E2 Subject1

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E2 Motors and Motor Starting
#2 Compressor Relays and Capacitors

Single Phase Compressor Starting
• Single phase compressors have a
start winding and a run winding
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Split Phase Compressor Motor
C
S

Ω
Ω
R
VAC
DC
COM
V/
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Starting a Split Phase Compressor
• Power must first go to both the
run winding and the start winding
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Split-Phase Compressor Motor Starting
Power is also
needed to start
C
S
START
WINDING
Once started, the start
windings are removed
from the circuit
R
RUN WINDING
Power is needed for
the motor to run
LINE
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Relays
• A relay is used to energize the start
winding
• The same relay is also used to take the
start winding out of the circuit
• The next slide is a diagram of where start
components are located in a compressor
motor circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Diagram of Compressor Start Components
For the motor to run,
power is needed to
Common and Run
N
L1
C
S
R
Add torque with a
Start Capacitor
START
RELAY
For the motor to start,
power is needed to the
Start terminal.
After start up, A Start
Relay opens the circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Types of Compressor Starting
• RSIR: Resistance start, induction run
– Uses a start relay only
• CSIR: Capacitor start, induction run
– Uses a start relay and start capacitor
• CSCR: Capacitor start, capacitor run
– Uses a start relay and both start and run
capacitors
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Two Types of Starting Relays
• Current Relays
• Potential Relays
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current and Potential Relay
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current Relays
• Used on compressors under one
horsepower
• Switch contacts are normally open (NO)
• Relay coil energized by high starting
current
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current Relay
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Motor Amp Draw on Start up
• Current relays respond to amp draw
• Relay contacts close on high starting current
• Relay contacts open as amperage drops
Amperage Draw
Motors draw high amps (LRA) on start up.
60A
LRA
Amperage drops as
speed increases.
40A
20A
0A
Start Up
RLA
20% 40% 60%
80% 100%
Motor Speed
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Starting with a Current Relay
• Current relays are used on refrigeration
systems with fixed metering devices
• When system pressures are equalized only
a relay is needed to start the compressor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Split Phase Motor with Current Relay
1- High starting amps energize relay coil, close contacts
2- Line voltage goes to start windings
S
3- Motor speed increases, amperage decreases,
relay coil allows contacts to open
C
R
START WINDING
4- Start Winding drops out
5- Motor continues to run,
drawing normal current
RUN WINDING
S
M
CURRENT
RELAY
L
POWER ON
Original Diagram from
Copeland Handbook
LINE
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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How a Current Relay Works
• The drawing on the next slide shows how
the start winding is energized, then how it
is taken out of the circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current Relay
Jumper wire
Power In
1
2
S
M
Relay Coil
To Start
Terminal
To Main (Run)
Terminal
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Energize Start and Run Windings
Voltage ready for
Start Winding
Contacts close
Voltage through coil
High starting current
increases coil magnetism
Power to
Start Winding
Power to Main
(RUN) Winding
Plunger is pulled up
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start winding de-energized
No voltage to
Start Winding
Plate falls,
contacts open
Power to
Start Winding
As motor speed increases,
amperage falls
Power to Main
(RUN) Winding
Plunger falls
Compressor continues running
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Adding a Start Capacitor
• A refrigeration system with a TEV requires
more starting torque
• Adding a start capacitor in series with the
start winding is all that is needed
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Capacitor Start Induction Run Motor (CSIR)
START
CAPACITOR
C
S
START WINDING
R
RUN WINDING
S
M
CURRENT
RELAY
L
LINE
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Capacitors
• They provide more phase shift to the start
winding
• Start capacitors are designed to be in the circuit
for only a few seconds
• A resistor quickly bleeds off capacitor charge to
prevent excessive arcing across the relay
contacts
• Note: Always replace capacitors with the same
microfarad rating (MFD or µF) and equal (or
greater) volt amp capacity (VAC)
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Capacitor
Bleed Resistor
15,000 Ohms
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Terminal box on a small compressor
• A current relay plugs into the start and run
terminals
• The external overload is mounted inside
the terminal box
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current
Relay
and
Overload
C
S
R
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Current
Relay
and
Overload
C
S
R
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Terminals - Current Relays - Overloads
C

Jumper
Wire

S
R
L1
N
Remove jumper wire when installing start capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Two-wire Overload
• Single phase overloads are usually in the
common wire
• Its bimetal disk warps when heated
• It responds to motor heat and amperage
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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2-wire bimetal overload
L1
Power on
3
Load
1
2
Normal operating condition: 1-2 closed
If the load draws high current,
the heater from 2-3 becomes hot
This warps bimetal 1-2, and
opens the circuit between 2 and the Load
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Potential Relays
• Used for starting single phase
compressors up to five horsepower
• Contacts are normally closed (NC)
• The relay coil is energized by Back EMF
(electromotive force) generated in the
start winding
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Potential Relay – Top View
“Dummy” terminal
S
2
To start
terminal
From common
terminal
Contacts
Solenoid Coil
“Dummy” terminal
1
C
5
R
From run terminal
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Potential Relay Exposed
2
1
5
Normally Closed (NC)
contacts between
terminals 1 and 2
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
Relay Coil
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Potential Relay – Normal Position
Normally closed
contacts
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
Relay Coil
De-energized
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Potential Relay – After Start Up
Contacts 1 to 2
are pulled open
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
Relay Coil
energized
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Potential Relays in Operation
• The normally closed contacts allow full
voltage to the start winding
• The relay coil is energized
• The contacts open
• Back EMF keeps the coil energized, which
keeps the contacts open
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Potential Relay
Capacitor Start Induction Run (CSIR) Motor
2
Back EMF
keeps the coil
energized
S
START
WINDING
1
POTENTIAL
RELAY
START
CAPACITOR
5
C
R
RUN WINDING
LINE
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Adding a Run Capacitor
• A run capacitor is added to the starting
circuit
• When the potential relay opens the run
cap stays in the circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Potential Relay
Capacitor Start-Capacitor Run (CSCR) Motor
2
Back EMF
keeps the coil
energized
1
RUN CAPACITOR
POTENTIAL
RELAY
START
CAPACITOR
5
C
S
START
WINDING
The run capacitor stays
in the circuit for greater
motor efficiency
R
RUN WINDING
LINE
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Run Capacitors
• When the compressor is running, a run
capacitor provides partial voltage to the
start winding
• This lowers compressor amperage,
increasing motor efficiency
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Run Capacitors
Old style
New Style
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Run Capacitors on PSC Compressors
• No start relay is used on PSC motors
• A run capacitor is permanently wired into
the start windings
• PSC compressors are used on fixed
metering device air conditioning systems,
where pressures equalize during the off
cycle
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Permanent Split Capacitor (PSC) Compressor
Run Capacitor
S
Run Cap allows partial
voltage to start winding
C
Start Winding
R
Run Winding
Line
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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PSC* Compressor with Run Capacitor
Compressor
starts and runs
efficiently
LINE
C
S
R
Partial voltage
through run cap
Run Capacitor
Energize start
winding
Compressor
*Permanent Split Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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PTC Relays
• Positive Temperature Coefficient (PTC)
solid state relays
• The resistance of the ceramic disc
increases with temperature
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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P.T.C. Relay Cutaway
Wire spring holds disk and
serves as a conductor
Start
Run
Power from
Run terminal
Power to
Start terminal
Ceramic Disk
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Location of the PTC Relay
• The relay is wired in parallel to the run
capacitor
• It allows full voltage starting, then drops
out of the circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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PTC Relay and Run Capacitor
PTC Relay
Relay is wired in
parallel with the
run capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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PTC Relay in Operation
• When cool, the disk allows full voltage to
the start winding
• The disk heats up quickly, stopping the
flow of voltage
• Power then takes the path of least
resistance through the run cap to the start
terminal
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Assist with PTC* Relay
PTC
Relay
Voltage stops
when relay heats
Starts with
full voltage
to start winding
LINE
C
S
R
Runs with
partial voltage
through run cap
Run Capacitor
Compressor
*Positive Temperature Coefficient
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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“Hard Start” Kits
• Used on air conditioning compressors
when compressor has trouble starting
• Contains a solid state relay and start
capacitor
• Installed parallel to the run capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Hard Start Kit (for PSC Compressor)
PTC Relay
Connect Leads to
both sides of the
RUN Capacitor
Start
Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Power to Hard Start Kit
PTC Relay
Full power plus
start capacitor
to start winding
Start
Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
Incoming power
on start up
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Hard Start Kit Out of the Circuit
PTC Relay
PTC Relay heats up
Current flow stops
Start
Capacitor
Incoming power
now goes through
RUN cap
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Hard Start Kit Added to PSC Compressor
• The following slide shows the start kit in
the starting circuit
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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PSC Compressor Start Assist
Hard Start Kit
(PTCR & Start Cap)
Full Power plus
Start cap to Start
PTCR heats up,
Stops current flow
LINE
C
S
R
Current now
goes through
only the run cap.
PSC Compressor
Run Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Solid State Potential Relays
• Use only if the OEM (Original Equipment
Manufacturer) potential relay is not
available
• Use only as a temporary replacement of
OEM potential relay
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Electronic potential relay start kits
Hard Start Kit
Replacement Relays
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Diagram of SS Potential Relay
• OEM potential relay coils operate on Back
EMF
• Solid state potential relay coils operate on
time to open the start circuit
• The wiring hookup is basically the same
as the original relay
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Electronic Start Relays
(Universal replacement relay PRO-90 by SUPCO)
L1
Run
Cap
N
O.L.
Run Cap acts like
a jumper wire
C
2
5
R
S
Timer opens 1-2
1
4
6
Run cap provides
efficient running
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
Start
Cap
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Solid State Current Relay Kits
• Useful on small hermetic refrigeration
compressors
• Replaces the current relay and capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Kit for Small Refrigeration Units
PTC Relay
Incoming
Power
Start
Capacitor
To START
terminal
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
To RUN terminal
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Installing a Start Kit
• The following slide shows how the start kit
is hooked up to the compressor
• Use the original overload, NEVER jump
out the overload
Note: This kit can be used even if the
original compressor did not have a start
capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Replacing a Start Relay with a Start Kit
Connect L1 & Run
Remove Relay
L1
L1
N
Use existing
overload
Connect
to Start
PTC Relay
&
Start Capacitor
Start Compressor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Start Kit with Overload
• Some kits include an overload
• This kit can replace all the starting
components at one time
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Electronic current relay start kit
Power Leads
Terminal
connections for
Run, Start, &
Common
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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Inside a “3 in 1” Kit
C
S
R
N
L1
OVERLOAD
PTCR
Start
Capacitor
© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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© 2005 Refrigeration Training Services - E2#2 Compressor Relays and Capacitors v1.2
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