potterton kingfisher boiling intermittently

[D_Hailsham]

This is a semi-gravity system IIRC. No m/vlvs.

Yes, but it could have been turned into a C Plan

The boiler will fire with no pump if you select h/w on the programmer. There is no boiler interlock on gravity hot water.

So it carrys on heating up until the boiler thermostat or overheat stat turns it off.

 

[gassafeman]

Yes, but it could have been turned into a C Plan

Yes, but that will make no difference to the problem.

So it carrys on heating up until the boiler thermostat or overheat stat turns it off.

but...

If the pump has stopped but the boiler continues running, the fault is in the HW circuit or the boiler.

Thats not true on a Gravity system.

Paul.

 

[gassafeman]

Yes, but it could have been turned into a C Plan

Yes it may have, but that will make no difference to the problem.

So it carrys on heating up until the boiler thermostat or overheat stat turns it off.

but...

If the pump has stopped but the boiler continues running, the fault is in the HW circuit or the boiler.

Thats not true on a Gravity system.

Paul.

 

[D_Hailsham]

Yes, but it could have been turned into a C Plan

1. Yes, but that will make no difference to the problem.

So it carries on heating up until the boiler thermostat or overheat stat turns it off.

but...

If the pump has stopped but the boiler continues running, the fault is in the HW circuit or the boiler.

2. That's not true on a Gravity system.

1. The problem is that the system is sometimes "boiling" when it is on HW only. This means that the control system is not turning the boiler off. The main controls are the boiler thermostat and the overheat thermostat. If there is a C plan, the cylinder thermostat is also involved.

2. What's not true, the first quote or the second?