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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    The boss has a small holding and wants to run electric up to his new barn he's building. It's approximately 100m away from his house.

    He's not 100% what type of loading he will need but apparently he's been quoted 20k for a Battery back up generator setup. Not sure of the full spec but seems excessive.

    I'd imagine sending a new armour cable up through the field would be cheaper, could then maybe add in some kind of pv or battery storage also.

    Any thoughts?
  2.  
    For me its a no brainer - dig a trench, put in the electric cable on one side of the trench and the water pipe on the other. If there is main gas to the property then I would consider putting in a gas pipe as well, capped off at both ends as a bit of (cheap) future proofing. If the ground has stones then put the pipe in land drain plastic pipe or similar (and if SWA cable is not used then put that in as well)
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2019
     
    Posted By: Peter_in_Hungaryput in the electric cable on one side of the trench and the water pipe on the other

    I don't think that's allowed as stated. AFAIK, water has to be below electrics. Certainly it needs to be deep enough to prevent freezing.
    • CommentAuthorphiledge
    • CommentTimeFeb 10th 2019
     
    Boss needs to work out likely loading before doing anything! Theres no point in running a 2.5 SWA for some LED lighting and then decide he wants to use a welder in the barn. Alternatively lay a duct with a draw wire in it and he can pull in whatever cable he wants when the time comes. If its running across a field make sure its laid deep enough toclear any future ploughing/groundwork
  3.  
    Posted By: djh
    put in the electric cable on one side of the trench and the water pipe on the other

    I don't think that's allowed as stated. AFAIK, water has to be below electrics. Certainly it needs to be deep enough to prevent freezing.

    What happens over here is that once the various authorities have provided their supply what happens after that is up to the contractors to install down stream - and water and power will go in the same trench because that is seen to be reasonable. Sometime a warning tape is placed halfway up the trench on backfill if there is though to be a danger of someone without knowledge of the site machine digging the area.

    750mm deep would be deep enough to avoid frost and cultivation. Even when we have had -18 over night for a couple of weeks and not rising above -5 during the day I have not seen ice below 300mm (on a stand pipe that was not drained down) But if it is a JCB doing the digging , providing the soil is not too rocky the extra 250mm to go to 1m deep doesn't make much differance
    • CommentAuthorjfb
    • CommentTimeFeb 10th 2019
     
    No need to go lower than 750mm at all. Need to get a grip on potential electrical loading and what is possible from the house supply. Realistically if youbare going to want to do anything sensible you will be looking at 6mm minimum.
  4.  
    Wot jfb said +1
    even if you can't imagine ever using anything other than lights - next month you will need a decent power tool or welder in the barn.

    BTW 6mm I presume means 6mm2 not 6mm diameter
    •  
      CommentAuthordjh
    • CommentTimeFeb 10th 2019
     
    In the UK, water needs to be 750 mm. There needs to be 375 mm cover over everything.

    Work out what the power loads might be (especially kettles and heaters etc) then ask the electrician who will connect, test and certify it what size cable is needed and what earthing is required.
    • CommentAuthorjfb
    • CommentTimeFeb 10th 2019
     
    Yes mm2
  5.  
    EASYGRID-10000- Offgrid system in powder coated steel enclosure (1513 x 824 x 1051 mm WxDxH) - includes 41 kWh of 14,517.37 1.00 14,517.37 LA-41KWH gel 2 volt batteries (48V), 10000VA inverter/charger, control panel with remote data logging, 6.8kW solar
    charge controller and genset auto start connection.

    002 EASYGRID-SOLAR- 5 string solar array kit - Comprises of 25 x 275W Canadian Solar Polycrystalline panels - each panel 3,695.80 1.00 3,695.80 250V-6.8KW dim 1650x992mmx40mm - includes string combiner box (up to 5 strings) and PV cables. Does NOT
    include roof or ground mounting components.

    003 PVC-STRING-COM- Breakout junction box for solar PV connection into Easygrid units - utilises the Harting connection into 157.69 1.00 157.69 BREAKOUT-1 the Easygrid. Accomodates 1x 3core SWA cable connection from PV Combiner via SWA gland (SWA
    cable and PV Combiner not included in this part number).

    004 GEN-JCB-G017QX- JCB G17QX Generator - Canopy Set - Prime Power 13.2kVA / Standby 14.2kVA - 1500rpm - Single 8,168.67 1.00 8,168.67 1PH-230V Phase - 230v (765 KG)

    005 GEN-BATT- GEN BATTERY CHARGER UPGRADE. 71.40 1.00 71.40 CHARGER Connection point to supply power to internal battey charger within generator 230v 6a
    UPGRADE

    006 EASYGRID-OPT-63A EASYGRID OPTION: 63A Plug and Coupler set for Easygrid 5000 and 10000 units (supplied loose, 106.00 1.00 106.00 -PLG/COUP does not include cable, cable to be quoted seperately)

    A bit hard to copy and paste but the above was the quote they've received for £32,000 including VAT
  6.  
    Posted By: Victorianecothe quote they've received for £32,000 including VAT

    For a barn with grid power that already has a meter 100m away ??? !!!!
    • CommentAuthorphiledge
    • CommentTimeFeb 11th 2019
     
    <blockquote><cite>Posted By: Victorianeco</cite>The boss has a small holding and wants to run electric up to his new barn he's building.</blockquote>

    I dont really understand why batteries and generators are being quoted?? 100 metres of 6mm SWA is a couple of hundred pounds. Add a small consumer unit, glands and a spark to connect up and your looking at £500 if he trenches the cable himself.
  7.  
    I admit I am not up to date with UK regs (and apart from the general cavalier attitude to electric fit ups over here) but could it be done with a fused spur and so avoid the need for (expensive) professionals. Although contemplating the 32k off grid fit up doesn't seem cash is an issue.
    • CommentAuthorSprocket
    • CommentTime7 days ago edited
     
    I would just put in a 32amp cable. If your main supply is not up to that load then you can always fit a 16A breaker for now. It's probably 10mm cable. I have about 50m supply in 6mm cable and I wish I had put 10mm in now as it drops a bit when charging EV at 32amp.
    Find a local independent (but decent, up to spec) electrical contractor and check spec for requirements.
    Dig the trench yourself(it's across a field, it's easy, just hire a digger for the day or two.
    Put electrical cable and water in trench (diff depths, tape etc... check with electrician).
    Bring up tails at each end in appropriate place and let plumber and electrician deal with them.
    •  
      CommentAuthordjh
    • CommentTime7 days ago
     
    One point if you plan to use ducts, by the way. It's easy to pull armoured cable and water pipe through ducts, except where the ducts bend. So make sure that the ducts come up out of the ground gradually, not via a tight bend. It can be problematic maintaining the required depth underground at the same time so give it some thought in advance. The options are basically either to bring the duct out well inside a building or to terminate it near horizontally in an underground pit inside the building or go deeper before bringing it to the surface.
    • CommentAuthorCWatters
    • CommentTime5 days ago
     
    You can also put the cable in the duct before you bury it. The duct we used was supplied with a thin draw string. First thing we did was pull through 3/8" or 10mm polypropylene rope. Then the cable, then buried it. We pulled a second draw rope through with the cable so there would be one left in it just in case.

    Perhaps also run a network cable to the barn? Probably needs to be a screened cable if in same trench as the mains cable.

    Check the supply to the house cope with another significant load?
    • CommentAuthorCWatters
    • CommentTime5 days ago edited
     
    Just had a look on the TLC Voltage drop calculator here..
    https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

    If you feed it 32A * 230V = 7.36kW it recommends 16sqmm rather than 10sqmm cable.
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Posted By: CWattersYou can also put the cable in the duct before you bury it.

    That's fine for the first time, but doesn't help if you want to replace the cable or pull through an additional one. And if you're not considering such things, why not run the armoured cable directly in the ground?

    The duct we used was supplied with a thin draw string. First thing we did was pull through 3/8" or 10mm polypropylene rope. Then the cable, then buried it. We pulled a second draw rope through with the cable so there would be one left in it just in case.

    It's very easy to blow a draw string through a duct with a shop vacuum cleaner. As you say, that is used to pull through a rope and that pulls through the cable and another rope. We taped the cable to the rope, to avoid any bulky knots that might have jammed.
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