Electrical Basics
Breakers
These are Breakers for compressors on a HUSSMANN Superplus Rack. They are used to disconnect power from the compressors. You can still have CONTROL power that will energize the contactor, but will not run the compressor.
How it Works
Compressor Contact
A contactor is used to complete the circuit for the LINE voltage to go to the compressor. Basically it is a switch.
The TOP of the contactor is ALWAYS the LINE side. The BOTTOM of the contactor is always the LOAD side.
How it Works
Time Delay / Relays
The reason for time delays is to keep the compressor from constantly starting/stopping. If a compressor does this too many times it will cause premature compressor failure. For example burnt windings, open windings etc.
How it Works
Phase Monitor
A phase monitor is to keep the compressors from SINGLE PHASING, meaning attempting to start on two legs of power instead of three. This can cause failure of compressor windings.
The phase monitor is wired into the CONTROL side of the circuit, so if it does not sense power from all THREE phases it will LOCKOUT the CONTROL side of the compressors.
How it Works
Condenser Wiring
These are contactors and fuses for the condenser fan motors. This is only on AIR COOLED condensers located outside.
How it Works
Copeland Control Module
This is a CONTROL MODULE, located on the inside the steel housing box on COPELAND compressors. It is the final electrical device to get power to turn on a compressor.
How it Works
More Electrical
9 Watt (120 VAC) Motor (CW)
This motor is the most popular item replaced in grocery store cases. They are used on meat cases, frozen food cases, dairy cases, and produce cases. It is suggested you keep at least a dozen or so of the particular fan motors on your service vehicle.
208 VAC Relay
This relay works with COMMON, N/O, and N/C contacts. It can be used for many reasons, but it is most commonly used in RIIC/RIFF cases to bring fans on/off during defrost and normal operation.
How it works: When the cases are in normal refrigeration mode the relay will be DEENERGIZED, fans ON in refrigeration mode. The relay will ENERGIZE, turning fans OFF. The relay gets energized by the power from the defrost heaters. Most common voltage for defrost heaters is 208 VAC.
Transducer
Generally these are used to measure different PRESSURES: suction, liquid, etc. Sometimes these go bad. To determine if a transducer is bad: Put your gauges on a schrader port in close proximity to the transducer unit and compare the values read on your gauges, versus what the EMS says. If you are 1-3 PSI off, don’t get alarmed. If you are reading say 195 head pressure, and the EMS says its 350 PSI then you have a bad transducer.
Phase Monitor / Motor Saver
With these particular motor savers, just because there is a ‘Green light” IT DOES NOT mean its good, the green light can be on and unit is bad the way to check it is to use you meter to check the bottom control wires, if the voltage is ZERO its good, if you read voltage it is BAD, for time being the control wires can be wire nutted together to get the rack going.
ICM 450 Phase Monitor
What you see here is another style of phase monitor.
Three Phase Breaker
I know I have posted other pictures of breakers, however this is of much importance, dut to the fact of the “A” phase wire ( BLACK) connection is burnt up, very important to be on the look out for this kind of stuff when performing a store PM service, in this case the wire had to be replaced.
Crouzet Time Delay
What you see here are known as CROUZET (Compressor) time delays these are commomnly used on racks in Wal-Marts.
They are stage on various seconds of time delay for the compressors so the compressors do not all come on at once.
Crouzet Time Delay
Picture # 2 of same compressor time delay.
Breakers
How it Works
BREAKERS = A breaker is specifically designed to disconnect LINE voltage from going to a compressor, motor, etc, and kills the power. ALL breakers have a LINE and LOAD side, in which the LINE side of the breaker comes from a MAIN panel breaker, to the LINE side. From there the LOAD side goes to the LINE side of the CONTACTOR, then to the LOAD side of the compressor. Line means incoming power and load is what is going to the device that needs to run.
Breakers can have 1, 2 or 3 POLES, i.e., how many legs of power enter it. A 120 VAC breaker will have ONE source of power coming to it, HENCE a SINGLE POLE breaker.
A 208/220 VAC breaker will have 2 legs of power coming to it, meaning a DOUBLE POLE BREAKER.
A 3 phase breaker will have 3 legs of power coming to it, so it is a 3 pole breaker. There are two types of three phase power that we deal with in grocery store refrigeration systems. 208 and 480, being the most common.
Now for the safety aspect of things. ALWAYS use your meter to check power! I can’t emphasize this enough. Your meter is your best friend. Failure to ALWAYS use your meter can result in YOUR DEATH or destruction of equipment.
Contactors
How it Works
CONTACTOR = This is the device that actually does the work to bring on the compressor, an electric motor, or defrost heaters. They are constantly pulling in/out many times a day based on what it is needed for. They do tend to wear out fairly quickly, because when they pull in/out the CONTACTS arc, which causes it to build resistance and burn up. Do not be afraid to change them. They are one of the most changed items on a refrigeration system next to the 9w 120VAC motor.
To check the contacts, first turn OFF the BREAKER and the CONTROL toggle switch. Remove the front plastic cover and inspect the contacts. If they look burned up, then replace them. Often times when a contactor is burned up, it will be the source of oil failures on compressors due in part to not making full contact. Hence, causing compressor to SINGLE PHASE.
To check and see if a contactor is getting control voltage to the coil, first turn off the breaker. Put your meter leads on the terminals for the coil. If you measure voltage, then you have a bad contactor coil which will need to be replaced. If it does NOT read voltage, then you will need to check the controls in the circuit, such as the LPC, HPC, OFC, and make sure the compressor is being called for to come on.
Time Delay / Relays
How it Works
TIME DELAY/RELAYS = These are wired in SERIES with the CONTROL side of the contactor. They prevent the compressor from SHORT CYCLING. They do go bad and you will have to either remove it from the circuit, or put a JUMPER wire across it. The relay is simply a switch on ONE side of the control power. To check it put your meter on one side of each terminal. If there is NO power after a few minute delay, then it is probably bad.
Phase Monitor
How it Works
PHASE MONITOR = This unit is to disconnect CONTROL power in the event of a power outage, a dropped phase, or uneven three phase power event. It prevents compressors from SINGLE PHASING. They go bad quite frequently and sometimes you have to jump it out because it will take the entire rack out.
Condenser Wiring
How it Works
CONDENSER WIRING = Instead of using breakers fuses are used. So if a motor over amps or shorts out, then the fuse will BLOW, meaning open up internally. Sometimes what you will have to do is shut the whole condenser down just to remove/replace fuses. It is only for a few minutes. To check a fuse, use your ohm meter on it once they are removed. If it reads 0 ohms then it is good. If your meter does not read an ohmic value then it is bad. At that time, use your ohm meter on the LOAD side of contactor to check windings. Do not worry about the specific number, just check for a reading in general. L1 to L2, L1 to L3, then L1 to L3. If they check out with a reading then go by each leg to a GOOD ground source. If no reading then motor is good. If you get a reading on any PHASE/LEG to ground, then the motor is GROUNDED and needs replacing.
NOTE: Sometimes these motors are NOT readily available, you may have to order. If you do remove the motor, then put a piece of CARDBOARD over the hole where the old motor was. If you don’t then all the air will blow out that hole. When installing a new motor, make absolute sure you have PROPER ROTATION. If you don’t, then SWITCH ANY TWO PHASES TO REVERSE ROTATION. This statement is true FOR any 3 PHASE motor.
Copeland Control Module
How it Works
COPELAND CONTROL MODULE = This is located in the electrical box on the compressor commonly known as the “PECKERHEAD”. The module is part of the CONTROL circuitry. Let’s say you get a compressor failure, and the EMS is calling for the compressor to be on. Use your meter to check ALL the controls, (HPC, LPC, OFC, DEMAND COOLING). The switches should be CLOSED. If they are you will read 0 VOLTAGE ACROSS all controls. Next, check the module for voltage across M1 and M2. If you read voltage, the module is BAD. You need to turn off the breaker, turn off control power, and check with your meter to make sure no voltage is present. At that time put a JUMPER across M1 and M2 , then put lid back on the peckerhead. Turn on the breaker and toggle switch for control power, and the compressor should come on.
Follow these steps on your journey to becoming a Journeyman!
