Unit Section Start-Up Checklist - Johnson Controls VPC Installation, Operation & Maintenance Instructions Manual

20. SEQUENCE OF OPERATION ON
COOLING CYCLE – VPP UNITS ONLY
1. Room thermostat calls for cooling, connecting R
to y and O terminals (Reversing valve energized
only in cooling).
2. The compressor and outdoor fan start immediately
on a call for cooling. air circulating fan also starts
immediately with cooling operation.
3. When the room thermostat is satisfied, terminals
y and O on the thermostat are de-energized.
4. The compressor, outdoor fan and indoor fan stop
immediately when the thermostat is satisfied. The
reversing valve returns to the default position.
5. a compressor restart delay timer is activated at
the end of each cooling cycle. a minimum delay
time of 3 minutes is required to ensure that system
pressures have equalized before a compressor
restart.
21. SEQUENCE OF OPERATION ON HEATING
CYCLE – VPP UNITS ONLY
A. OUTDOOR AMBIENT ABOVE 40ºF
1. Room thermostat calls for heat, connecting R and
y terminals (O terminal de-energized).
2. The compressor and outdoor fan start immediately
on a call for heating. air circulating fan also starts
immediately with heating operation.
3. When the room thermostat is satisfied, terminal Y
on the thermostat is de-energized.
4. The compressor, outdoor fan and indoor fan stop
immediately when the thermostat is satisfied.
5. a compressor restart delay timer is activated at
the end of each cooling cycle. a minimum delay
time of 3 minutes is required to ensure that system
pressures have equalized before a compressor
restart.
B. OUTDOOR AMBIENT BELOW 40ºF
1. Room thermostat calls for heat, connecting R and
y terminals (O terminal de-energized).
2. The normally closed contacts of the Low ambient
relay (R2) route the thermostat signal through R3
to energize the electric element switching sequenc-
ers.
16
The heat/cool interlock relay (R3) pre-
vents the electric heat from being en-
ergized through terminal Y of a single-
stage heat pump thermostat.
3. On 2kW through 5kW models the electrical heater
is energized between 1-24 seconds after time
delay is energized. Indoor fan is interlocked simul-
taneously with heating element operation.
4. On a unit with two heating elements (6kW, 8kW,
or 10 kW), the 2nd element will be energized
approximately 90 seconds after the first stage is
energized.
5. When the room thermostat is satisfied, terminals R
and y on the thermostat open, de-energizing the
1S/2S sequencer relays.
6. The bank of heating elements will be disconnected
in descending order, the indoor fan will continue
to run until the elements are de-energized.

22. UNIT SECTION START-UP CHECKLIST

Before starting unit for the first time, be sure you
can answer "yes" to each of these questions:
1. Is the unit level?
2. Have you cleared away all loose construction and
insulation materials?
3. Is unit installed within proper clearances to com-
bustible materials?
4. Does electrical wiring follow current National Elec-
trical Code aNSI 70 or CSa C22.1 as well as local
codes?
5. Is unit electrically grounded?
6. Is room thermostat properly installed?
7. Is duct work system correctly sized and sealed?
8. Are air filters in place and correctly sized?
FORM 145.20-IOM1 (908)
JOHNSON CONTROLS