Trane SINTESIS ADVANTAGE CGAF Series Installation Operation & Maintenance page 41

Evaporator Flow Switch
Specific connection and schematic wiring diagram
are shipped within the unit. Some piping and control
schemes, particularly those using a single water pump
for both chilled and hot water, must be analysed to
determine how and/or if a flow sensing device will
provide the desired operation.
Flow Switch Installation – Typical
Requirements
1. Mount the switch upright, with a minimum of
10 pipes diameters of straight horizontal run on
each side. Do not install close to elbows, orifices,
or valves. The arrow on the switch must point in the
direction of the flow. For additional information,
consult the flow switch information sheet coming
with the part.
2. To prevent switch fluttering, remove all air from the
water system. Tracer UC800 provides a 6 second
time delay after a "loss-of-flow" diagnostic before
shutting the unit down. Contact a Trane service
representative if nuisance machine shutdowns
persist.
3. Adjust the switch to open when water flow falls
below nominal values. Evaporator data is given
on the General Information Section. Flow Switch
contacts are closed on proof of water flow.
CAUTION! Control voltage from the chiller to the flow
proving device is 110V AC.
Note: In case of winter water drainage for freeze
protection, it is mandatory to disconnect the evaporator
heaters to protect them from burning due to overheat.
It is also mandatory to fulfill the drainage, using
pressurized air, and ensure that no water stays in the
evaporator during winter season.
Minimal Installation Water Content
The water volume is an important parameter because
it allows as table chilled water temperature and avoids
short cycle operation of the compressors.
Parameters which influence the water temperature
stability
− Water loop volume
− Load fluctuation
− Number of capacity steps
− Compressors rotation
− Dead band (adjusted on chiller controller)
− Minimum time between 2 starts of a
compressor
CG-SVX039C-GB
Minimum Water Volume for a
Comfort Application
For comfort application we can allow water temperature
fluctuation at part load. The parameter to take into
account is the minimum operating time of the
compressor. In order to avoid lubrication problem
on a scroll compressor it must run at least 2 minutes
(120 seconds) before it stops.
The minimum volume can be determined by using the
following formula:
Volume = Cooling capacity x Time x highest capacity step
(%) / Specific heat / Dead band
Minimum operating time = 120 seconds
Specific heat = 4.18 kJ / kg
Average Dead band = 3°C (or 2°C)
Note: To estimate the biggest step, it is usually
more reliable to make a selection at lower ambient
temperature where efficiency is higher and compressors
steps bigger. It is also essential to take into account the
brine specific heat, in case of the use of glycol.
Process applications will need more water volume to
minimize the water temperature fluctuation at part load.
Expansion Tank (option)
The factory-installed expansion tank initial pressure
should be adjusted about 0.2 bar lower than the static
pressure of the circuit at the pump inlet. The expansion
tank volume has been selected for typical loop volume.
It is recommended to check the expansion tank volume
with the installation information.
The following data is required:
C = Water capacity of the circuit
e = Expansion coefficient (difference between max and
min water temperature, in operation or not)
Pi = Initial pressure of the expansion tank
Pf = Final pressure: Max is given by the pressure relief
valve
Minimum Volume of expansion tank = (C x e)/(1-Pi/Pf)
Expansion coefficient of water various temperatures
°C
0
10
20
30
40
50
Water loop and expansion tank volume
- Water loop CGAF 080 HE/XE, CGAF 090:
- Water loop CGAF 140-190:
Expansion tank volume (option):
Note: Maximum pressure of the circuit is 400 kPa with
pump package and 1000 kPa without.
Evaporator Piping
e
0.00013
0.00027
0.00177
0.00435
0.00728
0.01210
607 l
777 l
50 l
41