Johnson Controls DOA096B21S Series Engineering Manual page 27

(2) Freeze Protection Control
DOAS operates the forced heating operation for freeze protection of the heat exchanger if the outdoor
air inlet temperature is 32
However, the operation is stopped if the outdoor air inlet temperature is 19.4
temperature in the circuit is decreased.
In addition, the operation is stopped when the condition is not available for the heating operation.
(The operation connected DOAS and other indoor units, etc.)
Forced Heating Control
No
Operation
Yes
Forced
Yes
Heating
Operation
No
< 35.6
> 32 F (0 C)
o o
(2
Outdoor o
Air Inlet
Temp.
< 32 F (0 C)
o o
Forced Heating Operation: ON
Yes
Thermo-OFF
No
Yes
I.U Fan: OFF
No
Forced Stop Control 1
Yes
Defrosting
Operation
No
No
Heating
Operation
Yes
Yes
Forced Stop
Operation
No
Outdoor
Air Inlet
No
Temp.
< 19.4 F (-7 C)
o o
for 3 min.
Yes
Compressor: OFF
I.U Fan: OFF
Forced Stop Operation
: ON
TC-16005-rev.2
o o
F (0 C) or less during the cooling or airflow operation.
I.U. : Indoor Unit
F
o
C)
Outdoor
Air Inlet
Temp.
> 35.6 F (2 C)
o o
Forced Heating Operation: OFF
I.U Fan: OFF
I.U Fan: ON
Outdoor
Air Inlet
No
Temp.
> 19.4 F (-7 C)
o o
for 3 min.
Yes
Thermo-ON
I.U Fan: ON
Forced Stop Operation
: OFF
Forced Stop Control 2
Yes
Forced Stop
Operation
No
Outdoor
Air Inlet Temp.
10 min. has passed
< 32 F (0 C) and
o o
No
Since Forced Stop
I.U Heat Exchanger
Liquid Pipe (Freeze) Tem.
< 39.2 F (4 C)
o o
for 30 min.
Yes
Forced Stop Operation
: ON
Thermo-OFF
I.U Fan: OFF
DOAS
o o
F (-7 C) or less, or the
I.U. : Indoor Unit
Yes
No
Thermo-ON
I.U Fan: ON
Forced Stop Operation
: OFF
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