Help required with Apollo Boiler

[Sheltie]

Any help/advice would be appreciated ref this problem.

My boiler cuts out after a few minutes running - obviously overheating. The main burner & the pilot go out & I have to wait about 5 mins before I can re-light it.

I think that there is a problem with the mid-position valve as it is staying in the rest position (lever to the left), but in this position the water seems to circulate for a while (into my hot water tank) before the boiler cuts out.

If I hold the mid-position valve over to the right, it affects the water flow as all pipes around the valve immediately run cold - this seems to be proving that the pump is working OK. However, even with the cold water circulating into the boiler it still shuts down after a few minutes.

Obviously the mid-position valve needs replacing (or just the electronics?), however, even with it stuck in a single position presumably something should heat up (rads or hot water tank) & the boiler shouldn't close down!

Any ideas guys?

 

[Duzzer]

Are pipes hot coming off boiler when pilot goes out and do they stay hot when it goes out

 

[Sheltie]

Are pipes hot coming off boiler when pilot goes out and do they stay hot when it goes out

Boiler pipes get hot when boiler is on - as already stated when I force the mid-position valve to the right (towards the lock position) all pipes immediately get colder and after a short time the boiler shuts down with a load click. The piot goes out at the same time as the main burner so the pipes all go cold (pump still running).

I should have added that the pump runs continuously i.e. it dosn't stop at all requiring the plug out to kill it. This is probably an overrun stat fault - could this fault also cause the boiler to overheat/shut-down?

 

[ChrisR]

How hot is it really getting?
Is the pump shifting the hot water round the system?
Is the pump running when the boiler is first switched on...?

 

[Sheltie]

How hot is it really getting?
Is the pump shifting the hot water round the system?
Is the pump running when the boiler is first switched on...?

Top of boiler gets very hot before it switches off.

I can feel hot water in the pipework around the Pump & mid-position valve. No rads get hot (or even warm) before boiler shuts down.

The pump starts running as soon as I apply mains & before boiler is started - this has only been happening a few days.

Any answers and/or suggestions appreciated.

 

[croydoncorgi]

Possibly, the impeller has fallen off the pump shaft, so motor may be turning to no pumping effect.

 

[Duzzer]

If boiler is shifting heat straight after pilot cutting out i wouldn't be suspecting it's cutting out because of over heating most common probs are overheat stat and thermocouple need replacing or if the pilot flame isn't burning right may need pilot assembley if you have a multi meter i could tell you how to test them

 

[Sheltie]

If boiler is shifting heat straight after pilot cutting out i wouldn't be suspecting it's cutting out because of over heating most common probs are overheat stat and thermocouple need replacing or if the pilot flame isn't burning right may need pilot assembley if you have a multi meter i could tell you how to test them

I had a spare (new) thermocouple & replaced this straight away. With the boiler switched off (unplugged) the pilot stays on, so I assume the thermocouple is working OK. The pilot does go out the same time as the boiler closes down (with a loud click). I thought that this was due to the overheat stat cutting the gas supply (including to the pilot). Are the overheat stats prone to being 'over-sensitive'? As already stated - the pump has recently taken to continually running even before, during and after the boiler has tripped out - the pump continues to run until I switch off the mains to the boiler (no longer stops running 5-10 mins after the boiler goes off).

As above - if I manually move the 3 position valve any warm/hot water in the pipework local to the boiler & pump instantly changes temperature so I assuming that water is circulating.

I get the feeling that the boiler is closing down due to overheating before the pump is able to circulate to the rads - I may be wrong though. With the 3 position valve in its 'rest' position I can feel hot water going into my hot-water tank - the boiler still closes down though after a few minutes.

 

[Duzzer]

Try a new overheat thermostat the tc lead carries a milli volt through it and if the leads on the stat are not sound you can get it were theres enough voltage to just get the pilot to hold soon as you start it up the voltage can drop slightly and take the pilot out. The click you hear is the electro magnet letting go not the over heat stat. So its not necessary the oh stat knocking the pilot off due to excess heat but just getting old, replace and let us know

 

[Sheltie]

Try a new overheat thermostat the tc lead carries a milli volt through it and if the leads on the stat are not sound you can get it were theres enough voltage to just get the pilot to hold soon as you start it up the voltage can drop slightly and take the pilot out. The click you hear is the electro magnet letting go not the over heat stat. So its not necessary the oh stat knocking the pilot off due to excess heat but just getting old, replace and let us know

Obviously the supplies shop is closed today. What would you expect to happen if I (temporarily) short the interruptor in the TC? Would this prove the above problem - I have tried this & the heater still shuts down after a minute or so!

 

[stevesey]

...the tc lead carries a milli volt through it ...

Hm - current flows through things, not volts

 

[Duzzer]

Ok your right but when using multi meter i'd be testing with setting on milli volts testing one side of oh stat and then the other if their was a big drop in the milli volts across the stat would change stat