Motor Feeder size
Motor Feeder size
(OP)
Per CEC,the motor feeders need to be sized not less than 1.25FLA. But I have seen a lot of cases where motor feeders have been sized not less than 1.15FLA but smaller than 1.25FLA, especially for some large motors, which are protected by electronic devices. Apparently it is against code requirements. But as an engineer, we can make our own judgement (OBIEC). SO long as the cables are not higher than the overload relay settings, the cables should be protected. Do we need to get the deviation from the client to do so?





RE: Motor Feeder size
Also, be careful of what you think you see. If you observed smaller conductors on a piece of factory assembled equipment, understand that there are different rules for that. In Canada, that would fall under CSA listing and conductor sizing (if CSA is anything like UL in this regard) is not the same as the installation code (CEC/NEC). The equipment can use smaller conductors because it has been (presumably) engineered to an overall specification and listed by that agency.
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RE: Motor Feeder size
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RE: Motor Feeder size
RE: Motor Feeder size
Duh. How many times have I seen someone panic and start changing settings when a new piece of equipment doesn't meet his expectations. There are several experts here and possibly more in the field who have no problem reprogramming a VFD to supply more than 1.15% of rated current, passwords notwithstanding.
With your attitude that you know more than the code, you may be the first to decide that it will be OK to set the current limit higher than 1.15% when you have a problem during start-up.
You may find it humbling to check the CEC and see the backgrounds of the committee members who write the code. In many instances the committee members are in a position to be exposed to or be aware of a very much higher number of incidents than most designers.
Bill
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