Re: Battery Boxes...What One Company Designed

[Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 17 Sep 2005 19:18:03 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331582@xxxxxxxxxxxxxxxxxxx>:

>In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@xxxxxxx>,
MFHult@xxxxxxxxxxxxxxxxxxxxx (Marc F Hult) writes:
>
>[big snip]
>| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000
>|watts.
>|
>| A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
>| kick in during power outages that has additional capacity for additional
>|28vdc
>| and 120VAC UPS needs. Controller is a Bouchette A120
>|
>| http://www.bouchette.com/Products/A120C.htm
>|
>| The choice of 28vdc was driven in large part because this the highest nominal
>| voltage that meets the requirements of the under-30-volt sections of the
>| National Electrical code (NEC).
>
>What NEC circuit class does your 28V wiring fall under?

Depends on which circuit *after* the UL-listed class 2 supply you ask about.

As needed and appropriate, and depending on overcurrent devices and intervening
converters, the subsequent wiring complies with:

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 2/3  (This is what my 24vdc dimmers operate under)

725.21 A0
Class 1 Power-Limited Circuits. These circuits shall
be supplied from a source that has a rated output of not
more than 30 volts and 1000 volt-amperes.

725.51 Wiring Methods on Supply Side of the Class 2
or Class 3 Power Source. Conductors and equipment on
the supply side of the power source shall be installed in
accordance with the appropriate requirements of Chapters 1
through 4. Transformers or other devices supplied from
electric light or power circuits shall be protected by an
overcurrent device rated not over 20 amperes.

725.41 Power Sources for Class 2 and Class 3 Circuits.
(A) Power Source. The power source for a Class 2 or a
Class 3 circuit shall be as specified in 725.41(A)(1), (2),
(3), (4), or (5):
FPN No. 1: Figure 725.41 illustrates the relationships between
Class 2 or Class 3 power sources, their supply, and
the Class 2 or Class 3 circuits.
FPN No. 2: Table 11(A) and Table 11(B) in Chapter 9
provide the requirements for listed Class 2 and Class 3
power sources.
(1) A listed Class 2 or Class 3 transformer
(2) A listed Class 2 or Class 3 power supply
(3) Other listed equipment marked to identify the Class 2
or Class 3 power source

Comments/corrections/additions welcomed.

 ... Marc
Marc_F_Hult
www.ECOntrol.org