Glow worm ultimate 100FF problem

[Cordwangle1]

My boiler keeps firing up and switching off every couple of seconds. Neon indicator no.4 flashes on and off as it does this. Sometimes it will stay on for a while and eventually it heats everything up, but something is obviously amiss.
Any ideas?

 

[kevplumb]

if open vent system check the header tank

if sealed system check the pressure

check the pump is running

 

[Cordwangle1]

The pump is working. I do have a header tank in the attic which has over- flowed when the water has got too hot. Running the hot tap for a while stops this.
How would the header tank affect the boiler? I haven't been up there to look yet, as it's a bit involved getting to it, but I have ladder, screwdriver and torch ready!
What exactly would I be looking for?

Thanks.

 

[kevplumb]

you should have 2 tanks a large one and a smaller one the small one is for the heating

make sure there is water in it

 

[Cordwangle1]

I checked both tanks and they are full of water.
The boiler seems to switch itself on and off every second or so, it does get the water hot though.
As I removed the front cover it fired up properly and stayed lit, I turned it off again and then started it again and it started switching off and on again.

 

[mickyg]

when its lighting how long does it take for the pilot to light?

 

[Alfredo]

Check you havn't got a blocked cold feed pipe from the F&E tank. The tank may be full, but if its not getting through the boiler may be running out of water to heat/circulate and going out on overheat. It might work after a bit as the water may have expanded as it warms giving the boiler just enough to run on for a wee while.

I'm not saying it is the cold feed blocked, but I'd always check it anyway.
On cold system stick a hose on a radiator drain cock and run bit off and check if ball valve in F&E (small) tank operates. If it operates...not blocked cold feed. If ball valve fails to operate...its most likely a BCF.

Alfredo

 

[simond]

The fact that it runs with the cover off makes me wonder if there is a combustion problem here. Could be a holed/damaged/blocked flue, dangerous stuff.

Does the boiler get hot when the cover is on, or is it just cycling on and off with little/no heat?

 

[Cordwangle1]

Just been down there, when the boiler is switched on it starts to spark, pilot seems to struggle to light and when it does the flame doesn't seem very strong (it's still sparking). Sometimes the main burners will light, and the sparks stop, sometimes it'll burn for a few seconds before switching off and trying to light again. Sometimes the main burners lighting seems to blow the pilot out and it switches off again. Removing the case definitely makes a difference, the burners light and more or less stay lit. Put the case back on and it starts to stutter again. It isn't working fine without the case but it is a lot better.

 

[simond]

Check that the gas valve next to the meter is fully on.

Otherwise you need an RGI to measure the inlet and outlet pressures on the boiler, and check the unit isn't running on vitiated air.

 

[mickyg]

get an rgi, sounds like a simple fault very common to this boiler. Cant say more, dont wanna encourage diy

 

[Alfredo]

Defo NOT cold feed then..so ignore my post

Alfredo

 

[Cordwangle1]

The fan packed up. It had been noisy but was still running, when it packed up I realized that it had obviously been on the way out. I have replaced it, hoping that it would solve the problem. However, still wouldn't run properly with the case on, but would with it off.
Today, with the case off, continues to spark, lights up occasionally for a few seconds, then goes out again. Back to square 1????