jraef
Member
If those CTs are not UL listed AS a “motor over load protective device”, you can only use it as “supplemental” protection. So for instance you could have a legal motor OL device required per the NEC, set for the maximum allowable current for the motor, then you could have these OTHER devices in series that you can use to turn off the motor BEFORE the OL trips by setting them lower. Totally legit. But you cannot “roll your own” motor thermal OL scheme.
Are you absolutely sure that these single phase motors do NOT have built-in thermal protection? Because at 4.9A 120V, that’s a fractional HP motor and probably 90%+ of motors like that have a simple cheap thermal switch called a “Klixon” embedded inside, which IS going to be legally suitable as the motor OL protection per the NEC. Maybe your end user is unaware of that because sometimes the wording on the motor data plate is “Thermally Protected”, or sometimes as skimpy as “TP” with a circle around it. They may not understand what that means. It means that you do NOT need an external OL protective device.
Are you absolutely sure that these single phase motors do NOT have built-in thermal protection? Because at 4.9A 120V, that’s a fractional HP motor and probably 90%+ of motors like that have a simple cheap thermal switch called a “Klixon” embedded inside, which IS going to be legally suitable as the motor OL protection per the NEC. Maybe your end user is unaware of that because sometimes the wording on the motor data plate is “Thermally Protected”, or sometimes as skimpy as “TP” with a circle around it. They may not understand what that means. It means that you do NOT need an external OL protective device.
