OM 1239
21 www.DaikinApplied.com
Microtech III unit controller
interface to external equipment
•
The MicroTech III unit controller’s thermostat input
terminals may be directly interfaced with any standard
or night setback thermostat that uses mechanical dry
contacts. Power cannot be supplied from the water
source heat pump for electronic thermostats that require
a separate power supply for their internal operation
except those provided by Daikin. Only thermostats
offered by Daikin are proven to operate properly with the
MicroTech III unit controller. Daikin makes no guarantees
about any other thermostat or control device interfaced
by the end user with the MicroTech III unit controller.
•
Care must be used to isolate all external power sources
from the MicroTech III unit controller to prevent ground
loops and other unpredictable electrical problems. Only
dry mechanical contacts should be used to operate
or interface with the MicroTech III unit controller’s
thermostat and or control inputs. Use mechanical relays
to isolate two power systems when external equipment
with its own power supply is used to interface with or
control the MicroTech III unit controller’s thermostat and
or control inputs. For example, if you have a Building
Automation System (BAS), controller, etc., and you
wish to use a digital output from the building automation
system or controller that is internally powered, then you
must use an additional mechanical relay (not supplied by
Daikin) to isolate the MicroTech III unit controller.
•
Due to the nature of triacs and other solid state devices,
triacs cannot be directly used to operate the MicroTech
III’s unit controller’s thermostat or control inputs. To
interface triacs or other solid state switching devices to
the MicroTech III unit controller inputs, separate them
from the board using mechanical relays. To do this,
use the triac or solid state device to drive a mechanical
relay (not supplied by Daikin), then use the mechanical
relay’s dry contacts to drive the desired MicroTech III unit
controller input.
•
The MicroTech III unit controller’s valve or pump request
terminal {IV/PR (H8)} is an output signal to external
devices to allow water flow as required by the heat
pump. The IV/PR (H8) terminal follows compressor
operation inversely if connected to the normally open
terminal and simultaneously when connected to the
normally closed terminal. The IV/PR (H8) terminal can be
used as a signal to an external pump or valve to enable
flow to the unit. The compressor start is delayed for 30
seconds after the IV/PR (H8) output is energized.
Table 12: IV/PR(H8) terminal and compressor operation
IV/PR(H8)
Compressor On
Compressor Off
Normally Open
24 VAC
0 VAC
Normally Closed
0 VAC
24 VAC
Appendix A
Operation and maintenance of I/O
expansion module
Introduction
The I/O Communication Module is an expansion of the
main board and provides mandatory functionality to the
MicroTech III control system.
•
The MicroTech III unit controller in combination with
the I/O Expansion Module will be the standard control
system for two compressor water source heat pumps.
Adding an I/O Expansion Module (with an interconnect
cable) to the main controller allows:
•
Compressor #2 On/Off Control
•
Water Side Economizer Control
•
Active Hot Gas/Reheat (HGR)
The I/O Expansion Module has an independent LED
annunciator to identify operational fault conditions.
Initial power up
Figure 9: I/O expansion board configuration jumper terminals
I/O expansion module
configuration jumper terminals
M
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ontroller
