Step 3 - Make Duct Connections; Step 4 - Frame And Finish Unit; Concealed Unit Enclosure; Exposed Unit Finish, Touch-Up And Repaint - Carrier 42S Series Instruction Manual

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 sig-
nal 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 volt-
ages for heaters or controls are specified, wiring may differ from
that shown. Refer to wiring diagram on unit blower housing for
unit specific wiring.
Thermostatic Valve Control, 4-Pipe
The 4-pipe system provides the ultimate in economy and room
temperature control. Both hot water and chilled water are avail-
able at any time.
Normally an automatic changeover thermostat is used, but a man-
ual changeover thermostat is also suitable. Two 2-way valves, two
3-way valves, or one 2-way plus one 3-way valve must be select-
ed. 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 before thermo-
stat can send signal to open the chilled water or hot water valve.
NOTE: Wiring diagrams are for typical applications. If other volt-
ages for heaters or controls are specified, wiring may differ from
that shown. Refer to wiring diagram on unit blower housing for
unit specific wiring.
Step 3 — 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 lim-
its 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 protection may
be any of several methods, such as a low temperature thermostat
to close the outside air damper or a preheat coil to temper the out-
side air before it reaches the unit. It should be noted that none of
these methods will adequately protect the coil in the event of pow-
er failure. The safest method of freeze protection is to use glycol in
the proper percent solution for the coldest expected air tempera-
ture.
Insulate ductwork as required. Use flexible connections to mini-
mize duct-to-unit alignment problems and noise transmission
where specified.
The manufacturer assumes no responsibility for undesirable sys-
tem operation due to improper system design, equipment or com-
ponent selection, and/or installation of ductwork, grilles, and other
related components.
CAUTION
Prevent dust and debris from settling in unit. If wall finish or
color is to be spray-applied, cover all openings to prevent
spray from entering unit. Failure to do so could result in dam-
age to the unit and/or the reduction of unit efficiency.
Step 4 — Frame and Finish Unit
Models 42SG, SH, SJ, SU and SM have factory enclosures and
may be finished with normally accepted wall covering. However,
drywall secured with adhesive bonding alone is NOT
recommended.

CONCEALED UNIT ENCLOSURE

Concealed units are designed to have gypsum board or other types
of wall board applied directly to the unit cabinet surface to a maxi-
mum combined thickness of 5/8 in. Use low-profile sheet metal
panhead screws to secure wallboard to unit frame. Fasteners may
penetrate the cabinet no more than 1/2 in.
These fasteners must be located to avoid damage to internal com-
ponents and wiring in the same manner as anchoring fasteners. Do
not apply sheet metal screw or nails where they can penetrate coil,
riser pipes, or electrical junction box and raceways.
Do not secure wallboard to drain pan edges or to control box en-
closure. Condensate leaks or electrical shorts may result.
An alternate method of enclosing the unit is to frame one or more
sides with studding and apply the wall board to this framing. This
method requires specific unit features and return access panels
when used on the return-air side of a unit. Units not properly
equipped will exhibit poor cooling and/or heating performance
and could experience excessive or premature component failures.
Prevent sheetrock dust or other debris from settling on coil fins,
motor-blower assembly or other unit interior surfaces.

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.
Proper safety procedures should be followed regarding venti-
lation and safety equipment during touch-up and repainting
since materials may pose a health hazard. The manufacturer's
directions should be followed for the products being used.
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 "Pas-
ceo." These items should be available at most paint product stores.
It should be noted that the more conscientiously 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 between two compo-
nents, 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 5 — 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.
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CAUTION