HVAC Commercial Ref

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HVAC Commercial Ref
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HVAC Commercial Ref

• All commercial Refrigerators will have at least
  these 6 component
• 3 loads Compressor Condenser Fan Evaporator Fan
• 3 required accessories Thermostat Starting Relay
  Start capacitor

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HVAC Commercial Ref

• This drawing is the minimum required components
  wired for a Single Phase Medium Temperature
  Refrigerator

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HVAC Commercial Ref

• When a contactor is used the thermostat is
  replaced by the contacts of the contactor
• If it is a 2 pole contactor the second set of
  contacts are placed in the L2/N to the compressor
  and condenser fan
• The thermostat and safety controls are wired in
  series with the contactor coil

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HVAC Commercial Ref

• If a liquid line solenoid the thermostat controls
  the solenoid
• The compressor will cycle on low pressure caused
  by the system pumping down when the solenoid is
  closed

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HVAC Commercial Freezer

• Next lets break down a commercial Freezer wiring

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HVAC Commercial Freezer

• The brain of the commercial Freezer is the
  Defrost timer
• There are 2 types of timers one is time on-time
  off, The other is time on-time or temperature off
• Terminal identification will often change among
  manufactures so understanding timer operation is
  important!!

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HVAC Commercial Freezer

• Before adding controls and motors you need to
  understand the basics
• The timer motor is on as soon as power is
  supplied
• The normally closed contacts, in this case 1 to 4
  are for cooling
• The normally open contacts in this case 2 to 3
  are defrost
• The oval between 1 and 2 represents a jumper that
  can be removed
• This timer is time-temperature off or terminated
  the X terminal is connected to the Drop
  Solenoid which changes the switch contacts back
  to cooling if the temperature at the evaporators
  indicates it has been defrosted

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HVAC Commercial Freezer

• Add each system to the wiring diagram separately
• Here the cooling components are wired

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HVAC Commercial Freezer

• Next the defrost components are added

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HVAC Commercial Freezer

• Next the defrost termination components are added
• Note the evaporator fan L2 is now connected to
  the DTS to delay starting the fan after a defrost

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HVAC Commercial Freezer

• Next the defrost components are added

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HVAC Commercial Freezer

• Next the defrost components are added

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HVAC Commercial Freezer

• If a contactor is used to operate the compressor
• The thermostat and safety control are wired in
  series with the contactor coil
• The contactor contacts replace the thermostat on
  both sides of the compressor and condenser fan
  package

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HVAC Commercial Freezer

• If a Liquid line Solenoid is used the thermostat
  will control the solenoid
• The low pressure control will turn of the
  compressor when the pressure drops after the
  thermostat opens de-energizing the LLS closing
  the solenoid causing unit to pump down

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HVAC Commercial Freezer

• If no contactor is used the low pressure and
  other safety controls will be wired in series
  with the compressor package
• The low pressure control will turn of the
  compressor when the pressure drops after the
  thermostat opens de-energizing the LLS closing
  the solenoid causing unit to pump down

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HVAC Commercial Freezer

• If the condensing unit is outside or when a fan
  cycler is need this control is wired in series
  with the condenser fan

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HVAC Commercial Freezer

• Remember when developing wiring diagrams work
  with each system one at a time
• After all system are drawn check sequence of
  operation to see if all systems operate properly