Bleeding 1 half cold upstairs radiator .. but it sucks in?

[m0cke]

Hi all,

Just fired up the heating after the summer but two of the upstairs radiators were half cold, so I bled the first successfully with loats of air comming out but when I bled the second rad it was sucking in air (checked by using a piece of tissue which was sucked to the hole)

I warmed the system first and I switched off the pump and boiler before bleeding.

The system has had corrosion inhibiter in for many years, the system is about 16 years old and I have been here for 7 years without a problem.

I have tried 3 times to bleed this rad and every time it sucks in, when I then fire up the pump afterwards it is then full of air.. what is happening please?

Regards

mocke

 

[breezer]

i haven't a clue, but our resident "boiler" engineers will want to know what type of system, and what type / make / name of boiler

 

[m0cke]

Yes sorry I didn't give enough "system info"

OK Here goes.

It's a Vented system, the boiler is a Potterton Netaheat Profile which heats the hot water and central heating via a 3 way valve, the pump is in the airing cupboard in a vertical position flow from top to bottom, outlet side goes into the 3 way valve, about 12" above the inlet side there is a pot which has the vent to tank and feed from tank along with return from radiators. None of the radiators have thermostaic valves but there is a room stat and a hot water tank stat for control.

I'm not sure where the problem radiator is in the line though.

The boiler has just been serviced and repaired as it had broken down, the pilot gas valve had gone u/s.

Any help appreicated

Regards,

mocke

 

[ChrisR]

If air's going in then water must be going out, surely? Got any automatic air vents anywhere?
Is this a higher rad than the other? Is it posssible water's getting into the domestic hot water through a leaking coil in the HW cylinder?
Check for leaks at the back of the boiler.

 

[oilman]

If air is going in and it's a vented system, then water's not going in. This should come from the header tank and it sounds like there is a blockage in the feed pipe. If you drain some water from the system, does the level in the header tank change, and tank starts to fill?

Has the inhibitor been replenished at least every 3 years? If not it may no longer be effective.

 

[m0cke]

Thanks both,

Both the radiators are on the same level on the same wall in the house with a stud wall between them, I open the valve on the one that will bleed and there is quite alot of pressure there, yet when I open the valve on the one that wont bleed it does make a noise until the valve is nearly right out and then it's a different hiss .. what I would call a sucking hiss lol.
I did notice that the feed tank had like an orange fur inside it and I couldn't see the feed pipe inlet so I made sure it was clear.

I had to fit an immersion heater last week as we had never had one but because the boiler packed up we needed hot water, the water in the immersion tank was clean and the coil looked in good condition but I guess that doesn't mean a thing.


I will book for the engineer, the system is insured with domestic & general so it's not worth me playing with it I suppose.

Thanks again.

mocke

 

[m0cke]

OK, looks like i'm going to have to tackle it myself.
The insurance does not cover air locks, blockages or sludge.
If it proves to be anything else then I can claim.

So guy's where do I start?

Do i switch off the supply to the expansion tank, try draining some water from the drain down stairs and see if the level drops in the expansion tank?
If it doesn't what do I do next?
If it does what do I try next?

Will be attepting this after 6pm today

Thanks

mocke

 

[oilman]

Yes, turn off tank supply, drain water, see if level drops. If it doesn't you will have to cut the pipe at the T where the feed pipe joins the rest of the system, or just above it. Then clear the blockage.

 

[m0cke]

Hi again,

Thanks for all the advice, it was a blocked feed pipe and I managed to resolve the problem last night with much puffing and swearing, I just hate plumbing, give me something electrical and i'm at home .. and you know electric & water dont mix .. lol

Thanks again, we now have a fully bled and working central heating system again!

Regards,

mocke