Nortec MES2 - Manual (Page 24)

21 | Installation
The MES2 humidifier can be operated with either On/Off controls or On/Off Safety and one
modulating input. See On/Off or Modulating Control (J10) on page 26 to configure the MES2 for
modulation. For control wiring use minimum 18 AWG and keep as short as possible. For
Modbus wiring use 18-24 AWG shielded, twisted pair 120 Ω impedance cable.
Remote fault indication is provided via a normally open relay which is closed when the controller
is in a fault condition. The dry contact may be connected to maximum of 1 amp at 24 VAC or 24
VDC.
Modbus Wiring
The optional Modbus interface board can be installed onto the MES2 control board to provide
Modbus control of the MES2. In order for Modbus control to be active a jumper must be
installed on J26 of the control board. See Modbus Configuration on page 27 for information on
configuring Modbus communication.
Figure 19: Modbus Wiring
Note: Regardless of selecting on/off or modulating control method, Nortec humidifiers
must have a closed circuit across its on/off security loop control terminal to operate.
Nortec highly recommends the use of a high limit humidistat and an air proving switch
in series for this function.
A
B
Common
Modbus
RS485
Connection
Modbus
Board
(Optional)
Note:
1
2
3
4
Requires optional Modbus board
(PN 1509592)
Use 18-24 AWG shielded, twisted pair
Connect shield at one end only.
J26 must be installed for Modbus
control.
120 Ω impedance cable.