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@WWilts I think you'll need to do a light bulb end when bending to that radius. I've just laid UFH pipe at 135 centres and done the light bulb ends to achieve this. Did do a test on an offcut to see how small a radius I could achieve however it kinked before 135mm. Maybe it could be done with the use of a former?

@RHayes Today I took the cover off the control panel on the boiler to investigate to where the 5 core cable connected to, Am I correct in thinking I need a 5 core heat resistant flex, as I'll be connecting live, earth and neutral (as per the image) to my S Plan, and then the black will be in the same connection at the boiler as the image but go to 1 on my S Plan. Then the grey will be in the same connection on the boiler and 10 on my S Plan. And both should be sleeved with brown at both ends. I will then still have to have a jumper in the same connectors as per the image.

@OldSpot Thanks for confirming that. Since speaking with EPH with regards to their digital cylinder stat I too am thinking the same. Trying to understand whether 2 stats at different locations will mean a worthy amount extra of time between cycling over a single stat measuring from 1 point but with a wider hysteresis. With that EPH thermostat I could set the hysteresis to cover a temp range between 40-65deg (it's adjustable in 0.5° increments. I guess the next decision would be at what point to fit the single stat? 2/3's up the tank?

@OldSpot have you come across any enclosures for the DPDT relay? Also I've been in touch with a company called EPH Controls. They do a digital thermostat that has adjustable hysteresis which can be set to 0° so thinking this could be ideal to have 2 fixed set points. They're a bit dearer though at around £70 each.

My system is in the testing phase under pressure but as I was tidying up I thought I'd get this little job out of the way. Undid the screw, pulled the knob and index off, spun it round then tightened it back up. However I noticed that moving this dial affected the pressure. Which made me think...:should the mixing valve be open or closed whilst pressure testing?

@LA3222 interesting to know. I got that hydrometer this morning and have left it on the landing and currently for the last few hours it's saying 16° and 60% humidity. Sand got delivered this morning and I'll start laying it from tomorrow. I'll keep an eye on the hydrometer and take note of how much it rises and when it falls.

Tbh that was my thoughts at the beginning however I stuck to the Wunda plan, which doesn't show any pipe runs in that first void for 2 reasons. Firstly to avoid a notch as the pipes naturally fall from the manifold into that second run, and secondly I was concerned (having never installed wet UFH before) about the bend radius being sharper to get out of the bathroom and round the corner. Was I thinking too safe? I've got some 25mm insulation for another part of the renovation from which I can cut a rip to pop into that first run instead of the pug mix.

Hi Nick, Its only a 4 port manifold and there's 3 pairs of flow and return that are together for around 3m. Space is tight otherwise I would've split them up a bit, and I couldn't use a run between the adjacent joist as I was concerned about the bend radius. I've attached a couple of pictures which might help explain what I mean.

So today I finished laying my UFH pipework according to the Wunda design. Went near enough exactly as per their design except in a few circumstances where it was not possible to install the pipework. However paranoia is setting in with regards to the flow and returns that are bunched together leaving the manifold to go to their relevant zones. Is there a specific spacing that should be adhered to? First time installing UFH (well first time installing wet UFH), and I did have on my mind the bend radius (not wanting to kink the pipe) and wanted to keep notches to a minimum and utilise as many existing if possible (of which there were a few). I have had a search and read through some existing threads, however these seem to be more aimed at screeded applications where the spacings isn't also affected by components such as joists.

@saveasteading thats exactly it. Near enough all sand. It's mixed 8:1 and tbh I don't know exactly what the cement actually does in this mix. @LA3222 I'll get that hydrometer in the morning and see what the readings are. Plan is to install the pug mix from Weds so I'll keep an eye as to what there doing and just wait till it gets back to what the reading is tomorrow.

@RHayes This is the mixer valve in question

@saveasteading the mix is definitely done dry. it's not there for any structural benefit, rather it's there as a thermal store for the UFH. it doesn't go hard, and is also known as a biscuit mix as that supposedly is the texture of it. Here's the blurb from Wunda and Continal http://wundagroup.com/wp-content/uploads/2017/02/F05T-Pug-Screed-System.pdf https://www.ufh.co.uk/system/pug-dry-mix @LA3222 Looks like I'll have to leave it a couple of weeks before laying the ply T&G flooring. What did you use to test the humidity levels? I've found this on Screwfix https://www.screwfix.com/p/htc-1-thermometer-hygrometer/2806x any good? Also what reading where you aiming for? Today was a wet day and house was very dry with the inside temp being 19-20° according to the little UFH manifold temperature gauges I left in a couple of rooms that had already had their pipe laid.

The mix is done dry, no water added. I guess it's just the natural moisture from the sand you're referring to?

@dpmiller I've not considered that option as I thought it to be a more complicated way to achieve a similar outcome to the single thermostat that could be supplied by Newark Cylinders. On the assumption the stat from there has a hysteresis of 8-10º. I saw that as an option that involved more components and more wiring for a similar goal, so hadn't entertained the idea.

@RHayes Thanks for your reply., So the way I'm seeing it is I could use the single stat I can get through Newark with no other components. Haven't confirmed with them the hysteresis on these however from info I've read should be around 8-10º. Option 2 would be to go for the Thermosense sensors and controllers, and set these to 0º hysteresis. How would these wire up? I can make out the power inputs on the back of the units, and from @dpmiller input, 10-12 will be for the sensor. Option 3 seems to be using 2 stats (I assume the ones provided by Newark will suffice), and connecting these up via a DPST relay. I've searched for a double pole through relay, as you mentioned, but can't find any examples of these. Do you have a link to one? With this set up, unless the stats have adjustable hysteresis so can be set to 0, then surely the stats will each have a 8-10º range of the desired temperature further increasing the range?

Thanks for the quick replies. @saveasteading although the heating is off in the house it's surprisingly warm. New windows and plenty of insulation has been installed so that's helping. House is very dry. I'll take some temperature readings during the day tomorrow when I'm back installing my pipe runs. Would it help if I had a fan heater on the first floor whilst installing the pug mix? I was initially thinking I could wait 1-2 days before starting to lay the plywood T&G flooring.

Hi all, what's the rough length of time I should allow before laying a ply T&G sub floor down over 25mm pug mix (8:1)? no wet trades have occurred and UFH being installed as part of a first floor refurb with no occupants.

I've installed one of these and seems to do the job fine. https://www.laddersandscaffoldtowers.co.uk/acatalog/Wooden-Loft-Ladders.html

Noted. Definitely will be doing this. Forgot to take a picture of the valve today, will try and remember tomorrow.

I bought 100mm, 50mm and 25mm end of last week and had them delivered Tuesday just gone. Much lower quantity then you're after though. Ordered from insulationshop.co All were received in excellent condition.

@Nickfromwales thanks for the reply. I'll get one fitted.

Hi @Nickfromwales the pug mix will be sat on PIR boards that are 100mm thick.

Is this needed before laying pipes and putting the pug screed on? Wunda instructions say yes, however lots of images/threads etc I've read on pug screed installs doesn't show it.

Hi @RHayes tbh, after looking over the system again last night I realised there's still a temperature gauge on the flow. And all the other images I found of the Wunda manifold showed them either the same way as mine, or even ones where there was no temperature digits. So assumed it was just going off the gauge on the flow. so I just assembled it all so I could get it up on the wall today. I'll pop a pic up tomorrow when I'm back at the house.

I need to set up my pumpset for my UFH system and the mixing valve supplied by Wunda has the hot on the left, cold on the right. However when fitted the marker to show what temperature its set to would be at the back and not visible. Are they all like this?