Swap ST699 to LP522 with Y plan

[Smellypunks]

I am looking to swap out an old ST699 Honeywell programmer for Drayton LP522. Now I am confident with most electrics but have not done a boiler programmer before. I am attaching some images of new and old for general consumption.

Now to the wiring... Here is the current setup. With 5 wires coming in by way of a 3 core flex going to positions 3,6 and 7. Then a second cable bring the L and N. There are also connections being made within with unit (blue wire) from L to position 5 and position 5 to 8.

From the LP522

Now the LP522 has the universal backplate and it is clear where the L and N go but I am not sure on the other three incoming wires. Also I am thinking I do not need the extra two internal connection is the correct?

Is it position 3 -> position 4, and position 6 -> position 3. But what about position 7 (hot water NC) where does that connect to?

Thanks in advance.

 

[RandomGrinch]

Now the LP522 has the universal backplate and it is clear where the L and N go but I am not sure on the other three incoming wires. Also I am thinking I do not need the extra two internal connection is the correct?

Correct, no need for the internal link wires.

The brown wire in ST699 L would go to LP522 L
The Blue wire in N to N
The Green/Yellow wire in Hot water NC (7) to LP522 terminal 1
The Blue wire in Hot Water NO (6) to LP522 terminal 3
The Brown wire in Heating NO (3) to LP522 terminal 4

Ideally, at some point this could be rewired; there are currently no markings on the wiring to denote switched lives, and we are no longer supposed to use green/yellow wires in flex, as anything other than an earth wire.

...and that's definitely an interesting use of a wiring centre!

 

[Smellypunks]

RandomGrinch, top notch! yes the house needs a lot of updating but that will be done when the new boiler goes in.

So the blue wire going into NO (3) currently should have a brown sleeve I take it?

So best to switch from flex cable to T&E when rewiring?

So yes that makes sense Hot water off is NC (7).

Yes the wiring centre is a mess and will be replaced in good time.

 

[ericmark]

Yes it seems plumbers don't know wiring regulations, the Y plan uses the N/C contact on the cylinder thermostat and programmer, non of the other plans do, the C and Y plan both allow the boiler to cool by heating the domestic hot water (DHW) where the S plan does not, and so some boilers can be stressed using the S plan, but if the boiler is of a type which is not stressed with S plan that is a better option.

As to programmer, I stopped using one years ago, find it far better to have the thermostat swap from 20ºC to 17ºC to on and off, in fact my thermostat today slowly raises the temperature by 0.5ºC per two hours to stop over shoot.

At £68 for a programmer, and £79 for Hive two channel, it seems pointless to fit a new programmer.

 

[RandomGrinch]

So the blue wire going into NO (3) currently should have a brown sleeve I take it?

Yes, so should the green/yellow, currently on HW NC (7).
But it's not something you need to worry about now, epecially if it's going to be updated in the near future.

So best to switch from flex cable to T&E when rewiring?

A flex would be fine to run between the wiring centre and programmer - but would ideally be a 5 core and earth flex for your Y plan configuration.

yes the house needs a lot of updating but that will be done when the new boiler goes in.

Good luck with the updating - the good thing about changing to the 'Universal' backplate - a number of smart stat receivers (2 channel Hive, Wiser kit 2, etc.) will attach straight on, with no need for further rewiring - although existing room stats may need to be linked out.

 

[ericmark]

- the good thing about changing to the 'Universal' backplate - a number of smart stat receivers (2 channel Hive, Wiser kit 2, etc.) will attach straight on, with no need for further rewiring - although existing room stats may need to be linked out.

The bad thing is so many diffrent configurations for same back plate, programmers and thermostats use same one, and Drayton Wiser alone has three diffrent thermostats 1, 2, and 3 channel all wired diffrent and all same back plate, so putting a twin channel thermostat on a back plate wired for single channel can put 230 volt AC where should be 24 volt DC.

 

[Smellypunks]

Yes the universal backplate sounds like a good idea but its still not fully 'universal' from what you are saying.

Well its all done, is working as it should. Think it took me longer to program it than to do the wiring

One thing with this model is that the LCD backlight is on all the time. Not sure I was expecting that.

Thanks for your help.

 

[Adam_151]

https://imgs.xkcd.com/comics/standards_2x.png