MEC 20 MICROPROCESSOR ENGINE/GENERATOR CONTROLLER
PM047 Rev 13 05/03/30
39
Thomson Technology
Diagnostic LED’s are provided on each expansion module as shown in FIGURE #17. Their
functions are described as follows:
WATCHDOG - This LED flashes on and off at a very high rate which indicates that the expansion
module microprocessor is functioning normally.
MESSAGE - This LED flashes on and off at irregular intervals which indicates that the expansion
module is correctly receiving all data messages from the MEC 20.
Two expansion modules may be connected to a single MEC 20 controller to provide a maximum
of 32 output contacts. Two modules are interconnected together using a single communication
cable to the MEC 20 controller. Refer to FIGURE #19 for interconnection details. The first
expansion module addresses standard C282/NFPA110 MEC 20 fault circuits
1
and the second
expansion module addresses all additional fault circuits. To select which faults are addressed
by each expansion module, jumper pins and clips are provided on the circuit boards. Refer to
FIGURE #18 for jumper pin location and configuration settings.
1
C282 or NFPA 110 standard faults exclude analog faults Over/Under voltage, Over/Under Frequency, Overcurrent, spare digital inputs #5-#12 and
programmable output #6 (i.e. must specify second expansion module to obtain contacts for these faults).
GRD
GRD
GRD
G:\ENGINEER\PRODUCTS\MEC20\MEC20_17.VSD
M EC 20
Engine
Controller
J7
J6
Expansion
M odule #1
(C282/NFPA Standard
Fault Circuits)
Expansion
M odule #2
(Additional Fault C ircuits)
J17 off
J17 on
To rem ote
com m unication
system (optional)
8 conductor Shielded
Cable c/w RJ45 connectors
300M (~1000')
m axim um cable
length
FIGURE #19
MEC 20 EXPANSION MODULE INTERCONNECTION DIAGRAM
