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Rick Ridley
Rick Ridley, UK Heating Engineer
Category: UK Plumbing
Satisfied Customers: 1561
Experience:  30 Years on the tools, now retired, Ex CORGI
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I have a Protherm 80E combi boiler - GCN 47 920 17 It

Customer Question

I have a Protherm 80E combi boiler - GCN 47 920 17
It developed a fault last week (after F1'ing every now and again) and will now not light at all. I had an engineer out who was getting odd readings on the voltage to the fan. He recommended replacing the Ignition PCB which I did (with a second hand module) - this did not work.
I have since done the following things:
- Tested old fan - working ok..... Replaced fan with new.
- Replaced old PCB with new.
- Tested all connections - OK
- Tested logic coming off the board - OK
- Tested thermistors (changed the shutoff thermistor) - OK
- Replaced both electrodes.
The issue seems to be that the fan is not getting enough volts. It rests on 40 and rises to 80 when heat is called, it can spike to 120/200 at this point but the fan never goes on. Without the fan going on, the gas will never light I believe.
When the unit is turned on it starts with an F1 safety lockout warning, you can reset this and then call for heat. The pump sounds like it is running but yet the fan never gets enough volts. Everything we have tested seems to be ok, the wires have connections, the logic all works etc. At one point both sides of the fan seemed to be getting 240V
Can anyone think of anything I am missing or something which needs to be tested? I have a new Ignition PCB coming tomorrow as well as the 2nd thermistor to fit for good measure, this will then be everything replaced bar the air switch which acts completely correctly. Everything appears to work as it should, so we must be missing something.
Submitted: 1 year ago.
Category: UK Plumbing
Expert:  Andrew Smith replied 1 year ago.

Could be a faulty neutral at the PCB?

How did you measure the voltage - did you do one wire at a time with the other lead against the earth?

Customer: replied 1 year ago.
Hi Andrew,How would I check the neutral? I think my Dad already did this but just so I can be sure we have already covered it off.We measured the voltage across the fan terminals.Thanks,
Customer: replied 1 year ago.
Voltage from fan to earth (both sides) is 120v resting and 240v when heat is called.Thanks,
Expert:  Andrew Smith replied 1 year ago.

Live to earth and neutral to earth is both 120v so it should not run?

The same with 240v.

You need 240v live to earth and 0v neutral to earth for it to run

Customer: replied 1 year ago.
Hi Andrew,Thanks for your help but I think this one is going to be impossible to cure on this forum, I have an engineer coming to visit again to go through the board and test.Thanks,

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