Replacing Randell 102 - odd wiring

[sipetch]

Hi,

I need to replace a Randell 102 and have purchased a Horstmann Centaurplus C27.

I tried to swap the units over today using the wiring guide provided with the C27 but had no joy.

The boiler is a Potterton Suprima 60L (pumped) but there's no hot water circuit, only heating.

I've examined the wiring and its not quite standard (I think possibly owing to rhere being no hot water circuit) but I can't quite get my head around how to correctly connect up the new timer.

The wiring at the 102 is as follows:

View media item 19821
From my understanding terminal 1 should be the boiler live but its connected up to the thermostat, rather than pin 2. I presume this has been done as there is no hot water circuit but given the HW and CH can be controlled separately with the C27 can this now be corrected?

Any advice would be much appreciated.

 

[tamz]

If the existing 102 is wired as shown your boiler would be on constantly. A thermostat if it has a neutral, also has 2 switch wires. Check again

 

[sipetch]

Ah yes sorry - there's also one wire from the thermostat that goes direct to the boiler/pump

 

[tamz]

Terminal 3 wire can't be the boiler live as it has a constant live feed. Your boiler / pump is fed from the stat so where does that one go?

 

[sipetch]

That definitely looks to be how its wired up. I thought the boiler always had a live and the pump live was switched from the thermostat / timer. Hmmm

 

[tamz]

So that is the permanent live to the boiler

Better if you fully explain the system

No matter

Terminal 5 goes to N
Terminal 6 and 3 goes to L
Terminal 1 goes to 4

You should have got a C17 and saved about a fiver. No need for the hot water side.

 

[sipetch]

Ok great, sorry for the confusion.

I'll give it a try tomorrow and report back.

Many thanks.

 

[namsag]

Are you sure its a 102 and not a 103 you have

 

[sipetch]

Its definitely a 102 and its now working with the new timer - many thanks for the advice.