Orion System Water Source Heat Pump Module Tulsa - Manual (Page 13)

Technical Guide
Water Source Heat Pump Module
13
Sequence of Operation
Modes of Operation
NOTE: See Unit Confi gurations Chart on page 10 for more
information about compressor staging.
Digital Stage 1 / Digital Stage 2
On units with two Digital Scroll Compressors, the fi rst compressor (A1)
will be designated as Digital Stage 1 and the second compressor (A2)
will be designated as Digital Stage 2.
On units with four Digital Scroll Compressors, there may be instances
where compressor numbers on the module do not correlate with the
mechanical compressors’ numbers. Therefore, Digital Stage 1 refers to
the fi rst set of Digital Scroll Compressors (A1/B1) that will stage on
together and Digital Stage 2 refers to the second set of Digital Scroll
Compressors (A2/B2) that will stage on together. Please refer to AAON’s
wiring diagram for specifi c wiring of the unit.
Compressor Operation (Heat/Cool)
A compressor can energize if the following is true:
1. There is 24 VAC applied to the appropriate Binary Input for
the Compressor.
2. If two compressors are enabled simultaneously, a 5 second
staging delay will occur.
3. Suction Pressure is above the Low Suction Pressure Cooling
(Heating) Setpoint.
4. Proof of Flow for the appropriate water loop is made.
5. Leaving Water Temp is above the Leaving Water Safety
Setpoint (Heating Only).
6. A minimum off time of 3 minutes is met for that compressor.
NOTE: If the WSHP Module receives a signal on the Heat Enable
input, it will operate using the Heating Mode Setpoints.
Cooling Mode
NOTE: Control of digital compressor(s) is only available when
the WSHP Module is connected to the VCM-X WSHP
Controller or SA Controller.
Fixed Compressors Only
When a Cool Signal is received, the WSHP Module will go into Cool-
ing Mode. If this unit has only fi xed compressors, they will sequentially
stage according to Table 1 on page 10, using Stage Up and Stage Down
delays to maintain the Supply Air Setpoint that is broadcast from the
VCM-X WSHP Controller or SA Controller.
Digital Scroll Compressor Control
When a Cool Signal is received, the WSHP Module will go into Cooling
Mode. At this point, Compressor A1 (and B1*) will energize and Digital
Stage 1 Analog Output will modulate as necessary to maintain the Sup-
ply Air Temperature at the Active Supply Air Setpoint that is broadcast
from the VCM-X WSHP Controller or SA Controller.
When Digital Stage 1 reaches 60%, a stage up timer is started and Digital
Stage 1 will continue to modulate up as necessary. If Digital Stage 1
stays above 60% for the stage up timer, Compressor A2 (and B2*) will
energize and both Digital Stage 1 and Digital Stage 2 outputs will go
to ½ of the current position of Digital Stage 1. For example, if Digital
Stage 1 is at 80% when Digital Stage 2 energizes, both systems will go
to 40% and start modulating together.
If both systems are energized and they go below 30% and the Supply Air
is below the Supply Air Setpoint by the Cooling Stage Window value,
the stage down timer is started. If the systems remain below 30% for
the duration of the stage down timer, Digital Stage 2 will deactivate and
Digital Stage 1 will go to 60%. Digital Stage 1 will stage down if it is
at 0% for the duration of the stage down timer.
* If confi gured for 4 modulating compressors.
Heat Pump Heating Mode
Heating Mode works the same as Cooling Mode except the Reversing
Valve is switched and the sequence is opposite. Compressors modulate
up when below the Heating Supply Air Setpoint and modulate down
when above the setpoint.
Dehumidifi cation Mode
Fixed Compressors Only
In the Dehumidifi cation Mode, if this unit has only fi xed compressors,
they will sequentially stage according to Table 1 on page 10 to maintain
the Suction Pressure Setpoint. Compressors A1 & B1 will stage on to-
gether fi rst followed sequentially by A2 & then B2. Stage Up and Stage
Down delays will apply.
Digital Scroll Compressor Control
In Dehumidifi cation Mode, compressors will be controlled to maintain
the Suction Pressure Temperature Setpoint. Digital Stage 1—Compres-
sor A1 (and B1*) will modulate up to 100% before Digital Stage 2—
Compressor A2 (and B2*) can be energized. When Digital Stage 2 is
energized, Digital Stage 1 will be locked at 100%.
* If confi gured for 4 modulating compressors.
Staging Delays
Staging Delays minimum run times and minimum off times are sent
from the VCM-X WSHP Controller or SA Controller.