Runnin' Down a Mystery. Does the Classic Accept 4AWG Wire?

[5 Minutes 2 Midnite]

Has anyone used 4 AWG cable on the terminals of the Classic (150 in my case). The manual states that the DC terminal connector will take up to #4 AWG THHN.

I happen to be using #4 AWG thin stranded. It does not even come close to fitting. I want to verify please that #4 THHN does indeed fit before ordering some.

[Vic]

Hi 5 - 2..,

YES,   The Classic terminal block DOES accept #4 AWG THHN Stranded cable.   The THHN stranding for that wire,  is usually 19 strand.   I HAVE used #4 THHN,  it fits easily,   but that is the largest THHN that it will accept.

The almost NO screw terminals are Rated for use with fine-stranded cable  --  not only is the diameter of fine-strand cable too large for many busbars designed for a certain gauge cable,   the fine strands can migrate out from under the screw (cold flow),  and cause a once-good connection to become high-resistance.   This can be dangerous,  and possibly result in damage to the buss or terminal,  it could possibly result in a fire.

If at all possible,  use THHN cable of the appropriate gauge for the current flowing in the circuit.

Link to a THHN Wire Table:
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM5

Vic

[5 Minutes 2 Midnite]

Mystery solved.

Great explanation. Puts me another few seconds down the learning curve.

So.... what is the argument for when to use the fine stranded? Is it only good for battery cables where you're crimping on a connector?

I bought 50' of fine stranded for a run between the combiner and the wiring panel (Magnum MMP). So what.... butt connectors and THHN at the termination points?

[Vic]

Hi 5 - 2..,

Yes,  you are correct  --  generally,  fine-strand cable is intended to be used with appropriate Crimp lugs,   and other crimp connections.

Being a bit too nit-picking,  any of the crimp connectors used,  should be designed for the stranding of the cable,   and one should use the Crimper and crimp dies designed for the cable,  as well.

Almost all of us DO use fine-strand cable for battery interconnects,  inverter cables,   and connections to large circuit breakers used for inverters,   and other very large loads.

THHN is a compact cable,   pulls easily through conduit,  can be easily formed for good lead dress (neatness),   and virtually all of the terminals and bussbar connections are designed to work well with building wire (THHN,  THWN,   THW,   etc).

Some people use Ferrules on the end of fine-strand cable,   but even these can create compatibility issues,   at busbars,   and other screw terminal connections.

We all have probably made crimp connections,   that were not exactly by-the-book   ...   one needs to be careful,   and watchful.

All just my opinions.    Vic

[5 Minutes 2 Midnite]

Yeah. My finely tuned Jedi senses were setting off alarm bells when I tried to insert even 6AWG fine in the controller terminal block. Even at 6AWG it was a tight fit and a strand or two peeled off and wanted to kiss the adjacent terminal.

That is when I went back to the drawing board.

I've tried to make all my mistakes before spending $$. A few things have slipped by though and have had to make some minor design changes, and thus more $$.

Trying to find all the mistakes before flipping the switch. Baby steps.

It's about 3 minutes to Midnite right now. I should change my handle. ;>

[ClassicCrazy]

I think VT has posted his solution for a mod to make it so he could put on ring terminals  instead of using the screw terminals . It is on the forums here somewhere.

Larry

[Jacotenente]

Switching out all of mine for #4 THHN. Lowe's sells it by the foot. I like "color coordination" but, Lowe's didn't have #4 in red (only black). However, they have #6 THHN in red and black (which will be used for the PV inputs from the MNDC250PLUS. Didn't check Home Depot for the #4 THHN in red. Both honor military with 10% discount.

[5 Minutes 2 Midnite]

Just to close the loop on this I finally picked up some #4 THHN. Sure enough it slipped right into the terminals on the controller.

The vendor who sold me the fine stranded wire (Windy Nation) did not think the #4 THHN would fit, thinking that if his fine strand #4 wouldn't fit neither would the THHN. But in fact his #6 didn't really fit without shedding a few strands. The simple fact is that particular fine stranded wire is significantly bigger around. Good wire, just fat.

I feel a LOT better having the THHN wire attached to the controller now. Looks right. Feels right. End of story.

jim

[ClassicCrazy]

Just to close the loop on this I finally picked up some #4 THHN. Sure enough it slipped right into the terminals on the controller.

The vendor who sold me the fine stranded wire (Windy Nation) did not think the #4 THHN would fit, thinking that if his fine strand #4 wouldn't fit neither would the THHN. But in fact his #6 didn't really fit without shedding a few strands. The simple fact is that particular fine stranded wire is significantly bigger around. Good wire, just fat.

I feel a LOT better having the THHN wire attached to the controller now. Looks right. Feels right. End of story.

jim

Thanks for the follow up . Yeah the bigger strands makes the difference and compresses better in those terminals.

Larry

[boB]

Glad you got it fitting !

boB

[harryn]

If you asked me this question yesterday, I would have said - "No it doesn't".

Of course I was trying to help a guy install one and we were using ABYC, 600 volt, tin plated stranded wire.  The size of the 4 awg wire vs the size of the terminal hole are not even close.

Today I attempted to use quality cable inverter lugs as a possible alternative to inserting the wire itself, but even two of those have interference.

Changing wire type is complicated, because the other end is terminated with a heavy 4 awg Quality Cable magna lug that is put onto the MNEDC breaker thread, and my supplier is setup for that wire type.

Any suggestions for a crimp on termination that can be inserted into the classic terminal block?

Thanks

Harry

[Vic]

Hi Harry,

This has been touched on before,   in a few different Threads.

The Classic,   and most other CCs generally use screw terminal connections fot PVs and the battery cable.

These terminals are really designed for coarse-stranded cable.   THHN,  and other similar cables fall into this category.

Almost NO Fine stranded cables are designed for this type of terminal connection.   Fine strand cables should not be used.

Was unable to find the Anchor stranding spec for their #4 AWG cable,   but did see some #6 gauge that had about 261 strands  --  this would seem to be inappropriate cable for almost any screw terminal.

It is fairly common to use a short piece of THHN cable,  up to #4 AWG size,   and then make the transition to fine strand,   if you choose,  at  the battery circuit breaker, using standard APPROPRIATE crimp lugs on a breaker with stud terminals.   Of course the correct lug must be used to match the stranding and design of the cable.

Just being a bit redundant.  FWIW,   Vic

[boB]

What Vic said...

Try one of these guys maybe....

http://www.ferrulesdirect.com/

https://www.digikey.com/products/en/connectors-interconnects/terminal-blocks-accessories-wire-ferrules/364?k=ferrules&k=&pkeyword=ferrules&pv1989=0&FV=ffe0016c%2C5800996%2C580021f%2C5800229%2C580022d&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25


boB

[harryn]

Anyone know what size the hole diameter actually is?

Is there an actual spec on the existing terminal block for what wire it is designed and qualified for?

I read the manual and spec sheet, but perhaps missed it.

So, it appears that the hole diameter is approx 0.25 inch max - with 0.23 inch being a more comfortable fit.

I sliced through a lug on the existing wire and even with a thin ferrule it would be 0.30 inch.

Guess I will keep looking.

Thanks for the help - much appreciated.

[ClassicCrazy]

Just to close the loop on this I finally picked up some #4 THHN. Sure enough it slipped right into the terminals on the controller.

The vendor who sold me the fine stranded wire (Windy Nation) did not think the #4 THHN would fit, thinking that if his fine strand #4 wouldn't fit neither would the THHN. But in fact his #6 didn't really fit without shedding a few strands. The simple fact is that particular fine stranded wire is significantly bigger around. Good wire, just fat.

I feel a LOT better having the THHN wire attached to the controller now. Looks right. Feels right. End of story.

jim

Jim said in the discussion above what size wire fit in the terminal .

Larry