Heatcraft Refrigeration Products 4346B001 - Manual (Page 3)

3
Low Pressure Open Gravity Return System
Steam Main
Gate Valve
Typical Steam Coil Piping
Strainer
Control Valve
Union
12” Minimum
Open Vent
Vacuum Breaker
1/2”-15” Check Valve
Gate Valve
Union
Union
Strainer
Dirt Pocket
Return Main
Combination Float
and
Thermostatic Trap
Vent
Steam Main
Gate Valve
Strainer
Control Valve
Union
Vacuum Breaker
1/2”-15” Check Valve Vent
12” Minimum
Union
Union
Strainer
Dirt Pocket Return Main
Gate Valve
Float or
Bucket Trap
When two or more steam coils are furnished in a unit,
provide separate traps for each coil. Size traps with
ample capacity using the maximum heating load and
service factor recommended b y the trap manufacturer.
Select control valves in accordance with the
recommendations of the control manufacturer using
actual heating loads.
Install suitable strainer ahead of all automatic valves and
traps to catch dirt and scale. Provide adequate air vents
to expel air and other non-condensable.
Control valves used for Type “J”, “NFS”, “RA” and
“NFD” coils must be gradual acting modulating type with
veeport.
Where a control valve is used for Type “S” or “R” coils
and when the entering air temperature is below 35ºF.,
use a two position valve. Locate control element in the
entering air stream so that valve will remain open with
a minimum of five pounds steam pressure when the
entering air temperature is below 35ºF.
When the system is started up the damper should remain
closed for approximately ten minutes after the steam
valve is opened.
Properly locate all temperature sensing elements at a
point of true average air mixture temperature.
Refer to “Typical Steam Coil Piping Diagrams” for
controls positioning and piping configuration.
When face and bypass dampers are used, it is good
practice to install on the coil a valve which closes as
the face damper closes to prevent over heating due to
damper leakage or heat picked up by the air wiping the
exposed coil face.
Water Piping
All piping must be supported independent coils.
Swing joints or flexible fittings must be provided to absorb
expansion and contraction strains. Rigid piping may also
reduce effectiveness of vibration isolators.
The water supply should always be connected to the
bottom inlet of the coil. The coil connections are identified
with stickers.
Water coils , 3 through 10 rows, are supplied with a vent
and drain connection (1/4” MPT) which extends through
the unit casing.
For protection of coils exposed to freezing temperatures,
refer to page 6.
Coils must be adequately vented in order to prevent air
binding.
Direct Expansion
Both the liquid distributor and the suction line extend
through the casting.
The expansion valve utilized must be of the external
equalizer tube type. The expansion valve bulb must be
located on the suction line between the coil and the 1/4”
external equalizer tube. Never locate the bulb in a trap.
All refrigerant piping practices used should be in
accordance with local codes and latest ANSI Standard
B9 Safety Code. Hard drawn type “L” or “K” copper tubing
should be used. Soft tubing where bending is required
may be used provided it is protected in accordance with
local code restrictions.
Good Practice should be followed as to pulling adequate
vacuum, tubes cleaned of foreign material, etc.
High Pressure System