Boiler airlocked

[TheKipster]

Hi everyone,

I'm a bit boned at the mo so if anyone can help out I'll be forever grateful!!!

Basically, I drained my system three times. Twice when refilling I did it through the F&E tank. The last time I filled it from bottom up using a hose pipe attached from a mains tap to my bottom dump valve thingy.

Each time I get the heating started again, it gives it 20 or so seconds then safety cuts in and turns the boiler off. So my theory is it has an airlock. I have bled all the radiators, bled both the valves by the tank and still the same.

So.. questions... How do I get the air out the system?

And if it is the pump as it can't pump the air to the valves, how do I find out if the pump is screwed?

I would get a plumber in but apparently there's a shortage round here at the mo and I can't get one for another week...

Boiler is an Apollo 15/30 and the pump is a Grundfos Super Selectric.

 

[keego]

If it is fully pumped, i.e it has a three port valve have a look on the pipework
feeding the cylinder & heating circs for a gate valve. If it has them fitted turn the one feeding the central heating off & also the bypass if it has one, then fire up the boiler & make sure the pumps set to #3.
If it is a gravity system then take the thermostat out, then fire up the boiler & boil it into submission.

 

[ChrisR]

Bled the pump? (remove screw and wait for water)
If you do searches on
airlock
bleed
vent
blocked feed

you'll probably find everything you need.


Oh yes - put any motorised valves' levers in the Man position while you're filling, too. ANd the vent by the hw cydlinder is easy to forget.

 

[TheKipster]

Yep, pump has been bled, steady flow of water comes out. It's dripping rather than gushing but still seems to be bled.

One of the suggestions I found was to run the system with one radiator on and that should push the air through to the radiator and I can bleed it out there. But that hasn't work. So I'm thinking it might be the pump and wondering how I can find out??? It's going round and I can feel it going round. I touch my screwdriver in and it gets moved around. Does that mean it's working???

 

[ChrisR]

It means it's going round, but
it cold be blocked solid with sludge
the rotor may have come off
the shaft may have broken
it may be very weak

If the pump valves are the gate valve type you might try to use them, but don't bother if they're screwdriver type. Then remove the 4 allen screws, get the body of the pump off and have a look.

If you get yourself a 22mm Speedfit cap, and a long 1/2" to 15mm compression tap connector (or join shorter ones together), and empty the f&e tank, you can do this.
Then you can get the ***** air out!

 

[TheKipster]

Thanx for the replies Chris...

We've taken the whole pump apart and checked for sludge in the fan bit. There wasn't any and it was all clean inside and nothing "looked" broken.

So with your diagram... you're saying connect a bypass pipe from the mains entry to the f&e tank to the feed into the system? And I'm guessing then force the entry open by lowering the ball so it forces water into the system? Then when it comes flooding out from the overflow I know it's done???

 

[TheKipster]

Right, that's it, I'm giving up

Have a plumber coming round on Monday to sort it out. Will post up the results in case anyone else has the same problem...

 

[bengasman]

Try the same two methods of filling but open the diverter valve or zone valves manually before you fill. Push the lever and lift a bit at the end so it catches in the notch