Carrier MINIMUM LOAD CONTROL ACCESSORY 30RB060-390, Installation Instructions Manual

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NOTE: Locate the 3-way valve as close as possible to the
chiller to minimize head pressure control response time.
FOR ALL UNITS
Dual Chiller Control Option — If the dual chiller algorithm is
used, and the machines are installed in parallel, an additional
chilled water sensor must be installed for each module. For
30RB315-390, a factory-supplied thermistor and well are
shipped in the control box of each module. Install the wells in
the common leaving water header. See Fig. 34.
Parallel chiller control with dedicated pumps is recom-
mended. Chiller must start and stop its own water pump locat-
ed in its own piping. If pumps are not dedicated for each
chiller, then isolation valves are required. Each chiller must
open and close its own isolation valve through the unit control
(the valve must be connected to the pump outputs).
See Dual Chiller Control Option section on page 58 for
more dual chiller leaving water sensor information.
Minimum Loop Volume — The preferred minimum loop vol-
ume is dependent on the type of application. In order to obtain
leaving water temperature stability for comfort cooling appli-
cations, a minimum of 3 gallons per ton (3.25 liters per kW) is
required on all unit sizes. For process cooling applications, ap-
plications where high stability is critical, or operation at
ambient temperatures below 32 F (0° C) is expected, the loop
volume should be increased to 6 to 10 gallons per ton (6.46 to
10.76 liters per kW) of cooling.
In order to achieve this volume, it may be necessary to add a
water storage tank to the water loop. If a storage tank is added
to the system, it should be properly vented so that the tank can
be completely filled and all air eliminated. Failure to do so
could cause lack of pump stability and poor system operation.
Any storage tank that is placed in the water loop should
have internal baffles to allow thorough mixing of the fluid. See
Fig. 35. For units with heat reclaim option, a minimum con-
denser loop volume of 6 gallons per ton of heating (0.5 to 0.83
gallons [1.9 to 3.1 L] per 100 Btu/h of heating) capacity is nec-
essary. In come cases, this will require the installation of a hot-
water buffer tank.
System Piping — Proper system design and installation proce-
dures should be followed closely. The system must be
constructed with pressure tight components and thoroughly
tested for leaks.
Installation of water systems should follow sound engineer-
ing practice as well as applicable local and industry standards.
Improperly designed or installed systems may cause
unsatisfactory operation and/or system failure. Consult a water
treatment specialist or appropriate literature for information
regarding filtration, water treatment, and control devices.
Figure 29 shows a typical installation with components that
might be installed with the hydronic package of the 30RB unit.
NOTE: It is recommended for units with the hydronic package
that an inlet isolation (shutoff) valve be placed exterior to the
unit to allow removal and service of the entire pump assembly,
if necessary. The hydronic package is supplied from the factory
with a combination valve for isolation of leaving water. Also,
if the unit is isolated with valves, a properly sized pressure
relief valve is recommended and should be installed in the pip-
ing between the unit and the valves, following all applicable
local codes.
Air Separation — For proper system operation, it is essential
that water loops be installed with proper means to manage air
in the system. Free air in the system can cause noise, reduce
terminal output, stop flow, or even cause pump failure due to
pump cavitation. For closed systems, equipment should be
provided to eliminate all air from the system.
The amount of air that water can hold in solution depends
on the pressure and temperature of the water/air mixture. Air is
less soluble at higher temperatures and at lower pressures.
Therefore, separation can best be done at the point of highest
water temperature and lowest pressure. Typically, this point
would be on the suction side of the pump as the water is return-
ing from the system or terminals. This is generally the optimal
place to install an air separator, if possible.
1. Install automatic air vents at all high points in the system.
(If the 30RB unit is located at the high point of the system,
a vent can be installed on the piping leaving the heat ex-
changer on the 1 /
4
in. NPT female port.)
2. Install an air separator in the water loop, at the place
where the water is at higher temperatures and lower pres-
sures — usually in the chilled water return piping. On a
primary-secondary system, the highest temperature water
is normally in the secondary loop, close to the decoupler.
Preference should be given to that point on the system
(see Fig. 36). In-line or centrifugal air separators are read-
ily available in the field.
It may not be possible to install air separators at the place of
the highest temperature and lowest pressure. In such cases,
preference should be given to the points of highest temperature.
It is important that the pipe be sized correctly so that free air
can be moved to the point of separation. Generally, a water
velocity of at least 2 feet per second (0.6 m per second) will
keep free air entrained and prevent it from forming air pockets.
Automatic vents should be installed at all physically elevat-
ed points in the system so that air can be eliminated during sys-
tem operation. Provisions should also be made for manual
venting during the water loop fill.
S UPPLY
RETURN
CON S TANT S PEED
CIRCULATING PUMP S
HEAT RECLAIM
CONDEN
S ER
MODULATING 3 -WAY
CONTROL VALVE
40 FT MAX
Fig. 33A — Three-Way Head Pressure Control
Valve Location (Preferred)
a30-4825
MODULATING 3 -WAY CONTROL
VALVE (A S CLO S E TO CONDEN S ER
A S PO SS IBLE)
HEAT RECLAIM
CONDEN
S ER
CON S TANT S PEED
CIRCULATING PUMP S
RETURN
S UPPLY
Fig. 33B — Three-Way Head Pressure Control
Valve Location (Alternate)
a30-4824
IMPORTANT: Automatic vents should be located in
accessible locations for maintenance purposes and
protected from freezing.