1. HVAC Commercial Ref

2. 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

3. HVAC Commercial Ref
This drawing is the minimum required components wired for a Single Phase Medium Temperature Refrigerator

4. 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

5. 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

6. HVAC Commercial Freezer
Next lets break down a commercial Freezer wiring

7. 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!!

8. 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

9. HVAC Commercial Freezer
Add each system to the wiring diagram separately
Here the cooling components are wired

10. HVAC Commercial Freezer
Next the defrost components are added

11. 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

12. HVAC Commercial Freezer
Next the defrost components are added

13. HVAC Commercial Freezer
Next the defrost components are added

14. 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”

15. 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

16. 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

17. 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

18. 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