Swap programmer for timeswitch / wireless prog. thermostat

[TheKraken]

I have a Drayton ACL BiFlow system, using a drayton LWC1 wiring centre, and an LP241 programmer.

I'm looking to add more flexibility to the system, to allow for different timings per day, plus I've added TRVs to all but one rad, so need to move the thermostat to the non-TRV room. A wiresless thermostat would seem easiest in that case.

Having read a few threads here it seems if I buy a programmable wireless thermostat (a Drayton Digistat +3 RF?) I can use it to control the central heating, and replace the existing programmer with a more flexible timeswitch (a drayton 711 perhaps).

My only concern is about how easy it would be to rewire this using the LWC1 I already have. It strikes me this is designed to help wiring when a two channel programmer is used, not when a separate timeswitch / prog stat are used.

Can anyone offer any advice about the complexity of the work involved, or even some instuctions? Is there perhaps a different wiring centre to cater for the proposed setup?

Thanks in advance

 

[heatingman]

Is the lwc1, a yellow box 8x6 with long term strip and link wires (red) and a bit of card behind strip?

 

[TheKraken]

It's not yellow, but does have a 16 way terminal strip (horizontal) with red links, plus a 7 way vertical terminal strip (for power connections).

It's in this pdf.

 

[heatingman]

for greater flex, change prog for LP722, straight swop on backplate.

Are you on mid-position or two 2 ports and what type of cylinder, open/unvented.

 

[TheKraken]

It's a mid position valve.

I was planning to use a LP722, but from reading here was led to think that with a programmable thermostat I'd have to leave the heating on constant anyway, making the heating side of the LP722 redundant. I guess from an "ease of swap" point of view I can see the merit in choosing a programmer with the same backplate as my existing one though.

 

[heatingman]

have you established if there is a Permanent 240v in the junction box. Can I assume its an ACL valve, white/blue head?

 

[TheKraken]

Yep, there is a fused connection unit next to the wiring box supplying the necessary 240v.

The valve has a whote Drayton MA1 Mid Position Actuator on top.

 

[heatingman]

Ok, its a reasonably simpe task to substitute the rf stat for a hard wired.
Mount the rf receiver backplate adjacent to wiring centre. Refer to install instructions regards pipes/boiler etc.
Open the wiring centre, and find the heavy black lead from ACL valve head.
You need to establish which wires are to the old room stat. The signal back from the room-stat wil be connected to the WHITE wire, could be any colour, if its an earth (yellow/green) contact an electrician to re-wire/check system.
Trace the wire connected to this white wire, I need to know what type of flex and colours.
A photo would be good.
What type/make of room-stat, confirm cable colours and connections,
A photo would be good.

 

[TheKraken]

Okay here we go. Some of the pictures are available in larger size if you click them.

The thermostat (an ETS1) inside :

The flex carries 5 wires : one brown, two black, one yellow / green, one blue.

The key from the inside of the cover :

So the wiring is : brown - live, 2xblack - load/neutral, y/g - earth, blue - neutral

Inside the wiring centre :



The thermostat cable is next to the black sheathed once (labelled ROOMST), so the cables go to :

brown - 3, 2xblack - 2, y/g - mains earth, blue - mains neutral (there a difficult to see wire link on the right between the two topmost blue wires in the vertical connector block).

and the white pump cable (from the black sheath) goes to 4

And the key from the inside the cover :



so : 2=call, 3=com, 4=white?, and 2 and 4 are linked, and 3 is linked to 9 (htg on).

 

[heatingman]

The junc box needs to be re-wired as the cyl stat off and hw off from programmer are both using earth coded wires which is a big no no.
Is the roomstat a combined room/frost stat?

 

[TheKraken]

No, there is a seperate frost stat above the boiler (an Ideal Classic), but I'm not sure how/whether it attaches to the wiring box.

 

[TheKraken]

Okay, more information on the frost stat wiring. This is the frost stat from the front.

and from the rear.

It's clear that the blue(N) and brown(L) and y/g(E) wires from the wiring centre cable go straight to a connector block, which in turn go straight to the boiler.

A linked black Neutral wire is connected to front terminal 2

The two black wires form the wiring centre cable go to terminals 3 and 1.

The key from the frost stat looks like this :

Tracing the wires back to the wiring centre it's clear that :

Neutral comes from the vertical connector, linking with neutral from the programmer and valve (which I assume is linked to the 240v mains neutral), Earth come from the 240v mains, while Live comes from 12 (Boiler).

The two black cables go to 2 (Room Stat Call) and 240v mains Live. Given how they connect I'd assume that the 240v mains live goes to pin 1 (L) on the frost stat, and the 'room stat call wire' goes to pin 3 on the frost stat.

 

[D_Hailsham]

I was planning to use a LP722, but from reading here was led to think that with a programmable thermostat I'd have to leave the heating on constant anyway, making the heating side of the LP722 redundant. I guess from an "ease of swap" point of view I can see the merit in choosing a programmer with the same backplate as my existing one though.

You are correct in thinking that the heating side of a LP722 would be redundant as it will be controlled by your wireless programmer. In fact there is no real reason why you have to replace your existing LP241 to control the Hot Water side. It is not like CH, where you want different temperatures at different times of the day. You just set the ON/OFF times for heating the hot water and then forget it. If you need to over-ride the setting, you just press the Advance button.

Unless you are a Drayton fan, have a look at the Honeywell CM927 seven day wireless thermostat.

You need to check wireless communication before you fit the receiver in place. The easiest way to do this is to attach the receiver to a length of wire with a three pin plug on the other end. which can be plugged into the mains, via an extension lead if necessary. You can then try the receiver in different positions and check it communicates with the transmitter in the living room.

The wiring for a T4360 is HERE. You will see that, as it is a frost stat, the Neutral connection is not used. Terminal one should be connected to the L terminal in the wiring centre and Terminal 3 to Terminal 2 in the wiring centre.

The Drayton RF3+ and the Honeywell CM927 both have built in Frost protection. So you may be able to dispense with the frost stat; unless your boiler is in the garage or another unheated area.

Here is a modified copy of your pic showing the wiring changes needed.

 

[TheKraken]

Rather confusingly I found a second set of instructions of the T4360 here, which seems to suggest that the Neutral connection is required???

Additonally, the boiler is in an unheated utility room, so the frost stat would still need to be seperate.

Thanks for you efforts with the picture by the way.

 

[D_Hailsham]

Rather confusingly I found a second set of instructions of the T4360 here, which seems to suggest that the Neutral connection is required???

Additonally, the boiler is in an unheated utility room, so the frost stat would still need to be seperate.

So leave the frost stat as it is; obviously the neutral is not important.

Thanks for you efforts with the picture by the way.

Easier than writing a long set of instructions