gloworm micron 60ff - pump running all the time.

[chedz]

Hi, hopefully someone out there can help me and save me from wasting lots of money.

I have a gloworm micron 60ff with megaflow. Just recently the water pump has been running 247. If the controller has HW and CH off, the pump just runs. This means the rad in the bathroom is hot all the time. the boiler itself if not running just the pump. the only way to stop the pump is to isolate the entire boiler.
The PCB was replaced about 2 years ago.

Could it be a thermistor at fault, thinking the water in the boiler is hot and needs pumping? The manaul for the boiler has a fault finder section which suggests PCB - Replace. But this isn't cheap so I don't want to rush into spending £100 if it could be something else?

Thanks a lot for any info!!!

Mr C

 

[chedz]

just one more thing....
does anyone know if its possible to check the thermistor? I would have thought putting a meter across it to measure resistance would tell me if its functional? Does anyone know the resistance expected for such a part (Number 227057 according to the manual)

cheers!

Mr C

 

[mickyg]

If the controller has HW and CH off, the pump just runs. This means the rad in the bathroom is hot all the time. the boiler itself if not running just the pump.

how is the rad hot if the boiler is not on? I'm guessing it comes on occassionally and you haven't noticed. Probably a fault with one of your motorised valves.

 

[chedz]

The water in the tank and heat exchanger I assume are hot and thats whats going round and round?

The rad in the bathroom comes on when the boiler is on for CH or HW. I assumed it was just pumping all the hot water remaining in the system round. I really haven't noticed the boiler kicking in, and I've monitored it quite closely.....my bed is directly above it

Cheers

 

[chedz]

hi mick

you know what, you were right! I've just set both the HW and CH to off on the programmer, then turned the boiler on (at the electrical wall socket), hey presto the boiler burner comes on..... I guess at night time the water is hot so it only comes on every now and then and I haven't noticed.

One of the valves has a micro switch in it that connects when the value is open. I tried pulling a wire off this to simulate the value being shut, but the boiler keeps running. Does that imply that the valve is ok?

What I don't fully understand is what this microswitch in the valve does? There is a motorised valve on the CH pipe that has no switch in it, only the HW valve has the switch.

I would have thought if the controller was set to OFF-OFF the burner should not be coming on? Is there some funny override involving the switch inside the valve?

Thanks for any wise words!

Mr C

 

[mickyg]

there is a permanent live to one side of the microswitch on both valves. If the switch is stuck on then a permanent supply will feed the boiler and pump. Try remving the orange wire from each valve in turn and trying, this should tell you which one is faulty.

 

[chedz]

Micky,

you are the man! I found that indeed both valves have a microswitch and one of them (CH) was full of cr@p. Dust had got in there and it was jammed up. What fooled me a bit was that the cam on the valve was different on the 2 valves, one opened the switch, one closed it to complete the circuit.....but after a bit of poking with the meter and some head scratching its sorted now!

I've just ordered a new microswitch and will replace it with a nice new one later in the week!

Thanks for the help!

Mr C