Reznor CAUA Unit Installation Manual - Manual (Page 29)

Form I-CAUA, P/N 164771 R8, Page 29
6.4.2 Discharge,
Plenum, Option CD
(Sizes 350 and 400
only)
The optional discharge plenum is designed to be used with a screened mounting base
(Paragraph 6.3.3) to create a "packaged stand-alone" upflow system that circulates
building air. However, the discharge plenum may also be used in place of ductwork in
applications that do not have an optional mounting base.
The discharge plenum is available in three types. Option CD60 and CD61 are for a
heater without a cooling coil; Option CD60 is designed for an open area and Option
CD61 includes field-installed blockoff plates to block off one or two sides. Option CD62
can only be ordered with a cooling coil and includes blockoff plates to provide higher
velocity required for cooling.
smoke or reflected light may be observed inside the casing to indicate the pres-
ence of leaks in the heat exchanger. The covers for the openings must be attached
in such a manner as to prevent leakage.
6.4.3 Ductstat
Installation - Two-
Stage, Makeup Air,
Option AG3
Two-stage makeup air units are equipped with a two-stage
gas valve, but instead of control from a two-stage room ther-
mostat, the outlet air temperature is monitored and controlled
by a two-stage ductstat. ( NOTE: This option is available only
when the heater is equipped with makeup air Option AD4.)
The ductstat is factory mounted in the control compartment
of the heater and has a capillary that must be field installed.
To complete the installation, uncoil the tubing, extend the
capillary, and mount it in the ductwork. Follow the instruc-
tions provided by the ductstat manufacturer.
The ductstat is set to 70°F and has an adjustable range with
a fixed differential of 2-1/2°F. Due to different CFM settings and outside air tempera-
tures, the average downstream outlet temperature may not match the ductstat setting
exactly. After the installation is complete, adjust the setpoint of the ductstat to achieve
the desired average outlet air temperature.
FIGURE 23 - Ductstat
with Capillary Tubing in
Option AG3
6.5 Blower, Motor,
and Drive
Model CAUA units are equipped with either direct drive motor(s) and blower(s) or
adjustable belt-drive blower(s) and motor.
Direct Drive - All direct drive blower motors are 1 horsepower. Sizes 150-200 have
a single motor. Size 150 has a 12-9 blower; Size 200 has a 12-12 blower. Sizes 250-
400 have dual motors with dual 12-9 blowers.
Belt Drive - The motor horsepower on a belt drive unit is whatever was specified on
the order ranging in size from 1/3 HP to 5 HP. Check the heater rating plate and the
motor rating plate.
As part of the startup procedure, check belt tension. Proper belt tension is important
to the long life of the belt and motor. A loose belt will cause wear and slippage. Too
much tension will cause excessive motor and blower bearing wear. Adjust the belt ten-
sion by turning the adjusting screw on the motor base until the belt can be depressed
3/4". (See FIGURE 24.) After correct tension is achieved, re-tighten the locknut on the
adjustment screw. Be sure that the belt is aligned in the pulleys.
Most blower motors are equipped with thermal overload protection of the automatic,
reset type. If the motor is not equipped with thermal overload protection, the unit will be
equipped with a starter. The adjustable setting on the starter will be factory set to match
the amp draw of the motor and sealed. No change should be made to the starter set-
ting unless the original motor is replaced. Starters are equipped with a manual reset. If
an overload condition is experienced, the condition must be corrected and the starter
must be manually reset.
3/4”
(19mm)
FIGURE 24 - Check Belt
Tension
Adjusting Blower
Speed
The blower speed may be adjusted to achieve the desired outlet temperature, as long
as the adjustment is within the temperature rise and the static pressure limits shown
on the heater rating plate. Direct drive motors are factory set at medium speed for
heating and high speed for optional cooling (if ordered). Belt drive motors are factory
set between maximum and minimum blower speeds. Belt drives may also be ordered
with an optional variable frequency drive that changes motor speed by changing the
electrical frequency to the motor.