MCM-Inst-1.10
Page 3 of 27
1 Precautions
●
Only
licensed electricians
or qualified personnel should install the MCM. The mains voltages of
100 to 600 Vac can be lethal!
●
Follow all applicable local and national electrical and safety codes.
●
The terminal block screws are
not
insulated. Do not contact metal tools to the screw terminals if
the circuit is live!
●
Verify that circuit voltages and currents are within the proper range for the MCM model voltage
group.
●
Use only UL Listed or Recognized current transformers (CTs). Depending on the meter options,
you may use either CTs with built-in burden resistors that generate 0.333 Vac (333 millivolts AC) at
rated current or milliamp output CTs that generate 40 mA at rated current.
Do not use 1 amp or 5
amp output CTs: they will destroy the meter and may create a shock hazard.
●
If your MCM model does not include a circuit breaker or fuses, then protect the line voltage
conductors supplying the MCM with fuses or circuit breakers. See
below.
●
Disconnect equipment from HAZARDOUS LIVE voltages before access.
●
If the meter is not installed correctly, the safety protections may be impaired.
●
Torque all screws as specified on the information label on the inside of the enclosure door.
1.1 Symbols
Read, understand, and follow all instructions including warnings
and precautions before installing and using the product
Potential shock hazard from dangerous high voltage
Earth ground
UL Listed mark for the USA and Canada. It is located on the UL
508A label inside the enclosure and applies to the entire MCM.
The UL Recognized mark for the USA and Canada appears on
the MCM cards and some accessories.
1.2 Terminology
current sensor (or current transformer or CT):
the terms current sensor and current transformer
(CT) are used interchangeably in this guide. They refer to devices that measure AC current and
output a millivolt signal representation of the current. The MCM may also support milliamp output
current transformers when ordered with the correct option.
meter element (or element):
a meter element combines a voltage signal with a current signal to
measure and report AC power and energy, as well as additional parameters of interest. Each meter
element accepts one CT input. There are three meter elements in each submeter block. See
for more details.
Modbus RTU:
a version of the Modbus protocol primarily used over RS-485 (EIA-485) links.
Modbus TCP:
a version of the Modbus protocol used over Ethernet TCP/IP networks.
primary SMB:
the first submeter block in an MCM system, with a Modbus address offset of 0 relative
to the address assigned with the DIP switches or using Modbus
Address
register.
submeter block (SMB):
the MCM is composed of multiple SMBs. Each SMB has three CT inputs and
behaves much like an independent three-phase meter. See
details.
