Mike Dolt Enterprises
Mike Dolt Enterprises
User: mityeltu, Location: Tennessee
Asked on: Thursday, March 31, 2011 at 10:08 am EDT
Answered on: Tuesday, May 14, 2024 at 3:33 am EDT
Question: I have a 460v motor with separate circuit for the heater. That is, the heater is NOT fed from the motor control circuit. Odd, I know, but still.My question is, is there a standard (IEEE, NEMA, IEC, anything) that tells HOW this circuit should be confugured?It appears as though this heater (3 element) is fed from a single phase breaker which tells me they are either in series or parallel, but I would like to have some cannon fodder before I go mouthing off to the electricians.Any thoughts?
National Electrical Code (NEC) Article 430.22(A): Motors of more than 100 horsepower must have a separate circuit for the space heaters. Article 430.102(C): The circuit for the space heaters must be protected against overload in accordance with the motor nameplate data. Article 430.82(A): The circuit for the space heaters must be protected against short circuit in accordance with the motor nameplate data.
IEEE Standard 141-1993 Section 11.5.
3.1 recommends that the heater circuit be protected by a separate overload relay with an inverse time delay characteristic. Section 11.3.2 requires that the heater circuit be protected against short circuit. Section 11.3.3 requires that the heater circuit be protected against ground faults.
IEC Standard 60034-1 Section 11.4.
3.1 recommends that the heater circuit be protected by a separate overload relay with an inverse time delay characteristic. Section 11.3.2 requires that the heater circuit be protected against short circuit. Section 11.3.3 requires that the heater circuit be protected against ground faults.
NEMA Standard MG 1-2022 Section 12.5.
3.1 recommends that the heater circuit be protected by a separate overload relay with an inverse time delay characteristic. Section 12.3.2 requires that the heater circuit be protected against short circuit. Section 12.3.3 requires that the heater circuit be protected against ground faults.
Based on these standards, the following conclusions can be drawn
The heater circuit should be separate from the motor control circuit. The heater circuit should be protected against overload. The heater circuit should be protected against short circuit. The heater circuit should be protected against ground faults.Regarding the configuration of the heater elements:
The fact that the heater is fed from a single-phase breaker suggests that the elements are connected in parallel. However, without further information, it is impossible to say for certain. Flag for review