Microtech 4 Lite Unit Operation; Preparing Unit For Operation - Daikin PreciseLine Series Installation And Maintenance Manual

MicroTech 4 Lite Unit
Operation

Preparing Unit for Operation

Power-up
There is a 115 VAC control circuit transformer and several
24VAC circuit transformers within the unit to control the various
loads and sensors within the unit. See as-built schematics that
are sent with the unit to familiarize yourself with the various
features and control circuits.
NOTE: Unit ships with factory installed jumpers in the
emergency stop circuit between terminals TB12-T10
and TB2-Ground on size 006-050 and TB2-299 and
TB2-236 on sizes 060-100.
Fan Only
The unit enters the Fan Only operating state after the power
up and anytime there is no requirement for heating, cooling,
or dehumidification. Once entering the Fan Only state of
operation the unit will then, based on sensor inputs transition
into any of the remaining states of operation - heating, cooling,
economizer, econo-cooling, or dehumidification.
Fan Operation
Within 30 seconds (default configurable) on units configured for
an airflow status switch, the controller expects to get feedback
from the switch that the fans are operating properly. If MCB-the
controller does receive that feedback, the controller assumes
the fans did not start. It then shuts down the unit and generates
an alarm. Units configured for DPS control, the supply fan(s) is
modulated to maintain the duct static pressure setpoint.
Two-Positions Damper Operation
On units equipped with a two-position outdoor air damper, the
outdoor air damper will be commanded open any time the fan
is running in the occupied state.
Economizer Operation
If the unit is equipped with a 0-100% modulating economizer
and the conditions are suitable for free cooling, the unit
attempts to satisfy the cooling load by using the outdoor air
economizer before using mechanical cooling.
The transition to economizer operation will occur if all the
following are true:
• The control temperature rises above the occupied cooling
setpoint by more than half the occupied cooling deadband
• The economizer operation is not disabled
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MicroTech 4 Lite Unit Operation

Compressor Operation
Single Compressor
In this configuration a single output is used for compressor
control. When mechanical cooling is required, it will be
energized. When mechanical cooling is no longer required, it
will be de-energized.
Two Compressors
When cooling is required, the Compressor 1 output will be
energized. When mechanical cooling is no longer required,
it will be de-energized. If Compressor Stages is 2, the
compressor 2 output will be energized when the control
temperature reaches the active cooling setpoint plus the
compressor cooling differential. If the Compressor 2 output
is energized and the control temperature falls below the
active cooling setpoint + Compressor Cooling Differential –
Unoccupied Off Differential, then Compressor 2 output will
de-energize.
Four Compressors
When Compressor Stages is 4, the controller will use a PI
control to stage the 4 compressor stages.
If the Supply Fan Control is 'Constant Speed', the PI loop
will stage to control to space temperature. If the Supply Fan
Control is 'Duct Static Pressure' or 'Single Zone VAV', the
PI loop will stage to control discharge air temperature to the
Cooling Discharge Air Temperature Setpoint.
The compressor outputs Compressor 1, Compressor 2,
Compressor 3, and Compressor 4 each represent 25% of the
heating capacity.
• When cooling output is >0%, Compressor 1 will be
energized and it will be de-energized when the cooling
output is 0%.
• When cooling output is >25% Compressor 2 will be
energized and it will be de-energized when the cooling
output is 20%.
• When cooling output is >50% Compressor 3 will be
energized and it will be de-energized when the cooling
output is 45%.
• When cooling output is >75% Compressor 4 will be
energized and it will be de-energized when the cooling
output is 70%.
Compressor Staging
For all compressor configurations, when mechanical cooling
is no longer required, all outputs will be de-energized subject
to minimum on times. Additionally, when a stage of cooling is
de-energized, the interstage timer will start and the next stage
of cooling will not be initiated or deactivated until the interstage
timer expires.
51 IM 1267-7 • PRECISELINE AIR HANDLER