Demand Limit Control, Option — (Requires Optional 8-Input Module)
The demand lim it may be exte rnally control led with a 4 to 20 mA signa l from an ene rgy
management system (EMS). The option is set up o n the Config table. When enabled, the
control is set for 100% dema nd with 4 mA and an operator c on figured minimum dema nd set
point at 20 mA.
The Demand Reset input from an energy management system is hardwired into the number
one, 8-input mod ule. The sig nal may be int ernally powered by the module or external ly
powered. If the sign al is externally power ed, the signal is wir ed to terminals J1-1( +) and J1-2(–).
If the signal is internal ly powered, the signal is wired to terminals J1-3 (+) and J1-2(–). Whe n
enabled, the control is s et for 100% demand with 4 mA and an operator configur ed minimum
demand set point at 20 mA.
Surge Prevention Algorithm
This is an opera tor configurable feature which can determine i f lift conditio ns are too hig h for
the compressor and the n ta ke corrective action. Lift is defined as the dif f erence between the
pressure at the impeller ey e and the impeller disch arge. The maximum lift that a particular
impeller wheel can per fo rm varies with the gas fl ow ac r o ss the impeller, and the size of the
wheel.
The algorithm first det ermines if correctiv e ac t ion is necessary. This is do ne by checking 2
sets of operator configured data points, which are the MINIMUM and the MAXIMUM Load