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Re: Battery Boxes...What One Company Designed - Page 4

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Posted by Marc F Hult on September 18, 2005, 3:42 am
 
On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message

MFHult@nothydrologistnot.com (Marc F Hult) writes:


They have gotten very much cheaper, smaller, cooler, more robust, more powerful
-- and Ul. and ULc. What is not quite what I'd like is efficiency for this
particular family of devices. They are rated at  ">80%" at unspecified load. In
real world, this might mean 60% under low load. Course they may just be rating
conservatively.

The RV market is big enough to the create volume needed to avoid niche-market
pricing. This particular design (sold under at least three names) has been
around long enough for the engineering to tested and solid. I imagine RV owners
as a group are not the most gentle on equipment.

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.

The other important part of a distributed DC system is use of isolating DC-DC
converters. There are plenty of NOS devices to be had in a variety of Vin and
Vout, nominal telco 48vdc being especially prevalent on the resale market.  

I generally assume that all equipment that came with a wall wart and is located
more than  ~10m from the primary battery bank should be isolated (again) unless
known otherwise. DC-DC converters also provide the current limiting to 'convert'
the battery into Class 1. The NEC specifically states that a plain old zinc dry
cell is Class 2 (not 1) because the potentially high current capabilities. I
wonder how many door bells of yesteryear, connected with 20AWG bell wire, were
in violation ? ;-)

Marc
Marc_F_Hult
www.ECOntrol.org

Posted by Dan Lanciani on September 18, 2005, 5:13 am
 
MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
|
| MFHult@nothydrologistnot.com (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.)

Another issue is that even if the supplies are listed as class 2 you can't
interconnect them unless they are also listed for _that_.  (721-45(b) in
the 1999 NEC)

| The other important part of a distributed DC system is use of isolating DC-DC
| converters. There are plenty of NOS devices to be had in a variety of Vin and
| Vout, nominal telco 48vdc being especially prevalent on the resale market.  
|
| I generally assume that all equipment that came with a wall wart and is located
| more than  ~10m from the primary battery bank should be isolated (again) unless
| known otherwise.

I assume that anything that came with a wall wart needs to be isolated
regardless of location unless it has no other external connections.
Sometimes the negative power input is not common with the "common" of
any other connection.  Very annoying...

| DC-DC converters also provide the current limiting to 'convert'
| the battery into Class 1.

You probably want to "convert" to class 2, but I don't know if DC-DC
converters are generally listed for that.  (If you convert to class 1
then you are stuck with class 1 wiring materials and methods on the
load side, making the whole thing more trouble than running high voltage
to a wall wart. :()

|The NEC specifically states that a plain old zinc dry
| cell is Class 2 (not 1) because the potentially high current capabilities.

It's sort of the other way around.  A dry cell (provided it is < 30V and has
<= the capacity of a series string of No. 6 carbon zinc cells) is considered
an inherently limited class 2 power source.  That is, the power available from
such batteries is *low* enough to be considered class 2.  Any more power and
it would be class 1 (or worse).

|I
| wonder how many door bells of yesteryear, connected with 20AWG bell wire, were
| in violation ? ;-)

Bell circuits have used current-limited class 2 transformers for a long
time (though I don't know when they actually started calling them that).

                Dan Lanciani
                ddl@danlan.*com

Posted by Marc F Hult on September 18, 2005, 3:04 pm
 On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message

MFHult@nothydrologistnot.com (Marc F Hult) writes:

distribution

Interesting.

Thanks for the clarification about Class 2. I musta had at least NEC Class 2 and
Class I, Division 2 all jumbled up ;-)

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.

http://search.globalspec.com/engineering-search/engineering-standards/abstract
/24003535340/UL_Standard_for_Safety_Power_Units_Other_Than_Class_2

http://ulstandardsinfonet.ul.com/scopes/1012.html


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" .

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

So the principal questions would seem to revolve around

1) UL 458 vs UL 1012(?) listing of the PD91x0 charger/supplies

2) Use of Class 2 DC-DC converters such as

http://www.axiomatic.com/24vdc-power-supply.html  
http://www.ecnmag.com/article/CA502827.html?filenameN20050201ec51ps616.xml
to provide a Class 2 source from Art 720 distribution

3) Compliance with Art 720 + Art 240, rather than Art 725, if listed Class 2
DC-DC converters are not used.

Power for telcomm equipment is yet another set of NEC provisions that may
pertain depending on what it being powered.


... Marc
Marc_F_Hult
www.ECOntrol.org

Posted by Marc F Hult on September 18, 2005, 4:07 pm
 

In ASCII, continuing from previous diagram:


28vdc -+->Circuit Breaker--->Dimmer module--->12vdc track UL w/remote xfmr
       |    (Art. 720 + 240)     (Art 725.21 Class 1)                        
       |
       +->Circuit Breaker -------------> devices
       |             (Art. 720 + 240)
       |
       +---->  DC-DC converter ----+---> device
              (Art.725 Class 2)    +---> device ground
      
14vdc -+---->  DC-DC converter ----+---> device
       |       (Art.725 Class 2)   +---> device ground
       |
       +----------------------------> device(s)
              (Art 725.21 Class 1)  

0 ----------------------------------> ground
           (Art. 720 and 725 class 1)

Not shown are low-voltage outdoor lighting or telecomm.

Marc
Marc_F_Hult
www.ECOntrol.org

Posted by Dan Lanciani on September 19, 2005, 8:23 am
 MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
|
| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| >|
| >| MFHult@nothydrologistnot.com (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

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