CEMP-E
TI 811-12
18 August 1998
(a)
Day of week/holiday.
(b)
Time of day.
(c)
Cooling and heating operation.
(d)
Equipment status.
(e)
Cooling and heating building occupancy schedule.
(f)
Space temperature(s).
(g)
Building heat constant (operator adjustable).
(h)
Building cooling constant (operator adjustable).
(i)
OA temperature.
(j)
Required space temperature at occupancy (heating).
(k)
Required space temperature at occupancy (cooling)
(l)
Equipment constraints.
(m) Cooling and heating high-low alarm limits.
(2)
Program outputs
(a)
Start signal.
(b)
Stop signal.
c. Application notes. The optimum start/stop program operates in conjunction with the scheduled
start/stop, demand limiting, and ventilation-recirculation programs.
4. ECONOMIZER PROGRAM. The use of an economizer cycle in air conditioning systems can be a
cost effective conservation measure, depending on climatic conditions and the type of mechanical
system. The economizer cycle utilizes OA to reduce the building's cooling requirements when the OA dry
bulb temperature is less than the required changeover temperature. At optimum conditions, the space
temperature is maintained at setpoint without the addition of mechanical cooling.
a. Changeover Temperature. The changeover temperature is equal to the return air (RA)
temperature minus a fixed differential temperature. The fixed differential shall be determined site-to-site
depending on local weather conditions, to minimize periods when the OA enthalpy would be greater than
the RA enthalpy.
b. Cold Deck Type Systems. For cold deck type systems (such as Reheats, Multizones, Dual
Ducts, and Variable Air Volume systems), the UMCS shall modulate the OA, RA, and relief air dampers
based on the conditions shown in Table 7-1.
7-3
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