Fuse spur switch won't turn on after replacing Honeywell ST9400C

[Mense]

I will turn off the electric supply to the entire house (for safety) and then put the blue in neutral and see what happens.

I am not too familiar with electrics though have done little jobs in the house now and then. Not a complete novice.

I mean I can switch the blue wire to neutral myself without having to call him. Should there be no wire going into CH off (where the blue is currently)?

 

[CountryFan]

I mean I can switch the blue wire to neutral myself without having to call him.

It was more to make him aware

Should there be no wire going into CH off (where the blue is currently)?

Correct

 

[dilalio]

The programmer needs a live supply and a route back to earth (via the neutral) this is what allows current to flow and to power/ light up the programmer.

The programmer then transfers that live current down either or both of the sleeved wires to activate the heating /hot water /both, depending on the relays within the programmer which are actuated by the buttons on the programmer or by the auto clock function.

So, 240v at the programmer, display lit and showing digits. 2 channels - 1 for heating, 1 for hot water - which power up the sleeved wires to activate motorised valve(s).

 

[jj4091]

Connecting the blue (neutral )to pin 2 places a short directly onto the live when the programmer is fitted to the wall plate, as can be seen in the circuit diagram of the instalation instructions. As others have said your builder must have moved the blue wire on the back plate and caused your problem as the old one would have caused the same problem if he hadn't. Hopefully no damage will have been caused to your replacement one but it may be a possibility.

 

[Mense]

Didn’t work. I switched the blue cable from where it was to neutral. Nothing. The spur switch did not turn on. The red light did not come on. Tested with voltage pen as well . No electricity to the programmer, relay box, etc.

 

[CountryFan]

Didn’t work. I switched the blue cable from where it was to neutral. Nothing. The spur switch did not turn on. The red light did not come on. Tested with voltage pen as well . No electricity to the programmer, relay box, etc.

Then you have likley blown a fuse or tripped an mcb.

 

[Mense]

Blown a fuse on the spur switch box? I changed that before but will give it another try with a known working fuse.

The MCB is not tripped this time. The switch is up.

However, it definitely got tripped when the builder swapped the programmers over the first time.

 

[Mense]

This is how the wires are now after changing the blue one. Is it correct?

 

[Mense]

If I get a competent electrician over to fix it, how much should I expect to pay?

 

[CountryFan]

This is how the wires are now after changing the blue one. Is it correct?

Looks ok to me. Just make sure you haven’t clamped on the insulation. If it’s not working, then voltage testing would be my next advice.

 

[CountryFan]

If I get a competent electrician over to fix it, how much should I expect to pay?

That’s difficult to answer based on location and how companies operate. Your builder should be the one sorting it really.

 

[bernardgreen]

R

Thread 'HONEYWELL ST9400C & ST9500C:'

21 Jan 2019

Hi all -

My existing programmer is a Honeywell ST9400C for CH and HW, each circuit having a motorised valve. I wish to replace it and have been offered a ST9500C. I understand this is normally used to control 2 separate heating zones, but in all other respects it seems identical to the ST9400C.

Can anyone advise if it is a simple swap with my existing programmer or do I need to make any wiring modifications? I am thinking for Zone 1 & Zone 2 I can just substitute CH & HW (or vice versa).

Regards.

• RONCHAM
• Replies: 15
• Forum: Plumbing and Central Heating