Trane XL824-Installation-Guide
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Document DEVICE REPORTTrane XL824-Load-valuesInstallation Guide
6. Basic Operation
6.1 PI Control
The 824 Control uses proprietary control schemes to provide comfort and energy efficiency. The Control senses indoor temperature and determines capacity needed based on the following parameters:
· Mode of operation
· Proportional Error - distance from setpoint
· Integral Error - Time away from setpoint
72º
Set Point Temperature
2 Seconds
Integral Error
A
Room Temperature
B
C
D
A = Proportional Error
B + C + D... = Integral Error
6.2 Load Value - Heating
The 824 Control uses proportional plus integral error to determine the amount of capacity required. The calculated capacity is displayed as load value.LoadValue is a numerical representation of the needed capacity to maintain setpoint. The load value range is dependent on the applied system.
0-100 0-200
Single Stage Heat Pump Only Two State Heat Pump Only
0-200 0-300 0-400
Single Stage Heat Pump + 1 Stage Electric/Wet Heat Single Stage Heat Pump + 2 Stage Electric/Wet Heat Single Stage Heat Pump + 3 Stage Electric/Wet Heat
0-300 0-400 0-500
Two Stage Heat Pump + 1 Stage Electric/Wet Heat Two Stage Heat Pump + 2 Stage Electric/Wet Heat Two Stage Heat Pump + 3 Stage Electric/Wet Heat
0-100 0-200 0-300
Single Stage Indoor Heat Only Two Stage Indoor Heat Only Three Stage Indoor Heat Only
0-175 0-275 0-375
Single Stage Heat Pump + 1 Stage Gas/Oil Heat Single Stage Heat Pump + 2 Stage Gas/Oil Heat Single Stage Heat Pump + 2 Stage Gas/Oil Heat
0-275 0-375 0-475
Two Stage Heat Pump + 1 Stage Gas/Oil Heat Two Stage Heat Pump + 2 Stage Gas/Oil Heat Two Stage Heat Pump + 3 Stage Gas/Oil Heat
6.3 Load Value - Cooling
0-100 Single Stage Compressor 0-200 Two-Stage Compressor A Load Value of 50 represents a request of 50% demand for single stage cooling units ("Y") or 50% demand for stage one of multistage cooling units ("Y1"). A Load Value of 150 represents a request of 100% demand for stage one ("Y1") and 50% demand of stage two ("Y2") for multistage cooling units.
6.4 Duty Cycles
Indoor temperature control is achieved by duty cycling the equipment when the load value is less than 100% of the current stage of operation. The duty cycle rate is dependent on the calculated load value. The duty cycle chart below indicates the number of cycles at 50% load (i.e. LV = 50).
6 CPH
2 CPH
1 Hour
As with all PI-based controls the indoor temperature will fluctuate above and below the user selected setpoint to maintain comfort in the space. Adjusting the factory set CPH (Cycles per Hour) can affect how tight the Control operates around the setpoint. The CPH can be adjusted in the Installer Setup>Equipment Settings (2 6 CPH)
· Factory default for compressor operation is 3 CPH
· Factory default for indoor heat is 5 CPH
Effects of changing the cycle rates
Lower CPH results in longer run cycles with less cycling but the indoor temperature may deviate above and below setpoint.
Higher CPH results in tighter indoor temperature control but shorter, more frequent cycles.
6.5 Overshoot Clamp
The 824 Control will enforce an "off cycle" anytime the control overshoots more than 2.5°F. Once the indoor temperature is within 0.75°F of setpoint an "on cycle" is allowed dependent on load value and minimum off times.
Cooling Overshoot Clamping Example
75º
Actual Temperature
74.25º
72.5º OFF Cycle Enforced ON Cycle Allowed
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6.6 Stage Thresholds
The threshold to allow operation is a Load Value greater than 5 and operation is always terminated with a Load Value less than 1.
Load Value also determines when additional stages of operation are requested. To prevent rapid cycling between stages, a stage threshold is enforced. The stage threshold is dependent on the applied system.
COMPRESSOR STAGING THRESHOLDS
STAGE 2
STAGE 3
STAGE 1
100-110 Y1 to Y2
100-115
HP to W1
100-125
HP to Dual Fuel
LV=200
LV=100
STAGE 5
STAGE 1
LV=400
AUX ELECTRIC HEAT - STAGING THRESHOLDS
STAGE 2
STAGE 3
STAGE 4
100115
Compressor
to
W1
200215
W1
to
W2
300315
W2
to
W3
LV=200 LV=300
LV=100
AUX FOSSIL HEAT - STAGING THRESHOLDS
STAGE 2
STAGE 3
100- Inhibit - Compressor to W1 125
175190
W1
to
W2
W2 to W3
175190
STAGE 4
STAGE 1
LV=300
LV=200
LV=100
STAGE 4
STAGE 1
AUX WET HEAT - STAGING THRESHOLDS
STAGE 2
STAGE 3
100- Compressor to W1 125
200215
W1
to
W2
824 Programmable Wi-Fi Comfort Control
6.7 Stage Inhibits
When the stage threshold is exceeded, a stage inhibit is applied. The stage inhibit calculates the rate of recovery over a 10-minute period and determines if the next stage is required to meet the current demand. If the rate of recovery is great enough, a new 10-minute inhibit is enabled. The Control will not go to the next stage of operation until it determines that the current stage cannot satisfy the current demand. Stage inhibits only apply between compressor stages and compressor heat to indoor heat. Stage inhibits do not apply to indoor heat stages.
Stage inhibits can be disabled in the 824 Control Installer Setup>Comfort Settings.
Stage Inhibits - Compressor Staging
Y1 "ON"
Y2 "ON"
Y1 "ON"
LV = 110
LV = 100
START INHIBIT
10 Minutes
LOAD VALUE (LV)
Stage Inhibits - Compressor to Aux Heat
Y1 "ON"
W1 "ON"
W1 "OFF"
LV = 115
LV = 100
START INHIBIT
10 Minutes
LOAD VALUE (LV)
Stage Inhibits - Duel Fuel
Y1 "ON"
W1 "ON"
LV = 125
Y1 "ON" 45 Second Cool Down
LV = 100
START INHIBIT 10 Minutes
LOAD VALUE (LV)
LV=300
LV=200
LV=100
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