Trane US Inc. CONT8241 ユーザーズマニュアル

 

824 Programmable Comfort Control

18-HD72D1-1  

page 29

6.  Basic Operation

6.1  PI Control

The 824 Control uses Trane’s proprietary control schemes 
to provide both comfort and energy efficiency. The Control 
samples the indoor temperature every five seconds and 
determines the capacity needed based on the following 
parameters:

•

Mode of operation

•

Proportional Error - distance from set point

•

Integral Error - Time away from set point

6.2  Load Value

The 824 uses Proportional Error plus Integral Error to 
determine the amount of capacity required. The calculated 
capacity is displayed as Load Value. Load Value is a 
numerical representation of the needed capacity to maintain 
the desired set point. The Load Value range is dependent 
on the applied system.

6.3  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).

As with all PI-based controls the indoor temperature will 
fluctuate above and below the user selected set point to 
maintain comfort in the space. Adjusting the factory set 
CPH (Cycles per Hour) can affect how tight the control 
operates around the set point. The CPH can be adjusted 
in the Installer Settings>Advanced>Equipment (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 
set point.

Higher CPH results in highter indoor temperature control 
but shorter, more frequent cycles.

6.4  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 .75°F of set point an “on cycle” is 
allowed dependent on load value and minimum off times. 

Show illustration…

6.5  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.