I HAVE A NEW INSTALLATION GOING ON. I HAVE AN 480V ATS BEING FEED FROM A NORMAL POWER TRANSFORMER . THE EMERGENCY FEED COMES FROM A TRANSFORMER SUPPLIED FROM A GEN SET. NEITHER HAVE OVERCURRENT PROTECTION ON THE SECONDARY. I FEEL THERE SHOULD BE A SEVERICE DISCONNECT ON BOTH FEEDS . ALSO THE ATS LOAD TRAVELS ABOUT 40 FEET TO A 1600 AMP MAIN IN THE BUILDING. HAVEING A BATTEL BETWEEN THE A&E AND THE ELECTRICAN. ANY CODES TO HELP ????? THANKS
ATS WITH NO OVERCURRENT PROTECTION
- Thread starter j rae
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zog
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Turn off your caps lock, I tried to read that 3 times and could not do it.
The following is from the document http://www.cumminspower.com/www/literature/technicalpapers/PT-9005-30-CycleDangers-en.pdf
Along the same lines, NEC 110-10 states that electrical components such as transfer switches shall be protected against extensive damage from short circuits:
110.10 Circuit Impedance and Other
Characteristics: The overcurrent protective
devices, the total impedance, the component short
circuit current ratings, and other characteristics of
the circuit to be protected shall be selected and
coordinated to permit the circuit-protective devices
used to clear a fault to do so without extensive
damage to the electrical components of the circuit.
This fault shall be assumed to be either between
two or more of the circuit conductors or between
any circuit conductor and the grounding conductor
or enclosing metal raceway. Listed products applied
in accordance with their listing shall be considered
to meet the requirements of this section.
Since transfer switches are not overcurrent protective
devices except where integral protection is provided,
they must be protected by upstream overcurrent
protective devices that are capable of safely opening
under short circuit conditions and protecting the
downstream transfer switch.
Along the same lines, NEC 110-10 states that electrical components such as transfer switches shall be protected against extensive damage from short circuits:
110.10 Circuit Impedance and Other
Characteristics: The overcurrent protective
devices, the total impedance, the component short
circuit current ratings, and other characteristics of
the circuit to be protected shall be selected and
coordinated to permit the circuit-protective devices
used to clear a fault to do so without extensive
damage to the electrical components of the circuit.
This fault shall be assumed to be either between
two or more of the circuit conductors or between
any circuit conductor and the grounding conductor
or enclosing metal raceway. Listed products applied
in accordance with their listing shall be considered
to meet the requirements of this section.
Since transfer switches are not overcurrent protective
devices except where integral protection is provided,
they must be protected by upstream overcurrent
protective devices that are capable of safely opening
under short circuit conditions and protecting the
downstream transfer switch.
Need more info to nail it down... but to start, all transformer secondary conductors must be provided some means of ocp. But there are various ways to accomplish a compliant installation. Some types of transformers are permitted to have their secondaries protected by the primary ocp. You mention 480V but need to know whether 1?, 3? delta or wye, and number of wires? Who owns power transformer? Is all wiring to the main outside, or considered outside the building? Main should be inside nearest the point of entry.
Initial thoughts are: power transformer is consumer owned; service disconnect is on primary side of power transformer; all pre-main wiring is outside, or considered such.
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