MortarThePoint

Typically, how long are appliance cables for non-fitted appliances? Most importantly drier and washer? A bit of a 'how long is a piece of string question' I know but allows me to establish zones.

The architect has shown about 5m of extractor ducting to where it then exits the house. Two questions: Is there no maximum ducting length between hood and final exit? I have a soil pipe to get behind, can I use the rectangular ducting with it's longer edge vertical, rather than horizontal as shown below?

Is it normal to plaster the whole wall behind kitchen cabinets (including base cabinets) or is it usually left as bare blockwork?

Howdens have a pretty generous service void behind (some with 72mm) so routing pipes etc should be easy there. Some others have little or no service void (Ikea have none). I might plan to have the electrics go down in the permitted zone in the corner of the room and then go along in the red circled area then popping up in chases where needed. That can all be done when the kitchen is finalised (scoff) and about to be installed.

Every time I discuss the kitchen with my wife she has a different idea. I asked her to do a design, which she did but it still doesn't seem to have finalised things in her mind. The main difficulty for me is how to manage the services (water and electric). Water is easier as I presume it can get routed through when the units layout is finalised (?). The walls are blockwork so the pipes would need to be wall mounted. Is there normally a gap behind units for this? I'm clearly not an experience kitchen fitter. There are no water connections downstream of the kitchen, so it doesn't affect anything else. The electrics are more complicated as they get chased into the wall. We are tiling the whole floor (inc. under units) and is it normal to plaster behind kitchen units? Either way, as there needs to be plastered wall above the units, any cable drops need to be finalised before plastering. Under counter sockets are pretty easy, but the countertop ones are more difficult. since they need to be the correct distances from things like the sink and cooker. I don't know what tiles we'll be using for the kitchen splashback so hard to get the height of the sockets spot on for that. Any tips?

The 43m limit is a real nuisance and wish I'd know it before. I've measured on site more accurately and it works out to be very close to 40m to go along the back of the house and round the end of it. That comes right up against the 43m limit allowing 3m for the pole. I'm wondering about drilling a hole into the sub floor void to route the cable under the end of the house and save about 6m of length. It will be tough to get the height just right and also to feed it through. Any advice? I've shown this adapted route in solid purple below. Would have been easy to have built a 6m length of soil pipe in when the foundation blockwork was being done but that ship has sailed. The ground under the void is 675mm below DPC, so 525mm below ground level. I'll check, but think 450mm would be deep enough below the patio, so 500mm below ground level would be fine. I'd be OK with location C if I can have an internal meter, so I might try my luck there.

Wish I had ordered last year when I started this thread, but space on site...

Be careful here as when I looked at partitions it seemed like the whle Rockwool thing being good for sound was a myth:

This looks like it's going to get a bit tricky unfortunately. I decided on Plan F on the front of the house, but that's about 45m from the pole. I didn't check that with UKPN at the time D'Oh 🙄 UKPN say they have a Small Connections limit of 43m (inc. 3m for pole), so I'm too far and need t go yo the Projects Team, gulp / cha-ching! The price would be £2100 for a 3-phase connection by the Small Connections team plus £17/m for cable, so quite envious of @Redoctober's connection all for £900. Heaven knows what the Project Team cost will look like. [NB: the 3-phase side of it was only adding ~£300]. The about 45m is routing along the back of the house and then around the Utility and putting the meter box in the least impactful position and close to the CU. Not going round the Utility (Plan C) would make it around 36m but we'd walk past it every day. Kind have wish I had gone @ProDave 's route in 2019 when I had a 3-phase connection removed for demolition. One question I had on that was voltage drop. Having a log run of SWA on the customer side of the meter means the customer pays for the voltage drop doesn't it? That could put the bill up by up to 5% couldn't it (thinking main load will be ASHP).

I appreciate the benefit of higher sockets and that was why I asked my BCO if I could have a mix. All bedrooms are having 4 double outlets and feels like the two more discretely positioned ones could be high (e.g. by the beds) and the other two, which are in the open, lower down. A teenager probably uses sockets 10 to 100 times as many times as an OAP. Sadly my dad's given up playing Scalextric.

Very interesting. Do you have a reference for that? I asked my BCO if I could have some lower and he thought all had to be high, but that wasn't considering non-general use.

The regulations vary across the UK, so this is relevant to the English Regs (Part M). Most commentary I can see on the English regs potentially seem to make a subtle mistake. Where do you measure the 450mm to? Clause 1.18 of Part M says "their centre line". But then it references a slightly unrealistic drawing. Both copied below. Whether you applaud the regulations intent aside, it needs to be understood as many want to put the sockets as low as 'allowed'. I would read 1.18 to mean the Green line below, or perhaps the Blue at a stretch though that's going to vary by socket manufacturer. I see lots or commentary referencing the Black line or perhaps even the Red line where people have added a little extra for carpet thickness etc. Where have people gone with this in their own builds? Personally, I've always lived in older heights and would prefer the sockets lower upstairs in bedrooms (NB: logically the NI regs don't mandate a height here as in most dwellings there is no wheelchair access to the first floor, but that's irrelevant in England).

Interesting that NI building regulations limit the requirement to the entrance and principal storey, i.e. the ground floor in most cases. Not so for the English Regs which apply to all habitable rooms so include first floor bedrooms.

One better, I'll be using RCBOs which is effectively an RCD for each circuit. I wanted something to highlight that capping / conduit is nothing to do with protecting cables beyond he plastering stage.

Some relevant extracts from the Onsite Guide: ------ This is poorly written as everything I have seen suggests its (a) or (b) or (c) or (d) or (e) or (f) but there is no or at the end of (b) here.

There's been lots of planning and not much doing what with a pick up in day job demand. I'm starting to doubt the benefit of using conduit/capping at all for sockets. If chased into the wall, e.g. with a 15mm x 10mm chase. With a 10mm chase depth it would be an amazingly cack-handed plasterer who managed to damage a cable. Oval conduit is pretty cheap (£0.35/m) so it's not so much of a cost decision. As @PeterW say's, complete rewiring is likely far down the line, and how many modifications would actually be made easier by conduit. Adding a new socket might be midway between two existing sockets and so benefit from the conduit. I think I am already leaning towards an excessive number of sockets (four 2-gangs per bedroom) so it feels unlikely I'd want more. Maybe using conduit in selected rooms that are more likely to need changes, like the living room. Oval conduit in some ways feels a bit like insurance against making some mistakes. Conduit for wired data connections is a no brainer on the other hand.

Valid, I wanted to qualify that it wasn't a problem. >£100/yr is possibly decadent for what it is, <£20/yr feels OK.

Narrower pipe definitely helps so probably takes it to a trivial cost. Volume of pipe to basin, v = pi * 10 * (0.0088/2)^2 = 0.6l --> mass of water m_w = 0.6kg So about a third of the water volume, so all energy costs go down by 3. 365 * (4 * 4) * ((2.5p/3 + 0.3p/3) - (1.2p/3 + 0.18p/3)) = £28/yr without ASHP 365 * (4 * 4) * ((2.5p/3 + 0.3p/3) - (1.2p/3 + 0.18p/3)) = £22/yr without ASHP and just priming Haven't included the pump power in any of this, but likely small if shuts off after only enough time to prime the pipes. The 300s is 5mins average occupancy and was naively used for the duration of hot water circulation. It was a guess, but Model 1b doesn't account for much anyway after the correction prompted by JohnMo's comment. willbish's comment pretty much eliminates it and, if set up correctly, potentially the whole difference.

If you were to harvest grey water for toilet flush, then an alternative simpler and potentially more energy efficient approach would be to have a valve near the basin to 'waste' that opens when presence detected and closes when hot water detected (or after set time). The water wouldn't be totally wasted and there's no need for a return pipe.

A rather hacked solution which wastes about the same amount of energy is to fill the cistern from the hot water supply. Problem is it probably wouldn't fill before you reached the basin.?

Thanks JohnMo! I was surprised by the numbers that came out, so hoped someone would shoot a hole. I have assumed a 5C temperature loss, but that may be too much. Thinking again, the water is only in the pipe for 2*1.77l / 12l/min = 18 seconds. An online calculator [1] suggests 8W/m based on 55C/25C/15mm pipe/15mm insulation which would make for 20m * 8W/m = 160W which is 4% of the previous figure so more like it. 8W/m from 0.177l/m for 18seconds works out as a dT of (8*18)/(4200*0.117) = 0.2C. So my guess was WAY out. That makes the model 1b contribution much smaller: Model 1b: flow and return circulated for 5 minutes (=300s) each time loo occupied Energy wasted, E2 = dT * q * t_occupied * c_w = 0.2C * 0.2kg/s * 300s * 4.2kJ/kgC = 50kJ = 0.014kWhr --> cost 0.3p (0.005kWhr & 0.1p if ASHP) [equivalent to 160W for the 5mins] No water wasted before hot water starts coming through Checking Model 1a: dT/dt = 0.2C / 18s = 0.67C/min. That means it would take about an hour to get back to 25C as it's not linear. That seems OK for model 1a. So Model 1b doesn't account for much and it's the difference between 2.5p and 1.2p per loo usage of Model 1a and Model 0 that counts. That makes the annual difference: 365 * (4 * 4) * ((2.5p + 0.3p) - (1.2p + 0.18p)) = £83/yr (£21/yr if ASHP) Much more palatable. [1] https://cheguide.com/heat_loss_insulation.html

I've always been happy to wash hands with cold water (using the cold tap), but that's probably frowned on in the post Covid 20 seconds world. As our house is laid out, we only have one basin at a significant distance. I had wondered about having a thermostated redring style water heater to heat the first bit coming through.

It's half as wasteful as having flow and return cooling down.

It would be less wasteful to have a sensor that shuts off the circulation when hot water is detected in the return pipe back at the tank. That would limit the damage to Model 1a, so around 200kWhr/year (elec).

It's nice to have hot water straightaway when you turn a hot tap on. To achieve this, I think some have a flow and return to the basin in question and hot water is circulated to it when the bathroom light is turned on or a PIR is tripped. Isn't this hugely wasteful? Approximate calculation: Water circulation flow rate, q = 12l/min = 0.2l/s (guess) Hot water temperature, T_w = 55C Room temperature, T_r = 25 Drop in water temperature flow vs return, dT = 5C (guess, insulated but still) Pipe ID, d = 15mm Pipe length to basin, L = 10m Volume of pipe to basin, v = pi * 10 * (0.015/2)^2 = 1.77l --> mass of water m_w = 1.77kg Model 0: system with only a flow. Water heated up and then allowed to cool down before next use some hours later Energy wasted, E1 = (T_w - T_r) * m_w * c_w = (55C - 25C) * 1.77kg * 4.2kJ/kgC = 223kJ = 0.06kWhr --> cost 1.2p. Potentially 1.77l of water wasted before hot water starts coming through, cost 0.18p. Model 1a: flow and return water heated up and then allowed to cool down before next use some hours later Energy wasted, E1 = (T_w - T_r) * (2 * m_w) * c_w = (55C - 25C) * (2 * 1.77kg) * 4.2kJ/kgC = 446kJ = 0.12kWhr --> cost 2.5p (0.04kWhr & 0.8p if ASHP) No water wasted before hot water starts coming through Model 1b: flow and return circulated for 5 minutes (=300s) each time loo occupied Energy wasted, E2 = dT * q * t_occupied * c_w = 5C * 0.2kg/s * 300s * 4.2kJ/kgC = 1260kJ = 0.35kWhr --> cost 7p (0.12kWhr & 2.3p if ASHP) [equivalent to 4.2kW for the 5mins] No water wasted before hot water starts coming through With a hot flow and return system it would be approximately the sum of 1a and 1b, so about 10p for each time the loo is used. It would be less wasteful (of energy and money, but not water) to automatically run the hot tap until it is warm each time, ready for instant hot water. But that would be seen as an awful waste. Why isn't a flow and return system seen as the same. Annual cost based on loos used 4 times a day by 4 people: 365 * (4 * 4) * (0.12kWhr + 0.35kWhr) = 2,745kWhr (900kWhr) 365 * (4 * 4) * 10p = £584/yr (£200/yr if ASHP) Wouldn't be a waste in winter as it would heat the house, but that may be only half of the year. So best case you're still looking at wasting about 500kwhr and £100 per year. Have I misunderstood how these systems work?