SimonD

.A properly sized combi will not provide unwanted bursts of cold water, nor will a properly sized unvented cylinder, but an unvented cylinder will run out of hot water and need re-heating whereas a combi won't. But a combi also has its drawbacks, especially if it has to provide simultaneous hot water to multiple outlets. First you need to sit down and figure out your hot water usage and patterns. For example, do you use lots of short bursts of hot water or do you tend to draw large amounts of hot water at a time, like for baths and showers? Also, what are your usage patterns in terms of timing for the main bathroom and the ensuite. Then you need to check your mains water flow rate and pressure (both static and dynamic). Together, this information will provide you with a more sound basis for your decision making because it will guide you in the direction of the best solution for you and the best solution might be worth the price of storage. But it's difficult to say without more information. Regarding specific products likened to storage combis, Alpha Innovation provide a boiler that has storage and pre-heat for DHW here: https://www.alpha-innovation.co.uk/products/FlowSmart/FlowSmart/1836534677 which is slightly different to a normal storage combi. Storage combis are great if you draw lots of small amounts of hot water as it reduces dhw cycling but some non-storage combis have a pre heat function that can be useful for this, so as i say figure out your usage needs first.

Go back to your supplier and buy some self-balancing trvs packs with lockshield valves. You then use an app to set the valve to the correct flow and off you go. Balancing using just the lockshields can be a painful endeavour, depending on the brand of lockshield. Lots of videos on YouTube as always which will help you. Oh, and for fitting both your trvs and lockshields I'd recommend you buy to Loctite 55 thread sealing cord - easier and quicker to get a good seal compared to using ptfe tape.

If you do replace all your trvs I'd recommend seriously considering self balancing replacements. They're a dream to get the system balanced and working properly.

24.5kWh for half an hour with a 30kW combi boiler does seem rather wrong. Best way to check is by taking readings directly from your gas meter. Then calculate actual readings. BTW what heating controls have been installed? For a 2 bed semi, the heating output of this boiler is minmum about 6kW which is probable double your actual heat requirement on a mildish autumn day.

Sarking is the best and the preferred option as specified by the Federation of Traditional Metal Roofing Contractors. For several reasons including better pull out resistance for the fixings. Plywood is acceptable and tends to be 'preferred' by the installers as it's cheaper and quicker to install and is certainly an acceptable solution. With some it's even okay to use osb.... so in order of best to worst: 1. sarking 2.plywood 3. osb (but don't use osb if you need high pull out resistance for screws or alternatively you need to reduce fixing spacing around both the perimeter and rest of roof area - this needs to be calculated).

There's a few on Abe Books but all seemingly to be shipped from the US here's one: https://www.abebooks.co.uk/servlet/BookDetailsPL?bi=31377729374&searchurl=kn%3Djohn%2Bkrigger%26sortby%3D17&cm_sp=snippet-_-srp1-_-title2

I scanned the articles rather than listened. It seems we repeat this same circle every so often with someone from the architectural world making the same complaint. Once upon a time it was Prince Charles complaining about the Southbank and city planning me thinks. I totally agree that a lot of what is being built is horrible, especially the monoculture estates being thrown up merely to maximise the profits of large developers while screwing the customers. I'm sure that being an architect designing these things must be soul destroying. Shame it's often missed that simple and efficient can also be highly aesthetic, but can also be more difficult to design as it's about more subtle relationship and proportion rather than a grand statement.

+1 - fit your lovely staircase as late as possible. In the US they often build a construction staircase that then gets covered with proper treads and risers etc. but don't seem to see that too often here. I built my construction staircases using plywood for stringers, osb offcuts for the risers and reclaimed timber for the treads. Cheap as chips. It has also been useful as we've been able to real world test the stair angle and riser/tread relationship to decide on a different angle slope for the proper staircase I'll be making shortly.

I use either: https://www.tcfixings.co.uk/home or https://www.metrofixings.co.uk/ I've always been able to source the metalwork/brackets and other fixings as specificied by structural engineers from both these companies and Metro are efficient if they don't have stock and need ordering. HTH.

Of course, my memory is flawed and behind the times. It was from DRC that the fuel for the Hiroshima and Nagasaki bombs was sourced. Knew it was of some historical significance...

Very sensible as a transitional technology option. The reality on the ground is that here in the UK we have an intractable problem with heating and hot water which is not easily resolved by fabric alone, nor is it a binary choice of fossil fuel/heatpump. 80% of boilers (about 1.2 million per yer) installed are combis and across the country we have about 23 million homes with gas boilers installed, 80% of which are combis. So not only would we need to be installing nearly a million heat pumps per year to get rid of just our gas boilers by 2050, we'd also have to be resolving satisfactory hot water provision in many households where a hot water cylinder and/or necessary buffer isn't an option, including many newbuilds as they haven't been designed with sufficient spare room, unless they lose a spare room. To do this we would also have to change the whole economic model of energy across the UK as it is currently skewed in favour of gas v electric and we have to invest significantly in infrastructure, especially if impractical evangelists suggest direct electric heating for hot water - I was just having a conversation with an electrician yesterday about the installation realities of electric boilers and combis which is an entirely different story....which unfortunately doesn't involve a plug and 13amp socket. Now working in the industry, I've been astonished by the lask of joined up thinking across the whole spectrum from policy makers, to the instrustry, to the evangelists......

Doesn't most of it come from the DRC?

Wow, now that's going to be a reliable source these days.....

I provided a link above on the delay. What actually happened with the government was that the policy was going to come into effect 2025, then they watered it down to merely a consultation, and now the consultation has been kicked down the road 🙄

It seems customers are waking up to it. Hopefully pressure will mount on the developers https://www.theguardian.com/money/2023/oct/16/housebuilders-just-want-the-cheapest-thing-possible-how-futureproof-are-new-build-homes But with this lot in government, the can will probably be kicked down the road indefinitely if they can: https://www.theguardian.com/society/2023/oct/05/delayed-consultation-on-net-zero-construction-a-blow-to-uk-homeowners

Yup, been there too with the Mira shower tray - totally rubbish finish around the waster area. I resolved it by getting out my orbital sander and smoothed it off properly. Will not buy another as having used some Mcalpine traps, I'm not convinced the Mira ones are that good either.

Yeah, you need an adapter. My Marcrist actually came with the adapter even though it's sold as needing one to be bought to use the machine.

The acoustic performance of the wall doesn't depend on the sound insulation - most on the market are pretty identical to each other in terms of both the frequency and absorption because the materials are so similar - what you need to do is go to the insulation manufacturer to get the performance of a specific build up design.

Of course. Their developer buddies will now be sending out dinner invitations that show the politicians their cheque books, reminding them how much money they've 'donated' to the party over the years while teasing them about more...

When you install a new boiler, you need to add new controllers because the overall efficiency of the boiler is calculated using a combination of boiler/controller.The controller could be programmer & thermostat and/or weather compensation.These need to be modulating and not on/off (e.g. relay) to achieve the best energy efficencies. There are still loads of installers putting in new on/off controls. And even if they're sold as smart controls,like the Hive, they don't necessarily provide boiler modulation. Balancing is adjusting the lockshield valves to get all rads warming up and just as importantly making sure you have the right temperature differential across the system. The close coupled tees may be installed in the airing cupboard off the primary pipework, but it depends on the overall pipework layout. There are many ways to provide hydraulic separation and close coupled tees do the same thing but obviously sometimes the other options may be more suitable - without seeing your system it's difficult to say exactly. I think you should let him have a look and maybe report back on the findings.

It's a Mira shower. I can't remember the model but it looks similar to the Atom on the website. Pressure is a smidgen over 3bar dynamic.

Thanks @John Carroll interesting observations. @windsor-tg This is how my thinking is developing, although remember it's just conjector right now and hopefully not totally wide of the mark . As @John Carrollsuggests, the results when running on no1 point towards a restriction somewhere as does the bypass getting hot as this is designed to bypass when there's too much restriction in the heating circuit. What I'm thinking is that it's the size of your circulator that is causing the main problem. This is because not only does it deal with up to 8m head, it also has a high flow rate - so about 2.25m3/h in 1 and 3.25m3/h in 3. Your radiator heating circuit is about 24kW without including the towel rails, so lets say 30kW for arguments sake in total. To transfer this amount of heat around your heating system at 70C with a target temperature differential of 20C (so your return at 50C) requires a flow rate of about 1.3m3/h so whilst your pump is more than capable of providing this, it is oversized for your needs and causing a problem within the boiler. The Vaillant 438, which I believe is the model you have has the attached pressure loss curve. As you'll see from this curve, at 1.3m3/h (or 1300l/hour as per the Vaillant chart) you have a pressure loss of only 2.5m head. However, if you take 2.25m3/h and 3.35m3/h you get 2250l/hour and 3350l/hour respectively. These figures bring the pressure loss across the boiler to above 4m head and off the chart. I suspect that when you're in no1 on your pump, the total system so close to the 6m head that you get the high differential temperatures and when it's in no 3 it's enough to cope with the boiler pressure loss plus the rest of the system - but just. This would also be why you're seeing the bypass heating up as there's probably a lot of fluid going through there due to the high resistance within the system. I suspect that the reason it's so obvious when you're only running your ufh is that because the ufh manifold blends flow & returns, this is increasing back pressure too much within the whole system. In terms of heating circulator, something like the Grundfos Alpha 25-80 would have possibly been better because it has a high head capacity but much lower flow rates - perfect in the region of 1-1.5m3/h Circulator sizing is an important part of system design but appears to be commonly overlooked. Unfortunately, the only way you can test this is probably by installing a lower flow rate circulator pump and then see if it works any better. Overall I don't think the solution to your heating system will be cheap as it probably needs balancing as well as a few components. If you do decide to go for a new boiler, get a system boiler as that has the pump built in which will be variable output, get modulating controls, and probably ask the installer to connect the ufh to the primary heating circuit using close coupled tees.

At the moment I suspect you're not just having issues with the UFH but have a more fundamental system problem. This is because in all your tests so far the boiler return temperature is too low whether or not your system is on rads, ufh or both. It's just that the problem is made much more obvious with just the ufh running. So running these test is going to tell more about the system without ufh distraction.

Yes, please, but run the system for a good hour to 1.5 hours on each pump setting to really let it stabilise.

Would you mind running your ch on its own with ufh off. You can run it in existing setup with pump in 1 and then later with pump in 3. I'd like to see flow and return temps over time. It would also be interesting to see behaviour with boiler range rated back to max output. If you can set flow temp to 70 that would be great too. You have 21 rads? What are their sizes and are they single/double etc.