TonyE

My sincere thanks George, I’ve been worrying about this day and night! I assume the High Chairs would normally be placed right up to the edge of the mesh around the perimeter? With the slightly off-set U bar heights (where it turns the corner of the slab, one higher than the other) if I set back the high chairs a little it’d ease the difference. It was just a thought.

Hi everyone, Ive got a 250mm deep slab foundation which has been specced by my SE to have 2 layers of A393 mesh Top and Bottom. Ive also got 170mm U bars around the perimeter and its at this stage that I'm struggling to understand how I install the U bars to ensure I keep the concrete coverage correct. Slab make-up is: 30mm Bottom Cover (Spacer) A393 Bottom Layer: 20mm (2 bars in sheet: long and lat) U Bar: H12 170mm (150mm High Chair inside this) A393 Top Layer: 20mm (2 bars in sheet) 30mm Top Cover SO if I add up the math: 30mm+20mm+170+20+30= 270mm too high.... Therefore I assume that the U bar must sit alongside one bar of the A393, thereby reducing the total height by that one bar of mesh (both on top and bottom layers). So, 30mm+10mm (1 bar on bottom mesh)+170+10(1 bar on top mesh)+30= 250 and the 150mm high chair would span the 150mm between the 2 sheets...... This seems logical... HOWEVER if i have U bars around both sides of the mesh (perimeter of the foundation) the U bars on the x/y axis will then hit the horizontal bar... So the u ar can sit alongside on the one axis but not on the other....??? Does this mean I have to place the u-bar that fouls the mesh below the A393 mesh.... Ive resorted to getting lots of pencils and pens and trying to work out how I place the U-bars along both axis (length and width of slab) to work out how the u bar placements change the total height and also impact on the High Chair height..... I'm due to start laying the steel tonight and would appreciate any advice.......

I’ve also recalculated the SWA using 80AMP and it still requires either 50MM for the longer run and 35MM for the shorter run…… ho-hum. On similar posts on this forum, I see that using 50MM inside the CU can be very tight…. IMHO I’d like to route the cable on the 65m run (alongside a road) instead of having to go off-road (steep-incline) with the shorter run. So in summary I think the advice is: 80Amp Fuse Switch, 50MM SWA, 3 core?

Thanks for the advice. 80 AMP switch fuse, I assume that will be installed inside the temp box? I’ll re-run the SWA calcs based on this load. Regards the cores of the SWA, I have a single phase supply…. From your reply, as it’s not 3 phase, you say I don’t need 5 core. But what amount of cores is required. Thanks

Hi everyone, I’m doing a self build and I’m planning/prepping to install the main feed for the house. When we got to site I had a new connection from SSE and this was taken from the pole into a temporary box which houses a mini CU, meter and 100 Amp fuse etc. I then use this supply to power my site/caravan. when SSE installed the connection the chap advised that when we build the house that we could then just run an SWA from this temporary box straight into our new house and its proper CU. This was explained as being much cheaper than getting them to come back out to move the meter and install a new electric cable/feed directly from pole to the house. So I have 2 options, as per my picture below…. It’s a long run from the temp box and both options require a fair trench digging (trench: 450mm deep, 110mm twin wall conduit, bedded on sand and with marker tape). Taking into account the voltage drop and wanting to get the max out of the Single Phase supply (I have GSHP etc) I see a 100 amp fuse in the temp box; the SWA calcs say either a 35MM SWA for one option (shorter run) or a 50MM SWA for the other option…. Can anyone offer advice on this intended setup, the size of SWA and also the amount of cores required? I think I need 5 core so I can re-use the earthing rod that’s already installed… but am I right? Or is it better with 4 cores and then I need a new earthing around the house? Advice appreciated!