20
Step 9 — Install Piping
HOT WATER PIPING
Recommendations for Water Coils — See Fig. 19.
1. Piping should be in accordance with accepted industry
standards and all components rated for the system
pressure expected. The 50XCW coils are rated for
maximum of 400 psig DWP (Design Working Pres-
sure).
2. Coils should be piped such that they will drain. A drain
and vent are provided.
3. Water coils should not be subjected to entering air tem-
peratures below 38°F to prevent coil freeze up. If tem-
peratures over the coil are below this, glycol or brine
solution should be used. Use a solution with the lowest
concentration that meets the coldest air expected. Excess
concentration will greatly reduce coil capacity.
4. Whenever a hot water coil is subjected to freezing tem-
peratures, some means of adequate freeze protection is re-
quired. A heating coil can be subjected to freezing tem-
peratures by outside air during the winter. Use of a freeze
protection thermostat is recommended.
5. During winter operation, either the outside-air supply
must be closed off or a minimum water flow must be
maintained if freezing outdoor air is admitted. For sum-
mer operation, it is recommended that if possible the hot
water coil be closed off, drained, and residual water
blown out. If the residual water cannot be blown out, an
inhibited glycol antifreeze should be added to the coil.
6. The return air duct system should be carefully designed to
get adequate mixing of the return air and outdoor air
streams to prevent cold spots on the coil that could freeze.
7. Two-position control valves, modulating control valves,
or three-way control valves may be used to control water
flow. Select the valve based on the control valve manu-
facturer’s recommendations for size and temperature rat-
ing. Select the control valve based on pressure drop equal
to the coil.
8. Pipe sizes should be selected based on the head pressure
available from the pump. It is recommended that the ve-
locity not exceed 8 ft per second and that the piping sys-
tem be designed for approximately a 3-ft loss per 100
equivalent ft of pipe.
9. Design the piping system to allow for expansion and to
minimize vibration between the unit and piping system.
HOT WATER CONTROLS — Several methods of control
are possible depending on the heating medium to be used, loca-
tion and type of thermostatic control and whether or not modu-
lating or ON/OFF type control is used. Figure 20 shows a typi-
cal control scheme for ON/OFF hot water heating coil in
50XCW units.
Install heating thermostat or connect to the heating side of
an available heating/cooling thermostat so that the unit operates
the fan in the desired operation, either continuous or cycling
with the heating coil. The thermostat should provide the re-
quired connection to activate the fan and the cooling and heat-
ing should not be able to be activated simultaneously.
The freeze stat and the heating relay (HR1) are field-
supplied and installed. Refer to Fig. 18 for typical thermostat
wiring.
W1
Y1
G
W
3
CK1
CK2
R
C
W2
Y2
R
S
2
R
S
+5
R
S
1
R
S
GND
UNIT
GROUND
33
C
S
250-01
R
G
Y1
C
Y2
TB2
50XC
(12
S
IZE UNIT AND LARGER)
WIRE NUT
S
HIELD (CUT AND
TAPE BACK)
REMOTE
ROOM
S
EN
S
OR
(P/N ZONECCORR
S
01)
W1
W2
D1
D2
NOTE: Remote sensor is field-installed option.
Fig. 18 — Typical Thermostat Wiring Connections
a50-8510