Table of Contents
Advertisement
Form 201.28-NM1.1
Issue date: 08/06/2021
The discharge pressure unload point is fixed at 255
psig.
Table 18 - Discharge pressure load limiting/unloading
Discharge pressure
Discharge Pressure Cut-
out- 20 psig and Discharge
Pressure Cutout- 15 psig
Discharge Pressure Cutout- 13.5 psig
Discharge Pressure Cutout- 12 psig
Discharge Pressure Cutout- 10.5 psig
Discharge Pressure Cutout- 9 psig
Discharge Pressure Cutout- 7.5 psig
Discharge Pressure Cutout- 6 psig
Discharge Pressure Cutout- 4.5 psig
Discharge Pressure Cutout- 3 psig
Discharge Pressure Cutout- 1.5 psig
Discharge Pressure Cutout- 0 psig
Suction pressure load limiting/unloading
Suction pressure load limiting helps to protect the
evaporator from freezing. A system is permitted to
load normally as long as the Suction Pressure is above
the "Suction Pressure Cutout + 2.6 psig". Between
"Suction Pressure Cutout + 2.6 psig" and the "Suction
Pressure Cutout + 1.7 psig", loading is inhibited, even
though increased loading is required.
Between the "Suction Pressure Cutout + 1.7 psig" and
"Suction Pressure Cutout", forced unloading is per-
formed every 2 seconds according to Table 19 on page
129. This situation would occur if the suction pres-
sure cutout transient override control is in effect (See
Low Suction Pressure Cutout (Software) Fault on Page
127). The suction pressure cutout is programmed un-
der the PROGRAM key. The default Suction Pressure
Cutout is set at 26.1 psig.
Suction pressure load limiting is active at startup, to
only prevent loading of the compressors. Suction pres-
sure limit unloading will not occur until the system run
time reaches 5 minutes of operation to allow the sys-
tem to stabilize.
JOHNSON CONTROLS
Table 19 - Suction pressure load limiting/unloading
Suction Pressure is between
"Cutout +2.60 psig" and
Unloading
"Cutout +1.70 psig"
Suction Pressure Cutout+1.53 psig
0 Hz
Suction Pressure Cutout+1.36 psig
1 Hz
Suction Pressure Cutout+1.19 psig
2 Hz
Suction Pressure Cutout+1.02 psig
3 Hz
Suction Pressure Cutout+0.85 psig
Suction Pressure Cutout+0.68 psig
4 Hz
Suction Pressure Cutout+0.51 psig
5 Hz
Suction Pressure Cutout+0.34 psig
6 Hz
Suction Pressure Cutout+0.17 psig
7 Hz
Suction Pressure Cutout
8 Hz
9 Hz
10 Hz
Suction Pressure is between
"Cutout +2.70 psig" and
"Cutout +1.80 psig"
Suction Pressure Cutout+1.62 psig
Suction Pressure Cutout+1.44 psig
Suction Pressure Cutout+1.26 psig
Suction Pressure Cutout+1.08 psig
Suction Pressure Cutout+0.90 psig
Suction Pressure Cutout+0.72 psig
Suction Pressure Cutout+0.54 psig
Suction Pressure Cutout+0.36 psig
Suction Pressure Cutout+0.18 psig
Suction Pressure Cutout
Sensor failure cutout fault
The Sensor Failure Cutout prevents the system from
running when a critical sensor (transducer, level sen-
sor, or motor winding temp sensor) is not function-
ing properly and reading out of range. This safety is
checked at startup and will prevent the system from
running if one of the sensors has failed.
The sensor failure safety will also fault and shutdown
a system while in operation, if a safety threshold is ex-
ceeded or a sensor reads out of range (high or low).
Following is the Status display fault message.
SYS X YYYYYYYY SENSOR FAILURE:
ZZZZZZZZZZZZ
SECTION 7 - OPERATION
R-134A
Suction pressure
R-513A
Suction pressure
Unloading
0 Hz
1 Hz
2 Hz
3 Hz
4 Hz
5 Hz
6 Hz
7 Hz
8 Hz
9 Hz
10 Hz
7
Unloading
0 Hz
1 Hz
2 Hz
3 Hz
4 Hz
5 Hz
6 Hz
7 Hz
8 Hz
9 Hz
10 Hz
129
Advertisement
Table of Contents
