Orion System Water Source Heat Pump Module - 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 7 for more
information about compressor staging.
Compressor Operation (Heating and Cooling)
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 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 an off signal on the Cool
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.
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 7, using Stage Up and Stage Down
delays to maintain the Supply Air Setpoint that is broadcast from the
VCM-X WSHP Controller.
Digital Scroll Compressor Control
When a Cool Signal is received, the WSHP Module will go into Cool-
ing Mode. At this point, Compressor A1 will energize and modulate as
necessary to maintain the Supply Air Temperature at the Active Supply
Air Setpoint that is broadcast from the VCM-X Modular Controller.
When Compressor A1 reaches 60%, a stage up timer is started and will
continue to modulate up as necessary. If Compressor A1 stays above
60% for the stage up timer, Compressor B1 will energize and both
compressors will go to ½ of the current position of Compressor A1. For
example, if Compressor A1 is at 80% when Compressor B1 energizes,
both compressors will go to 40% and start modulating together.
If there are additional fi xed compressor stages and modulating Com-
pressors A1 and B1 have modulated together up to 100%, then after
a stage up delay, fi xed Compressor A2 will stage on while A1/B1 are
allowed to modulate. If A1/B1 again modulate up to 100%, then after
a stage up delay, fi xed compressor B2 will stage on while A1/B1 are
allowed to modulate.
Staging down will happen in the reverse order as just described if the
Supply Air Temperature falls below the Supply Air Temperature Set-
point by the Cooling Stage Window value and the stage down timer
has elapsed. After the fi xed compressors have staged off, or if there are
no fi xed compressors then the staging down of the digital compressors
A1 and B1 will continue as follows. If Compressors A1/B1 modulate
together down to 30% and the stage down timer elapses, Compressor B1
will deactivate and Compressors A1 will go to 60%. Compressors A1
will stage down if it is at 0% for the duration of the stage down timer.
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 7 to maintain
the Suction Pressure Setpoint. Stage Up and Stage Down delays will
apply.
Digital Scroll Compressor Control
In Dehumidifi cation Mode, the compressor(s) will modulate to maintain
the Suction Pressure Temperature Setpoint broadcast from the VCM-X
WSHP Controller. If there are two compressors, Compressor A1 will
modulate up to 100% before Compressor B1 can be energized. If Com-
pressor B1 is energized, Compressor A1 will be locked at 100%.
If there are additional fi xed compressor stages and Compressor B1 has
modulated up to 100%, then after a stage up delay, fi xed Compressor A2
will stage on while B1 is allowed to modulate. If B1 again modulates
up to 100%, then after a stage up delay, fi xed compressor B2 will stage
on while B1 is allowed to modulate.
Stage down will again be the reverse as just described with Compressor
A1 being the last compressor to stage off.
Staging Delays
Staging Delays minimum run times and minimum off times are sent
from the VCM-X WSHP Controller.