Alan Ambrose

>>> the length of the diamond cutting edge (and hence friction) is also proportional to diameter, hence the square I thought this, but forgot to write it, duh: Imagine a core drill with one tooth (or diamond grain) which can be magically set at any radius. The torque required to rotate the bit (or equivalently the torque required to hold the drill) will be proportional to the set radius of the drill / cut. Next, imagine you can magically add more teeth to fill the core drill to make it a full circle. The torque required to rotate the core drill will be proportional to the number of teeth. And the number of teeth will again be proportional to the radius. So, the total torque for a normal core drill will be proportional to the radius squared. Of course, there are other factors too. The above will be correct assuming we keep the downward pressure per tooth constant - which means we need to ramp the total bearing pressure linearly with radius. For conditions within a reasonable operating range, you can imagine that the torque required will also be a linear-ish function of the bearing pressure per tooth and also roughly proportional to drill rpm.

Will this work? One evening, adjust your lighting to your preferred minimum as though you were having a power cut. Measure the current / power draw. You can get a similar figure during daylight too if you need any lights on then. That’ll give you the max realistic power draw you need to cope. Then you can make a little table for run time vs. battery capacity. Check the number of hours between sunset to bedtime on the shortest day and the longest. Those few numbers should allow you to make the trade off you need.

Do you need every channel of every LED strip turned to full brightness in a power cut? A LED takes about 9 times less power than an old fashioned filament bulb. So your 960W of backup LED power is equivalent to about 190 old fashioned 60W bulbs. That’s a lot of lighting to use in a power cut . Maybe just pick a few essential lights for that not very common ‘use case’?

>>> It is force (N, mass x acceleration) at a distance (m, metre). So Torque = Nm So basically, the longer the handle, the more torque can be applied. <<< True, but the length of the diamond cutting edge (and hence friction) is also proportional to diameter, hence the square.

Well we're in the wrong forum for the detailed behaviour of filament bulbs, fuses and MCBs (try eevblog or some of the more inquisitive physics/electrical youtube channels). Here's the short answer: The bulb is normally ~40W i.e. 0.2A i.e. not much. This is a total guess on my part, but I am going to suggest that the current spiked to, say, 10-30A for, say, 100ms. If you had current clamp and an oscilloscope, and could repeat the experiment at will, you would be able to see the fast spike and estimate the maximum current amplitude. That spike was enough to blow the fuse and trip the trip. The fuse blew in say 800ms, but while that was going on the MCB tripped - yes, the MCB shut off the current, but the fuse was already red hot by that time. There's endless detail (as there is in any subject if you dig deep enough) but here's a bit more: https://physics.stackexchange.com/questions/341134/how-to-calculate-melting-time-of-a-fuse https://library.e.abb.com/public/114371fcc8e0456096db42d614bead67/2CDC400002D0201_view.pdf >>> I'm trying for an analogy in chain terms but can't think of one. OK this: suppose you have a chain with a breaking load of 10T. There are two weak links of various sorts, one 1T, one 0.5T. You suddenly drop a 500T load on the end of the chain (remembering to stand well back). Everything flys apart, both weak links shatter with the shock load and two bits of the rest of the chain shoot past your ears dangerously (the final part is still secured to the ceiling). Theoretically the main chain would break too but the very short time before the weak links break means that there isn't any time to do the work (force x time) to make the main chain break before the weak links give way and remove the force. In this case, the analogy for the main chain is the mains cable. Now, be happy that this worked as it should ... because you didn't melt any mains cable and you didn't have a fire. I think that mice don't nibble cable so much but rats and squirrels like to sharpen their teeth on everything. So best to remove the problem promptly.

>>> Later you could even start the construction so the consent is locked in. There’s a gotcha on that if you’re in a high CIL area and this is a self-build.

An old-fashioned filament bulb? There’s often a big fast spike of current when they fail and a corresponding flash of light (think thermal runaway) which will take out fuses / trips etc. Not so much of.a problem these days since we don’t use many filiament bulbs. But … a big spike of current can still be a thing when electronic components: capacitors, transformers, resistors etc in modern LED assemblies, dimmers etc go pop.

Also going gently with rpm & pressure and holding firmly & evenly & perpendicular to avoid sudden friction lock-ups / biting. Any anti-rotation leverage you can get is good. i think torque required (& therefore kickback) is something like the square of diameter, so use the smallest diameter that will meet your needs.

Anyone? @craig

>>> Most commonly you would just trim out the floor joists and infill I probably should have said - this is for the cutout in the ground floor slab and down to the basement, also RC of course (for the pit). So can't be done so easily afterwards.

>>> We have a continuous air gap at the bottom and top with insect/rodent mesh also at the bottom and top. +1 And it's a right pain to do it after the fact mouse...I used this: https://www.ebay.co.uk/itm/354744433416?var=624078758378

OK following up with this. Here's a few ballparks on costs: https://www.lifton.co.uk/domestic-lifts-prices-how-much-do-home-lifts-in-the-uk-cost/ https://www.onlylifts.com/blog/how-much-does-a-home-lift-cost-in-the-uk-domestic-lift-elevator/ https://gartec.com/blog/how-much-does-a-lift-cost-uk/ Typically, the 'home' version of these uses a frame and no pit or a small pit of, say, 200mm, electric traction rather than hydraulic (rack and pinion, ball screw, chain drive etc) and runs at 0.15m/s i.e about 18s to travel one floor. By comparison, the slow-ish lift in the building I'm in atm covers one floor in 5-6s. I'm guessing that the slow speed is a regulation somewhere. Oh yeah, the 'machinery directive' and also Part M. Cost is say £20K average for wheelchair size although a slightly fancy 1.5m circular glass lift comes in at say, £65K. Those are 2-stop / 1-floor lifts, so a bit more for more floors. So, I'm considering a circular floor cutout of, say, 1.6+m and a pit of, say, 200mm. By comparison, a spiral staircase of those dimensions is about £3K.

Have you used a planning consultant to read the planning runes yet? Looks like the various decisions needs some subtle-ish interpretation. I also think that LPAs get a bit more real when they see a consultant, who is ‘one of them’ get involved.

Oh I see - ‘phase change material’.

Re: reusing the slab - you’ll want to allow for a bunch of insulation (anywhere between 100 &300mm) and check you have enough foundation strength there to support a house rather than a shed, so it may just be easier to re-make the slab. That also gives you more design flexibility if you need it. I vote also for a build schedule / financial arrangement that doesn’t leave the builder with the body of an 80 year old

I obviously haven’t been paying attention: ‘PCM cells’?

At least one has you, at least, owning the materials before delivery. That’s some protection although how well it works in practice I can’t say. There have been several threads here on BH which covered escrow. I think we should all demand it for these purchases. I’ve shown the calcs before, not crazy expensive.

Yeah it cuts both ways. It helps if you are familiar with the county court system though - I can file a new money claim in about 5 minutes. A few days later the client gets a formal looking writ from the court with a deadline for response. This won't phase the professional non-payer but will often help the casual non-payer 'come to terms with their priorities'. Don't let your receivables build up unnecessarily, collect as soon as you can. Act professionally and on a timely basis with quotes, invoices, statements, payment follow up, discrepancies, complaints, final notice, letters before action etc - if you signal that you're careless about being paid ... then guess what.

If you can see the airwash working then it's probably OK - you should be able to see the incoming air influencing the flame. There's nothing to stop you using a vacuum cleaner with a soft nozzle to suck out anything that's obstructing the flow though. If you are super careful, you can probably remove the vermiculite panels and see how it all works - but I probably wouldn't bother. If it's not broke etc. Is there a problem right now or are you just being cautious?

I have similar objectives to you i.e. a good amount of glazing - so, I'm planning on putting in the max amount of glazing while squeaking through the regs. My strategy (which I won't know completely works until I have planning and BC approval) is as follows: + read and understand the Part O simple calc. Bear in mind these opaque calcs were written by and for the big developers and originally drafted to prevent overheating of city centre flats FFS. Why single self-build dwellings should be landed with them you'll have to put down to a lack of political nous on behalf of the self-build community. Consequently these calcs don't take account for external blinds, brise soleil, low G glass etc - which is all stuff the big developers won't do - they would rather give their customers smaller windows. + do an initial house design with the amount of glazing you prefer. Think about the house orientation re the sun. You may want to do a check against Part O Simple Method and PHPP simple % guidelines to see if you're anywhere in the ballpark. Note that restrictions on N glazing are fairly light, W & E glazing a bit more and max restriction on S facing. + send in your design for planning approval, knowing that you will probably reduce and/or amend the glazing later. That should be no problem, it's adding glazing later that will exercise the planners. + find a BC that will accept PHPP solar gain calcs, my LPA BC, for instance, will only accept Part O (or presumably TM59). + model well for solar gain with PHPP and tweak the design to get under the PHPP bar. You may need any or all of complete shading modelling / brise soleil / external blinds / lower G glass. + if you can't get what you want and you have an OK budget, try modelling with TM59 and see if that comes up with a better result than PHPP. + check that BC will sign off your calcs and run the glazing amendments past planning for approval. Depending on your design and your proclivity for running calcs yourself you may need a consultant for PHPP and even for part O if you prefer to spend cash rather than exercise your Excel skills. (Actually I believe there's an online calculator now.) You will almost certainly need a consultant for TP59 if you want to use that instead.

Well that’s a lot more difficult if you can’t see the detailed data - a bit like trying to diagnose a health problem without the use of blood tests, xrays etc. I think I would start by looking at the ongoing hourly data on a regular basis and see if you can see anything weird. Also switch the HP and DHW off next time you go away and observe the variation/consistency of the ‘baseload’. If the high demand was caused by an odd heating situation when the outside temperature is low (e.g. defrost weirdness, rapid cycling, strange resistance load switching itself on etc) you may not find the answer until it gets properly cold next winter. Maybe keep monthly data in a spreadsheet and calc the non-heating load and the CoP etc. Check out potential problems with your HP model on the forum for that model if there is one. If you can’t work from the data then you have to use a bit more experimentation / research / intuition / elimination / testing / comparison with similar set-ups etc.

So, you can’t look at hourly data for a high demand day?

Interesting, so actually designed for ‘senior care’ and building management.

Ah, I assumed from the green screenshot that the overall consumption was smart meter data, no?

I knew the Capitalisation Police would be along shortly