Double sloped stainless steel drain pan
The unit is offered with a standard stainless steel
drain pan that meets ASHRAE 62 requirements for
condensate drainage removal, thus improving IAQ.
An intermediate drain pan is offered on 40 ton to 80
ton units that has drip tubes to guide condensate to
the main drain pan.
To monitor condensate accumulation and notify
the customer of a possible overflow concern, a
condensate overflow switch option is provided for
all units.
Heating section
Gas heat
For gas heat, the gas utilizes an induced-draft gas
furnace designed for high efficiency and reliability.
The furnace uses an aluminized steel tubular
heat exchanger and operates at temperatures
sufficient to prevent acidic exhaust gases from
condensing in the heat exchanger at low fire rates,
unlike drum and tube style furnaces that generate
condensation formation. An optional stainless steel
heat exchanger is also available.
Fully modulating gas heat and greater steps of
capacity control offer superior design performance
while maintaining optimum occupant comfort. The
gas heat option allows up to 50:1 turndown for
modulating gas furnace and up to six stages for
staged heating control. Refer to the gas furnace
section in Table 1.
Electric heat
Electric heat is available either with staged or
modulating (silicon controlled rectifier (SCR)) control
from 50 kW up to 160 kW, applicable to 25 ton to 50
ton.
Depending on the size of the heat required, the
unit can have multiple steps of control helping
to provide tighter control of the supply and zone
conditioned air. With the utilization of this multi-
step function, the unit can effectively reduce energy
consumption by bringing on smaller stages of heat
while maintaining the maximum level of comfort.
Hydronic heat
The unit has a hydronic low or high heat option. The
unit ships to the site with a completed coil, including
headers and connections that are tested to ensure
leak-free operation.
Customers can opt to have valves shipped with
the unit. For ease of installation, the unit has hole
markings for the field to drill holes either through
the base or side of the unit.
Air management
Fans
High efficiency fans are used to improve application
flexibility and address sound and application
concerns. The fan section is equipped with a single
width, single inlet (SWSI) airfoil plenum wheel on 25
ton to 50 ton and dual SWSI airfoil plenum wheels
on 60 ton to 80 ton as a standard feature. Plenum
fans are direct drive. An exhaust fan is provided with
a double width, double inlet (DWDI) forward curved
centrifugal type fan, while the return fan has a SWSI
airfoil plenum wheel on 25 ton to 50 ton. On 60 ton
to 80 ton units with return fan, a SWSI airfoil direct
driven plenum wheel is available.
Premium efficiency motors
Premium efficiency motors are available for
optimum energy efficiency. All motors used on
the rooftop air conditioner meet U.S. EPACT 1992
minimum requirements. High efficiency motors
are standard. Motors are available in ODP or totally
enclosed fan-cooled (TEFC) construction.
Building pressure control
Return fan, exhaust fan, and barometric relief
damper are available to meet building pressure
control requirements. Fan tracking is offered as
an option with supply and return fan airflows. The
return fan capacity can be controlled to maintain
a constant difference between supply and return
airflow. A fan bypass option is provided on return
(25 ton to 50 ton) and exhaust (25 ton to 80 ton)
fans that enables the fan to continue operation, in
case of failure in the primary drive. A redundant
VFD option is available for DDP return fan (60 ton to
80 ton), to ensure continuous operation. Extended
grease lines are an option for return/exhaust fan
shaft bearings to simplify bearing lubrication.
Variable frequency drives
The unit is provided with a standard VFD for all
supply and return fan applications. An exhaust fan
with VFD is available as an option. The VFD can
optimize system performance by modulating the
fan motor speed to reduce energy consumption and
provide precise airflow control.
WARNING
Never operate the unit without a VFD controlling the
DDP supply and return fan. Bypassing the VFD will
cause a catastrophic failure of the DDP supply and
return fan.
Tempmaster
®
Omni™ Premier 25 Ton to 80 Ton Rooftop Units Installation and Maintenance Guide
17
Tempmaster
