SimonD

You should have seen what I came across recently when installing a heat pump. My electrician (who was the first electrician my customer had ever known to actually check in the meter box even though they'd had a lot of building work and re-wiring done) found that the armoured cable installed during previous extension work going from the meter box through loft and into the CU was undersized for 100A supply. Then he found that the armoured cable hadn't been made off correctly and the tails were single insulated, squeezed against the metal gland. The sparky who had installed it had then taken some spare insulation slit down one side and wrapped it around the single insulated tails to make it look like they were double insulated. Stunningly bad and the customer said the previous electrician apparently had a good local reputation......

I don't think I'd be sticking a wet finger anywhere near that installation 🙄 The whole thing look bl**dy awful.

Some years ago I bought a replacement charger for my macbook air, thinking it was a proper one and after a few months both my boys started complaining that they were getting electric shocks from the aluminium casing. I didn't believe them until I was sat there and got this tingling electrical feeling in my fingers and arms. When I went back to Amazon the seller had been deleted and there was no comeback at the time. I am very very careful about buying anything electrical from that place and some other markeplaces!

If you've got breeze coming from your sockets, it's very likely they punctured the membrane while installing the electrics - it happens a lot because the contractors simply don't understand airtightness.

Yeah, but like with just about everything we see on here at BH, we have a magnifying glass on the poor experiences of self-builders which shows it's incredibly difficult to find good professionals in just about every area of domestic building in the UK. E.g. I paid 3 sets of professionals and all three made fundamental mistakes and it was a humble bricklayer who knew how to use a tape measure and square properly in the end. And then the glulam manufacturer sent out a surveyor to confirm measurements before commencing production. All good then. Yes, totally. I got laughed at when I was seen with my own home made water level fixed to a datum point on my steel frame with more than 25m long tubing, going round the house to check my levels on the rebuilt brick walls, wall plate and glulam ring beam. Why not use a lazer level they said and I showed them than it some critical areas there was no line of sight and a water level was more accurate because of it. In the end, I think I had a deviation on one corner to corner level of 3mm thanks to this. It was brilliant also for measuring trench depths and topographical measurements as you don't have the issues with sight of lazer in sunshine, even when you use a green lazer and sensor. I still have it coiled away for the landscaping to come.

For any structural steel paints, I've used Promain to spec and provide a suitable buildup - the latest for me was a 6m long x 2.4m wide steel bridge where we used a 2 pack paint on top of a zinc base. https://www.promain.co.uk/

Where does the discharge pipe go? There should be some easy means to see if the prv is letting by so either a tundish or a pipe termination outside where the pipe is turned back on itself towards the wall to stop hot, over-pressure release squirting into someone.

In case it helps you to feel better, we had a full topographical and lazer scan of the existing building to provide base dwg files as most of this was staying in place, then had a measurement survey by an architectural technician and again by an architect. I had to admit I thought we had it covered until a Polish brick layer kindly informed me that the back of the existing house was 120mm longer than the front. Cue a run to the phone to stop production of the curved glulam beams all ordered at the same length. In the end the glulam company did a fantastic job of manufacturing 3 different length curved beams for the main structure. The only pain for me was laying the metal standing seam roof onto a not square roof and hiding that it's not quite square! As lesson learned in not demolishing and starting again, but I do wish professionals could measure properly 🙄

Engineers not needed at all. 😉 A long long time ago in what feels like a galaxy far far away, I used to run document control for projects building anything from oil rigs and oil refineries to pharmaceutical plants all over the world. The engineers used to come crawling to us to ensure the right drawing versions were in the right place and the right time, especially when we got to construction drawings and sub-contract tender and issue. Nowadays, unless you've got good prior experience, some companies like the one I worked for ask for a Masters in Library Science for senior roles doing this.

No, fully installable from the outside as there's an expanding seal and a tightening too. Simple as - BTW - With a strap boss you need access to both sides of the soil pipe.

Just use the Macalpine mechanical bossconn as I linked to above - all you need is a hole saw and then use the compression fitting, so no messing around with cements or glue, or solvent weld reducers, or having to wrap around the soil pipe. Takes a couple of minutes max and you don't have any worries about whether the connection has been properly sealed as quite often happens with the wrap boss. The advantage of the Macalpine is that you can even use then for the blow offs from UVCs and boilers whereas the regs guidelines state you should NOT use wrapped bosses for these, but mechanical ones only. The 40mm version direct from Screwfix: https://www.screwfix.com/p/mcalpine-mechanical-pipe-boss-connector-black-40mm/55722 Simple and no mess

I tend to buy this one: https://mcalpineplumbing.com/traps/condensate-traps-and-fittings/mechanical-soil-and-rainwater-pipe-boss-connector

That could be a bit of a challenge. Quite some time ago I was involved in a large litigation against a big company and some relatively new law (as in it had come into effect only about 12 years prior so case law still maturing). Part of that case involved debating whether the use of 'may' in the legislation actually meant 'must' or 'shall.' And if legislators and judges don't even know the meaning......

It's an interesting proposition, certainly. I've just looked at the company details and as it happens I've met one of the guys involved in this, but at this time it was in another company name - ecomove, which sold e-bikes, e-mopeds, e-scooters etc. in Bristol and has now changed its name and purpose I suppose. It's a small company carrying quite a lot of current liabilities. This is not necessarily a negative, it would just depend on cash flow of the business and the likelihood of being around if and when you want to scale up or you had an unfortunate warranty claim - and we know lots of much larger tech companies that do u-turns on products leaving customers in the lurch, so it's a risk for everyone. Good luck to them I say, I hope it does well. It's certainly something that's piqued my interest.

What do you mean by reasonably accurate? I've used my jigsaw with a blade with 150mm cutting length on both woodfibre and eps at similar angles to this. With this you need to make a jig so you have a flat surface on with the rest to jigsaw as it won't make the angle if using the large flat area of ther xps. The other option is to make up a plywood jig that sandwiches the xps and gives you a cutting guide to rest something like the Bahco insulation saw on. I'd probably for for the second option. But if money is no object: https://www.festool.co.uk/products/cordless-products/cordless-insulating-material-saw/577231---isc-240-eb-basic-gb https://produkte.mafell.de/en/sawing/insulation-saw/insulation-saw-dss-300-cc

Yes, absolutely. It doesn't just help with leaks, it helps lubricate the olive and nut so it's much easier to tighten it up without horrible squeeks and judder. On larger diameter compressions, you can use a bit of the paste on the thread which helps a lot too. The other thing you're going to be swearing about is the use of primary pro insulation. God awful stuff and the sealant is a messy nightmare - you also have to mend the outer protective layer on regular occasion. I only use Armaflex or Kaiflex with the adhesive and tape. TBH I now use trunking wherever possible now. Also, your anti-freeze valves shouldn't be installed on top of each other, but about 150mm apart. But what you can do with your situation is get the half bend covers like these: https://www.bes.co.uk/inta-zeroguard-anti-freeze-valve-protector-26812/ so if the top valve dumps its contents, it doesn't pour it all over the one below. An alternative in some instances is to have 1 anti-freeze valve at the lowest point of the pipework. And lastly, to be picky, you've got a lot of weight hanging of the connectors on the heat pump, no pipe clips until the pipe goes through the wall and this is what's holding the weight of the pipes. Personally, I would have run the flexis straight from the heatpump and then have the isolation valves on hard pipe properly clipped to the wall for support.

Way back when I was at uni studying aerospace engineering we spent time with one of the profs who assigned us a project developing exploratory approaches to more effectively harvest waste heat from power station cooling towers - either to inject this waste energy back into the heating process or take it elsewhere (yes, i know not really aerospace but the prof had a strong interest in energy conservation and it taught us quite a bit). This was a long time ago and heat pumps were very much part of the ideas. We're not very good at thinking this way, unfortunately, but better in other countries where they employ district heating.

Today I had a call from a mate who was going to install an oil boiler and now wants to talk heat pumps!

I'm not that surprised. Sometimes it's better to have a system that is not too reactive and reactivity can significantly reduce efficiency. I think the figures in test A are okay. But I also caution against focusing too much on just the boiler temperatures and consider radiator temperatures and room temperature changes in relation to room volume. That way you'll properly know if the whole system you've got is in the right ball park. What are your expectations of what your heating system should be doing - specifically in regard to heating the space? I'm still of the belief that to get this thing running properly, you need to add some decent modulating controls, like weather compensation - but that, I know, is not what you want.

Yes indeed, but for the really geeky ones of us, you've got to use Reynolds and relative roughness depending on material and even better the fluid temperature, and then using the Reynolds number you can even geek out over whether the flow is laminar, transient or turbulent 😊 This free calculator is pretty good: https://www.h2xengineering.com/pressure-drop-calculator/

Yes they're crazily low. By my calculation the pressure drop in your longest ufh loop, 95m and flow rate of 2l/m is something like 12.8kPa. And then we have 10m on the 28mm pipework, assuming up to 7kW is just under 3.5kPa. So you are fine.

It's funny the cash in hand malarkey. From the other side, it's so common for me to be asked by customers if I'll do the job cash in hand. I never do jobs cash in hand because they're the ones that show up the nature of the customer - they want cheap cash in hand deals but at the same time also want all the regulatory sign off and building regulations notifications is incredible. And they want all the back-up as and when suits them. As a trade, you need your wits about you to choose your customers wisely too!

I think there are 2 options here. 1. is to calculate the press loss in each loop to correctly determine the index circuit and then see if you have enough residual head at the heat pump. My suspicion is you probably do. If you wanted to do this then as you have the flow rates already, you might already have the pressure loss figures from the design documentation somewhere? If not, the pressure loss can be calculated from the flow rates. It's a bit laborious. 2. is you just take a punt and remove the buffer and additional pump and see what happens! I think you'll probably be okay, we won't know for sure until you get it up and running. Then there remains the question as to why they installed a buffer in the first place. Was it: - just a mindless design that plonked it in there; - to do with a calculated or feared pressure loss issue; - to do with system volume as your system doesn't hold the minimum volume per minimum kW output of the heat pump; - to actually buffer excess output from the heat pump as it's oversized? I would be worth doing a system volume calculation to make sure you have sufficient volume. That way if you don't, you could plumb in the buffer as a volumiser and this will save you a headache and repipe if you just cut it out and then have issues. The last thing worth doing is to understand your house heat loss co-efficient - this is how much heat your house loses per Kelvin change in outdoor temperature. To do this we need your calculated heat loss at the required design outdoor temperature and design indoor temperature difference. This figure is useful because we can then find out at what outdoor temperature the heat pump will reach minimum modulation to understand where it might start to cycle and then understand if the buffer was put in for this reason, although I doubt this because the buffer is so small.

This is critical. Your index circuit basically means the sum of the sections of your heating system that adds up to the greatest pressure loss. For every meter that your heating water flows through a pipe is loses pressure. To know whether the pump can deal with this, we need to know the maximum pressure it has to overcome and at what flow rate. If you look at your specification chart, you have a max flow rate of 1205l/h and at this flow rate, if you look at your chart, it gives a residual head of just over 4m head. To know if the pump will be okay with this, you need to know if the circuit that has the greatest pressure loss is less than 4m head. Do you have a circuit diagram or do you know how your heating system is plumbed?