Electric Defrost Sequence - Low Temperature
1.
Power from the defrost contactor energizes Defrost Heaters and 208V Evaporator Fan Relay Coil (7). Relay Contacts open the fan
circuit and energizes the Drain Pan Heater.
2.
If the Defrost Heater raises internal air temperature above 90°F, the Defrost Limit Thermostat (4) will open.
3.
Temperature rise of the evaporator closes the Relay Control Thermostat (5) at about 35°F, energizing 120V A.S. Relay Coils (6).
These relays’ contacts open the Frame and Door Heater Circuits, and prevent the Fan Circuit from energizing upon defrost
termination.
4.
When Defrost Termination Thermostat ends defrost period, the defrost contactor opens the Defrost Heater and Evaporator Fan Relay
Coil Circuits. The Drain Pan Heater goes off.
5.
Temperature fall of the evaporator opens the Relay Control Thermostat (5) at about 20°F, de-energizing 120V A.S. Relay Coils (6).
A.S. Relay Contacts close the Frame and Door Heater Circuits, and Fan Circuit.
5 of 6
P/N 0445823_B
HUSSMANN CORPORATION • BRIDGETON, MO 63044-2483 U.S.A. • WWW.HUSSMANN.COM
C
C
Defrost Termination
Thermostat
Refrigeration
Thermostat
(Optional)
Pink
2
3
}
To
Condensing
Unit
A.S. Relay
Coil
BR
Evaporator Fans
1
Fan Relay
COM
N.O.
Rod Heater (Drain)
9
Y
Y
N.C.
7
7
1
3
W
B
Relay Control
25
Fan Relay
B
5
6
B
B
COM
N.C.
6
A.S. Relay
24
Door A.S. Heaters
Frame A.S. Heaters
21
22
2P
P
2P
P
12
11
10
120V P
OWER
16
13
OR
L
120V POWER
OR
Switch
N
EUTRAL
17
20
208V
Evaporator Fan
Relay Coil
1
3
R
R
Defrost Heater
R
5
4
B
B
7
R
N.C.
7
8
8
Defrost Limit
208V
208V
Terminal Blocks in Raceway
Low Temperature with
Electric Defrost
20
21
22
26
17
1
2
3
4
5
6
7
8
10
11
14
13
16
LIGHTS
(120V)
DEFROST HEATERS
(208V)
CIRCLED NUMBERS = PARTS LIST ITEM NUMBERS
THESE ARE MARKER COLORS (WIRE MAY VARY.)
CAUTION:
When multiplexing
merchandisers equipped with defrost
heaters, if branch circuit overcurrent
protection is larger than the
individual merchandiser’s defrost
circuit load, then additional
supplemental overcurrent protection
may be required per NEC Articles
210 and 240.
R = Red P = Purple 2P = Purple (2 Bands) DB = Dark Blue B = Black
BR =Brown Y =Yellow OR = Orange W = White
Fan and Heater Circuits - Electric Defrost (standard)
Low Temperature
24
25
12
FANS & A.S.
(120V)
LIGHTS
(Neutral)
FANS & A.S. (Neutral)
Permanent Internal
Jumpers
R
P
W
BR
OR
R
R
R
B
B
R
R
B
P
2P
B
B
OR
B
2P
Y
14
26
C.O.R.
1
2
3
4
6
O.O.R.
Removable External
Jumpers
DB
C.O.R.
2
Defrost Termination
Thermostat
FIELD WIRED
DB
N
EUTRAL
Dark Blue
Refer to
Innovator Reach-In
Glass Door, Installation and
Service
manual, P/N 0425683,
for
Innovator
door and frame
replacement parts.
C
6
120V
Fan Relay
N.C.
120V Fan
Relay Coil
6
