Specifications

GUIDE SPECIFICATIONS 7-46 kW DX units

for ﬁ eld installation and shall include sump, motor, and automatic control. The pumps shall be rated for 130 GPH @ 20 foot

maximum head (40 GPH @ 20 feet with check valve).

H. Tandem Scroll Compressors - Provide units with tandem hermetic scroll compressors with two-step modulation for stage

control. Each circuit shall contain two scroll compressors. Modulation shall allow one or both compressors (per circuit) to run

depending upon the load of the system, resulting in part-load efﬁ ciency equal to full load efﬁ ciency.

I. Hot Gas Bypass -Units shall be provided with hot gas bypass. The hot gas bypass valve shall be installed between the com-

pressor discharge line and the leaving side of the expansion valve through a side outlet distributor. The system with the evapora-

tor under full load shall maintain pressure on the leaving side of the hot gas bypass valve to keep the valve port closed. Should

the load on the evaporator decrease to the point where the coil is below the desired setting, the pressure on the discharge of the hot

gas bypass shall put pressure on the diaphragm overcoming the spring pressure of the seat allowing some hot gas to mix with the

normal liquid discharge of the expansion valve raising the evaporator pressure.

J. 3-Way Water Regulating Valves - Units shall be provided with a 3-way head pressure actuated regulating valve. The maximum

water pressure shall be ___ psi.

K. High Efﬁ ciency Filters - The environmental control unit shall include ﬁ lters with ___ MERV rating.. The ﬁ lters shall be four-

inch (4”) deep pleated design.

L. Pre-Filters - The environmental control unit shall have one-inch (1”) pre-ﬁ lters in addition to the unit ﬁ lters.

M. Upﬂ ow Plenum - Units with top (upﬂ ow) discharge shall be provided with plenum. The plenum shall have a front discharge

air grille and be fully insulated with one inch (1”) thick, 11/2-pound density ﬁ berglass insulation coated with neoprene. The ple-

num height shall be 18 inches and shall be painted to match the unit color.

N. Floorstand - Units shall be provided with ﬂ oorstands and vibration isolation pads. The ﬂ oorstand shall be a complete welded

base engineered to support the operating unit. The ﬂ oorstand height shall be ___ inches and adjustable ± 2 inches.

O. Pump Package - A centrifugal pump shall be provided to circulate water or glycol solution. The pump shall be rated for ____

GPM @ ___ feet of head and shall operate on ___ volts.

P. Pump Auto-Changeover - Dual pump packages shall be provided with a pump auto-changeover control and NEMA 4 ﬂ ow

switch. The pump auto-changeover control shall be factory wired and mounted in the dry cooler control box. The pump auto-

changeover control shall provide automatic pump changeover in the event of a pump failure. Upon pump changeover, an audible

alarm shall sound at the indoor unit and a message (“STANDBY PUMP ON”) shall be displayed on the indoor unit microproces-

sor. The NEMA 4 ﬂ ow switch shall be ﬁ eld installed.

Q. Pump Enclosure - A pump enclosure shall be provided for the centrifugal pumps(s). The enclosure shall be vented and

weather resistant. Pumps shall be factory mounted in enclosure ready for ﬁ eld piping and wiring.

R. Automatic Lead/Lag Panel - Unit shall be furnished with an automatic lead/lag control panel. Panel shall be capable of

controlling a minimum of four units. Upon occurrence of an alarm on one of the primary units the panel shall automatically shut

down the primary unit and start standby unit(s) as required. In addition the panel shall rotate the primary and standby units after a

user programmable number of hours to insure reliable operation and equalize run hours on all units

S. Zone Master Teamwork Operation - Each unit shall be furnished with capability to function as the zone master and control the

operating mode of up to 32 units located in the same zone. Capabilities shall include:

• Unit lead/lag and standby rotation with an 8 hrs to seven days schedule

• Unit auto changeover by selectable standby or off (critical) alarms

• Standby unit activation by average zone temperature

• Zone functions inhibit preventing units from conﬂ icting operation

• Secondary operating schedule for an economical control solution

• Programmable unit’s status control (On/Off/Standby)