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In winter the system is switched over to hot water. Two
changeover devices are required for this. One device switches
the action of the thermostat and the other locks out the electric
heat when hot water is in the coil.
With this system, the fan runs continuously unless manually
switched to OFF or AUTO position. Fan must be on before
thermostat can send signal to open chilled water valve or turn
on electric heater.
Two control methods are available:
1. Use the standard automatic changeover thermostat with a
dead band between heating and cooling.
2. Use a manual changeover thermostat. With this method
only one changeover is required.
Be sure to include a 2-way or 3-way electric valve with this
system.
NOTE: Wiring diagrams are for typical applications. If other
voltages for heaters or controls are specified, wiring may differ
from that shown. Refer to wiring diagram on unit blower hous-
ing for unit specific wiring.
Thermostat 2-Pipe Total Electric Heat with Valve Control
— With this system, the complete heating requirement for the
space is provided by the electric heater; the water system is
never changed over for heating. It is therefore possible, just as
with 4-pipe systems, to have heating or cooling at any time of
the year.
The fan runs continuously unless it is manually switched to
OFF or AUTO position. Fan must be on before thermostat can
send signal to open chilled water valve or turn on electric
heater.
Normally, an automatic changeover thermostat with a dead
band between heating and cooling is used, but a manual
changeover thermostat is also suitable. A 2-way or 3-way valve
must also be used so that the chilled water is off whenever the
heater is on. No changeover device to sense water temperature
is necessary.
NOTE: Wiring diagrams are for typical applications. If other
voltages for heaters or controls are specified, wiring may differ
from that shown. Refer to wiring diagram on unit blower hous-
ing for unit specific wiring.
Thermostatic Valve Control, 4-Pipe — The 4-pipe system
provides the ultimate in economy and room temperature con-
trol. Both hot water and chilled water are available at any time.
Normally an automatic changeover thermostat is used, but a
manual changeover thermostat is also suitable. Two 2-way
valves, two 3-way valves, or one 2-way plus one 3-way valve
must be selected. An automatic changeover device to sense
water temperature is not required.
With this system, the fan runs continuously unless it is
manually switched to OFF/AUTO position. Fan must be on be-
fore thermostat can send signal to open the chilled water or hot
water valve.
NOTE: Wiring diagrams are for typical applications. If other
voltages for heaters or controls are specified, wiring may differ
from that shown. Refer to wiring diagram on unit blower hous-
ing for unit specific wiring.
Step 4 — Make Duct Connections —
Install all
ductwork to and from unit in accordance with project plans,
specifications, and all applicable codes. Duct construction must
allow unit to operate within duct external static pressure limits
as shown on job submittals. Units designed to operate with
ductwork may be damaged if operated without intended
ductwork attached.
Units provided with outside air should have some method
of low-temperature protection to prevent freeze-up. This pro-
tection may be any of several methods, such as a low tempera-
ture thermostat to close the outside air damper or a preheat coil
to temper the outside air before it reaches the unit. It should be
noted that none of these methods will adequately protect the
coil in the event of power failure. The safest method of freeze
protection is to use glycol in the proper percent solution for the
coldest expected air temperature.
Insulate ductwork as required. Use flexible connections to
minimize duct-to-unit alignment problems and noise transmis-
sion where specified.
Set unit markings for minimum clearance to combustible
materials and first 3 ft of ductwork. Install ductwork, accessory
grilles and plenums so that they do not restrict access to filter.
The manufacturer assumes no responsibility for undesirable
system operation due to improper system design, equipment or
component selection, and/or installation of ductwork, grilles,
and other related components.
Step 5 — Frame and Finish Unit
EXPOSED UNIT FINISH, TOUCH-UP AND
REPAINT — Return access and exposed cabinet units may be
furnished with a baked enamel finish. Small scratches in this
finish may be repaired with touch-up paint available from the
factory. Some colors of touch-up paint are available in aerosol
containers and all touch-up paint is available in pint, quart, and
gallon cans.
To repaint the factory-baked enamel, the finish should be
prepared by light sanding with no. 280 grit sand paper or
no. 000 or no. 0000 fine steel wool. The surface may also be
wiped with a liquid surface etch cleaning product such as “No
Sand” or “Pasceo.” These items should be available at most
paint product stores. It should be noted that the more conscien-
tiously this preparation is done, the more effective it will be.
After this preparation is accomplished, the factory finish
should provide excellent adhesion for a variety of air-dried top
coats. Enamel will give a more durable, higher gloss finish,
while latex will not adhere as well and will give a dull, softer
finish. Top coats involving an exothermic chemical process be-
tween two components, such as epoxies and urethanes, should
be avoided.
Factory aerosol touch-up paint may require a number of
light “dust coats” to isolate the factory-baked enamel finish
from the quick drying touch-up paint.
Step 6 — Cut Out Openings for Grilles and
Thermostats —
On all units with optional supply-air or
return-air grilles, dampers, thermostats, and switch plates, cut
out openings where specified on the job plans. Be careful not to
cut wires, piping or structural supports.
For remote-mounted thermostats use a steel thermostat
shield ring to protect drywall from thermostat wiring where
applicable.
CAUTION
Prevent dust and debris from settling in unit
. If wall finish
or color is to be spray applied,
cover all openings to pre-
vent spray from entering unit.
Failure to do so could result
in damage to the unit and/or the reduction of unit
efficiency.
CAUTION
Proper safety procedures should be followed regarding
ventilation and safety equipment during touch-up and
repainting since materials may pose a health hazard. The
manufacturer's directions should be followed for the prod-
ucts being used.