Trane IntelliPak CG-SVX02B-EN Installation & Operation Manual page 6

Lead/Lag (Standard)
When Lead-Lag is enabled, for each capacity add request,
the CGM will begin sequencing the compressors "On" that
have:
a. the least number of starts; or,
b. the least run time (if number of starts are equal)
At each capacity subtract request, the CGM will begin se-
quencing the compressors "Off" that have:
a. the most run time; or,
b. the least number of starts (if more than one
compressor has the same run time)
If a compressor is locked out for any reason when a capac-
ity add request occurs, the next available compressor which
meets the specified criteria will be started.
If a compressor can not be turned "Off" due to the minimum
"On Time", the next compressor which meets the specified
criteria will be turned "Off".
On dual circuit units, as the first two capacity add requests
are initiated, one compressor on each circuit will start be-
fore any additional compressors on any circuit is started.
When staging down from three compressor stages to two
compressor stages, the CGM will turn the compressors
"Off" on the circuit that has the most compressors operat-
ing.
With Lead/Lag enabled, HGBP operation (if applicable) will
be bypassed and the system will go directly into pumpdown
when the last subtract command is initiated.
When the UCM is powered up (after a power loss), or any
time the compressor's start time and run time are equal, the
lead compressor for single circuit units (20 through 30
Tons), will be the first "On" and the lag compressor will be
the first "Off". For dual circuit units (40 through 60 Tons), the
"On" sequence will be A-C-B-D and the "Off" sequence will
be D-B-C-A.
Loss of Charge/Flow (Refrigerant) Control
Is accomplished by Loss of Charge Cutout (LCC)
switch(es), located on the suction line(s) near the scroll
compressor(s). The LCC are connected to the SCM or
MCM Low Pressure Cutout (LPC) binary input.
The LCC contacts are designed to open if the suction pres-
sure approaches 7 ± 4 psig. If the LCC opens after a com-
pressor has started, all compressors operating on that cir-
cuit will be turned off immediately and will remain off for a
minimum of three minutes.
The LCC contacts are designed to close when the suction
pressure exceeds 22 ± 4 psig. If the LCC is open when a
compressor is requested to start, none of the compressors
on that circuit will be allowed to operate. They are locked
out and a manual reset diagnostic is initiated. If the LCC
opens four consecutive times, during the initial three min-
utes of compressor operation on a circuit, the compressors
Condenser Fan Output Control (MCM relays and fan motor contactors)
Unit
Tonnage Circuit
20 1
25 1
30 1
40 1
2
50 1
2
60 1
2
* Output under the Low Ambient Damper, if installed.
Output A
MCM Fan
Relay Contactor
K1 1K8
K1 1K8
K1 1K8
K1 1K8
K5 1K10
K1 1K8
K5 1K10
K1 1K8
K5 1K10
General Information
on that circuit will be locked out and a manual reset diag-
nostic is initiated.
Evaporator Freeze Protection
Is accomplished by Freeze Protection Cutout (FPC)
switch(es), located on the suction line(s) near the scroll
compressor(s).
The FPC are connected to the SCM or MCM Low Pressure
Cutout (LPC) binary input, in series with the LCC
switch(es.) The FPC switch is used to prevent the refriger-
ant from becoming cold enough to cause the chilled solu-
tion in the Evaporator to freeze. This pressure switch is typi-
cally set to trip at a higher refrigerant pressure, typically 20
to 45 PSIG depending on the selected leaving water
setpoint range of the unit.
If the FPC opens after a compressor has started, all com-
pressors operating on that circuit will be turned off immedi-
ately and will remain off for a minimum of three minutes.
If the FPC is open when a compressor is requested to start,
none of the compressors on that circuit will be allowed to
operate. They are locked out and a manual reset diagnostic
is initiated.
If the FPC opens four consecutive times, during the initial
three minutes of compressor operation on a circuit, the
compressors on that circuit will be locked out and a manual
reset diagnostic is initiated.
Saturated Condenser Temperature Sensors (Standard)
Are analog input devices mounted inside a temperature well
located on a condenser tube bend. They monitor the satu-
rated refrigerant temperature inside the condenser coil and
are connected to the compressor module (MCM). As the
saturated refrigerant temperature varies due to operating
conditions, the condenser fans are cycled "On" or "Off" as
required to maintain acceptable operating pressures.
Head Pressure Control (Standard)
Is generally achieved by staging condenser fans on on if
the Saturated Condensing Temperature (SCT) rises above
the Saturated Condensing Temperature Control Band Up-
per Limit (SCTUL) and staged off if the SCT falls below the
Saturated Condensing Temperature Control Band Low Limit
(SCTLL), in an effort to maintain the SCT within this fixed
temperature range.
For 20 and 40 ton units, two outputs (A and C) per circuit
are controlled. For 25, 30, 50 and 60 ton units, three out-
puts (A, B and C) per circuit are controlled. Each output
controls a condenser fan motor contactor. Output C will en-
ergize on initial call for fan staging, and will remain ener-
gized as long as a compressor on that circuit is on. The
third condenser fan motor associated with Output C will be
located under the low ambient damper, if that option is in-
stalled.
Output B
MCM Fan
Relay Contactor
na na
K2 1K12
K2 1K12
na na
na na
K2 1K12
K6 1K13
K2 1K12
K6 1K13
6
Output C*
MCM Fan
Relay Contactor
K7 1K7
K7 1K7
K7 1K7
K7 1K7
K8 1K9
K7 1K7
K8 1K9
K7 1K7
K8 1K9
No. of
Stages
2
3
4
2
2
3
3
3
3