Help wiring a Honeywell ST9100C Timer for Boiler

Hi there

Wondering if anyone can help with the wiring of a Honeywell ST9100C timer for my boiler.

I have a simple single channel combined heating/hot water system with the following components:

Potterton Flamingo 20 -30 boiler (old but reliable) with built in thermostat

Grundfos Selectric pump

Mains feed from a normal plug socket.

I am replacing an old Sangamo Timer that has a much simpler wiring configuration but has started squeaking very loudly. The wiring currently has three terminals and an earth. The first terminal takes the live feed from the mains, the second takes the all neutrals from mains, boiler and pump and the third takes the live to the boiler and pump. All three earths are earthed to existing timer.

The Honeywell has N, L, T1, T2, T3 ,T4 and parking terminal for external earth continuity. I just need the timer to power the boiler according to timer settings and have no motorised valves or room thermostats.

Can anyone help? Much appreciated if you can.

see the attached Honeywell ST9100c Wiring

Basically this should help !

Many thanks MrGas, sorry for the delay. Just one last question please. A friend told me that this timer is switch rating is not high enough for my boiler and I need a relay to up the current. Does this sound right?

kapenta said:

A friend told me that this timer is switch rating is not high enough for my boiler and I need a relay to up the current.

Click to expand...

Ignore your friend! There is no need for a relay. Just wire it up as shown in the instructions and make sure that the fuse supplying the heating system is 3amp. This could be in a 3 pin plug or a fused spur.