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Yeah you are totally right. After doing all my calculations I found it was actually basically double this rate exactly like you said. I've planned all my pipe spacing to hopefully make balancing pretty easy. And thanks for the note on the expansion vessel I'll make sure to do that.

After Johnmo's feedback ive been away and done a load more research and calculations and looks like if I use 28mm copper the velocity and pressure drop will be comfortably within limits. Thanks for that Any feedback from anyone on anything else in the plan (positioning and types of valves etc). any problems you can see or things i'm missing or doing wrong? appreciate any feedback if you have it. Thanks again Colin

So i checked some stuff on this. Sorry i'm on learning curve here so apologies if i am say something stupid. The specs all say DN25 which i discovered is the nominal diameter which is different. im guessing this would be standard 28mm pipe (or possibly 35?). The connections to the in line anti freeze valve etc are g1". But I will try and confirm pipe size with the company soon. would 28mm (or 35mm) sound a better size? Flow rates: looking over my underfloor heating plans I added up the flow rate for each loop and came to a total of 10.2 l/m (i think this translates to 0.612m3/h). Does this sound right and do I need to add for DHW or anything else? Pressure drop: I did a pressure drop calculation using an online calculator based on a 28mm copper pipe (inside diameter 25.6mm), flow rate of 10.2 ltr/min, over a distance of 6m and a temperature of 40c and it gave me a result of 0.37096 Kpa or 0.00371 bar. My problem is i have not got far enough into my research to really know what this means or why its important but I will do some research. But does this sound ok?

thanks for the reply I haven't done that, I didnt really think there would be a problem here so I clearly need to do some researching on this. The outlet from the heat pump is 25mm and all the gubins they are quoting me with the heatpump (anti freexe valves, 3 way valves etc.) are 25mm which is why i went with that Yeah I know, the heat pump company are insistent on it for warranty reasons. I will at least use it as a volumiser and not buffer This was on the install drawing from the heat pump company so I just followed that. not necessary then?

Hi again all As i work through all the plans for my full renovation of the house im buying im now hoping to get some of your knowledgable feedback on my water plans. The house is an old house which will get a complete renovation and currently the house has nothing other than the mains mdpe coming in so I need to design and install and full system. Ive done a fair bit of basic plumbing but never on this scale and designing a full system so i have been trawling this forum to get tips and come up with a plan but im sure there are plenty of errors in this first draft. NOTE: Im sure all of my symbols that I made are not correct so apologies for that, hopefully they are close enough for you to see what I mean. I have gone here for the manifold system after seeing all the advice on this form. For simplicity I have opted to go without a HRC. The runs to the kitchen sink will be approx 6-7 metres from manifold (manifold next to UVC). The runs to bathroom will be approx similar. Most of the pipes will run under insulation on concrete floor ( I insulate pipes and cut slots out of bottom of PIR boards to acomodate pipes) Im doing this house in Slovakia and for some reason I cant seem to find the UVC multiblock valves here (with the balenced feed and tee for expansion vessel) so I will just put in a balancing valve separately (Or would a PRV suitable instead?) followed by a tee off for expansion with a safety valve. I hope it makes sence and i thank you in advance for any tips or criticisms you have, im sure there are plenty

Thanks very much for the help. I'll run some more numbers and scenarios using heatpunk and h2x to figure out the best spacing as you suggest

Thanks for all the advice so far, it's been really helpful. Whist I tried to sell the merits of fan coils to my wife we are still pretty committed to underfloor heating. After going over all floor and ceiling levels again yesterday I figured I could manage 100mm of insulation throughout all of the older part of the house and half of the newer part (maybe even 200mm in bathroom) leaving me only two rooms (living and bedroom making up approx 28m2 together) where I can only manage 50mm insulation. Would it make sense to do this and maybe do 100mm centres in the rooms with 50mm insulation and 150mm everywhere else. Coupling the slab does seem like a good option as well but thinking with 100mm of insulation through 80% of the house this might be a more economical option.

hmm I had thought about it due to the air conditioning effect in summer (which does get extremely hot). Will need to look into costs and efficiency of these as i dont really know anything about them but will definitely do some research. thanks for the advice

Thanks. yeah I'm looking into this just now and my options

Thanks. I really want to avoid the radiators unless absolutely necessary. running costs is important and I want to make it as good as I can while im renovating just now but its not the only factor anf given our budget and age of the house I can accept some higher running costs, as long as its not going to be super high. I will be putting at least 200mm exterior insulation around foundations as well as exterior walls anyway so hopefully this will be sufficient. I will need to do more research on getting good airtightness, I am replacing all doors and windows with triple glazing and will make sure they are sealed. I will also be plastering inside as well as the exterior below and above insulation. then need to figure out how to block up any holes.

And the newer part:

Yeah for sure I could do that. I have just been looking again at the house with this in mind and took done photos. Hopefully it's clear in photos but from what I can tell the older part has approx 1m above ground (to nothing at the back of the house) of stone foundation then a 100mm slab followed by the dpc and walls. The newer part is also about a meter of concrete slab (to nothing at back again) exposed above ground followed by dpc and walls. So if I insulate these well (and dig down at the back to insulate below ground as you suggest) do you think it's feasible to do this one without huge running costs?

Thanks I'll take a look at them.

Thanks very much for the advice, so another vote for no insulation, I'll definitely need to consider this approach.

Thanks for the reply John I appreciate it. I had thought about your idea of the no insulation route and have seen a little talk of this approach on this forum but wasn't sure about it. The slab as far as I can tell is pretty deep, especially since it's built in sloping ground. I would say at least a meter. would a temperature of 39c be ok for a constant heating mode? And would I be right that once I hear the slab (which could take some time at the beginning of winter) then running costs would be similar as long as I keep it running? Thanks again Colin