Wiring Confirmation Please (S-Plan)

[robbieduncan]

I have read the wiring guide in the manual (very helpful) and the Y-Plan wiring guide in the boiler manual (Greenstar CDI). I have carefully examined the wiring I have and understood what is there.

I have a standard S-Plan system with a single 240V stat in the downstairs hallway. There is a programmer in the same location as the boiler and unvented cylinder and a 10-way wiring centre. The unvented cylinder has a combined stat and high-limit stat (two stats wired in series in a single pocket). I've tested that I can fit the hot water probe from the EvoHome hot water pack down the middle of the existing stats so should be OK there. I will either remove the variable stat (25-65 degree) and just leave the high-limit stat or just turn the variable stat to the max temperature I can. I intend using the existing wiring to the downstairs hallway to provide 240V to the wall mount for the controller. With all that said I'd appreciate a knowledgable eye looking at this wiring diagram I've produced for the target state. Beyond this I am aware I need to plan the component locations to keep the 30cm separation.

Note the large boxes across the cables are the labels I intend placing on the cables when I do this

[Richard]

Yep looks good to me...

Just bear in mind the 300mm separation is minimum and I would recommend more...

[robbieduncan]

Yep looks good to me...

Just bear in mind the 300mm separation is minimum and I would recommend more...

I will do my best but even getting 300mm between both relays and the hot water cylinder temp sender will be hard. It’s all in one (large) cupboard with the boiler, cylinder and expansion tank. I wish there were wired versions of these components: I have a wired connection to the controller and from a simplicity and reliability point of view it would be nice to use that for comms. Also a non-battery temp sender for the hot water cylinder: there is plenty of power in the location!

Edit to add: pretty off topic but has anyone used anything like this to power the CS92? (And/or HR92 TRV heads)? https://www.ukchristmasworld.com/produc ... -pack.html

Obviously a plug is not ideal in a cupboard in a bathroom but I’m sure I could disassemble the plug and put it in a nice plastic project box with permanent power connection. Would remove once set of batteries from the system which I would really appreciate

[Richard]

Yep looks good to me...

Just bear in mind the 300mm separation is minimum and I would recommend more...

I will do my best but even getting 300mm between both relays and the hot water cylinder temp sender will be hard. It’s all in one (large) cupboard with the boiler, cylinder and expansion tank. I wish there were wired versions of these components: I have a wired connection to the controller and from a simplicity and reliability point of view it would be nice to use that for comms. Also a non-battery temp sender for the hot water cylinder: there is plenty of power in the location!

Edit to add: pretty off topic but has anyone used anything like this to power the CS92? (And/or HR92 TRV heads)? https://www.ukchristmasworld.com/produc ... -pack.html

Obviously a plug is not ideal in a cupboard in a bathroom but I’m sure I could disassemble the plug and put it in a nice plastic project box with permanent power connection. Would remove once set of batteries from the system which I would really appreciate

The issue you will have is the RF communications just won't work if the devices are too close to each other... This is where 90% of installations we are called about don't work that could.

As for your battery idea, I don't see why this wouldn't work in the CS92A but I've not personally tested anything like this. Bear in mind CS92A batteries in a normal environment will last 2+years anyway and not sure the cost of the adaptor warrants it?

[robbieduncan]

Yep looks good to me...

Just bear in mind the 300mm separation is minimum and I would recommend more...

I will do my best but even getting 300mm between both relays and the hot water cylinder temp sender will be hard. It’s all in one (large) cupboard with the boiler, cylinder and expansion tank. I wish there were wired versions of these components: I have a wired connection to the controller and from a simplicity and reliability point of view it would be nice to use that for comms. Also a non-battery temp sender for the hot water cylinder: there is plenty of power in the location!

Edit to add: pretty off topic but has anyone used anything like this to power the CS92? (And/or HR92 TRV heads)? https://www.ukchristmasworld.com/produc ... -pack.html

Obviously a plug is not ideal in a cupboard in a bathroom but I’m sure I could disassemble the plug and put it in a nice plastic project box with permanent power connection. Would remove once set of batteries from the system which I would really appreciate

The issue you will have is the RF communications just won't work if the devices are too close to each other... This is where 90% of installations we are called about don't work that could.

As for your battery idea, I don't see why this wouldn't work in the CS92A but I've not personally tested anything like this. Bear in mind CS92A batteries in a normal environment will last 2+years anyway and not sure the cost of the adaptor warrants it?

Thanks for the quick replies ☺ I agree the cost of the adaptor vs the cost of batteries makes no sense (even for the 5.99 I have now found it for). However hot water failing because I’m not at home and the wife doesn’t know how to/doesn’t want to learn how to replace the batteries on one of the boxes in the heating system is not going to be a good outcome! This would resolve that potential issue. Ideally there would be a CS92A-240 which took a permanent 240V supply but I guess I’m in the minority wanting that

[Bart]

At least from the HR92's you should get a low battery warning before they start to malfunction due to lack of power. I don't know about the sensor though.
(cheap) power supplies might actually introduce noise both from the switching voltage regulator inside and ripple on the voltage provided so I'd be careful with these.
The min 30cm requirement indeed rises challenges when there is a lot of equipment in a small space - I have the same issue, but no problems with radio communication yet. Pulling wires all over the place just to place the wireless communication devices at sufficient distances certainly is ironic.
Someone somewhere once argued on the internet that these wireless systems are best suited for upgrading existing installations - when starting from scratch, wired alternatives, if existing, might be more reliable.

[robbieduncan]

At least from the HR92's you should get a low battery warning before they start to malfunction due to lack of power. I don't know about the sensor though.
(cheap) power supplies might actually introduce noise both from the switching voltage regulator inside and ripple on the voltage provided so I'd be careful with these.
The min 30cm requirement indeed rises challenges when there is a lot of equipment in a small space - I have the same issue, but no problems with radio communication yet. Pulling wires all over the place just to place the wireless communication devices at sufficient distances certainly is ironic.
Someone somewhere once argued on the internet that these wireless systems are best suited for upgrading existing installations - when starting from scratch, wired alternatives, if existing, might be more reliable.

Indeed. When we redid from scratch in our previous house we had fully wired Heatmiser system. I’ll start with batteries and consider what I can do with power supply later. Thanks for the advice on potential instability from cheap power supplies. I would much rather use high quality power supplies but this battery replacement market seems to only have a single manufacturer

[robbieduncan]

Just thought I'd post a quick update. I was able to get enough time to install the system over the weekend. All went smoothly (apart from my own stupidity) and the system is up and working. I followed my wiring diagram pretty much exactly (need to update a few wire colours based on the actual cabling used). Only thing I have not done is the permanent feed to the wall bracket. I need to do a little investigation first as I have a 2 core + earth cable at the junction box that used to feed the thermostat and 3 core + earth at the thermostat! So somewhere something "interesting" is happening