EPH Controls to Drayton Wiser Wiring -

[rystaman]

Evening all,

I've just bought a Drayton Wiser Kit 1 to replace my EPH Controls (RF1A-OT) and just want to clear something up with the wiring.

Here is the current wiring setup:

And here are the instructions for the Drayton Wiser Kit 1 (Combi Potterton boiler)

Am I missing anything from the below?

1. Install new backplate
2. Fused main going into L and neutral into N (which will now be on the left rather than the right)
3. L and 1 need to be linked (I assume with just a switch wire?
4. The black wire currently in 2 on the EPH into 1 on the Drayton Wiser
5. The black wire currently in 3 on the EPH into 3 on the Drayton Wiser

A couple of questions too:

What does the clock mean on the instructions on the Drayton Wiser above the Neutral and Live terminals?

What are the black wires currently in the EPH? I assume from the boiler for controls but not sure if I can just transplant it as the above

I'm not 100% sure why there isn't a wire currently in 1 on the EPH and why there's a loose black cable not connected to anything

Also looks like I've got two neutrals that have been wrapped around each other and shoved into the N terminal?

Any help would be massively appreciate by the folks on here!

 

[stem]

Do not link L and 1. There is no link between COM and L now, so you won't need it going forward. [That is why it is shown as a dashed line] If you do make the link and your boiler uses a different voltage for its control circuits, the results will not be good.

Two black switching wires are in terminals marked ON and COM, so that's where they need to remain with the new controller ON and COM. Straight swap over. Electrically speaking both the EPH and Drayton are a simple on/off switch.

The black wires the only wires responsible for operating the heating. However the EPH and the Wiser need 230V mains to provide them with operating power, that's the N & L represented by the clock symbol on the Wiser and the ~ symbol on the EPH. Again a straight swap over.

The loose black wire you mention maybe a plastic strengthening core and not actually a wire at all. Even if it is a wire, if it's not used now and the system is working it won't be needed going forward.

For central heating in the UK, the OFF terminal is very rarely used it's probably vacant in over 99% of installations.

 

[rystaman]

Do not link L and 1. There is no link between COM and L now, so you won't need it going forward. [That is why it is shown as a dashed line] If you do make the link and your boiler uses a different voltage for its control circuits, the results will not be good.

Two black switching wires are in terminals marked ON and COM, so that's where they need to remain with the new controller ON and COM. Straight swap over. Electrically speaking both the EPH and Drayton are a simple on/off switch.

The black wires the only wires responsible for operating the heating. However the EPH and the Wiser need 230V mains to provide them with operating power, that's the N & L represented by the clock symbol on the Wiser and the ~ symbol on the EPH. Again a straight swap over.

The loose black wire you mention maybe a plastic strengthening core and not actually a wire at all. Even if it is a wire, if it's not used now and the system is working it won't be needed going forward.

For central heating in the UK, the OFF terminal is very rarely used it's probably vacant in over 99% of installations.

I appreciate the response here. So the dashed line doesn't indicate connecting them via a switch wire?

On reflection, I'm a silly ******* the instructions say: "One channel only: Note that the output contacts are voltage-free*, so power needs to be put on to Terminal 1 either by linking from Terminal L or from a separate supply with a 3A fuse."

It already comes from a separate supply with a 3A fuse as the EPH is. My tired misreading could have really f'd my boiler...

Thanks for the clarity on the clock and ~ symbol as I didn't have a clue there.

How come the OFF terminal is rarely used in the UK? Just curious.

So these all seems quite simple after replacing the backplate. I'm weirdly sceptical haha.

 

[stem]

Some boilers require a switched 230V live from the thermostat, so only the switched live wire goes to the boiler, and the other wire (the permanent live) comes from the link from the L terminal.

Other boilers have two dedicated terminals for their control, so the power comes from the boilers PCB, this maybe 230V or it maybe 24vdc. In this case the two wires will go to the switch inside the thermostat as is the case with yours. To the thermostat it doesn't matter what the voltage is it's just an on/off switch it will switch whatever voltage is connected to it. The danger arises if a boiler sends 24vdc to the switch and then the switch is linked to the 230V L terminal. Putting mains voltage on a circuit designed for 24vdc is a very bad idea. Many DIYers have fried their boiler's circuit board by making a link they didn't need.

The line representing the link between L and 1 is therefore dashed, because sometimes is should be there, and other time it definitely shouldn't. It's optional.

In most installations, when the thermostat switches 'on' the two wires in COM and ON are simply connected together, when they are, the heating operates. When the thermostat turns 'off' the wires are disconnected which interrupts the circuit and the heating stops.

There are a very few installations, where the heating is controlled by a design of motorised valve called a MOMO. [Motor On / Motor Off] Here when the heating is required the ON terminal is energised and the motor winds the valve open, when the heating is not required the OFF terminal is made live and the motor winds the valve closed. If any MOMO's still exist here they will be incredibly rare.

 

[rystaman]

Some boilers require a switched 230V live from the thermostat, so only the switched live wire goes to the boiler, and the other wire (the permanent live) comes from the link from the L terminal.

Other boilers have two dedicated terminals for their control, so the power comes from the boilers PCB, this maybe 230V or it maybe 24vdc. In this case the two wires will go to the switch inside the thermostat as is the case with yours. To the thermostat it doesn't matter what the voltage is it's just an on/off switch it will switch whatever voltage is connected to it. The danger arises if a boiler sends 24vdc to the switch and then the switch is linked to the 230V L terminal. Putting mains voltage on a circuit designed for 24vdc is a very bad idea. Many DIYers have fried their boiler's circuit board by making a link they didn't need.

The line representing the link between L and 1 is therefore dashed, because sometimes is should be there, and other time it definitely shouldn't. It's optional.

In most installations, when the thermostat switches 'on' the two wires in COM and ON are simply connected together, when they are, the heating operates. When the thermostat turns 'off' the wires are disconnected which interrupts the circuit and the heating stops.

There are a very few installations, where the heating is controlled by a design of motorised valve called a MOMO. [Motor On / Motor Off] Here when the heating is required the ON terminal is energised and the motor winds the valve open, when the heating is not required the OFF terminal is made live and the motor winds the valve closed. If any MOMO's still exist here they will be incredibly rare.

So some boilers need that link between L and 1 (using the Drayton as a example) and because mine doesn't have it in the EPH there's a likely chance I would have fried my boiler if I had done it. I can see why sometimes you need the professionals here...

Ah gotcha, I was thinking what does the Off do if when the COM and ON are not connected the circuit is interrupted so would turn it off anyway.

So this actually does seem like something fairly simple to do for once... Much appreciated mate and thanks for the save