Boiler cutting out

[TheKipster]

Hi everyone,

Yesterday I flushed my whole system out, Which worked.

I then cleaned out my F&E tank & put some Central Heating Cleanser in it. Then let the tank fill back up, bleed all the radiators and switch the system back on again.

My problem is that the boiler will now not stay on. When I switch the system on I get a few noises in the system, then the boiler cuts out and extinguishes the pilot lit after 20 seconds or so.

My theory being that the boiler is shutting off as a precaution as it his heating air, not water. So I have an airlock. Though I bleed all the radiators again and it's just water that comes out. So where is the airlock in my system? And how do I get rid of it???

The boiler is a Thorn EMI Apollo...

Cheers

 

[hi-spec plumbing heating]

try the pump first

 

[TheKipster]

Pump is fine. I think. It was all working OK-ish before I flushed the system. The reason I flushed it coz I think there's sludge in my system and the water isn't getting through the radiators. Long story. But the pump was working then, it's just since I did the flush that I got this problem.

 

[hi-spec plumbing heating]

ya the pump is working. but you have drained the system so now it will be airlocked.

 

[TheKipster]

Ah, OK, so how do I get rid of the air??? There's none in the radiators...

 

[TheKipster]

btw It's a Grundfos Super Selectric

 

[hi-spec plumbing heating]

try putting it on the highest speed that can remove it.
or remove the large screw in the middle, hold a cloth underneath.
and also open your motorised valves. either manual or calling for heat.

 

[TheKipster]

OK, it's on the highest speed, I have the middle screw undone and there is a constant supply of water out of it...

I can see two valves of importance. One, I believe is the expansion pipe. Either that or it's the feed pipe, it's the smaller of the two. And there's my bypass valve. If I open it up it seems to work fine. But when I tighten it, the heater gets fired up and then 20 secs later it all goes off...

Any ideas???

 

[stardanny]

That would be airlock in return pipe stopping returning water to boiler.

Turn off all, but one radiator, valves off, turn the pump up high, high flow pressure through one radiator may be enough to push air out through boiler to vent pipe. Try it.

 

[TheKipster]

OK, well am giving it a whirl right now... When you say valves off, is that the opposite side of the radiator (get a spanner out) or a certain valve thingy in the airing cupboard (where all the pipes/boiler/pump is)...?

Sorry for the stoopid questions, this is my first plumbing project...

 

[stardanny]

Airlock happen where the return pipe has no pipe going to F&E tank to vent air.

The radiator valve next to the radiator, the one which you can turn on or off by hand, turn that off. Leave the other same rad valve alone as it is for balancing the system ( lockshield cap ) ( there are 2 valves on each radiators).

Do that to all the radiators but the one, say lounge, off and then switch heating on, set pump high. high flow pressure will push airlock out through boiler and up to vent pipe, once you feel hot water flowing on return pipe to boiler and air clearing itself, then turn on next radiator and turn off lounge. Do the same with each radiators. Once you get to last radiator, turn on all radiators and set pump back to normal.

Bypass should be left alone.

 

[TheKipster]

Doesn't seem to be working I'm afraid

As soon as the boiler kicks in it starts making funny noise and shuts down. And that's with one radiator on - Have tried different radiators aswell and same thing. I have the pump screw open in case any air needs to come out but water simply drips from it. Although, after the boiler shuts down, the pump squirts out a jet of water. Don't know if that has any relevance...

 

[stardanny]

give it time, it will take time.

 

[The Baker]

Try doing what has been suggested, but with the central Heating boiler thermostat set to zero, if thats possible.

This may allow the system to run for a long enough period to enable the pump to move the air around to high points such as Rads or to escape via the safety vent pipe because the boiler will not overheat and trip out.

Tim

PS, did you lock the three port valve (or two port valve/valves) in the open position whilst filling the system, and is there a bleed off point at the pipes that enter the Hot Water Cylinder?

 

[TheKipster]

Well the boiler thermostat has High, Low, or off. So it's currently set at off and it's all running through. Will give it another bash later on tonight. If it doesn't work, I'm staying at my parents!!!

I consultated my g/f's dad too. He said that... Flush it all out again. But when refilling it, attach a hose pipe to the outlet and pipe the water in from the bottom up. Rather than simply letting the water fill up from top to bottom ie f&e tank. That way, as air rises, and it fills bottom to top, all the air automatically gets pushed to the top rather than trying to escape upward through the water.

So if this doen't work I'll be taking a day off work soon and give that a whirl.

Thanx for all the help guys, will let you know how it gets on...