Water And Steam Coil Piping; Recommendations; Water Coils; Steam Coils - Carrier 39SH Installation, Start-Up And Service Instructions Manual

Water and Steam Coil Piping Recommendations
GENERAL — Use straps around the coil casing to lift and
place the coil.
CAUTION
To prevent damage to the coil or coil headers: Do not use
the headers to lift the coil. Support the piping and coil con-
nections independently. Do not use the coil connections to
support piping. When tightening coil connections, use a
backup wrench on the nozzles.
Piping practices are outlined in the Carrier System Design
Manual, Part 3, Piping Design.
WATER COILS — Typically, coils are piped by connecting
the supply at the bottom and the return at the top. This is not al-
ways the case, especially if the coil hand has been changed in
the field. Coils must be piped for counterflow; otherwise, a ca-
pacity reduction of 5% for each coil row will result. To ensure
counterflow, chilled water coils are piped so that the coldest
water meets the coldest air. Hot water coils are piped so that the
warmest water meets the warmest air. Some 39S coils have 3
connections on either side of the coil (for a total of 6 connec-
tions). In these cases, the middle connection is used as the re-
Fig. 51 — Water Coil Connection
turn connection. See Fig. 51.
STEAM COILS — Position the steam supply connection at
the top of the coil, and the return (condensate) connection at the
bottom.
Figure 52 illustrates the normal piping components and the
suggested locations for high, medium, or low-pressure steam
coils. The low-pressure application (zero to 15 psig) can
dispense with the ¼-in. petcock for continuous venting located
above the vacuum breaker (check valve).
Note the horizontal location of the 15-degree check valve,
and the orientation of the gate/pivot. This valve is intended to
relieve any vacuum forming in the condensate outlet of a
condensing steam coil, and to seal this port when steam
pressure is again supplied to the coil. It must not be installed in
any other position, and should not be used in the supply line.
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LEGEND
CW — Chilled Water
HW — Hot Water
LH — Left Hand
RH — Right Hand
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For coils used in tempering service, or to preheat outside air,
install an immersion thermostat in the condensate line ahead of
the trap. This will shut down the supply fan and close the out-
door damper whenever the condensate falls to a predetermined
point, perhaps 120 F.
NOTE: Do NOT use an immersion thermostat to override a
duct thermostat and open the steam supply valve.
For vacuum return systems, the vacuum breaking check
valve would be piped into the condensate line between the trap
and the gate valve instead of open to the atmosphere.
Figure 53 illustrates the typical piping at the end of every
steam supply main. Omitting this causes many field problems
and failed coils.
Figure 54 shows the typical field piping of multiple coils.
Use this only if the coils are the same size and have the same
pressure drop. If this is not the case, an individual trap must be
provided for each coil.
Figure 55 shows a multiple coil arrangement applied to a
gravity return, including the open air relief to the atmosphere,
which DOES NOT replace the vacuum breakers.
Figure 56 illustrates the basic condensate lift piping.
NOTES:
1. Flange or union is located to facilitate coil removal.
2. Flash trap may be used if pressure differential between steam
and condensate return exceeds 5 psi.
3. When a bypass with control is required.
4. Dirt leg may be replaced with a strainer. If so, tee on drop can
be replaced by a reducing ell.
5. The petcock is not necessary with a bucket trap or any trap
which has provision for passing air. The great majority of high
or medium pressure returns end in hot wells or deaerators
which vent the air.
Fig. 52 — Low, Medium or
High Pressure Coil Piping
53
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