ZenMad

Thanks everyone for the great input. I've asked 2 questions on this forum so far, and I've learned so much from everyone here already. So I tried to combine all my learnings, and put this together in a diagram. Here's what I'm doing: - Use HWC + System Boiler instead of Combi Boiler - Use Priority Domestic Hot Water set up - Use PEX pipes for CH and DW water supply, but use copper for connections between boiler and HWC as I've read that with PDHW boiler can heat water up to 80 degrees for the HWC which is about the max PEX can take safely. - Use multiple zones (1 for upstair radiators, 1 downstairs radiator, 1 of downstairs UFH) -- I want to split upstairs and downstairs as downstairs temperature should be lower than upstairs. - Use manifolds for CH. - Use manifolds for DW with an outlet for every wet room. In the wet room put another manifold where needed. Mostly doing this to save space in the boiler area. Just to call out once again that I have no plumbing experience what so ever, nor do even know if this is even possible or right! I just wanted to draw something out and get input from the professionals here before I'm sitting together with my heating engineer / plumber again to ensure the understand what I'm after.

@sharpener thanks for sharing. That's only partially relevant though. I'm not as much enquiring whether copper or PEX is better. I'm pretty set on using PEX. I was mostly asking for feedback on the setup I had in mind, and if there are any concerns with that one or whether there are any other suggestions from folks (e.g. size of pipes, specific combinations, things to watch out for, limitations, ...). I did hear that @Nickfromwales seems to be the expert on those kind of setups, but I assume others here are experienced on using PEX piping and manifold systems.

Hi experts, I'm new here, and want to start of saying that I'm not an expert in plumbing at all. We're doing a full home renovation. As we are stripping the entire house and changing the layout we are also planning on getting the entire central heating system and domestic hot water supply removed. Being from Belgium, where manifold-systems with PEX pipes are the norm, I want to get a similar setup in my house. What can I say: I like the control they provide. I've spoken to a few plumbers already, but to my surprise copper pipes and branch-systems are still widely popular and most plumbers I spoke to are unfamiliar or inexperienced with what I'm enquiring after. Here's a bit about the house: - 3 floors - Downstairs 110 sqm (living room / kitchen / hallway / toilet / garage) - First floor 65 sqm (bathroom / 3 bedrooms) - Loft 35 sqm (bathroom / 1 bedroom) There are a total of 10 radiators (3 on ground floor, 4 upstairs, 3 in loft) plus under floor heating throughout the entire ground floor. There is a combi boiler in the garage. Simply put what I'm after is 6 rows of manifolds : - Row 1: Water supply branches off and goes (a) into boiler and (b) into DCW manifold. This manifold (chain) has 15 outlets (with valves) that go to: Toilet (downstairs) Toilet sink (downstairs) Toilet bathroom (first floor) Bathroom sink (first floor) Bathroom bath (first floor) Toilet bathroom (loft) Bathroom shower (loft) Bathroom sink (loft) Kitchen sink Kitchen dishwasher Kitchen icemachine Dog shower (garage) Washing machine (garage) Garden watering system Outside tap front of house Outside tap back of house - Row 2: DHW from combi boiler enters DHW manifold. This manifold (chain) has 7 outlets (with valves) that go to: Toilet sink (downstairs) Bathroom bath (first floor) Bathroom sink (first floor) Bathroom shower (loft) Bathroom sink (loft) Kitchen sink Dog shower (grage) - Row 3: CH flow enter CH flow manifold. This manifold (chain) has 10 outlets (with valves) that go to: Bedroom 1 Bedroom 2 Bedroom 3 Bathroom (first floor) Bathroom (loft) Loft radiator 1 (loft) Loft radiator 2 (loft) Extra radiator 1 living room (to boost UFH) Extra radiator 2 living room (to boost UFH) Extra radiator kitchen (to boost UFH) - Row 4: Same setup as Row 3 for CH return. - Rows 5 & 6: UFH manifolds. I'm fine with using copper around the boiler, but for all water (CH & DW) leaving all manifold outlets I want to use PEX piping with press-fit connections. Would love to get thoughts on this? And hear out any concerns that folks might have? Like I said, it's been hard getting good input from plumbers. Thanks in advance for you input.

Thanks @JohnMo for sharing your insights, tremendously helpful. Like I mentioned I know very little about boilers, so you are totally right I should not just have made assumptions that bigger is better. What I was wondering though was: "if a 35kW system boiler is enough to take care of the CH (radiators + UFH), does there exist a combi boiler that gets the job done as well?" -- I just used the "there exists 40kW+ combi boilers" as an example. It sounds that "yes, if a 35kW system boiler is good then there will exist a combi boiler that gets the job done as well", or did I misunderstand that? Once again apologies for my ignorance, but everywhere I've lived for the past 15 years we've had a combi boiler and never really had any issues with DHW supply even in larger properties with multiple bathrooms. So I'm simultaneously trying to better understanding the pros / cons of both and energy efficiency is definitely a good one.

Hello experts, We have recently bought a house and are working with a builder on a large scale renovation of the property. We've been discussing boilers and what options are best. I would personally like to opt for a combi boiler and don't want a water tank. Here's what what I think matters. House size: Downstairs: 110 sqm (hallway + large open living room / kitchen + utility + WC). All ceilings are 2.6m high. First floor: 65 sqm (3 bedrooms + bathroom + hallway). All ceilings are 2.6m hig. Loft: 35 sqm (1 bedroom + bathroom). Ceiling is sloped one one side, but 2.2m high at it's highest. Heating consists of 10 radiators: 3 in open living room / kitchen (as extra to boost in case UFH isn't sufficient -- actually not sure if this is needed, would love input) 4 upstairs (one in each bedroom + 1 in bathroom) 3 upstairs (1 in bathroom + 2 in bedroom) Full UFH coverage downstairs (110 sqm surface area / 2.6m high). My rational is that with 2 bathrooms and 3 people living in the property it'll be very unlikely that we will have issues with our DHW needs. I don't know a lot about boilers, but I did some research and found that combi boilers go to ~43kW. As I was researching, I thought that maybe the Vaillant ecoTEC Plus 940 40kW Combi Boiler was a good choice. When I spoke to the builder about this he said that a combi boiler would not be powerful enough, but that he'd check. Later when came back with his quote which he said he discussed with his boiler specialist, he suggested an "Valliant EcoTEC Plus 635" system boiler and a 250-300l Megaflo watertank. That boiler is only 35kW though. When I asked him why I can't use the combi boiler I suggested earlier he was getting a bit defensive, after which he said he'd have to go and discuss this with the boiler specialist again. I wanted to get some thoughts here from all you experts on here. Also, I appreciate all recommendations regarding specific boiler models if people feel there is a particular one they would recommend.