Carrier Omnizone 50BVC, Установка, запуск, обслуживание, управление, эксплуатация и устранение неисправностей, Страница: 23 / 92

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Ball valves should be installed in the supply and return lines for
unit isolation and water flow balancing.
Pressure and temperature ports are recommended in both the sup-
ply and return lines for system flow balancing. These openings
should be 5 to 10 pipe diameters from the unit water connections.
For thorough mixing and temperature stabilization, wells in the
water piping should extend at least 1 /
2
pipe diameter into the pipe.
Measuring the condenser waterside pressure drop and referring to
Tables 5 and 6 can help to properly set the water flow rate.
Improper fluid flow due to valving, piping, or improper pump op-
eration constitutes abuse that may result in voiding of unit warran-
ty. The manufacturer will not be responsible for damages or
failures resulting from improper piping design or piping material
selection.
EVAPORATOR CONDENSATE DRAIN
The condensate drain connection is 1
1 /
4
-in. FPT and is located on
the same side of the unit as the condenser water connections. See
dimension drawings (Fig. 7-15) for exact location.
Drain lines should be pitched away from the unit with a minimum
slope of 1 /
8
-in. per foot and conform to all local and national
codes.
A trap must be installed in the condensate line to ensure free con-
densate flow (units are not internally trapped). A vertical air vent
is sometimes required to avoid air pockets.
Install a condensate-trapping drain line at the unit’s drain connec-
tion. See Fig. 18 for correct drain layout.
When calculating trap depth, remember that it is not the total static
pressure but the upstream or downstream static resistance that is
trapped against. For instance, when calculating the trap depth for a
cooling coil condensate pan, trap against the coil pressure drop in
that coil section and any other pressure drops upstream of it.
If calculating the trap depth for the cooling coil, use the total static
pressure drop (coil plus any other components upstream of it) plus
1 in. (P
1
= negative static pr 1 in.), as shown in Fig. 18.
Traps must store enough condensate to prevent losing the drain
seal at start-up. The “Minimum 1 /
2
P
1
” dimension ensures that
enough condensate is stored.
Drain pans should be cleaned periodically to avoid the build-up of
dirt and bacterial growth.
Fig. 18 — Condensate Drain Layout
HOT WATER HEATING COIL (OPTIONAL)
A factory-installed one or 2-row hot water heating coil is available
as an option. The coil is supplied with hot water from a boiler
through separate piping from the condenser water loop. All con-
trols, including the hot water valve, freeze protection, and the
valve control signal, for heating operation are field-supplied.
Piping should be in accordance with accepted industry standards
and all components rated for the system pressure expected. Pipe
coils so that they will drain, and provide a drain and vent. The fac-
tory installed VAV controller is not capable of controlling an exter-
nal heat source, including hot water.
Always connect the supply to the bottom of the coil, and the return
to the top of the coil. Refer to Fig. 7-15 for hot water supply and
return piping locations.
Water coils should not be subjected to entering-air temperatures
below 38°F to prevent coil freeze-up. If air temperatures across
the coil are going to be below this value, use a glycol or brine solu-
tion. Use a solution with the lowest concentration that will match
the coldest air expected. Excess concentrations will greatly reduce
coil capacity. A coil freeze protection system that shuts off the
supply fan and opens the hot water valve to 100% should also be
considered.
The return air duct system should be carefully designed to get ade-
quate mixing of the return air and outdoor air streams to prevent
cold spots on the coil that could freeze.
A 2 or 3-way, field-supplied modulating control valve or a simple
two-position on-off valve may be used to control water flow. Se-
lect the valve based on the control valve manufacturer’s recom-
mendations for size and temperature rating. Select the control
valve CV based on pressure drop and flow rate through the coil.
This information is available from the SCU Builder software pro-
gram or Tables 7 and 8.
Pipe sizes should be selected based on the head pressure available
from the pump. Water velocity should not exceed 8 fps. Design
the piping system for approximately 3 ft of loss per 100 equivalent
ft of pipe. The piping system should allow for expansion and min-
imize vibration between the unit and piping system.
WATERSIDE ECONOMIZER (OPTIONAL)
The optional waterside economizer (pre-cooling coil) is factory-
installed and piped internally, in series with the condenser water
circuit (Fig. 19). A diverting valve and factory controls are includ-
ed with the option. The condenser water supply is connected to the
economizer water in and the condenser water return is connected
to the condenser water out. In addition, when unit is shipped with
economizer option, the economizer drain must be connected to a
separate trap. Follow the same steps for the economizer drain as
described for evaporator condensate drain. An aquastat is used to
modulate water flow through the economizer. The controller is
mounted to the low voltage control box. Electrical connections are
factory installed and wired. The remote bulb is shipped internal to
the unit and requires field mounting. Care should be taken not to
dent the bulb or miscalibration may occur. The aquastat has a tem-
perature range adjustment (–30°F to 100°F) and is field set. See
Fig. 7-15 for connection locations and sizes. See Tables 9 and 10
for economizer waterside pressure drop data.
NOTE: P
1
equals negative static pressure plus 1 inch.
1/2
P
1
P
1