[RE-wrenches] NEC 690.74

Phil Undercuffler solarphil at gmail.com
Mon Nov 29 22:07:23 PST 2010


My recollection is that MTW is Machine Tool Wire, which indeed is not
recognized by the NEC.  It's an "other" category of wire intended to be used
by manufacturers as internal wiring on products which they then get listed.
So a wire with other ratings (such as USE, RHW, THHN) can also have a MTW
rating and be fine, but a wire with only an MTW rating should not be used as
field wiring by an installer.

Also, do you have a source for RHW-2 battery cables?  Or did you mean to say
RHW, such as the typical Cobra X-Flex?

Phil Undercuffler
On Nov 29, 2010 7:41 PM, "Philip Boutelle" <philboutelle at gmail.com> wrote:
> Found the thread, very helpful.... thanks Glenn.
> The current parallel discussion on Battery Cables REvisited is helpful
too.
> The inspector (She, btw) is extremely thorough. Although she has asked for
> proof of purpose-specific listings on just about everything, it seems I
> misquoted her in my previous post; I looked up her earlier plan review
> comments, and here's her original quote (from when my plans said to use
MTW
> for the battery cable): "MTW is not NEC approved for use". I think that to
> her, if it isn't explicitly in the NEC then I can't use it (lists go from
> being partial & inclusive to complete & limiting).
> -Phil
>
> On Mon, Nov 29, 2010 at 6:03 PM, Glenn Burt <glenn.burt at glbcc.com> wrote:
>
>> Hi Phil,
>>
>>
>>
>> I posted some information that is relevant back in March of 2009. It
should
>> be in the searchable archives…
>>
>>
>>
>> -Glenn Burt
>>
>>
>>
>> *From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
>> re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Philip Boutelle
>> *Sent:* Monday, November 29, 2010 8:08 PM
>> *To:* RE-wrenches
>> *Subject:* [RE-wrenches] NEC 690.74
>>
>>
>>
>> Wrenches,
>>
>>
>>
>> We have a string of batteries being inspected by a local AHJ. In
plan-check
>> comments, I was asked to ensure that the flexible cable was UL-listed, so
we
>> made sure of this when it came from the suppliers. We used 4/0 RHW-2. Now
>> our inspector is asking if "RHW-2 is fine-stranded in Article 400 of the
NEC
>> as required by 690.74?"
>>
>>
>>
>> Article 400 doesn't explicitly define any cable types for use in battery
>> systems, and the one general disclaimer is in 400.4: "Types of flexible
>> cords and flexible cables other than those listed in the table shall be
the
>> subject of special investigation".
>>
>>
>>
>> Has anyone had a similar request before? Anyone done a "special
>> investigation" on cables, and have results to share? Any other thoughts?
>>
>>
>>
>> Thanks for any help,
>>
>>
>>
>> -Phil
>>
>> Real Goods Solar
>>
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