Is allowed by code in your county to parallel wires to have higher gauge ? - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: October 19, 2020, 05:15:11 pm
content: I need a 6 AWG(16mm^2) wire to provide power to my shed, but i have yet to find a place in my area that sells 6AWG by the meter and 1 box (150meters) is too much. If i were going to use it all then i would have no bouts in buying, even if i use the same color for the return wire I would still have an excess of almost half a box guage 6 wire are not cheap buy, only need 30-40meters.Here comes the idea of buying 2 150 meter boxes of guage 10 (6mm^2) and twisting them. Twisting 3 wires will give me a current carrying capability sligtly higher than a guage 6 can. It will be more price if i count by the meter, but definitely cheaper than buying a 6 AWG box. My main concern is , is this allowed by NEC building code? I mean no one will really come after me if do it nonetheless ( given i do it properly ) and they will never really know ( not unless i really mess something up )Any licensed individuals can shed some lights into this ?

author: elekorsi
author_rank: Regular Contributor
timestamp: October 19, 2020, 05:41:36 pm
content: Don't do that, i have never seen it and i am sure that it's against all the standards - at least for residential buildings. In industry it is done often, when you need larger cross sections, for example n x 240mm2, n x 300mm2 (n = number of conductors) per phase. I don't know what is the minimum cross section limit for this, but it is usually with 240mm2.I am sure that every decent installation material seller will cut it to your length.Another thing that i noticed is that you want to use separate wires and not cable. As you said that it is for the shed, i assume that it is outside... Use appropriate cable instead (i don't know your earthing system, so 4G16mm2 or 5G16mm2). The appropriate type of cable should be chosen, depending on where it will be installed (underground, underground in protective conduit, free in air, etc.)

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 19, 2020, 05:55:39 pm
content: Not allowed according to my 1990 NEC.A technical reason is that should one become disconnected, then you have the potential of an overcurrent situation with the remaining conductor. The exceptions don't cover your installation.

author: mzzj
author_rank: Super Contributor
timestamp: October 19, 2020, 05:58:21 pm
content: You might want to look for aluminium cable in that size and length. Terminations are more expensive but cable itself is over 50% cheaper than equivalent copper cable. (at least around here)

author: Cerebus
author_rank: Super Contributor
timestamp: October 19, 2020, 06:07:35 pm
content: It sounds like you're planning on using single insulated wires. That would be , erm, 'highly unusual' for an outdoor installation anyway and I doubt meets regulations anywhere.Outdoor cabling is usually either uninsulated wires flown overhead (well out of reach, obviously) rated for use as catenary cables or a solid cable with overall insulation, a reinforced earthed screen and multiple insulated interior conductors - known generically here as Steel Wire Armoured or SWA. Your local trade name may be different. It can be affixed to a wall or, using a suitable grade, buried. Looks something like this:It requires terminating with suitable earthed cable glands. Around here electrical factors often sell this as cut lengths precisely because reel lengths are often uneconomical for domestic jobs.

author: elekorsi
author_rank: Regular Contributor
timestamp: October 19, 2020, 06:08:33 pm
content: QuoteYes, but if Aluminium, then it must be 25mm2. And use only appropiate cable lugs, dedicated for Al cables (never connect Al cable directly to copper or into terminals which are not meant for Al cable)

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 19, 2020, 06:37:00 pm
content: If it is not a main feeder input cable to house, but a cable to a shed then in our country it is possible - you may parallel wires. But I don't know rules of other countries.

author: H.O
author_rank: Frequent Contributor
timestamp: October 19, 2020, 07:12:53 pm
content: Not the correct way to do it no. But I suppose youcould, theoretically, do it provided you fuse each of the wires for it's rated current carrying capacity.For example, if using 3 wires each rated for 16A you have one 16A fuse/breaker PER WIRE - not a single fuse/breaker rated 48A.Whether or not you are ALLOWED to do it, in your region, is not for me to say.Don't skimp, and jepordize your personal safety or that of your property - buy the proper cable for the application!

author: niconiconi
author_rank: Frequent Contributor
timestamp: October 19, 2020, 07:28:51 pm
content: Speaking of parallel wires for mains wiring, the UK had an interesting system in the early 20th century called the "ring circuit". Instead of running a wire as a point-to-point link or a bus, it starts from source, and loops back to the source again: +Vac -> load -> +Vac. Effectively, for loads close to the middle of the ring, there are two wires in parallel and doubles your current rating. Nevertheless, it has long been retired for many decades due to troubleshooting difficulties from its additional failure modes, e.g. if a loop is broken, it can silently fail without symptoms, potentially creating a dangerous overcurrent condition. BTW, any amateur radio operator from the 21th century definitely won't approve this system as well - huge loop area, dramatically increases the radiated EMI from all the switched-mode power supplies even morehttps://en.wikipedia.org/wiki/Ring_circuit

author: Cerebus
author_rank: Super Contributor
timestamp: October 19, 2020, 07:58:55 pm
content: Quote from: niconiconi on October 19, 2020, 07:28:51 pmNo, not long retired, still very much current practice.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 19, 2020, 08:10:30 pm
content: Quote from: mzzj on October 19, 2020, 05:58:21 pmThat requires different terminations which is another rabbit hole.In the Netherlands you are allowed to pair two single 2.5mm2conductors inonepipe, however then youmustuse a 2p+2n circuit breaker to fuse each live conductor separately, but they must trip together. (typicaly a clip on the unit)It's very common to wire up stoves and oven this way.However you're probably not going to install one appliance on it. But install a sub-distribution.Then don't screw around and just go ask the local electrician to provide you with the right stuff.You want to sell the place eventually right?

author: free_electron
author_rank: Super Contributor
timestamp: October 20, 2020, 12:42:17 am
content: why not install two circuits ? if you need 1 100 ampere circuit : run two 50 ampere circuits. each circuit has its own fuse.

author: coppercone2
author_rank: Super Contributor
timestamp: October 20, 2020, 01:25:31 am
content: Quote from: free_electron on October 20, 2020, 12:42:17 amwelding and heating equipment capability of shed will be degraded as will the ability to use stuff with high surge that can benefit from the breaker (big saw). That makes for a very boring shed, but I would recommend two circuits anyway, 1 100 amp circuit for equipment, another 15A circuit for lights. What sucks is tripping the breaker and losing lights. Dangerous. And the low resistance from high copper saves bill money.you can look at welding heavy plate, electric forging, casting and tree-to-wood production with a 100A breaker.. a powerful shed.Actually a 3rd breaker would be nice if you can run electric heaters to the shed so you can heat it up for winter repairs and stuff (it might save you money if you can work in there in the winter with ease at moments notice, way more powerful then the small savings on wire). You don't want to trip the breaker because you need to run heaters. His country is kinda cold.nmv thought it was slovenia not philipinesI would just pay for the copper and leave the rest for sale on ebay for people that need less an d take 20 feet for the labIf you think the utility such a shed brings, particularly also if you can make noise at night, the freedom it offers is well worth the price. You could also pump water there...

author: Jeroen3
author_rank: Super Contributor
timestamp: October 20, 2020, 08:37:36 am
content: A way to deal with that is to fuse the cable as cable. With gG cartridge fuses or type C/D breaker, and put the sensitive type B breakers in the shed. So each socket can have it's own breaker.However, you may lose the option for earth leakage protection on the cable.

author: Whales
author_rank: Super Contributor
timestamp: October 20, 2020, 08:52:06 am
content: Quote from: niconiconi on October 19, 2020, 07:28:51 pmActually, wouldn't it do the opposite? Current would be split & travel inoppositedirections around the ring. It wouldn't be a 50/50 split in most cases, but it would still be something.

author: richard.cs
author_rank: Super Contributor
timestamp: October 20, 2020, 09:18:31 am
content: Here in the UK paralleled cables for increased current capacity are allowed*, but with restrictions, and we wouldn't normally twist them - in fact they would usually be spaced apart a little for better cooling. The restrictions are essentially that they be the same size and length, follow the same route, and that they are de-rated appropriately for being grouped with other loaded cables. Most commonly we do this for very large cables which are otherwise just too awkward to manage, e.g. >95 mm2(3/0 AWG), it's allowed* for smaller cables but usually offers little advantage. We would also expect individual cables like this to be enclosed in some outer containment such as conduit or trunking.* Well, technically everything is allowed if you can show by an appropriate engineering method that it provides equivalent safety.PS the ring final circuit is similar but different - because the loads are distributed around the ring equal current sharing is not guaranteed, and cables are generally rated >2/3 the breaker rating. It's actually a little suspect if you think about it too hard, but has worked well in practice for a long time.

author: Yansi
author_rank: Super Contributor
timestamp: October 20, 2020, 09:56:53 am
content: You can parallel as you wish, as long as each parallel branch is fused/protected separately.

author: Miyuki
author_rank: Frequent Contributor
timestamp: October 20, 2020, 10:44:18 am
content: Why not just use universal clamps to connect AL cableLike this (photo)Or similar, they are not expensive, just need to be used as designed with set torqueAnd when I look at cable prices, AL25 is like 40% of CU16 and cost about the same as a single CU6 and you will need two of them

author: magic
author_rank: Super Contributor
timestamp: October 20, 2020, 11:49:20 am
content: Quote from: niconiconi on October 19, 2020, 07:28:51 pmAre you sure? I think the loop area that counts for EMI is the loop between each live wire from the breaker to the load and its corresponding neutral return wire. This is no worse than in the usual "bus" topology.It should only cause serious problems when some point of the loop breaks on live but remains connected on neutral or vice versa. Or maybe some other asymmetric difference in resistance between live and neutral.

author: H.O
author_rank: Frequent Contributor
timestamp: October 20, 2020, 01:12:43 pm
content: OT But can't help noticing, those conductors on the top side of the fuses looksquitesmall for 40A fuses.

author: Miyuki
author_rank: Frequent Contributor
timestamp: October 20, 2020, 01:32:54 pm
content: Quote from: H.O on October 20, 2020, 01:12:43 pmIt looks so because those NH2 fuses are so bigIt should be 10mm2, but even 6mm2 shall be fine

author: Cerebus
author_rank: Super Contributor
timestamp: October 20, 2020, 02:05:28 pm
content: Quote from: H.O on October 20, 2020, 01:12:43 pmOr alternatively, everything else is comedically oversized for a 40A circuit, making the 40A side look anaemic. A 40A circuit only needs 6 mm2which isn't particularly chunky and that looks about right for 6 mm2, as far as I can judge scale from that photo. The cabinet hinges and the 125kA breaking rating on the fuses gives some indication of scale.

author: Pack34
author_rank: Frequent Contributor
timestamp: October 20, 2020, 02:14:09 pm
content: Quote from: H.O on October 20, 2020, 01:12:43 pmBlack and grey are swapped after the fuses as well.

author: richard.cs
author_rank: Super Contributor
timestamp: October 20, 2020, 02:17:32 pm
content: Quote from: Pack34 on October 20, 2020, 02:14:09 pmI hadn't spotted that. Swapping any 2 phases will of course reverse the rotation, it may well be deliberate.

author: pigrew
author_rank: Frequent Contributor
timestamp: October 20, 2020, 02:33:39 pm
content: In USA, according to the NEC code 2017 310.10(H) we're allowed to do that with some conditions. The conductors must be identical, and each must be at least 1/0 AWG. (106kcmil = 50 mm^2).Smaller conductors can be paralleled if (frequency >= 360 Hz) in some cases, too.The solution, as others have mentioned, is to use aluminium feeder cable. If it goes outdoors, you'll need appropriately rated cable. In the case of a detached shed, you'll likely need a earth rod installed at the shed, but the neutral should NOT be connected to the earth in the shed.

author: Yansi
author_rank: Super Contributor
timestamp: October 20, 2020, 03:58:12 pm
content: Quote from: Pack34 on October 20, 2020, 02:14:09 pmWell, even in the lower portion, phases have incorrect sequence: First should be brown, then black, then gray. This different sequence (black-brown-gray) is I think only used in the capital city of Czechia

author: SparkyFX
author_rank: Frequent Contributor
timestamp: October 20, 2020, 05:23:06 pm
content: Quote from: Yansi on October 20, 2020, 09:56:53 am+1 , because if you splice your circuit afterwards anyway, you would avoid not fusing properly in case one connection breaks. This means your distributor panel will have more than one supply, which is unusual and requires some effort to avoid problems (e.g. attention on RCD wiring), but is manageable.Quote from: Yansi on October 20, 2020, 03:58:12 pmFor Germany: Utilities can do it as they like, some connect houses in left hand rotating direction, some do right hand. Their terms and conditions apply. The only strict defined color is green/yellow for PE(+N) (unless wrapped with some different color tape to utilize it as something else). It isrecommendedto not change wiring color within the system so the next guy looking at it won't be confused. The photo shows the interface between two systems, no big deal there, no laws broken.

author: pigrew
author_rank: Frequent Contributor
timestamp: October 20, 2020, 06:49:59 pm
content: Quote from: SparkyFX on October 20, 2020, 05:23:06 pmIn USA, the individual conductors do not need individual OCP devices. In fact, this could be designed as a feeder circuit with no need for upstream OCP based on the wire size. However, this this case there would need to be a downstream OCP device (e.g. fuse, circuit breaker, or perhaps even motor resistance). Broadly speaking, we assume that if something goes wrong, there will be a short circuit and that will blow the fuse regardless of the protection's ampacity. This is the same situation as ring circuits where there's insufficient overload protection if the ring becomes broken.We also install individual RCD on each circuit (or even each outlet) here. I've never seen a RCD unit covering multiple circuits in the USA.

author: intabits
author_rank: Frequent Contributor
timestamp: October 20, 2020, 07:52:13 pm
content: Quote from: Miyuki on October 20, 2020, 10:44:18 amWhat's that cable/tube that loops into the cabinet and around its interior perimeter?

author: Monkeh
author_rank: Super Contributor
timestamp: October 20, 2020, 08:00:28 pm
content: Fire suppression, at a guess. CO2 or pressurised powder would be my guess.

author: rstofer
author_rank: Super Contributor
timestamp: October 20, 2020, 08:12:12 pm
content: As posted above, parallel conductors are allowed for sizes 1/0 and larger which is roughly a 125A conductor.Think about it, how could I possibly have a 2000A circuit when the largest conductor is 1000 MCM and rated 545A? OK, 2000A is a little over the top but 1000A still requires parallel conductors. As 500 MCM is about the largest I want to pull, that 1000A circuit will require 3 conductors in parallel.A 1000 kVA 480V 3 Phase transformer will have a secondary current of about 1200A and will require 4 parallel 350 MCM conductors per phase. These are VERY common transformers for industrial applications.