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The hardie board is being used to build up the height so I have the bathroom finished floor level the same as the rest of the floor. Did consider standard ply instead however thought at least with the Hardie board it would be better with the UFH beneath.

Is there any benefits to having a ply based T&G floor over chipboard? I've got carpet going over most of it, and in the bathroom 6mm hardie backer will be down on top prior to ditra mat and tiles. under everywhere is wet UFH.

@dpmiller thanks for this.

@RHayes @OldSpot So I've checked on the heat load in kW for the UFH at present (just upstairs) and its coming out at 7kW. Downstairs at present comes out at 8-9kW. Boiler is an oil combi boiler rated at 12-18kW. It was present when we moved into the house and I wasn't made aware of any changes to the boiler so assume its still factory set in the middle at 15kW. I actually received another email from Thermosense showing the connections on the back of these programmers. Looks like they'd also require power off the S Plan wiring centre. If I was to use these what would A1 and A2 on your diagram refer to? On the programmer I can make out, normally open, closed and normally closed. Connections 10, 11, 12 I can't make out what they are. They also noted the hysteresis on these is adjustable up to 50º from the set point. @OldSpot The latching relay you've done a drawing for...are they the type that look like RCBO's for a consumer unit? They're the only ones I can find when searching for them.

@RHayes Thank you for your offer. From how I've understood it then, having 2 stats at 1/3 and 2/3 of the tank height would most likely have the boiler running less frequently compared to 1 stat as the temperature is measured at 2 points?? Do you think there would be much difference in the frequency of the boiler firing up between the 2 options? The buffer vessel I'm going for from Newark Cylinders is 800mm in height so the difference between the 2 stat locations will be approx 266mm. Would the difference between the 2 water temperatures here be worth the extra stat, accompanying controller and extra wiring, vs a single stat?

Chisel attachment on an SDS is how I removed the plaster off mine. And yes gives you the opportunity to fit cavity closers.

@Dan F Have you found you can purchase directly from these manufacturers? Or still have to go through the UK reseller?

@OldSpot No problem. Tbh I'm a bit confused with the Thermosense stuff as they noted I'd have to have a programmer for each of the sensors. I was under the impression I'd have both sensors going into a programmer and from there the pair of cables going into the S Plan wiring centre...:but it seems this is not the case. be interesting to see how you do yours. Definitely keep me informed. Thanks

I've been installing my aluminium windows from Origin and had to specify I wanted to use straps, and they sent a load out with each window. And yes, if installing with straps you'll have to take back the reveal and make good after.

Porcelain Tiles have a showroom in North and South London.

I heard of a company called Porcelain Tiles through this forum, and subsequently have chosen tiles from them for my own bathroom. I then heard more and more positive feedback from tilers who used them. Maybe worth a try?

I'm having a different system to yourself. I'm going for a pug screed system, so on top of my joist at present I'll have chipboard T&G boards first, then the underlay, then carpet. However I've asked my structural engineer if I could use cement T&G boards as these should make the system more efficient. However they are much heavier. I'm a good 1-2 months away from potentially evening running the system....still doing the prep work!!

@CotswoldDoItUpper I'm in the process of installing UFH to the first floor in my home which will predominantly have carpet on top. I came across this underlay which may also be of use to yourself, https://wilsons-underlays.co.uk/thermalstream.html

Hi all, Moving on to sorting the waste and water pipes for my bathroom project and will be using 50mm pipe for the basin, bath and shower. I'll fit reducers at the sanitary end if needed. Would it still be wise to use 2no 45° fittings for all 90° bends or will the pipe work being 50mm suffice and enable me to use 90° fittings and have less joins? Thanks

@OldSpot @RHayes So Thermosense have got back in touch and recommend 2 mineral insulated thermocouple sensors and 2 programmable thermostat's. They have sent me the instructions for the thermostats STP321-STP322 Instruction Manual.pdf Can anyone with better knowledge on this type of install advise on how this all wires up? At present the call for heat from the UFH manifold is to the thermostat on the buffer however I'm struggling to make sense how this pair of cables now becomes 4 and all works together to allow the boiler to only fire when under a certain temperature and not exceed another. Thanks

@OldSpot So Thermosense got back to me today and have noted this is something they can do however they needed a bit of guidance as to which sensor would be most suitable. They have recommended something from their PT100 range, https://www.thermosense.co.uk/category/rtd_sensors_pt100_pt1000_prt.html or their thermocouple range, https://www.thermosense.co.uk/category/thermocouple_sensors.html Can anyone help as to identify which sensor would be best for this application? @PeterW is this something you've done before using components from Thermosense?

@OldSpot I spoke to Thermosense after @PeterW mentioned them in a previous post about having 2 stats on the buffer. They've asked for details of the buffer and what it is to achieve and say they can put something together and fingers crossed will be getting back to me this week. I'll post up what they say when I hear back.

@OldSpot I'd definitely be interested in this! Anything to reduce unnecessary firing up of the boilers good with me. Would these just be 2 standard stats? And how would that now wire up into the S Plan wiring centre?

@RHayes Thank you so much for this! It now makes sense to me with regards to the switching sequence. Seeing it on the drawing has made it all make sense. I'll definitely omit the zone valves now I'm understand how these come into play in other set ups. And yes the pump on the boiler will circulate to the buffer, then the Wilo pumps on the manifold can draw from the buffer and circulate around the zones calling for heat. You are 100% correct with the blue from the buffer stat being a switched live. Reason I did it in blue was to mimic the colours in the cable I'll be using to make it easier for me to start making sense and seeing practically how it will all go together.. And yes indeed, if its live I'll definitely be using brown sleeving, as I have had to do for all the 2 way lighting I've installed. I have attached the amended wiring diagram to show the correction and omitted the zone valve. Also shaded brown over other lives for the sleeving. I believe this now to be correct? Today whilst stripping out the bathroom, I came across the 5 core cable from the boiler which went into the Tado extension hub. So there's another cable connected which hasn't been allowed for on the drawing. I'll pull the control unit out from the boiler over the weekend, and see where this goes to. Hopefully can make sense of it and fit it into the S Plan wiring I've drawn up.

Also is it possible to not have a zone valve at all in this system? Even bearing in mind when there will be 2 manifolds?

So I've drawn up this schematic for my S Plan wiring centre and I hope most of it is correct. I'm lost as to where the brown cable from the zone valve (which is to go between the buffer and the boiler) goes so hoping someones can advise. I did think 4, but can't work out what else should be there. I'm did think it should be a switch live but I have this in 10. So definitely lost there. I've looked through the MI for the boiler and all I can make out is a T&E for power, but unsure what else is going from it to the wiring centre. I've put in a SL in my diagram as I can make that out, but unsure if there should be another. I'm starting the rip out for the bathroom and floorboards on the first floor this Friday so I'll be sure to see what other cables there are going to it. Also I've got hold of the buffer stat instructions from Newark Cylinders and according to that its a 2 core cable (COM and 1, which I believe to be 'call for heat'). So here it is, if anyone can help then that would be much appreciated. Hi all,

Thank you both for all this extra information. having no zone valve at the manifold will definitely simplify things for me and will make 1 less cable to get through to where the downstairs UFH/buffer and s plan wiring centre will be. i'm going to draw up a schematic for my system with regards to the S plan and I'll post that up. Hopefully it'll be correct or require little amendments! I'm definitely understanding more and more with regards to this so thank you all!

I'm just going off the wiring diagram from them and trying to adapt it to suit my project. On that it includes zone valves. also next year when the ground floor UFH goes in, then the zone valves will be needed to ensure the flow only goes round which ever circuit is calling for heat? Its also never been mentioned in any of the previous posts to not have them hence why I continued with having them.

According to the Wunda page the heating source is also for the boiler/zone valve. I'm assuming this is where the need for a S plan wiring centre comes into play. I could run a pair of cables from here to 1 and 10 on the S plan so its the same as the grey and orange as the zone valve? And then a pair of cables from the S plan (from 1 and 10) goes to the buffer stat? So this way I connect the zone valve, buffer stat and boiler together?

@RHayes thank you for this. I'm trying to get it noted down in the order of 1-10 and noting what will go to where. Getting a bit lost as the Wunda wiring diagram I have for the smart connection box doesn't have a switch relay, so although I can put the live into 1, I only have a neutral and an earth left (for 2 and 3). This is the diagram for the Wunda wiring centre I'll be getting? I have a feeling maybe the folder of wiring diagrams for different systems they supply may well be for there non smart wiring centres?? With regards to the thermostats the smart ones that Wunda supply are all wireless. There's a 'HubSwitch' which connects to my router in my AV cupboard which will over wifi pair with the smart connection box. I do feel I'm getting closer to understanding all this, just am a bit concerned with the amount of cabling I'll have to feed down various conduits etc, as if there's to be just 1 S plan wiring centre I'll have to install this downstairs where the ground floor UFH manifold etc will be. So I'm hoping the zone valve cabling can be extended. Or that I could have a S plan wiring centre for each of the manifolds.