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just done an ariel survey for a new install
A quick question… just done a survey for a new install, the house is 150+m from the barn where customer wants panels to go.
Currently 80m of 100mm duct is running from house to open point. I’ve been advised SWA DC will be OK to run through this duct with the current SWA AC cable.
Is this correct, I don’t think so.
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19 Replies
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I was told on my MCS assessment that I should never be using SWA for DC strings.
Usually PV ultra is why we use for a duct
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Doncaster Cables do PV Ultra with an SWA variant though
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6mm PV ultra. Won’t be cheap. Cost it in
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can this be run with 3 core 16mm SWA ? For 80+m in same duct ?
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yes because PV ultra is treble insulated. Each DC core is individually insulated, then there is a 2nd layer of white bonding core insulation, then there is an outer core of insulation cover similar to hi-tuff ac cable.
The ducting provides the mechanical protection.
They make a 6mm 2 core or 4 core version and it comes on 100m drums.
Try Midsummer, Ed’s Greentech or CEF for wholesale prices.
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Why don’t you want the inverter/battery in the barn and use/run AC back to the house.
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What about ruining them both in separate 32mm copex to increase separation and give an extra barrier. Then also earth the swa. I would also check with inverter manufacturer to see if they are sensitive to induced ripples. Why can’t you site the inverter locally and tranport the ac instead?
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Put a string inverter next to the panels. Then the appropriate rated SWA cable in the duct.
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Surely inverter local to panels would be easier?
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Cannot use SWA as DC needs to be double insulated (around positive and negative not just single insulation around the +ve&-ve and then secondary insulation around the complete cable).
I was pulled up on this on a job on an assessment years ago and had to remake with PV ultra
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Agree although SWA has a kinda double insulation with the white bedding layer…. DC rated to 500v
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To answer all queries about why not put inverter by panels, that was my thought, the answer from boss was the AC cable will need to be substantially bigger than the DC cable, & less flexible.
Also, the cable run will be over 150m in duct.
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It would also need to be >850mm depth to comply too…
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Sorry >450mm with SWA + warning tape 150mm above for domestic/private land
I’m thinking 700-900mm for utilities in public land, such as highways. Think NJUG guidence.
7671 s522 if we are being specific, says Adequate protection, so SWR, commonly accepted depth of 450mm, warning tape and RCD protection
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Ducting also needs to be N750 rated as per code of practice.
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code of practice also advises 50m+ should be in earthed metal containment
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can’t say I’ve heard of that, but I’ve also never run DC over 50m underground
Wouldn’t it be the AC that needs to be in earthed containment for over 50m?
Could you advise me on a page number in the COP?
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My house is 150m away from the barn where my solar panels are. We put the inverters down there and send AC up the line. 50mm 3 phase SWA.
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I have just done my own dual ducting using 63mm n450. 6mm pv ultra and comms (cat5 rs485 etc) in one and AC in another.
The code of practice state the dc ducting needs to be n750 instead of the more normal n450 but coils of n750 is seemingly impossible to buy in the uk all I could find were other large diameter 6m long smooth bore
So I took the sod it, n450 will do approach
Personally I wouldn’t be comfortable running AC and DC in the same duct, if you do or if you decide to put an inverter with the panels make sure you do your heat derate and especially volt drop calcs at max inverter output, aim for under 1% to prevent the inverter hitting 253v too often
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