heating Newbie" thread, and I wonder if mine is a sealed system, as there's a big red container thing in the shed near the boiler, like in some of the pictures in that thread.
Thanks in advance
Ken

JamesM

Hi Ken, You have a sealed system. The red container is an expansion vessel. Just like in the other thread, you need to find the valve that feeds the system. There can be other complications, but start with that. The valve is often on a pipe connected to a pipe from the boiler, which goes into the side of the hot water cylinder. This is the pipe that returns the hot water from the coil (in the cylinder) to the boiler.
The fact that you only have rads on the ground floor, and that this rad has air could mean that you could damage the boiler because of lack of water. On the other hand, have you checked that someone has not closed both valves on that radiator

kenmc

actually it seems like the bleed valve is *sucking* not blowing, so there's no air in the system, but a vacuum

JamesM

kenmc wrote:

actually it seems like the bleed valve is *sucking* not blowing, so there's no air in the system, but a vacuum

It could still be that there is not enough water in the system and when the water cools down it contracts and would suck in air when you bleed.
BUT, If there are pipes running underground from your boiler house to the main house, it could be that these pipes have corroded and are leaking.:eek:
How old is the system ? Are the pipes gunbarrel (black metal) or copper ? Some copper was dodgy in the 70s.
OR, the boiler itself could be leaking. Oil boilers generally last 15 to 20 years. Many last longer, but anything over 20 is a bonus. Is there water around the boiler.
You may still have to find that valve in the hotpress, or wherever it is - open it and a leak may show up.
Just looked at your post again - the fact that the closest rad to the boiler is the one with air likely means that there is a leak in the direction of the boiler - water getting out air getting in.
I hope that I am wrong in all this.
Jim.

kenmc

The system is only about 2 years old I think, copper piping as far as i know. I'll try find how I can add water to the system. Worst case could take the bleed valve out of the radiator and top up the rad???

JamesM

kenmc wrote:

The system is only about 2 years old I think, copper piping as far as i know. I'll try find how I can add water to the system. Worst case could take the bleed valve out of the radiator and top up the rad???

Even if you could get water in, it wouldn't last very long.
If you are sure that both rad valves are open, then the only answer is to find how to add water to the system.
The other thread should help you find out how.
Jim.