Nickfromwales

On reflection, the hot water pipe from the combo to the low use outlet can be in 10mm pipe. That will have lower dead leg characteristics and deliver hot water quite a lot quicker to that outlet. I do this a lot, works very well with plenty of flow rate. Answered in my previous, tee off before the control group. No. You’ll have cold and hot water blended, so if they’re not both from a softener then you’ll still have issues with limescale / furring up of outlets. Softener at the stopcock and everything from that. Softener needs to be before the control group so there is no practical way of sensibly integrating it between / across the balanced and unbalanced ( pre and post control group ) supplies afaic. Adds unnecessary complication and will not protect your appliances / outlets as it is intended to do. Why buy and install a softener to do half a job? So no Get in touch with Trevor@cylinders2go and mention my username and the forum and he will give you a discount on the UVC. It would be a Telford stainless unit, and you can have one or more immersion heaters, with a lifetime warranty. Plenty of members on here have purchased via him. With your stats, you’ll probably get 130-150L useful average storage from a 300L acc. I buy Zimlet units from Anchor Pumps.

Then a 3-ph inverter is a no-brainer. Have you sat down yet with a bit of paper, and drawn out your CU with the 3 phases and actually worked out how you are going to practically and safely ( and economically ) divide / allocate the loads of the dwelling over the 3 phases? What will go on which etc? All of the issues with ‘economical’ go away in an instant with a 3-ph inverter, so why would you not get one? Fronius is what we’ve just specified and installed ( my bonafide PV associates and I ( to save any of the previously received pedantic comments )) to alleviate such issues. This has left me much more flexibility to allocate phases throughout the domestic dwelling to maximise safety, practicality and above all safety for the clients. 3 story residence, so power and lighting most likely going on a phase per floor, kitchen ring on the same phase as the sockets in the open plan dining / living space ( as it’s immediately off the kitchen ), but appliances on fixed wiring will be ok to go over the other 2 phases. I’ve designed the electrical system to maximise divisibility / balance of the power available from each phase of the inverter, for best utilisation of the PV productivity + the output of the DC battery system, eg so the clients will not have to remain constantly mindful of how / when / which way to optimise this discipline ‘manually’ on a daily basis. The other downside of the single phase inverter is the max throughput. Even if your max PV generation doesn’t get close to the stated throughput threshold of the 3-ph inverter, you’ll still be guaranteed to be using every ounce of the PV you produce on a bright sunny day. Question here is of economics; 11 panel / ~4kWp array could be manageable by such ‘manual’ intervention, particularly if fortified with a diversion controller to scoff up any excess linear to it being produced, so it’s down to some maths to estimate the possible savings and how that overlays on the ROI eg when will it offset the uplift in capital expenditure. Next point would be, why go 3-ph CU at this time? Who’s idea was that? Why not go 2-ph, with the main domestic CU ( DB1 ) on ph-1 and then the remaining ph-2 ( DB2 in a garage for eg ) made off strategically to adopt an EV charger or 2 later down the line? You won’t have that much excess to harvest in an EV IMO, certainly not enough to warrant going 3-ph throughout with associated costs, 3-ph inverter so time for a reality check on the proposed 3-ph install IMO. Even with a 3-ph head + meter and initially just using the 2-ph setup, you can still retrospectively add a 3-ph compact CU for a 3-ph EV charger if you ever needed one. There would need to be a very good reason to go 3-ph in the house in this particular instance, and I’m not hearing one yet? Is there something significant you intend running off electricity that were not aware of atm?

A model T Ford will get me from Lands end to John-o-scrote, eventually, but I would rather drive it in its modern day equivalent ( particularly if the modern choice was about the same price with cheaper running costs, less things to go wrong, and a lifetime warranty when bought in stainless ).

It’s very important to most, hence it’s frequently discussed here. Why would you put pumps in and large CWS storage tank(s) when you could have a quieter, more efficient system? Plus the hot tank needs a certain amount of head for gravity then for all the other outlets that cannot be fed from the pump. No thanks ? CWS for a pumped gravity arrangement in this particular instance would need to be 75gal minimum.

The combi will have a cold mains feed, teed off in 15mm before the control group. The hot outlet of that will be 15mm pipe to the low use outlet and that alone. One pipe one outlet. DHW will come from the UVC for everything else. As above re flow of mains through combi. As long as the rising main gives the UVC what is called “cold mains priority”, eg the 22mm feed from stopcock to control group uninterrupted, then you’ll be as well off as you’re going to get. To maximise the preservation of the flow rates the outside tap should come from the rising cold mains BEFORE the first ( aforementioned ) stopcock. The cold fed domestic appliances and the WC’s should all then be fed from the softener cold outlet, with the softener being the very first thing off the stopcock. Stockcock > double check non return valve > drain off cock > 22mm tee. Off that tee comes the 22mm feed to the softener, and the 22mm cold feed to the UVC control group. Some may call this a bit OTT, but with a promise of no more than 2.1 bar and expected struggles with max flow rates, do this and max out your situation is my advice and what I would 100% do if this was one of my client’s full M&E projects. Soften everything other than the kitchen sink cold, American fridge cold feed, possibly the utility cold, or any other cold outlet routinely used for human consumption. Combi-mate conditioners can be used for treating the raw ( hard ) cold feed before these outlets / appliances ( like a boiling / chilled water faucet ) for max results. As always, follow the specific MI’s ( manufacturers instructions / installation advice ) for the items you wish to purchase, so knowing right now what is going in is paramount for this design to be right first time. MI’s can be downloaded for most common devices. Running 2 showers simultaneously will need a household discipline of no other significant outlets being used in parallel during shower times. Both combi boilers and UVC’s are cold mains dependant so ultimately use that cold mains potential and nothing else to push the hot water to the outlets. Starving them obviously had a detrimental effect, however with the static body of pre-heated DHW in the UVC, you will benefit from ‘same temp’ showers which just speed up or slow down, whereas with a combi they would just go cool / cold. Good quality thermostatic shower mixers for balanced pressure cold / hot systems is vital. Do not cheap out there. 28mm is OTT imho, as the above splits the 22mm main at the stopcock already. I would say allow space to add a 200 or 300L cold mains accumulator if there is room in a garage / ground floor space, and have that in the pipe run between the 22mm priority run and the control group so it’s only ever fortifying bathing / showering / mixer taps. Consider that as a parachute option for the eventuality of when the new mains becomes live and you have the system finished, you’re not happy with the max flow rates for the 2 showers together.

You do in every instance where there is existing foul / waste pipework that you cannot confirm the type / specifications of. If in doubt, pipe goes out. As @PeterW says, the boiler PRV is a normally closed valve so no through draft can occur, and if you're that worried about this rather insignificant cold bridge, just cut the pipe off inside, drill back through at 25mm diameter and push a 21.5mm pvc overflow pipe into the wall as a sleeve. Seal that both ends with a suitable sealant. Re-fit the 15mm copper pipe through the sleeve, and fill the gap around the copper pipe with expanding foam at both ends. Problem ( if one actually exists ) solved.

Hi. OK, you seem to be all over the place with the replies here, so let me clear a path for you. Incorrect. The heating circuit can easily support an UVC / TS etc, simply by adding 2-port zone valves to split the heating flow and then running that to the heating coil of the storage tank. The downside is that the combi then, ideally, wouldn't be used as the return path for the hot water a) due to the restrictions through the combi plate heat exchanger, and b) because the combi does one job or the other, eg DHW or heating out, not both together. This means that all the time DHW flows through the combi, it will ignore the heating circuit completely thus not maintaining the temp of the UVC. To get 2 showers running simultaneously, and with good flow, you will definitely need to store hot water in an UVC. I would not recommend the pump as with the new cold mains in place you should find things 'sufficient' as is. You'll lose the inherent restrictions, in-built into the DHW gubbings of a combi, by going mains > UVC > outlets, plus the hot and cold feeds to all the mixer outlets will also be balanced by the control group supplied with the UVC. That gives a 22mm outlet to the UVC and a 22mm outlet to cold mixer feeds, both at the same potential. For this setup you will need to plumb the house correctly, with all monoblock taps / mixers etc all piped back to the same place at the UVC. Cold feed appliances, WC's, and DEFFO the outside tap need to be tee'd off the cold mains the second it comes into the house. Ideally the outside tap should come off the rising cold mains before the first domestic stopcock within the property. The combi can be run to the most infrequently used hot tap in the house, and the one open for as little a time period as possible ( probably the cloakroom wash basin ) so the DHW priority when it's in DHW mode is not dominated by that outlet eg it stops servicing heating output to rads / UVC. Ignore the dynamic pressure readings as they are academic, because you can get great performance from a shower with little to zero dynamic pressure. It's flow rate l/p/m that matters here. Plumb the house to have a rising dedicated 22mm cold feed that services the UVC only to maximise performance.

Nope. It's either done right at the outset or not, simple as. You really need to instill this into the installers as sloppy work will fail in any instance. For reference, I did one like this over 8-9 years ago, pozi-joists, spreader plates stapled up underneath, stapled down atop, 22mm P5 deck board, 6mm plywood atop the P5 ( PVA glued and screwed down at 120mm centres religiously ) and then tiled with large format porcelain tiles using Ultra flexible adhesive. Still solid and crack free when I went there about 3 years ago to service the swimming pool heating setup ?

Hi. Alu spreader plates will work A-OK, used them a load of times in clients houses. Just make sure you have the joist detail done at 400mm centres not 600mm!!! Using an electric or air staple gun is my preferred method of installing the plates, and it’s important to make sure the butt up to each other and do not overlap. That will allow you to get them fixed down snug and be squeak free. If possible, you are best off keeping the underside of the finished floor exposed so you can go underneath and staple the plates up tight against the 22mm deck boards. Staple either side of each of the pipe “omega” channels so 4 runs of staples per joist void. That’s to make sure that the spreader plates are in very good contact with the deck board as it’s that which is then the emitter. If you cannot get underneath, you’ll need runs of 11mm osb set down between joists to make a cradle / support for the plates. You part fill those cradles with rock wool to make the plates distended, so the plates are then forced down under compression when you lay the deck boards. It’s very important that the plates are in good contact with the deck boards or results could suffer significantly. You’ll also need 2 manifolds, one upper and one ground floor, if it’s screed / slab ground and plates above, as you’ll need 2 different flow temps, ideally.

@Newbie1 OK. Instead of lifting the floor, I have an alternate solution which can at least be tried first. The problem here is the much higher heat loss from this area, so there either needed to be twice the amount of pipe, or a much higher flow temp. I see this a lot where plumbing merchants just bang out a generic design for the plumber, with little or no regard for its intended application, thus it doesn't always perform as promised. What you could do here is buy a single room - single loop UFH kit ( for garage conversions / conservatories etc ) LINK and remove the "cold" loop from the current manifold. Some UFH pipe connectors will be required, but do not worry about cutting / jointing this pipe, it will be fine. You can then choose 2 different flow temps, and bump up the flow temps to the "cold" area. I think this has a good chance of working, and e few £hundred is cheaper than a few thousand ( fingers crossed ). Don't worry about the thermostat atm, just fit that and make sure you run it with the other loops calling for heat, for the exercise of proving, and measure results. From there you ( we ) can decide a long term solution according to the results this quicker fix yields..

Yup. The extended longevity of the HP is a big bonus, especially if you’re using the HP for cooling. It’s a big swing from cool > very hot > cool again, x number of times per day, plus an awful lot of losses via the HP and connective pipework etc. With E7 / E10 or octopus etc it’s very easy and economical to go direct. I’m now looking at UVC’s with 2x 3kW immersions set at different temps. The lower ( 65oC ) to go onto grid and the higher ( 80oC ) for the PV. This is a plan to maximise economies during the summer and use the higher temps for the excess PV to offset the nighttime grid ‘top up’. During the winter the higher temp immersion would only be used typically to try and only heat the ( oversized ) UVC once a day in winter.

Deffo the next thing to do. Shut off the flow to everything else except the cold room and report back after 12 / 24 hours.

Not always. The water can crawl along the bottom of the pipe and under trapped air, giving around 75% less cross sectional area of contact from the heated water. The water will still flow in one end and out the other and register on the flow gauge.

Have the loops all been fully purged with cold mains water at full wallop to blast them clear of all trapped air? If this has not been done properly you’ll never get proper flow. Running the manifold with the automatic air vent as a means to remove trapped air is no good whatsoever as the flow rates are extremely low and absolutely will not get the air locks out.

The switch offers those with vaulted ceilings an easy option for test and hush, but I am routinely installing them now on both the first and second floors near sleeping quarters. The locate function actually silences all the detectors EXCEPT the one that has been activated. That is vital in a home where detectors are in several locations including plant spaces / compartments where the smoke could be concealed for some time. The new wired range ( I believe ) will support the wireless locate / test / hush switch. That opens up options for where to locate these, strategically, after moving in or to be able to move them around / add more retrospectively.

Deffo. Switching off the breakers in the CU which feed any 'danger' loads is necessary diligence to prevent inadvertent switch-ons, by a 3rd party for eg.

1. You categorically cannot ditch the thermostatic mixing valves on the manifolds. How else do you intend creating different temps for the differing disciplines?? 2. Different circuits on the boiler? Different ccts will only be fed with the designated flow temp. 3. Good luck with making that work with an emitter that takes a long time to get the rooms up to temp. Honestly. 4. You would need room stats for all zones from the get-go, and these are not optional. This point makes no sense whatsoever, sorry.

75mm minimum, 100mm better. Box ( surround ) all waste pipes with the same as well as you can.

I've never seen less than 75mm installed on domestic B-Regs installs. I usually spec 100mm acoustic with soil / waste pipes 'boxed in' to eliminate the noise of water flowing. I would not want 25mm in my house tbh, and didn't even know this could be bought at 25mm!!

This will do what you want, 100%. There is no need for it to be slotted as it has two parts which do not meet, creating a gap for the overflow to drain into. This will be dependant on the depth of the porcelain so a simple exercise of measuring the item out of the box, then dry assembled, and then installed, will assure you the two parts have not met and the drainage gap / 'slot' still exists. Expensive, but niche products always are

It's a temporary rig!! It's fine.

I got dragged over the coals here for doing that, so this needs connecting to a 16a supply via a 20amp DP switch with immediate effect. DO NOT leave it running on a 13a plug and an extension lead!!! That's a recipe for an electrical fire. Switch this off until you can rectify this. Have you adjusted the Willis heater stat to minimum?

Not. The first will emit the majority of the heat, with the second only having the residual heat to use. Connect in parallel, each with their own TRV

If you could get 3-ph electric then the Steibel Eltron 27kW ( 3x9 ) instant water heater is a very good bit of kit. Rated to fill a bath, and I’ve witnessed it running a shower and it’s very very good. Compare that to the same unit in single phase, and I can piss faster than it. Totally useless. Also, if you go for a huge electric shower, and decent instantaneous water heater, the cold mains will not be sufficient to run both at full capacity. You’ll end up using the shower on full power only if nobody else in the dwelling so much as opens a tap to fill the kettle. They’re HUGELY cold mains dependant so if you do go for an all instantaneous solution, expect to be fitting a ~200L cold mains accumulator to support the cold mains flow rates needed for reliable operation. Furthermore, factor in for much poorer performance in the winter, where the cold mains water is much colder……

Only where there is vibration, or risk of other considerable or sustained local movement. Soldered is perfectly fine for a static residential gas run, regardless of which family of gas is being transported.