Installation manual

IM-487 Page 29
Note: The valve actuator spring returns to a stem down
position upon power failure. This allows full flow
through the coil.
Figure 28. Hot Water Heat Section
(Shown with Factory Valve and Piping)
Steam Piping (All Units)
The steam heat section consists of two stacked coils (pitched
at 1/811 per foot [3mm per 30cm]), as shown in Figure 29.
When no factory piping or valve is included, the coil connec-
tions are 2.50" male NPT iron pipe.
Refer to the sections on steam coil piping and trap recom-
mendations for additional information.
Figure 29. Steam Heat Section
(Shown With Factory Valve and Piping)
Steam Piping to Coils in the Heat Section
Steam coils are provided without valves for field piping, or
piped with two-way valves and actuator motors.
With the factory piping and valve package, the two coil sup-
plies are piped in parallel and controlled through a single
two-way valve. The field supply connection is of the same
female NPT size as the valve. Field return connections are
made at the 2.50" male NPT fittings on each of the two
stacked coils.
Note: The valve actuator spring returns to a stem up posi-
tion upon power failure. This allows full flow
through the coil.
Figure 30. Two-way valve package
Piping Recommendations (Steam Coils)
1. Be certain that adequate piping flexibility is provided.
Stresses resulting from expansion of closely coupled pip-
ing and coil arrangement can cause serious damage.
2. 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.
3. 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. However, if the system has a flooded return
main, open the vacuum breaker to the atmosphere and the
trap design to allow venting of the large quantities of air.
4. Do not drain steam mains or take-offs through coils.
Drain mains ahead of coils through a steam trap to the
return line.
5. Do not attempt to lift condensate when using modulating
or on-off control.
6. Pitch all supply and return steam piping down a minimum
of 1 inch per 10 feet (3mm per 305cm) in direction of flow.
Steam Trap Recommendations
1. Size traps in accordance with manufacturers' recommen-
dations. Be certain that the required pressure differential
will always be available. Do not undersize.
Supply
Bypass
2.12 " ODM
Copper Coil
Connections
Upper
Coil
Air Flow
Lower
Coil
Return
Lower
Coil
2.12 " ODM
Copper Coil
Connections
Upper
Coil
Supply
Return
R e t u r n
S u p p l y