boilers & radiators!

skyblues

We've got an outdoor oil boiler, and the upstairs radiators were hot at the bottom & cold at the top. So I tried to bleed them, but although air came out NO water came out. I went outside to the boiler & fiddled with a pipe and steaming water came out, then NONE of the radiators would work.

I've left the heating turned on for a couple of hours now, and the radiators are lukewarm at the bottom, cold at the top, and the pipes are loud as hell, I can hear water gurgling & bubbling upstairs (no rads downstairs, underfloor).

ANy ideas what on earth is going on? I'm at the end of my tether!:eek:

Pete67

Your heating system is low on water, it needs to be topped up and any air in the system vented off. Depending on the design there are different ways of doing this. If the pressure in the system is low to start with, then opening the radiator vents can draw air into the system, especially with upstairs rads.

If you have two tanks in the attic, then the smaller one is probably the expansion tank for the heating system, check that the ballcock is working properly, water should flow into the tank if you depress the ball slightly. If the ballcock is stuck then it's quite likely that the tanks is now empty. You need to sort out the ballcock so that the expansion tank fills and then start venting the rads again until water comes out. Note that the expansion tank should only have about 6 inches of water in it when cold, this level will rise as the water in the system heats up and expands.

If only one tank then the system is probably a sealed system and is filled by opening a mains water valve to admit water. There is usually a pressure gauge close to the filling valve, top it up to 1 bar cold, and then start venting rads again. As you remove air, you will need to keep adding water to maintain 1 bar pressure. When you have all the air out of all the rads, start up the heating system and allow it to heat up. Watch the system pressure and ensure it does not rise excessively - should not go over 2 bar. If it does, the expansion vessel needs checking.

You will need to repeat the venting process after a few days as the new water you have added will contain dissolved gases which come out of solution when the water heats up. Look for an automatic air vent and ensure that the cap is loose so that air can escape. You might also consider adding a corrosion inhibitor. Good luck.

skyblues

Thanks for the reply, Pete.

Just been up the loft, only one tank there, the noise is coming from the hot press where there's a big immersion heater tank. There is a pressure guage next to it and its reading zero, no pressure at all. There is a black tap under the guage which I'm going to try and turn to get water through, we'll see how we go!

Thanks again

JamesM

skyblues wrote: »

We've got an outdoor oil boiler, and the upstairs radiators were hot at the bottom & cold at the top. So I tried to bleed them, but although air came out NO water came out. I went outside to the boiler & fiddled with a pipe and steaming water came out, then NONE of the radiators would work.

I've left the heating turned on for a couple of hours now, and the radiators are lukewarm at the bottom, cold at the top, and the pipes are loud as hell, I can hear water gurgling & bubbling upstairs (no rads downstairs, underfloor).

ANy ideas what on earth is going on? I'm at the end of my tether!:eek:

Did this just happen suddenly - if so you may have a leak in the system - that's an awful lot of air. Do the pipes run under the path to the boiler house ? How old is the boiler ?
If it has been bad for quite a while, follow Pete's advise and try to fill the system.
Jim.

skyblues

Thanks for the advice, well I went up into the loft again and saw a red tank, about the size of a football. THere is no tap though, thats underneath in the hot press.

There WAS a valve on top of the red tank though, like one on a football, and when I touched it it let out a load of air.

Is this my header tank do you reckon? If so I guess I need to take the top off somehow and look at the ballcock..

Its a nightmare!

JamesM

skyblues wrote: »

Thanks for the advice, well I went up into the loft again and saw a red tank, about the size of a football. THere is no tap though, thats underneath in the hot press.

There WAS a valve on top of the red tank though, like one on a football, and when I touched it it let out a load of air.

Is this my header tank do you reckon? If so I guess I need to take the top off somehow and look at the ballcock..

Its a nightmare!

No - that's an expansion vessel and should have air in one half of it - don't try to open it. You have a sealed system. There should be a valve somewhere that you can open and let water into the system.
Did all this start suddenly ?
Jim.

skyblues

Not really, it just got more noticeable with the cold weather.

The hot press is directly below the expansion tank, and in it there is a pressure guage that's currently reading 0. Right next to it there is a tap, and I can see that the pipes connected to this tap go straight to the expansion tank & main tank. The main tank if full, no problem there.

But when I turn this tap absolutely nothing happens, I don't hear anything and the pressure guage stays at zero. Does this mean that the problem is a lack of water in the system?

Outside in the boiler module there is a tap above the burner/ pilot light section, and when I unscrewed this slightly a load of hot air came out. I don't know if this is anything to do with it..


Thanks for the advice!

Pete67

If you can post up a couple of pictures of the expansion tank, and also the pipes in the hot press I'll try to help further.

311

Sorry for butting in ,that valve with the black lever is more than likely a pressure reducing valve.
It is probably isolated by a second valve along the pipe someowhere in the hotpress.

BUT ,because you have touched the pressure reducing valve ,you may have altered the setting on it and it now maybe too high for your system.

JamesM

skyblues wrote: »

Not really, it just got more noticeable with the cold weather.

The hot press is directly below the expansion tank, and in it there is a pressure guage that's currently reading 0. Right next to it there is a tap, and I can see that the pipes connected to this tap go straight to the expansion tank & main tank. The main tank if full, no problem there.

But when I turn this tap absolutely nothing happens, I don't hear anything and the pressure guage stays at zero. Does this mean that the problem is a lack of water in the system?

Outside in the boiler module there is a tap above the burner/ pilot light section, and when I unscrewed this slightly a load of hot air came out. I don't know if this is anything to do with it..


Thanks for the advice!

That thing that you unscrewed slightly is the safety valve - if hot air came out, this means that the boiler is dry - turn it off - do not run it again until you have water coming out of this valve - it could literly burst :eek:.
As 311 says, the black knob on the pressure reducing valve may not be at the correct position - or there may be another valve closed somewhere.
Jim.

skyblues

All sorted!

THere was a slight leak in the valve by the pressure guage, which meant there wasn't enough water in the system. First off I had to get a new valve, then open the tap to get water into the system, then bleed all the radiators (four times!)

Thanks for all the help, wouldn't have had a clue what was going on without it.

Pete67

Glad to hear you got it sorted. You probably thought of it already, but just in case, when you checked the red expansion vessel in the attic, did you let all the air out? If so, it needs to be recharged.

Do do this, close the water supply to the system, and drain off enough water to drop the system presure back to zero. Then pump up the bladder in the expansion tank to just under 1 bar. A car tyre foot pump works best as it will fit the air valve on top and usually has a pressure gauge built in. Then top up the water to bring the heating system pressure up to 1 bar (when cold) and you're done.

If there is no air remaining in the expansion vessel, then it cannot accomodate the increased volume of water when the system heats up, and the pressure in the system will increase dramatically. This will result in the safety valve lifting and discharging hot water. If the safety valve is faulty you risk bursting something else (boiler or radiator), which could be dangerous.