DIYbanter - View Single Post - Suggestion for 24V/120V relay to control new outlet?

Twayne[_3_]

In ,
bud-- typed:
wrote:
On Thu, 13 May 2010 17:16:30 -0500, bud--
wrote:

wrote:
On Thu, 13 May 2010 09:43:48 -0500, bud--
wrote:

This is generally read to say that the entire class 2
system is inside that enclosure. You can't take a wire
out of there to another place and still call it class 2.
If the wires can't leave the box there is no particular
usefulness in being class 2 - they can be class 1.

It would allow the use of a class 2 listed transformer.

The section quoted above says class 2 wires are
"introduced solely to connect the equipment". Reasonably
read, "introduced" can mean to enter the enclosure from
the outside.

IMHO "introduced" clearly allows external class 2 wires to
enter a box to connect to "the equipment connected to Class
2 ... circuits".
As I said in my previous post, 725.136-D has 3 options for
class 2 wiring entering a box that has power wiring.
Separation by at least 1/4" is one option. Only if the
first 2 options are not used does 136-D explicitly require
the class 2 wiring be class 1.
It is common practice for class 2 thermostat wires to
enter a "compartment" in a furnace/boiler where there are
exposed insulated power wires. IMHO the section I quoted
allows that practice if the class 2 wires are kept
separate from the power wires.

Again this is a listed assembly and I bet a new one has
some kind of plastic barrier when it is shipped. It may
not make it through the installation process and
electrical inspectors don't really look inside that
equipment. It is an interesting question I will bring up with the
IAEI..

I agree that it is listed apparatus and should generally be
beyond your purview (if wired according to manufacturer
instructions). But it is compliant with what I understand
is permitted by 725.136-D (class 2 and power wires in the
same "compartment").
I dug out an old copy of UL913 which is for
intrinsically safe apparatus. As you are no doubt aware,
intrinsically safe wiring is a lot touchier than class 2.
The standard has several methods to separate field wiring
terminals for intrinsically safe circuits from power
wiring. One of the methods is to separate the terminals
by 2" (and there are requirements for insulation rating
and securing the wiring). Intrinsically safe wiring can
be in the same enclosure (like a control panel) as the
power wiring and terminate in the enclosure. The
intrinsically safe wiring is certainly intended to leave
the enclosure.

You can certainly try it and see what your AHJ says but I
doubt it would fly with any inspector I know.

The AHJ would be arguing with what is explicitly allowed by
UL. And, IMHO, what is allowed by 725.136-D.

That also means you CAN pull a low voltage cable and
line voltage cable in the same raceway,as long as you
have separation where they terminate.

Hold your nose legal ... Pull your CAT5 and Romex
through the same conduit, extend the CAT 5 through the
box and terminate it in a LV ring next to the box. Some
might argue that you need a separation between the place
where you split open the RX jacket and the exit of the
CAT 5 but if you went in and out in the back of the box
with the LV cable, stuffed in a mylar insulator and
split the RX jacket on the outside of that you comply. A little dodgier
is CAT 5 and THHN in the same pipe.
Most AHJs will not let that fly.
You have posted that previously and it seemed quite
reasonable. When I looked at 725.136, it looks like class 2 and power
can be in the same raceway *if* the power (or class 2) is
wired in UF (725.136-I). What allows class 2 and Romex?
Do the jackets constitute a "barrier" (725.136-B)?

BTW there are plenty of inspectors who say I am wrong
about this "both in the same pipe" thing. They are far
more restrictive about how class 2 and line voltages need
to be separated.

But inspectors enforce the same code.......

I thought your options sounded reasonable.

IMHO 725.136-I clearly allows THHN power wires in the same
raceway with class 2 that is in UF. Now if they would just
make #18 UF...
I always liked taping UF with class 2 to the power conduit
for installations like external condenser/compressors.

A "Class 2" xfmr is simply a double-insulated transformer without an earth
ground on its plug, nor a polarized plug.
A "Class 1" xfmr requires a third wire, the earth ground pin on its plug.
The "Class of xfmr is a UL/CSA et al classification which approves the xfmr
and nothing else as safety approved. Secondary ckts attached to the output
of a xfmr are not subject to UL/CSA et al safety testing unless a voltage in
it equals or is more than 42VDC or 42V ac p-p. The original spec, UL1459
(now superceded but not changed in this area) is online for those who wish
to read it. I -think- the CSA spec was CS-03.
Whatever class 1 & 2 means ckt-wise, I don't know; it's not a UL/CSA et
al type spec but might be NEC, NFPA or otherwise.

HTH,

Twayne`