Daikin McQuay AWS250BDH VFD - User Manual

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Installation Manual IM 1167

Pathfinder

®

Air Cooled Chillers

Group: Chillers

Part Number:

IM 1167

REV

00

Date: December, 2012

© 2012 McQuay International

Model AWS-B (Rev 0B)

•

Standard, High, & Premium Efficiencies



Includes models with VFD and models with Remote Evaporator

170 to 550 tons • 600 to 1930 kW • R-134a • 60Hz

Table of Contents

Questions and Answers

H
Holly LeeAug 18, 2025
Why is Daikin McQuay AWS250BDH VFD Chiller compressor overload tripped or circuit breaker tripping?
- C
  Cathy HensonAug 18, 2025
  If the Daikin McQuay Chiller compressor overload is tripped, the circuit breaker trips, or fuses are blown, it could be due to several reasons: * Low voltage during high load condition. Check the supply voltage for excessive voltage drop. * Loose power wiring. Check and tighten all connections. * A power line fault causing unbalanced voltage. Check the supply voltage. * Defective or grounded wiring in the motor. Check the motor and replace it if defective. * High discharge pressure. Refer to corrective steps for high discharge pressure.
C
Craig AlvaradoAug 21, 2025
What causes high discharge pressure in Daikin McQuay Chiller?
- S
  Scott MyersAug 21, 2025
  High discharge pressure in a Daikin McQuay Chiller can be caused by: * Noncondensables in the system. Remove them from the condenser coil after shutdown, following EPA regulations. * Fans not running. Check fan fuses and electrical circuits. * Fan control out of adjustment. Ensure the fan setup in the controller matches the unit fan number and check the Microtech III condenser pressure sensor for proper operation. * System overcharged with refrigerant. Check discharge superheat and condenser subcooling, and remove any excess charge. * Dirty condenser coil. Clean the condenser coil. * Air recirculation from the fan outlet into the unit coils. Remove the cause of recirculation. * Air restriction into the unit. Remove obstructions near the unit.
J
James LittleAug 25, 2025
Why is Daikin McQuay AWS250BDH VFD compressor noisy or vibrating?
- T
  Tonya PalmerAug 26, 2025
  A noisy or vibrating Daikin McQuay Chiller compressor can stem from a few potential issues: * Inadequate oil injection. Verify that the oil sight glass shows visible oil during steady operation and check the pressure drop across the oil filter and oil separator sight glasses. * Liquid slugging. Check suction and discharge superheat.
H
hedwardsAug 31, 2025
How to troubleshoot Daikin McQuay Chiller compressor that will not load or unload?
- J
  Jeremy JohnsonAug 31, 2025
  To troubleshoot a Daikin McQuay Chiller compressor that won't load or unload: * Check the capacity control solenoids for proper operation. Refer to the capacity control section for detailed instructions.
J
John DavisSep 3, 2025
Why is the discharge pressure low in my Daikin McQuay AWS250BDH VFD Chiller?
- B
  Becky OconnorSep 3, 2025
  Low discharge pressure in your Daikin McQuay Chiller could be due to: * Wind effect or a low ambient temperature. Protect the unit against excessive wind into vertical coils. * Incorrect condenser fan control. Ensure the fan setup in the Microtech III controller matches the unit fan number and check the VFD fan if the unit has a VFD option. * Low suction pressure. Refer to the corrective steps for low suction pressure. * The compressor operating unloaded. See the corrective steps for failure to load. * A compressor problem, such as the compressor not pumping properly. Repair or replace the compressor.
T
Thomas GutierrezSep 7, 2025
What causes low oil level trip in Daikin McQuay AWS250BDH VFD Chiller?
- C
  Crystal TuckerSep 7, 2025
  A low oil level trip in a Daikin McQuay Chiller can be triggered by: * Insufficient oil. Check the oil line and separator sight glasses. * Low discharge pressure. Faulty EXV. * Low discharge superheat. Check and correct the cause of low DSH.
J
Joseph LandrySep 10, 2025
What causes high suction pressure in Daikin McQuay AWS250BDH VFD Chiller?
- M
  markgonzalezSep 12, 2025
  High suction pressure in a Daikin McQuay Chiller can be caused by: * Excessive load - high water temperature. Reduce the load or add additional equipment. * Compressor unloaders not loading the compressor. Refer to corrective steps for failure of compressor to load. * Superheat is too low. Check the superheat on the Microtech III display and inspect the suction line sensor installation and the sensor itself. * System overcharged. Check the charge, as an overcharge raises suction pressure. * Compressor bypassing gas. Check evaporator, suction, and discharge pressures.
A
Amy NelsonNov 13, 2025
What to do if Daikin McQuay AWS250BDH VFD Chiller compressor will not run?
- S
  Scott RodgersNov 14, 2025
  If the Daikin McQuay Chiller compressor won't run, here's what to check: * Ensure the main power switch is closed. * Verify the unit system switch is closed by checking the MicroTech III display. * Confirm the circuit switch is not in the pumpdown position, also via the MicroTech III display, and check pump operation for flow. * Make sure the chilled water flow switch is closed, using the MicroTech display and checking the chilled water pump. * Close any open circuit breakers. * Inspect for blown fuses or tripped circuit breakers, checking for shorts, grounds, overloading, or loose connections. Reset breakers or replace fuses after fixing any faults. * Reset the compressor overload at the button and clear the alarm on the Microtech III display. * Check the compressor conta...
C
Cole RoseNov 27, 2025
What causes low suction pressure in Daikin McQuay AWS250BDH VFD Chiller?
- Z
  Zachary ChapmanNov 27, 2025
  Low suction pressure in a Daikin McQuay Chiller can result from: * Inadequate refrigerant charge quantity. Check the liquid line sight glass for charge, inspect the unit for leaks, repair any leaks, and recharge the system to clear the sight glass at full load with all fans on and a minimum outdoor air temperature of 75°F. * A clogged liquid line filter-drier. Check the pressure drop across the filter-drier and replace it if necessary. * A malfunctioning expansion valve. Check the valve's superheat and opening position. Replace the valve only if you're certain it's not working. * Insufficient water flow to the evaporator. Check the water pressure drop across the evaporator and adjust the gallons per minute (GPM) accordingly. * Water temperature leaving the evaporator is too low....

Daikin McQuay AWS250BDH VFD Specifications

General

Category	Chiller
Manufacturer	Daikin McQuay
Model	AWS250BDH
Type	Variable Frequency Drive (VFD)
Component	VFD for Chiller

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