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Installation
Connecting the Voltage
51
Building Technologies
125-202
06/06/2017
CAUTION
Verify that the breaker is marked as the disconnect breaker for the meter.
NOTE:
The MD-BMS and MD-BMED is rated for 600V Over-Voltage Category III. Cat III is for
measurements performed in the building. Examples are measurements on distribution
boards, circuit-breakers, wiring (including cables), bus bars, junction boxes, switches,
and socket outlets in a fixed installation, and equipment for industrial use. Other
equipment could include stationary motors with a permanent connections to the fixed
installation.
Powering the Meter
Connect the MD-BMS or MD-BMED meter voltage leads as close as possible to a
building installed, dedicated circuit disconnect breaker using 14 AWG THHN Minimum
600 Vac wire rating (or equivalent, to maintain 600 Vac safety rating of the device).
Mark the breaker as the disconnect for the MD-BMS or MD-BMED. See
Wiring
Diagrams for specifics of the wiring connections.
Follow local electrical codes during the installation.
MD-BMS or MD-BMED meters are self-powered from the L1 and L2 lines. When 80 to
600 Vac or DC is placed across the L1 and L2 wires, the three phasing LEDs begin to
flash in sequence.
MD-BMS or MD-BMED Single-Phase Connections
The MD-BMS or MD-BMED Power Meters can be used to monitor single-phase loads.
There are several guidelines to keep in mind about this type of connection:
1. The MD-BMS or MD-BMED meter is powered from a potential between L1 and L2.
This can be phase-to-phase (230V) or phase-to-neutral (115V). With a single-
phase 230V panel, the L1 and L2 voltage leads are connected between the L1 and
L2 voltage sources. With a 115V circuit, the L1 voltage lead is connected to the L1
(hot) lead, and the L2 voltage lead is connected to neutral.
2. Each CT must be paired with the correct voltage source. The current and voltage
need to be in-phase for accurate measurements. For instance, CT 1 would monitor
branch circuit supplied by voltage source L1, and so on.
3. The neutral must be connected because the MD-BMS or MD-BMED meter uses
line-to-neutral measurements for all calculations.
Typical 230V Single-Phase Setup (US Wire Colors)
Connect the Black L1 voltage lead to Voltage L1, Red L2 voltage lead to L2 voltage,
and White Neutral voltage lead to neutral. CT1 would monitor L1 loads and CT2 would
monitor L2 loads. Based on the above guidelines, CT3 can be used if the Blue L3
voltage lead is connected to either L1 or L2. If voltage lead L3 and CT3 are in-phase,
the MD-BMS or MD-BMED meter will provide correct kW readings. If the Blue L3
voltage lead was connected to the L2 voltage source, then CT3 could monitor any L2
branch circuit. Or, if the Blue L3 voltage lead was connected to the L1 voltage source,
then CT3 could monitor any L1 branch circuit.