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This manual provides information regarding the MicroTech® III
control system. It specifically describes the operation and
programmable options for units with refrigeration only controls
(ROC) .
The ROC MicroTech III Controller is a device that is not
capable of complete, stand-alone operation . Information in the
controller can be displayed and modified by using the keypad/
display in the units main control panel . The ROC systems
require a third-party controller for the Rebel unit to function.
Adjusting PI Control Parameters
The rooftop MicroTech III controller uses a "velocity" form of
the traditional PI loop arranged such that the output is adjusted
based on a "gain" parameter multiplied by the "projected" error .
The projected error is determined based on the rate the error is
changing as shown in
Figure
Figure 1: Projected Error Timeline
The change in output (Do) after each sample period (ST) is
given by the following equation:
Do= Gain X Projected Error .
Although it is generally recommended that they are left at the
factory settings there are four PI loop adjustment parameters
available via the MicroTech III HMI . These are Gain, Period
(ST), Project Ahead Time (PAT) and Max Change .
Generally speaking, the PAT should be set roughly equal to the
"time constant" of the system being controlled and the Period
(ST) one quarter to half the PAT. The Gain is then set to
achieve control stability . If the system is unstable (hunting) the
control is too fast and the Gain should be decreased to slow
the control response . If the system takes excessively long to
reach setpoint during transient conditions (sluggish) the Gain
can be increased to speed the control response . The goal is
an acceptable balance between these two conditions . When in
doubt these parameters should be set to the factory settings .
OM 1263 • MICROTECH UNIT CONTROLLER
1 .
Additional Instructions and Information
For installation and startup instructions and general information
regarding a Rebel
rooftop unit, refer to the applicable model-
™
specific installation and maintenance manual
Table 1: Installation and Maintenance Resources
Unit
MicroTech III Remote Unit Interface
DPS 03 – 28
This equipment generates, uses, and can radiate radio frequency energy
and, if not installed and used in accordance with this instruction manual,
may cause interference to radio communications. It has been tested and
found to comply with the limits for a Class A digital device, pursuant to
part 15 of the FCC rules. These limits are designed to provide reasonable
protection against harmful interference when the equipment is operated
in a commercial environment. Operation of this equipment in a residential
area is likely to cause harmful interference in which case the user is
required to correct the interference at his own expense. Daikin Applied
disclaims any liability resulting from any interference or
for the correction thereof .
Electric shock hazard . Can cause personal injury or
equipment damage .
This equipment must be properly grounded. Connections and service to the
control panel must be performed only by personnel that are knowledgeable
in the operation of the equipment being controlled.
4
Introduction
(Table
1) .
Manual
IM 1005
IM 1125
NOTICE
WARNING
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Introduction
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