Splicing two different types of wiring - Is it ok to do?

Greetings,

Electrical code notwithstanding, is it ok (or safe) to combine two different types of wire.

These are the two, exact wire types I'm referring to:

Welding Cable #2 AWG - http://www.solar-electric.com/installation-parts-and-equipment/wiring-cables-and-connectors/hardware-wire/wc-2.html

#2 THHN® or THWN-2 - http://www.southwire.com/products/SIMpullTHHNCable.htm

Can those two wire types be spliced? Or will the THHN/THWN cause more resistance than the welding wire? I would be using a tinned crimp-type splice with heat shrink tubing. No solder will be used.

Why? It would save me $$ on wire since I already have the #2 THHN® or THWN-2 in stock.


thanks,

HF
«1

Comments

  • mike95490mike95490 Solar Expert Posts: 9,466 ✭✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    As long as you use connectors rated for the fine gauge strands AND for standard strands AND use a multi-ton hydraulic crimper, you should be fine
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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    gen: http://tinyurl.com/LMR-Lister ,

  • HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    Thanks for taking the time to respond. Actually I was going to use my trusty hammer-type crimping tool with a 10 pound hammer. No good?
  • scrubjaysnestscrubjaysnest Solar Expert Posts: 175 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    Another option would be the screw type splice block. It will be harder to insulate but like a breaker doesn't care about the wire. I prefer crimped and soldered connections my self.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    I prefer crimped and soldered connections my self.

    Likewise. Well crimped and then properly soldered to ensure good solid connections that stay that way.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    There are two schools of thought on soldered connections. I subscribe to the one that says solder is not good as solder has more resistance than copper. And I believe in the 'professional' grade crimping tools (they encircle the terminal and squeeze from all sides), matched to terminals that match the wire type and size. Special terminals for fine wire like welding cable. And then adhesive filled heat shrink tubing.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    The resistive difference between a soldered (or tinned) piece of wire end and a bare one is negligible to the point of not being measurable.

    The arguments against soldering a crimp connection usually include the possibility of the solder melting under heat, which means the connection is far too hot and you have a bigger problem. Another is the reduced flexibility, which again is a non-issue as the wire should not be required to flex so much that this makes a difference.

    john_p has tested the difference in connections and found the crimp + solder is marginally better (more secure) than crimp alone.

    A poor quality connection of any type is the real problem; botch the crimp and the solder won't help.

    Fine strand wire is difficult to crimp and/or to solder and should be done by someone who has all the right tools. The hammer crimper is likely to produce unreliable results.

    For joining dissimilar cables like this I'd prefer either two pro-crimped lugs bolted together or the double-compression bus bar connection (difficult to find in 2 AWG or larger sizes).

    No splice would be best. Using the splice as the spot to put the OCP is a good idea if it must be joined.
  • HairfarmHairfarm Solar Expert Posts: 225 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    It seems to me that soldering heavy gauge wire requires a small torch because a soldering iron is not hot enough, right?

    First crimp the wire into the tinned splice, then heat the splice/wire with torch until the solder melts into seam between the crimp and the wire. How else would you be able to heat #2 AWG wire for solder?

    thanks,
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    I do it all the time but never with fixed wiring inside a house. The biggest example I did this in was my AC stick welder that I converted to DC uses a couple different types of THHN and welding cable splices inside it.

    I used screw blocks on smaller splices like 4 gauge THHN to 4 gauge fine stranded welding cable and for larger than 4 gauge I used crimp connectors on the 2 gauge to 2 gauge connections, but I also have a proper linemans crimp tool.

    On my diesel suburban I converted it to LiFePO4 starting batteries. Before the conversion I had a 2 gauge welding cable battery to starter cable. Now I have a 2 gauge and 4 gauge battery cables going to the starter. The original 2 gauge main cable is soldered, so is the 4 gauge which happens to be THHN.
    I crimp the connector on to make a tight copper to copper connection and I fill in the joint with solder for really no other reason then to weather proof the connection, fill in the voids and passageways with solder so nothing else can get in there then seal it up with self sealing heat shrink. If the connection isn't going to be exposed to weather then there is no point in soldering.
    Yes you need a torch for 6 gauge and bigger. You can get a huge soldering iron for this job but they are very expensive.

    All the connections I make inside my welding machines and plasma cutter are not soldered, just crimped.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Re: Splicing two different types of wiring - Is it ok to do?

    I am not a fan of soldering connections (but I too have done more than my share of soldering). However, I believe that at least one person here has had good results with using a solder pot to dip crimped connectors into and solder.

    The reserve heat of the pot of solder and the thermal transfer of liquid solder will do better than an iron or a torch.

    Found it:
    2manytoyz wrote: »
    I work in the aerospace industry. Per our regs, we can either solder, or crimp, but we can't crimp and solder. FWIW, either are acceptable methods for flight hardware.

    Part of the issue is trying to crimp a soldered connection. The solder doesn't compress as well as unsoldered copper wires. Ends up failing a pull test. Also, if the connector gets hot, the solder can melt, and things can get "interesting" as the wire starts to slide out of the connector. This is why big power cables use compression fittings, not solder.

    Some of the industrial crimpers for large wire compress the termination so hard that the wire is almost fused together. I've seen pics of these cut apart after crimping, nothing short of impressive. I don't expect YOUR crimper to have these results.

    I have soldered connectors after crimping. It probably made no real difference, but it looked better having the ends of the wire tinned, and a nice solder fillet to the lug. That said, this was only on small conductor cables (~10 ga).

    Once I started moving up in wire size, soldering became much more difficult. Takes a lot of heat to get solder to flow in the ends of fat wire. Even with 6 ga wire, I ended up using a solder pot to tin the wire, then pre-tinning the inside of the lug, and finally heating up the wire and lug just prior to cramming them together.

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    We are also required to have the insulation back about the thickness of the conductor for a visual inspection, prior to covering it with heatshrink. This wasn't a work project, but old habits...

    I must say, soldering 6ga wire was PITA! No way I'd attempt that on 4/0 cable. I use an anvil type crimper instead. Makes decent crimps in a fraction of the time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,466 ✭✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    Not all screw type splice blocks work well with fine strands of welding wire. Crimping to a lug, and then bolting the lugs together is how I extended the battery cable from my small genset, to the main starting battery.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    Originally Posted by 2manytoyz:
    "Part of the issue is trying to crimp a soldered connection. The solder doesn't compress as well as unsoldered copper wires. Ends up failing a pull test."


    I TOTALLY agree! The "trick", if you are going to solder, is to CRIMP FIRST, BEFORE any soldering is done.
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    If you place a lug on an end of wire and dip it in lead now you have a not as conductive barrier of lead between the copper pieces.
    If you are going to solder make sure you have a good copper to copper mechanical bond first.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    oil pan 4 wrote: »
    If you place a lug on an end of wire and dip it in lead now you have a not as conductive barrier of lead between the copper pieces.
    If you are going to solder make sure you have a good copper to copper mechanical bond first.

    Not really.
    If a small layer of solder was such a barrier then none of the electronic goods in the world would work because they all use soldered connections.

    BTW solder isn't allowed to contain lead anymore, which leads to a different problem: narrower heat range of non-lead solder means greater possibility of a bad join. That could be a problem.

    On the whole a crimp & solder connection isn't anything to worry about.
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    mike95490 wrote: »
    Not all screw type splice blocks work well with fine strands of welding wire. Crimping to a lug, and then bolting the lugs together is how I extended the battery cable from my small genset, to the main starting battery.

    That reminds me, when I overhauled my generator and added an optima battery, 100 amp breaker and 1000W pure sine wave inverter I again used a mixture of fine stranded welding/battery cable and THHN cable. Used mostly crimp connectors on that, I think I used one single screw together lug connector to get power from the inverter to the starter. Everything from the battery, through the circuit breaker to the inverter was 4 gauge and mostly THHN, from the inverter to the generators starter motor it was mostly 6 gauge fine stranded OEM battery cable.
    I didn't solder any of those connections but I wrapped them with electrical tape.
    I like the THHN because I can bend it a certain way and it will retain that shape. Anything bigger than 4 gauge gets pretty difficult to bend. "Battery cable" is finer stranded but tends to retain shape some what and welding cable is very fine stranded and tries to not retain any shape.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    Not really.
    If a small layer of solder was such a barrier then none of the electronic goods in the world would work because they all use soldered connections.

    BTW solder isn't allowed to contain lead anymore, which leads to a different problem: narrower heat range of non-lead solder means greater possibility of a bad join. That could be a problem.

    On the whole a crimp & solder connection isn't anything to worry about.

    If its nothing to worry about then why does NEC forbid soldering of ground wiring?
    I still use lead solder.
    Crimping and soldering is the way to go if you are going to do it.
    Circuit boards aren't rated to operate to temperatures or carry current any where near THHN wire is rated for. That's why I am pretty sure soldering isn't allowed in fixed residential power circuits. I know industrial and commercial power circuits are not soldered.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    oil pan 4 wrote: »
    If its nothing to worry about then why does NEC forbid soldering of ground wiring?
    I still use lead solder.
    Crimping and soldering is the way to go if you are going to do it.
    Circuit boards aren't rated to operate to temperatures or carry current any where near THHN wire is rated for. That's why I am pretty sure soldering isn't allowed in fixed residential power circuits. I know industrial and commercial power circuits are not soldered.

    NEC does not permit soldering of ground wiring because it is not mechanically strong; all ground connections must be "permanent".

    Circuit boards operate at low Voltage and are indeed subject to temperature changes, quite often more extreme than household wiring. Current is not the issue; overcoming increased resistance is. Solder does not present such resistance increase. If it did the low Voltage PC boards would be the first thing affected by it.

    Solder, lead based or not, should not be in any way considered a conductive barrier. The thought is ridiculous.
  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Re: Splicing two different types of wiring - Is it ok to do?

    Tin/Lead solder is, roughly, 1/10th the conductivity (or 10x the resistance) of annealed copper.

    That is why it has been reported that high current/lightning strikes have "blown" the solder out of copper wiring connections (in my humble opinion).

    It is certainly also possible to melt a solder connection (relatively low melting point) vs the copper itself (relatively high melting point).

    A proper crimp connection should be "gas tight" and solder should not flow into the area between the crimp ring and the wire.

    The annealing temperature of pure copper is ~736 Centigrade. Although, it appears that copper wire can start annealing at temperatures as low as ~150-200C. Solders melt around 175 to 220 C (tin/lead to lead free).

    So, there would appear to be a risk of annealing the stresses in a crimp copper connection--Something I would guess that is not a good idea.

    This "high temp" copper crimp connection is rated to 650F or 343C -- So, perhaps the ability to anneal copper at the temperature of solder is not a big issue?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    So basically if your solder is half an inch thick ...
    Or gets hit by a few million Volts ...
    Or the wire gets heated up to the point where the insulation will ignite ...
    Your going to have a problem with the solder.

    Yeah. Right.

    Reality calling.

    The truth is a properly crimped fitting that has also been soldered and sealed with heat-shrink is electrically more conductive, mechanically stronger, and far more resistant to corrosion than crimping alone.

    This is not some laboratory theory but something that has been proven repeatedly by everyone who has done it and done it right.

    That is not to say it is necessary to solder a crimped connection, nor even desirable to do so in all circumstances. Why go to extra work and expense when it isn't needed? But in certain cases it is better to take that extra measure. Just where I'll leave to the individual's judgement. If you're not able to make that decision you probably aren't able to make the right connection either; there has to be some advantage to experience.

    I've had a lot of it and know what I'm talking about. You can believe or not: not my wires, not my money, not my system. But none of my connections of any type have ever failed.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    So basically if your solder is half an inch thick ...
    Or gets hit by a few million Volts ...
    Or the wire gets heated up to the point where the insulation will ignite ...
    Your going to have a problem with the solder.

    Reality calling.

    The truth is a properly crimped fitting that has also been soldered and sealed with heat-shrink is electrically more conductive, mechanically stronger, and far more resistant to corrosion than crimping alone.

    This is not some laboratory theory but something that has been proven repeatedly by everyone who has done it and done it right.

    That is not to say it is necessary to solder a crimped connection, nor even desirable to do so in all circumstances. Why go to extra work and expense when it isn't needed? But in certain cases it is better to take that extra measure. Just where I'll leave to the individual's judgement. If you're not able to make that decision you probably aren't able to make the right connection either; there has to be some advantage to experience.

    I've had a lot of it and know what I'm talking about. You can believe or not: not my wires, not my money, not my system. But none of my connections of any type have ever failed.
    My thoughts and over 40 years hands-on experience exactly. I couldn't have said it better.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    There are advantages to a properly executed crimp connection. Proper means using a proper professional tool that exerts high forces on the sleeve of the terminal being attached. The wire does not need any special cleaning before splicing. No flux, no cleanup. The tool exerts forces high enough to form what is known as a cold weld. The wire being squeezed cleans itself from friction, rubbing against other wires and the wall of the terminal. If you hacksaw one apart you can see there are absolutely no air voids. It is like a solid piece of metal. Done with the terminal sized to the wire being and with the proper tool the wire will break off near the edge of the terminal rather than pull out of the crimp itself.

    I used the word "proper" a lot. That is the key. Very few DIY electricians have any proper crimp tools. They cost more money than the dime store variety crimper that is found in most DIY toolboxes. Those are junk. Different terminals require different tools too, so owning 3 or 4 tools or a kit with 20 or so changable dies would not be uncommon. A good crimp tool uses dies that are specific to gauge and terminal type.

    So I'll go along with the idea that maybe most DIY may be better off soldering the terminal. That is, IF they can make a proper soldered connection at all. As was mentioned the new lead free solders make it more difficult to obtain good solid results.

    IMO, the larger the wire gauge involved the more important it is to have low impedance connections. If someone is comparing a crimped connection made with a low budget hardware/auto store tool I have little doubt they will find little difference between the plain crimp and the crimp 'n' solder method. But neither is what I would call high class or professional grade. The wire does not have to pull out of the terminal to fail. But perhaps under high loads it may run hotter due to higher resistance.


    As for soldering parts to a circuit board, solder is used for that application as it would be difficult to crimp a 32 pin socket to a PC board, wouldn't it?

    Anyhow that's my belief and I'm sticking with it.

    Oh, the one time I like to use solder is when fitting a terminal to a solid wire. Even the best tools can have trouble as the solid wire does not conform to the tool distortion as well as stranded wire.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • mike95490mike95490 Solar Expert Posts: 9,466 ✭✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    ....
    So I'll go along with the idea that maybe most DIY may be better off soldering the terminal. That is, they can make a proper soldered connection at all. As was mentioned the new lead free solders make it more difficult to obtain good solid results.....

    Man, have you ever seen some of the excuses for solder joints most people do ? Most of the time, it looks like layers of hot melt glue applied on top of the part.

    It's about $80 ebay for a 6 ton crimper that will do up to #00 wire
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    I should proof read..... left the all important IF out above. fixed that.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    Hi Don, which IF? Can you bold it?
    tks
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
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    West Chilcotin, BC, Canada
  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Re: Splicing two different types of wiring - Is it ok to do?

    I highlighted the IF for Don.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    I thought about replacing my linemans crimp tool because I fished it out of a dumpster in 2006 or 7. It is slightly broken but still fully functional, just difficult to change crimp die sizes, a hammer is required. I thought about replacing it with a new one. One like it on ebay has a starting price over $300 so I will just keep my broken one. The crimpers that use loose interchangeable dies are cheaper, but knowing my luck, I will lose them and end up with a set of crimpers that only does one size.

    What ever you do, stick to code for fixed wiring.
    The majority of electrical fires originate due to fixed wiring (wiring inside the wall). Usually improper installation, very old wire with compromised insulation, damage, incorrect breaker for a given wire size.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    NEC 110.14b

    Says you can solder or braze current carriers if they are mechanically bonded and electrically secure even with out solder.

    So pulling 2 conductors side by side and soldering them together, NO.
    Sticking a wire in a terminal lug and filling the cup with solder, NO.
    Crimping a conductor within a connector and throwing some solder on this connection, yes.

    Then the connection must be recovered with insulation at least equal to the rest of the wire.

    Printed and soldered circuit cards don't burn down houses, fixed wiring does.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?

    While we are on this subject, can anyone explain why it is often said that fine stranded wire needs special lugs. What is different about strand size inside a compression lug?
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Re: Splicing two different types of wiring - Is it ok to do?

    The fine strands squeeze out/twist/move from under the clamp screw. The fine strands tend to loosen over time, and the larger surface area may corrode/oxidize faster too (guessing). Thicker strands (and solid cable) has more "spring" to it and does not move from under the pressure of the clamp screws.

    Also, there is more "air gaps" in the fine stranded cables. This means that normal crimp connectors are usually too small to fit the same size cable crimp connector (8 awg course stranded vs 8 awg find stranded) and if you get a larger size, they do not crimp small enough to hold the strands.

    I needed to find very fine stranded heavy cable for -48 VDC power system (very tight space) and it was a pain to find UL listed cable and crimp terminations.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Splicing two different types of wiring - Is it ok to do?
    BB. wrote: »
    I needed to find very fine stranded heavy cable for -48 VDC power system (very tight space) and it was a pain to find UL listed cable and crimp terminations.
    -Bill

    To use it inside a house as fixed wiring it would have to be THHN cable. You can get fine stranded highly flexible SO or SJ cable from a local welding supply store in sizes as small as 4 gauge. But using SO and SJ cable as fixed wiring is specifically forbidden by NEC in the US. You cant put behind a wall or go through a wall.
    (I think Canada can use it as fixed wiring but only if the S cable is ran inside ridged metal conduit)

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.BB. Super Moderators, Administrators Posts: 32,235 admin
    Re: Splicing two different types of wiring - Is it ok to do?

    It was cable rated for the use inside fixed equipment--And the equipment was UL approved. Like I said, it was difficult to find all of the bits and pieces and meet the requirements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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