MCM-Inst-1.10
Page 9 of 27
3.1.1 Example Meter and CT Schedule
Chan-
nels
Submeter
Block
Modbus
Addr
CT
#
Panel
Ckt
#
CT
Amps
L1, L2,
or L3
Meter
Config
Load Name / Description
1-1
2
ADDR+0
2
CT1
P3
1 20 L1
10
Foyer Lighting
CT2
P3
3 20 L2
20
Foyer Outlets #1
CT3
P3
5 20 L3
30
Foyer Outlets #2
ADDR+1
3
CT1
P3
7 20 L1
10
Kitchen Outlets #1
CT2
P3
9 20 L2
20
Kitchen Outlets #2
CT3
P3 11 20 L3
30
Kitchen Outlets #3
ADDR+2
4
CT1
P3
2 50 L1
10
RTU #1
CT2
P3
4 50 L2
20
|
CT3
P3
6 50 L3
30
|
ADDR+3
5
CT1
P3
8 50 L1
90
Compressor (208V, no neutral)
CT2
P3 10 50 L2
50
|
CT3
P3 13 20 L1
10
Kitchen Outlets #4
ADDR+4
6
CT1
P3 15 20 L2
20
Men’s Bathroom Lighting
17 20 L2
20
Women’s Bathroom Lighting
CT2
P3
Figure 2: Sample Installation Record
In this example, the panel (P3) is a 120/208V three-phase wye panel. All of the loads have a neutral
connection except the delta connected compressor.
The first six circuits are single-phase, 20A, lighting and outlet branch circuits. For all six, L1 is matched
with CT1, L2 is matched with CT2, and L3 is matched with CT3. This is the simplest configuration and
does not require any changes to the
MeterConfig
registers.
The next three CT inputs are monitoring a three-phase, 50A, rooftop unit (RTU) load. Again the line
voltages are matched with the CT inputs and do not require any changes to
MeterConfig
.
CT1 and CT2 of Modbus address 5 are monitoring two legs of a delta connected compressor. The
MCM only requires two CTs for delta loads, but if only two CTs are used, then the
MeterConfig
registers must be changed. In this case, the CT1 input is associated with the L1-L3 (VoltAC) line
voltage (
MeterConfig
= 90), while the CT2 input is associated with the L1-L2 (VoltAB) line voltage
(
MeterConfig
= 50). Delta loads can also be measured with three current transformers using the
default
MeterConfig
settings.
CT3 of Modbus address 5 is monitoring a single-phase outlet load (Kitchen Outlets #4). CT3 monitors
the load on L1 or ØA (phase A), so
MeterConfig
must be changed to 10.
The final two loads in the example are lighting loads, both on L2 (ØB), so both need to have
MeterConfig
set to 20.
3.2 Electrical Service or Load Types
The MCM supports any electrical service from 100 to 600 Vac, line-to-neutral or line-to-line, 50 to
60 Hz, single-phase, split-phase, or three-phase, wye or delta, two-wire, three-wire, or four-wire. It
