Bled radiator - now no heat!

Lilee

Hi, looking for a little help here. The radiators in the converted attic room of my house have been only heating the bottom few inches for a few months now - I tried bleeding them last night (old-style radiator with the bleed knob at the inside of the radiator) but never got any water coming out. I tried the one in the bedroom first then the one in the bathroom. The air seemed to go from one to the other. But they haven't heated up since. Even the pipes aren't heating up anymore.

I'd like to know if there's something I can do myself since i'll not be able to call a plumber out until the end of the month.

I read that it could be the pressure of the system that needs to be reset and were told to look for a red canister in the hot press but there's nothing.

Any help would be much appreciated.

Thanks!

Pete67

You will need to find out how to pressurise the system before bleeding the radiators, especially those in a converted attic. If there is insufficient pressure you will actually draw air into the radiators when you open the bleed screw.

The rad canister you mentioned is an expansion vessel, and it can be located anywhere, sometimes in the hot press, sometimes in the attic. The means of filling the system is not always beside the expansion vessel either, but it often is.

Look for a pressure guage on the boiler, or near it, and see what pressure it's reading. It will need to be a minimum of around 1.5 bar before you start bleeding. There should be a filling valve somewhere, possibly near the pressure gauge to top up the heating system with water from the mains. As you bleed each radiator, keep an eye on the pressure, as it will drop when you let the air out. Alternate bleeding with topping up with water to replace the air and aim to keep the pressure around 1.5 bar.

blackbox

Try turning off the heating (i.e. the circulation pump) before you bleed the rads. The pump can cause the pressure to be lower in some locations.

With the pump off and no circulation you should have static pressure from the feed in the attic - this should be enough to displace the air in the top of the rads.

Fries-With-That

Just a thought, if you have older style radiators you may have an older type heating system with no pressure tank (the red thing you're looking for).

My dad had this problem in his old central heating system, only the top half of the rad in the attic would heat.

The problem was that the ball valve on the expansion tank was getting stuck and wasn't allowing water into the system to keep it topped up.

I would advise you to look for an expansion tank in the attic, it may be sitting on top of the cold water tank.

Check the water level in this tank before you try to bleed the attic rad, and it may be as a previous poster suggested that you have drawn air into the system preventing the other rads on the top loop from heating.

If you find that this was the problem you might want to look into getting a skirting type rad for the attic because the expansion tank may be too low to keep the attic rad topped up.

Pete67

It would be unusual with a converted attic space not to have a sealed heating system. It is quite difficult to get the expansion tank of an open system higher than the rads in the attic.

If the system is an open one, and the expansion tank is high enough and not empty, then water should come out of the air vents when you bleed the radiators. From what the OP said, once the rads were bled they stopped working completely. This suggests to me that the system is a sealed one, and the pressure is low.