Unit installation
18 OMRCPMICRO
Relay board outputs
All of the MicroTech panel outputs are controlled by solid-state relays which are driven by the model 250
controller. The controller activates a solid-state relay by sending a "trigger" signal to the output board via the
attached ribbon cable. The relay responds to the trigger by lowering its resistance which allows current to
flow through its "contacts". When the controller removes the trigger signal, the relay's resistance becomes
very high, causing the current flow to stop. The outputs are individually protected by a 5 amp fuse mounted
on the output board adjacent to each relay. Table 4 and Table 5 provide additional information about each
output. Refer to the MicroTech Stage Schematics for digital output wiring.
Table 4, ALR relay board outputs
4-Stage Compressor Capacity
6-Stage
Compressor
Capacity
8-Stage Compressor
Capacity
2-Compressor 2-Compressor 4-Compressor
Digital
Output
Number
Output
Description
035-070 050-070 050-070 085-185
0 Alarm Circuit Same Same Same Same
1
Chilled Water
Pump Relay
Same Same Same Same
2 Liq Sol circ #1 Same Same Same Same
3 Liq Sol circ #2 Same Same Same Same
4 Cooling
Compressor 1
Circuit #1
Compressor 1
Circuit #1
Compressor 1
Circuit #1
Compressor 1
Circuit #1
5 Cooling
Compressor 2
Circuit #2
Compressor 2
Circuit #2
Compressor 2
Circuit #2
Compressor 2
Circuit #2
6 Cooling
Compressor 1
Unloader 1
Compressor 1
Unloader 1
Compressor 1
Unloader 1
Compressor 1
Unloader 1
7 Cooling
Compressor 2
Unloader 1
Compressor 2
Unloader 1
Compressor 2
Unloader 1
Compressor 2
Unloader 1
8 Cooling Not Used Not Used
Compressor 1
Unloader 2
Compressor 3
Unloader 1
9 Cooling Not Used Not Used
Compressor 2
Unloader 2
Compressor 4
Unloader 2
10 Condenser Fan(s) M12
j
Same Same Same Same
11 Condenser Fan(s) M13 - Same Same Same
12 Condenser Fan(s) M14 - Same Same Same
13 Condenser Fan(s) M22 Same Same Same Same
14 Condenser Fan(s) M23 - Same Same Same
15 Condenser Fan(s) M24 - Same Same Same
Note: j Number of fans varies.
Refer to the Head Pressure Control section on page 28 of this manual for Fan Staging
information.
Table 5, WHR and THR relay board outputs
4-Stage Compressor
Capacity
6-Stage
Compressor
Capacity
8-Stage Compressor
Capacity
2-Compressor 2-Compressor 4-Compressor
Digital
Output
Number
Output
Description
WHR 040-085E
THR 040-110D
WHR 070-085E
THR 070-110D
WHR 095-210E
THR 120-170D
0 Alarm Circuit Same Same Same
1
Chilled Water
Pump Relay
Same Same Same
2 Liq Sol circ #1 Same Same Same
3 Liq Sol circ #2 Same Same Same
4 Cooling
Compressor 1
Circuit #1
Compressor 1
Circuit #1
Compressor 1
Circuit #1
5 Cooling
Compressor 2
Circuit #2
Compressor 2
Circuit #2
Compressor 2
Circuit #2
6 Cooling
Compressor 1
Unloader 1
Compressor 1
Unloader 1
Compressor 1
Unloader 1