Controls in the grounded side
- Thread starter ronaldrc
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Re: Controls in the grounded side
The only time I had this happen was on a water pump for irrigation. The pump starter was interlocked with a permit, or not permit, level switch.
We burnt out a motor when it kept running after water level dropped too low.
The pump was about 150 feet from the level switch, with the conductors firmly together in a cable assembly.
When I changed the control voltage to 240 it performed perfectly.
The only time I had this happen was on a water pump for irrigation. The pump starter was interlocked with a permit, or not permit, level switch.
We burnt out a motor when it kept running after water level dropped too low.
The pump was about 150 feet from the level switch, with the conductors firmly together in a cable assembly.
When I changed the control voltage to 240 it performed perfectly.
Ed MacLaren
Senior Member
Re: Controls in the grounded side
Ronald et al,
I said that all control transformer secondaries are required to be grounded except those that meet all of the following conditions.
a. the primary is not over 1000V, and
b. there is qualified maintenance and supervision, and
c. a requirement for control power continuity exists, and
d. ground detectors are installed on the control system.
I also said -
Control transformers up to 1 kva can have the secondary grounded to the control enclosure's equipment grounding conductor.
When the control transformer exceeds 1000 va, then the grounding conductor would have to run to a fully qualified grounding electrode, instead of just to the control enclosure.
This was my interpretation of the '96 NEC rules on the subject. Are you saying that there have been changes?
P.S. - See also ECM Article at http://www.ecmweb.com/ar/electric_code_applies_internal/
Ed
[ August 26, 2003, 10:23 PM: Message edited by: Ed MacLaren ]
Ronald et al,
That is not what I said.
I said that all control transformer secondaries are required to be grounded except those that meet all of the following conditions.
a. the primary is not over 1000V, and
b. there is qualified maintenance and supervision, and
c. a requirement for control power continuity exists, and
d. ground detectors are installed on the control system.
I also said -
Control transformers up to 1 kva can have the secondary grounded to the control enclosure's equipment grounding conductor.
When the control transformer exceeds 1000 va, then the grounding conductor would have to run to a fully qualified grounding electrode, instead of just to the control enclosure.
This was my interpretation of the '96 NEC rules on the subject. Are you saying that there have been changes?
P.S. - See also ECM Article at http://www.ecmweb.com/ar/electric_code_applies_internal/
Ed
[ August 26, 2003, 10:23 PM: Message edited by: Ed MacLaren ]
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