Re: Battery Boxes...What One Company Designed

[ddl@danlan.*com (Dan Lanciani)]

In article <jlpqi1pug6c0m8uiqalsq7hjeau43aqu44@xxxxxxx>, MFHult@xxxxxxxxxxxxxxxxxxxxx (Marc F Hult) writes:
| On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| <1331587@xxxxxxxxxxxxxxxxxxx>:
|
| >In article <ehopi1lk9nh29a8u247sbu1o1tt5cm65la@xxxxxxx>,
| MFHult@xxxxxxxxxxxxxxxxxxxxx (Marc F Hult) writes:
| >| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| >| <1331585@xxxxxxxxxxxxxxxxxxx>:
| >|
| >| >In article <as8pi1da45o1psehe0s983ql7439j8k3ek@xxxxxxx>,
| >| MFHult@xxxxxxxxxxxxxxxxxxxxx (Marc F Hult) writes:
| >|
| >| >|
| >| >|
| >| >| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
| >| >| previous post. See
| >| >|
| >| >| http://www.progressivedyn.com/power_converters.html
| >| >
| >| >Interesting.  I had no idea that you could get class 2 supplies with such
| >| >high power output.  Maybe I'll have to reconsider my low-voltage
| distribution
| >| >analysis...
| >| >
| >|
| >[...]
| >| IMO, Key here is UL and internal transformer isolation. But I haven't probed
| to
| >| see whether it is specifically UL for Class 2. I am satisfied that it means
| >| engineering needs.
| >
| >Hmm.  But if it isn't UL listed as a class 2 supply then it can't supply class
| >2 circuits.  Class 2 supplies have some pretty stringent requirements for
| >current limiting (not just over current protection--source impedance is a
| >consideration).  Last time I checked the most power allowed for a class 2
| >supply in the lowest voltage range was 100VA.  (At higher voltages the power
| >is reduced disproportionately IIRC.)
|
| Interesting.
|
| Thanks for the clarification about Class 2. I musta had at least NEC Class 2 and
| Class I, Division 2 all jumbled up ;-)

As in Class I hazardous locations?

| It would appear that the listing for the PD91x0 devices is probably UL 458 ("
| Chargers or charging functions incorporated into converter or inverters for use
| in recreational vehicles and boats, as covered by the Standard for Power
| Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and
| Marine Crafts").
|
| For home use, they may need to be listed under UL 1012.  " These requirements
| cover portable, stationary, and fixed power units having an input rating of 600
| volts or less, direct- and alternating- current, with at least one output not
| marked Class 2, and that are intended to be employed in ordinary locations in
| accordance with the National Electrical Code, ANSI/NFPA 70." ) I dunno.

Perhaps.  However, I just looked at the hookup instructions and it appears
that the outputs are directly paralleled with the battery bank, i.e., whatever
over-current protection the devices offer does not actually protect the load
side.  That suggests that no matter the listing the output is going to have to
be treated like the output of any other battery bank which can deliver very
high current, requiring, e.g., (expensive) class T fuses.  And of course, the
wiring at that point isn't even class 1.  (I used to think that it could be
class 1 subpar (b) which goes to 600V with no power limitations, but that's
for signaling/control only...)

| Previously I identified four sections of the code that seem to pertain:
|
| Article 411 lighting  (isolated; <30 volts/42.4v peak); max 20 amp branch
| circuit supply; max 25amp lighting circuit; Class 2 power source; not grounded )
|
| Article 720  ( <50 volts; =>12AWG wiring; Article 240 overcurrent )
|
| Article 725.21 Class 1 ( <30 volts and <1000 volt-amp )
|
| Article 725 Class 2  (supplying or active converting <100 watts at =<30VAC or
| =<60vdc )
|
| Power for telcomm equipment is yet another set of NEC provisions that may
| pertain depending on what it being powered.
|
| Article 411 is not particularly useful because it appears to pertain to a
| complete unit that is UL listed as a system. One can buy low voltage wiring
| systems as a package that conform to 411 that use bare wires a few inches from a
| tall person's head. But if is unclear that one can substitute or fix anything
| and still be compliant. Note the "Class 2 power source requirement" .

411 didn't used to (as of the 1999 NEC) require a class 2 supply and was
(according to the notes) intended to cover both interior and exterior
(landscape) lighting.  The wiring could be extended through/in a wall but
only by using Chapter 3 materials and methods.  So even then it didn't
really buy you much.  If they have added a genuine class 2 supply requirement
I would think that many of the existing landscape lighting transformers are
now out of spec since even the multi-output ones typically exceeded 100VA on
each output.  It may be that there is now a specific (and different) type
of class 2 listing for such supplies that makes this all work out.  There
is an unfortunate trend in this respect to make listings extremely application-
specific, thus thwarting non-standard or unanticipated custom assemblies.

| Article 720 is where I should have indicated that the DC _supply_ to my
| low-voltage lighting dimmers fall. As practical matter, one uses conventional (
| Sect 1-4 ANSI/NFPA 70) wiring  but keeps these conductors out of conduits and
| boxes that also contain 120/220 VAC. My DC dimmer panel is about 4 feet from the
| PD91x0  supplies so this is easy to do.
|
| Article 725.21 Class 1 (not 2  Thank you ;-) ) would seem to pertain to (in my
| case) to:
|
| 1) The distribution of power from the centrally-located DC lighting dimmers
| (24vdc input, 0-12vdc output) to my commercial track lighting that is UL-listed
| for remote transformers.
|
| http://www.ipnlighting.com/faq/linear_faqs.htm
|
| Each dimmer is rated at 250 watts and has its own 20 amp breaker.
|
| 2) The distribution of power from the 12vdc supply (tap) of my system  (80 x 12
| = 960 < 1000v-a) as 725.21 Class 1

Here's the problem I had when I looked at the whole low-voltage DC distribution
idea a while back.  Whether you classify your circuits under 720 or 725's
class 1 you still have to use the same Chapter 3 materials and methods that
you would use for line voltage circuits.  Plus you have to keep the two
(or maybe all three) separate.  Plus you have to deal with non-standard
(and thus more expensive) ancillary components like DC-rated switches and
fuses.  Plus you have the inherent loss disadvantages of low voltage.  As
far as I can tell, the only thing you gain under class 1 is the ability to
use No. 16 and 18 conductors, not that I'd want to.  Am I missing something?

				Dan Lanciani
				ddl@danlan.*com