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Andrew Smith
Andrew Smith, Engineer
Category: UK Plumbing
Satisfied Customers: 3629
Experience:  Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering
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Rick, I have a Potterton Profile 80e which overheats. The

Customer Question

Hi Rick, I have a Potterton Profile 80e which overheats. The system has been powerflushed, pump replaced, all 3 thermostats replaced, valve motors and valves functioning normally. Before the overheat protection trips all radiators will be hot.
My guess is that the temp control thermostat is correctly reading the water temperature, but that has no effect on what the burners are doing - i.e. Rotating the knob you heat a click in the right place but wherever the knob is set, the burners continue on full blast until eventually the overheat trips.
Any ideas as to the cause?
Submitted: 1 year ago.
Category: UK Plumbing
Expert:  Andrew Smith replied 1 year ago.

Do you have a thermostat?

Do the radiators get to about 84 degrees?

Just trying to work out if it is the modulating coil stuck fully open or whether the overheat stat is tripping too low?

Customer: replied 1 year ago.
Sorry Andrew, I don't have a tool I can use to check the exact temperature of the radiators. They are hot, but I suspect not hotter than 70c. The cover of the boiler is hotter, is there a basic tool I can get from Screwfix / plumbers merchant that will allow me to give you an accurate answer? ( The Overheat thermostat was the first thing I replaced. If that is disconnected the system eventually kettles and blows off into the header tank )
Customer: replied 1 year ago.
Is the thermostat control knob on this model supposed to achieve temperature by controlling the amount of gas applied (i.e. The size of flame) or is the flame supposed to be constant and simply switches off when the desired water temp is achieved? The issue seems like it is running as if set on max wherever you set the knob.
Expert:  Andrew Smith replied 1 year ago.

The thermostat reports back to the PCB, the PCB regulates the voltage to the gas valve to modulate the size of the flame.

When the temperature gets close the flame should be quite small.

You will need a meter to check the voltage to know if it is the PCB or the gas valve coil

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