Boiler in control of hot water

[rob_g]

I have an Apollo Fanfare 30/50S. Having searched the forums I can't see a similar problem to mine. There are no clunking/clicking noises, no banging and the pilot light stays on. However, when the boiler goes out the neon on the bottom of the tank is still lit, indicating the stat is still closed. The pump continues to run and after a while, once the water has cooled, the boiler ignites again.
It seems that the system is not being controlled by the tank thermostat which is set to 80deg C. Water is being pushed around the pipes and the Hi stat has been replaced.
Any thoughts on this please?

 

[twgas]

tank thermostat which is set to 80deg C.

do you like a hot bath or what

 

[twgas]

even on high the boiler will only just make 80 so the chances of cyl stat shutting off are slim

 

[rob_g]

Wasn't set by me. But it only actually operates around 40-45 dec, anything above that, it never opens.

 

[twgas]

is stat correctly positioned, it should be about 1/3 up the tank.

 

[rob_g]

Thanks Mick, so if the stat is faulty, (never opens above 45) Hi stat is shutting boiler down correctly?

 

[rob_g]

Stat is a 7" rod type so can only go in one place

 

[twgas]

try getting a surface mounted stat, or post a pic in case we're not on same wave length

 

[rob_g]

Thanks for the suggestion Mick, I'll get a replacement and see what happens.

 

[twgas]

try a pic first, it may save you a few quid

 

[rob_g]

here it is..
http://rob-g.myjalbum.net/Thermostat/

 

[twgas]

is that a boiler mate or something of that ilk

 

[rob_g]

It is indeed, but it's an early one. DHW pipe has been de-scaled a couple of years back, system has corosion inhibiter in it.
Until now it has not given any problems and CH has always been OK.

 

[twgas]

do you actually get hot water at the taps

 

[rob_g]

Yes, hot water at the taps but since the cylinder stat never opens the pump runs continuously. Water heats up when the boiler lights and appears to be circulating through the pump easily enough.
Pump is probably 4 years old, having been changed because it was noisy.