SimonD

I think you'll struggle to find a plumber who knows and understands manifold systems. You might just have to burn out your phone trying! What you're proposing however is not impossible but the manifold manufacturers for cold and hot water distribution manifolds tend to suggest a limit to the number of ports. In some cases this is as low as 7 and in some it goes up to about 10. In my build, I needed 16 cold water ports and 11 hot water, so I built my own and feed the cold water manifold from the centre rather than the end - no problem so far with flow and pressure any where. Heating manifold wise I have one with 9 posts and 1 with 6 ports and all were a dream to balance. I've yet to install a manifold system for a customer so @Nickfromwales is the man for long term experience in a variety of projects. Here are mine (although a bit messy at the time as the water distribution manifolds were in experimental mode to see if they worked ok with the number of ports!).

If you're a doing a large scale renovation then I presume you're upgrading the fabric of the building so that it becomes more energy efficient? I also presume that you're replacing the existing radiators? Your builder and their heating expert should have told you that your boiler needs to be specified on the basis of a room by room heat loss calculation and if it is going to be a combi, which should really be your last option, it is sized based upon DHW demand and required flow rates. Then they should have told you that the new system (i.e. new radiators) should now be designed for a maximum flow temperature of 55C Your DHW cylinder should also be sized according to usage and the figures you've given so far indicate that a cylinder of about 180l is all you would need, maybe 210 max. These are now part of of new Building Regulations and an industry requirement. For me all the warning bells are ringing. Try phoning around for another heating engineer and with the first question, ask them how they go about selecting the right boiler and radiators.

I can highly recommend https://themetalroofcompany.co.uk/ They tend not to sell direct, but will put you in touch with a local installer. I bought all mine from them but actually did the installation myself in the end due to the compexities of the install. However, they did put me in touch with a local one man band who priced the main roof without any penetrations and simply verge details at about £65/sqm with me supplying the scaffolding and doing some manual labour - this was at the height of Covid. However, once I decided wanted single welted verge detail to follow the curve of my roof and didn't want long flat panels along our deep eaves (due to total roof thickness), I ended up on my own. Your price will be higher due to the complexities of detailing around your roof penetrations, hips and valleys, as they can impact the whole layout of your trays and their machined widths. So what might appear to be a simple roof might not be that simple for standing seam installation. I've attached examples from the Federation of Traditional Metal Roofing Contractors guide below. This is part of my roof which was over 140sqm of steel in the end.

All seems pretty worrying really. I guess you've asked the 2nd quote whether they've actually sent you the right quote and not got it mixed up with something else? As a slight aside, if the company you refer to is the one I think it is, I always find myself watching the content with caution and won't rely on it without further due diligence. I tend to be even more cautious when such a private organisation that depends on hits/likes/views etc. starts promoting a de facto expert scheme.

Maybe we should start another debate about which fittings? 😉 I'm personally not a fan of Hep20 - my first ever one I used on an installation leaked on the mains to UVC. I've since had another leak with one too! And then I hate the demount tool with a vengeance especially when some (expletive deleted) has previously installed them in a tight space with poor access (never me of course). My preference is Polypipe followed by the most despised brand on Buildhub which is Speedfit 😁

Yup, we've trodden a similar path and this is one reason I now do what I do. I couldn't find anyone locally I trusted to actually design my new system for my build, so I decided to take it on myself. While I was doing so, a friend who has a heating business but a long way from me suggested I do the training and get my tickets, so I did. I only do it part time because I'm still building. It's a steep learning curve and much research needed in some cases but I prefer working on complex problems over chucking in replacement boilers as I find it more stimulating and satisfying.

It depends on the manifold. Off the shelf manifolds come with adapters for various types of pipe and mostly of the plastic types and MLCP, for example. But there's nothing to say that you can't use copper, more a question of why would you use copper when you can buy plastic pipe cheaply and run very long runs without any joints. By the time you've plumbed a house using short lengths of copper and any of the required fittings it'll cost a fortune more than the plastic version and have more risks of leaks. Like so many others, I'm now a fan of plastic pipes and manfolds, although unlike most on here, I made the manifolds myself in copper. I would be very wary of a plumber who comes in an throws away a design and then insists on a type of installation without consulting you first. Actually, I'd show them the door.

I'm not referring to my boiler, just talking about general principles of system design as I design and install systems myself (although I'm fairly new to this business). But it seems I'm recently in more demand to fix existing installations that don't work properly, especially newish builds with stupidly large boilers installed with no modulation and a random mix of poorly design UFH and rads, and nobody else wants to touch them.

This does highlight a big issue in that design approaches often don't cover the role that HEX dP and bypass arrangements within the boiler play in selecting for hydraulic separation or not, and that it's more than just down to flow rate differential between heating circuits. I had exactly this problem in a heating system I had to rectify a couple of months back where they'd had a good half dozen plumbers round to try and fix it without joy. I suspected that a major problem was HEX dP. I tried to get the pressure loss data from the boiler manufacturer's technical department who said they'd email it to me and eventually received a pump chart for a system boiler and not the HEX data for the boiler I was dealing with! No HEX data could be extracted from them. In the end I was proven to be correct and got the system working properly for the first time ever. But as I suggested earlier, it is also a warning that we should not assume that we can merrily design and commission gas boiler systems to run at less than 1/2 specified boiler dT 20. I always use my own measuring equipment in parallel to the boiler's to get a proper picture of what is going on. Atags are interesting things.I first came across a behemoth of one a while back which is a model sold by the 'other' Atag company in the UK which is more focussed on the commercial boilers. It was an amazing piece of machinery which did some pretty clever things with its built in modulation and that on start up it modulates from minimum output and ramps up from there as the system warms up. At some point I might get trained on their boilers to understand them better, particularly since they now provide an 18 year warranty.

Yes, I know the formulas to calculate the mass flow rates etc, but maybe my question and empirical experience wasn't clear enough. This is really the crux of it. There is the assumption that the boiler only cycles when, as you say, minimum output is greater than the load. However, my empirical observations suggest that something else goes on depending on boiler manufacturer implementation boiler modulation and controls. And this means that at low flow temperatures, the boiler sees a return temperature it thinks is too high relative to the also low flow temperature and therefore short cycles, even when the load is greater than the minimum boiler output. This is pretty much what I have observed and I don't quite know why yet. At the end of the day we're talking about a dynamic system that rarely works steady state, so return temp often fluctuates. Therefore, if the return temp is so close to flow temperature, there is less margin for fluctuations. Again I've seen this happen fairly often in the real world where a gas boiler is cycling and the internal return temperature sensor thinks it is close or equal to flow temperature. However, if I connect my sensors I can see a good 10C differential - this obviously happens when we get close to output/load limits or flow rates are too high through the system. So my essential question is whether it is appropriate to design for a dT that is less than 1/2 that recommended by most boiler manufacturers and CIBSE for example and does this actually work reliably and efficiently in practise?

It's interesting you're arriving at a boiler dT of 9.53 using a flow temp of 48C. Now, my experience playing with boilers is making me want to avoid running any boiler below a 55C flow temp. (unless it's modulating correctly through suitable controls - usually manufacturer ones). I ran a rather unscientific test on this the other day while I was sitting around waiting for a parts delivery all day long so was twiddling my thumbs. It's a system I have fully designed and installed using radiators and manifold distribution system. I tried to get the system running at 55, 50, 45, and 40C. It was a cold day so the full heat load was required for the most part. This system is modulated using Opentherm with weather and load compensation. During my test I found that as soon as I took the flow temperature below about 50, the boiler would start short-cycling. At a flow temp of 40C, I was getting cycles below 10 seconds, and 45C they were barely any better at about 15-20 seconds. When I finally brought the system back to 55C I got a consistent and constant run time of over 2 hours with a nicely consistent return temp oscillating between about 37 and 43C. Each time it got to 43C, pump/boiler would modulate to bring it back to 37C. At the lower flow temps, the boiler seemed to want a return temp of no less than about 35, which was what caused the short cycling and boiler temper tantrums. But also one question - how do you achieve the 24lpm boiler flow rate if the boiler pump flow rate is max 20lpm? Surely then you need hydraulic separation to run higher boiler flow/return temps and then higher flow rates for the low temp rads/ufh?

I think it's a bit of a hybrid. What isn't entirely clear in the video, but I think nececessary is CCTs to the UFH manifold which is still Delta T 7 with the balanced 'loop' Delta T 20. So it is using CCTs, they're just plumbed in differently onto this loop. This obviously takes more work and balancing. I'm still not sure, or convinced, of the overall benefit of this implementation, other than as an intellectual/academic debate between system designers, or its use under some necessary installation situations, like a retrofit/system rectification. If designing a new installation, would you do it this way as a first option? Probably not.. Ideally, your boiler wants to see about 20, not 25, unless like some boilers, the MIs specifically state 15 or even 11 in one model I've installed on a few occasions.

On the subject of Close Couple Tees and their location on the system, I thought this video provides some very sensible guidance.

For me you open up one of those pandora's boxes of what is really sustainable forestry. FSC and PEFC don't resolve issues with sustainability and ecology. Many of the largest so called environmentally friendly foresty systems are now openly being questioned about their impact on ecosystems - Sweden approaches are one particular example due to the monoculture and crop based approach. I think,like you've already done, do your research and then make a balanced and sensible decision you're comfortable with. Whatever you do will have some sort of environmental impact and it's an impossible task to try to disengage ourselves as individual buyers from that. Given all the other choices of timber you could be making, it seems you'remaking a pretty sensible one?

Yes, it means, at least IIRC on this, there would have to be a corresponding increase to the boiler flow temp which could then cause issues in any blending at the manifold - so why do it? I don't think the WB diagram is quite correct, but then in my experience of how they've implemented their boilers with modulation, EMS and controls, it wouldn't surprise me at all if they did mean it.

In that case, simply install a normally open 2-port vale on the flow to the heating system that is wired to close when the cylinder calls for heat and opens the normally closed 2-port - that way all your high temp flow will go to the cylinder and not your heating circuit. This is pretty easy to plum and wire in and gives you your priority hot water.

When running a mixed circuit with an unmixed circuit (UFH and Rads) you really should have hydraulic separation. Does the system currently have hydraulic separation with all the pumps - how many do you actually have? With your UFH figures, they seem low given the 10kW load. At between 5-7 delta T your flow rate is going to be more like 20-28lpm. Your flow rates with a delta 20 across the boiler will be about: 12lpm at the boiler for 16kW 4.3lpm through the rads (Delta 20) Ignore the flow rates for DHW as part of the heating load as you really should be running priority hot water. As mentioned above, you definitely don't want a CCT just before the mixer. So design for a flow of 55 from the boiler, return of 35, then a 40 flow ufh (unless there's specific need to run hotter due to floor coverings) and 35 return. Then ideally choose a new boiler capable of priority hot water, or is Opentherm compatible and use something like the EPH priority hot water Opentherm Pack. I personally prefer systems that have load compensation and weather compensation, as I think it is always good to have room temp data for the system, but just weather comp and priority hot water work fine.

I've used both Hotun and Macalpine self sealing tundishes, but not the Altechnic one. Your plumber should be on top of this as it's nothing unusual for an unvented installation.

Proper self-build solution! Kwikstage is just magic for everything 😁

The copper

Can't be entirely sure but it looks like they've used and compression reducing coupling like this https://www.bes.co.uk/22-mm-x-15-mm-reducing-set-17738/ In that case it should be fairly straight forwards to remove the coupling and 15mm to replace with something else. In a previous house we had black plastic mains supply too.

Get in touch with either Envirograf or Flametect, both companies of which provide coatings but it needs technical input for the corrct certification.

Oh, I missed that. You're very patient. It's a Topdon TC001. I've now been using it for over a year for work and it has been invaluable for diagnosing and fixing heating systems and boilers.

If you look at the below picture, you'll see the knee stud wall fixed to the top of the steel which also supports the glulam beams with the triple studs. This was designed to be the external wall by the architect. As you'll see from the picture, there is an additional stud wall behind. This is my redesign. This new exterior wall sits on my roof joists just behind the steel. Hope that makes sense.

Both your options will probably do the job. Personally I'd opt for something from the likes of Starrett, like this one made for sheet steel: https://www.amazon.co.uk/Starrett-FCH0400-102-Hole-Saw/dp/B01AWFCKDM?th=1 together with the appropriate arbor: https://www.amazon.co.uk/Starrett-Quick-Hitch-Arbor-Extra-Length/dp/B001LF8F0A?ref_=ast_sto_dp The arbor holds the hole saw in place, allows you to attach it to the drill and it drills a pilot hole in the centre of the hole and acts as a guide. For the size of hole you're looking to make, use a slow speed on the drill and be patient. A little cutting fluid like CT-90 can also help to prevent heat build up and eases the whole operation a little bit.