I was about to say turn the boiler thermostat to the middle position, but this an even better suggestion.
Boiler cuts out before radiators get hot
- Thread starter dominoman
- Start date
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So this is what I did, as suggested.
System and house totally cold, after a day off in snowy weather.
Turned boiler stat to minimum. Powered on the heating at 19 48.
At 1951 boiler switches itself off. Return pipe is still cold to the touch. Even the hot pipe leaving the boiler is not very hot.
I turned stat to halfway. Green light still flashes showing the call for heat but it doesn't fire up immediately.
About three minutes later it fires up. After 7 minutes it switches off again. Return pipe is warmer this time, but still fast from hot.
It's as if the heat sensor is calibrated wrong. It thinks the water is 40 degrees hotter than it is.
System and house totally cold, after a day off in snowy weather.
Turned boiler stat to minimum. Powered on the heating at 19 48.
At 1951 boiler switches itself off. Return pipe is still cold to the touch. Even the hot pipe leaving the boiler is not very hot.
I turned stat to halfway. Green light still flashes showing the call for heat but it doesn't fire up immediately.
About three minutes later it fires up. After 7 minutes it switches off again. Return pipe is warmer this time, but still fast from hot.
It's as if the heat sensor is calibrated wrong. It thinks the water is 40 degrees hotter than it is.
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Is your pump and pcb new or a refurbished one?
Pump is brand new. Installed when I had the whole system powerflushed a couple of months ago. A Grundfoss Alpha 2 and seems to be working well as far as I can tell.
The PCB is an eBay refurbished one.
I'd suspect the PCB, but the exact same thing was happening with the old PCB - which seems too much of a coincidence that both were faulty in the same way?
The PCB is an eBay refurbished one.
I'd suspect the PCB, but the exact same thing was happening with the old PCB - which seems too much of a coincidence that both were faulty in the same way?
If you still have the old pcb, try putting that back in and see what happens.
I know it doesn't make sense, but maybe worth a try.
Maybe something is telling the pump to stop pumping.
Maybe it's time to invest in a NEW pcb.
A new PCB is pretty expensive - so I just want to eliminate other, cheaper, options before I go ahead and do that.
Once I fit a new PCB if it's still the same I won't be able to return it.
The pump runs as expected. When the boiler cuts off (when it thinks it has reached temperature) the pump continues to run for several minutes. And the pump always starts at the same time as the boiler fan does - which is 20 seconds or so before the boiler tries to light.
Once I fit a new PCB if it's still the same I won't be able to return it.
The pump runs as expected. When the boiler cuts off (when it thinks it has reached temperature) the pump continues to run for several minutes. And the pump always starts at the same time as the boiler fan does - which is 20 seconds or so before the boiler tries to light.
I know what you mean.
Have you tried switching ALL the power off to everything and restarting the boiler.
Maybe worth a try.
Have you tried switching ALL the power off to everything and restarting the boiler.
Maybe worth a try.
Who replaced the fan?
Was the fan new or refurb?
Was the fan new or refurb?
UPDATE...
Last night I took out the old temperature thermistor and replaced it.
It was a 5 minute job. The old thermistor just clips into the return pipe to measure the hot water temperature.
As soon as I removed it I could see that was the problem. The thermistor was visibly blackened and cracked on the outside. I replaced it with a new one bought from eBay and not the heating works beautifully again. Nice toasty hot radiators!
In my case it was clear by looking at the thermistor that it needed replacing, but if you want to check it this table is fantastic.
This http://gasboilerforums.com/thermistoreadingsC-P.html
I used that to test my new thermistor and it was about 1.6 Mega Ohms when it came out of the packet, so at around 7 degrees C, which was the temperature of my house! The old thermistor measured only a few kilo Ohms.
Hopefully this will help someone else if they have the same problem. Test the thermistor. Very quick and easy to do if you have a multimeter – and very quick and cheap to replace if it is damaged
Last night I took out the old temperature thermistor and replaced it.
It was a 5 minute job. The old thermistor just clips into the return pipe to measure the hot water temperature.
As soon as I removed it I could see that was the problem. The thermistor was visibly blackened and cracked on the outside. I replaced it with a new one bought from eBay and not the heating works beautifully again. Nice toasty hot radiators!
In my case it was clear by looking at the thermistor that it needed replacing, but if you want to check it this table is fantastic.
This http://gasboilerforums.com/thermistoreadingsC-P.html
I used that to test my new thermistor and it was about 1.6 Mega Ohms when it came out of the packet, so at around 7 degrees C, which was the temperature of my house! The old thermistor measured only a few kilo Ohms.
Hopefully this will help someone else if they have the same problem. Test the thermistor. Very quick and easy to do if you have a multimeter – and very quick and cheap to replace if it is damaged
GREAT result. Well done.
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