IM777
Page 9
Water Cooling Coils
Note:
It is recommended that Glycol be used in water coils for
outdoor air handlers. Power failures and other mechani-
cal issues can expose coils to freezing temperatures.
1. Water supply, water return, drain, and vent connections
extend through the end panel of the coil section. All con-
nections are labeled on the end panel.
2. Water supply and water return connections are typically
male N.P.T. iron pipe.
3. When installing couplings, do not apply undue stress to
the connection extending through unit panel.
Use a
backup pipe wrench to avoid breaking the weld
between coil connection and header.
4. Follow recommendations of the control manufacturer
regarding types, sizing, and installation of controls.
Direct Expansion Coils
1. The coil distributor and suction connection extend
through the end panel of the coil section.
2. Check nozzle in distributor for proper tonnage.
3. When a thermostatic expansion valve is supplied with the
unit, it will be located outside the unit and connected
directly to the distributor (except on units with piping vesti-
bules). Do not apply heat to the body of the expansion valve.
4. The thermostatic expansion valve must be of the external
equalizer tube type. Connect the 1/4-inch diameter exter-
nal equalizer tube provided on the coil to connection on
expansion valve.
5. Use care when piping up the system to see that all joints
are tight and all lines are dry and free of foreign mate-
rial. For typical refrigerant piping, see condensing unit
product manual.
Steam coils
(refer to Figure 17 on page 10)
Note:
Steam traps should not be placed outdoors.
1. All steam coils in units are pitched toward return
connection.
2. Steam supply and steam return connections are typically
male N.P.T. iron pipe and are labeled on the end panel of
coil section. Connections extend through coil section end
panel.
3. When installing couplings, do not apply undue stress to
the connection extending through unit panel.
Use a
backup pipe wrench to avoid breaking the weld
between coil connection and header.
4. Support piping independently of coils and provide ade-
quate piping flexibility. Stresses resulting from expansion
of closely coupled piping can cause serious damage.
5. Do not reduce pipe size at the coil return connection.
Carry return connection size through the dirt pocket, mak-
ing the reduction at the branch leading to the trap.
6. Install vacuum breakers on all applications to prevent
retaining condensate in the coil. Generally, the vacuum
breaker is to be connected between the coil inlet and the
return main, the vacuum breaker should be open to the
atmosphere, and the trap design should allow venting of
large quantities of air.
7. Do not drip supply mains through the coil.
8. Do not attempt to lift condensate when using modulating
or on/off control.
9. Size traps in accordance with manufacturers' recommen-
dations. Be certain that the required pressure differential
will always be available.
Do not under-size.
10. Float and thermostatic or bucket traps are recommended
for low pressure steam. On high pressure steam, bucket
traps are normally recommended. Thermostatic traps
should be used only for air venting.
11.Bucket traps are recommended for use with on/off
control only.
12.Locate traps at least 12 inches below the coil return
connection.
13. Multiple coil installation.
a. Each coil or group of coils that is individually con-
trolled must be individually trapped.
b. Coils in series: Separate traps are required for each
coil, or bank of coils, in series.
c. Coils in parallel: A single trap may generally be used
but an individual trap for each coil is preferred.
d. Do not attempt to lift condensate when using modulat-
ing or on/off control.
14. With coils arranged for series airflow a separate control is
required on each bank or coil in the direction of airflow.
15. Modulating steam valves are not recommended on high
pressure systems.
16.Modulating valves must be sized properly.
Do not
under-size
.
17. Freezing conditions (entering air temperatures below 35°F).
a. 5JA, 8JA, 5RA and 8RA coils are strongly recommended.
b. 5 psi steam must be supplied to coils at all times.
c. Modulating valves are not recommended. Control
should be provided by face and bypass dampers.
d. Consideration should be given to the use of two or three
coils in series with two position steam control valves on
that coil or coils which will be handling 35°F or colder
air. The desired degree of control can be attained with a
modulating valve on the downstream coil.
e. Thoroughly mix fresh air and return air before it enters
the coil. Also, temperature control elements must be
properly located to obtain true air mixture temperatures.
f. As additional protection against freeze-up, the trap
should be installed sufficiently below coil to provide
an adequate hydrostatic head to provide removal of
condensate during an interruption in the steam pres-
sure. Estimate three feet for each 1 psi of trap differ-
ential required.
g. On startup, admit steam to coil ten minutes before
admitting outdoor air.
h. Close fresh air dampers if steam supply pressure falls
below minimum specified.
Содержание Skyline IM777
Страница 27: ...IM777 Page 27 Notes...
