Daikin SWP Series Installation Manual page 36

Economizer Start Up
The economizer modulates to maintain the cooling discharge
set point whenever the entering water temperature is below the
mixed air temperature to the unit by an adjustable differential
(0–10°F) and the unit is calling for cooling .
To verify operation of the economizer when entering water is
unsuitable, place the entering water temperature (EWT) sensor
in a cold water bath . Once the sensor is in the bath, observe
that the economizer control valve is open . Readjust the control
setting or remove the sensor from the bath and observe that
the economizer control valve drives close .
Electric Heat Start Up
The electric heater is staged to maintain the discharge heating
set point . To verify the electric heat operation, adjust the
heating set point through the keypad:
Temperatures
• Zone heating
– Electric
Expansion Valve Superheat
Adjustment
It is very important that superheat is set properly . Under
full load conditions it should be between 10°F and 12°F .
Lower entering air conditions, lower airflow rates, and higher
condensing temperatures reduce the load on the expansion
valve . Under reduced load conditions, the superheat could
be as low as 6°F to 8°F. Insufficient superheat causes liquid
floodback to the compressor and possible liquid slugging.
Excessive superheat reduces system performance and
shortens compressor life . Verify that the sensing bulb is
properly located and securely strapped to the refrigerant line .
See Figure 25 . Turn the adjusting stem clockwise to increase
superheat . Adjust the stem (one turn at a time, maximum) and
observe the superheat . Allow up to 30 minutes for the system
to rebalance at the final setting.
The supply fan inlet is located near the expansion valves .
Refrigerant Charge
Each unit is designed for use with R-410A .
Field mixing or changing of refrigerants can compromise
performance and damage equipment . Improper refrigerant
addition can cause equipment damage and severe personal
injury .
IM 1032-2 • Self-Contained Air Conditioning System
WARNING
CAUTION
Non-modular units ship with a full operating charge of
refrigerant and oil . However, in the event of a leak in
the system, some added charge may be required . In an
undercharged situation, any of the following may occur:
• If a circuit is slightly undercharged, bubbles appear in the
sightglass .
• If the circuit is severely undercharged, it may trip on its
low pressure safety .
If any of these conditions occur, first identify and correct the
source of the leak and then follow the charging procedure
described below .
Using the liquid line sight-glass as the sole means of metering
additional refrigerant charge into a self-contained unit, or any
AC unit, does not always provide the desired result . Depending
on the load conditions experienced by the equipment during
the charging process, adding refrigerant until the sight-glass
is clear of all bubbles may overcharge the system and cause
future operating issues . The better way to charge a circuit
is to use liquid subcooling and suction line superheat as
indicators, using the following procedure, which should prevent
overcharging of the circuit:
1 . Verify that superheat is set per the Expansion Valve
Superheat Adjustment section .
2 . Measure the discharge pressure reading and convert it
to a discharge temperature .
3 . Measure and record the circuit's liquid line temperature .
4 . Measure and record the entering condenser water
temperature using the MicroTech III display .
5 . Calculate liquid subcooling: subcooling = discharge
temperature – liquid line temperature
6 . If the calculated subcooling value is less than 8ºF, add
refrigerant .
7 . Monitoring discharge pressure and liquid line
temperature, add refrigerant until the discharge
temperature minus the liquid line temperature is equal to
8ºF ± 2ºF . If the system is running at light load conditions,
subcooling should be at the low end of the range . If the
system is running near design conditions, subcooling
should be near the upper end of the range .
8 . Verify that superheat is still in the prescribed range .
Table 13: Acceptable Refrigerant Oils
R-410A (polyolester [POE] oils)
Note: Do not use mineral oils with R-410A .
Copeland ULtra 22 CC
Mobil EAL
ICI EMKARATE RL
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