Trane CGA Series, Установка, эксплуатация и обслуживание, Страница: 10 / 24

In an inverter without expedients harmonic distortion can reach values higher than 100% (i.e. the components
Harmonics can, on the whole have a width greater than the fundamental component). In order to reduce the harmonic
content of the current (and therefore the THD) units object of this manual are equipped with appropriate limitation sys-
tems. Since the harmonic content depends on the ratio between the current required by the inverter and the short-circuit
current at the point of connection, the THD for a given plant varies depending on the absorption of the machine.
It should also be said that the harmonic distortion is reduced in value if the connection point (CCP) are also connected
other loads: the greater the weight of these utilities, the lower the current distortion. The total harmonic distortion at the
point where the unit is connected to the network is a function of the ratio between short-circuit current circuit at the point
of connection (ISC) and the current drawn by the unit (IL) and the percentage of power drawn the unit compared to the
total power supplied by the network at the connection point. The harmonic distortion in the connection point can 'assume
values very low (less than 5%) if the short circuit current is less than 20 times the current of unity and this constitutes a
percentage not more than 20% of the total load of the network. In any case, the harmonic distortion introduced by the
unit must be determined by reference to the specific application after a detailed analysis of the entire network of power
and loads supplied.
Water connections for air-water
Evaporator
The connection tubes have to be supported in order that their weight does not damage the plant. The following parts
have to be installed on the water circuit of the evaporator:
1. Two pressure gauges of adequate scale (in and out of the unit)
2. Two shock-absorbing joints (inlet and out of the unit)
3. One shut off valve (normal one inlet)
4. One setting valve (in outlet)
5. Two thermometers (inlet and outlet)
6. One circulation pump
7. One safety valve on the water buffer (if not equipped in the unit)
8. One automatic air vent valve (if not equipped in the unit)
9. One expansion vessel (if not equipped in the unit and one in addition depending on the volume of water in the
plant)
10. An inlet filter placed as near as possible to the evaporator connection.
11. One flow switch
The above-mentioned installation indications represent necessary conditions for the guarantee to be valid.
Trane is at your disposal to examine any different requirements, which have to be approved before starting up the
chiller.
It is necessary that the water flow rate to the unit is compatible with the evaporator one. It is also necessary that the
water flow rate is kept uniform while the unit is running: it is suggested to use always a pump system dedicated to the
unit and independent from the remaining part of the plant.
Before storing units in temperatures around 0°C evacuate the exchanger with compressed air in order to avoid
breakages due to ice.
Condenser
Condenser piping must follow the same installation procedures as for the evaporator. Condensing temperature and
water flow rate have to be in accordance with nominal values, unless the acknowledgement order shows different
indications. It is necessary that in the presence of condenser side dirty or aggressive water, an intermediate heat
exchanger must be installed before the chiller condenser.
The above-mentioned installation suggestions represent the necessary condition to keep warranty validity.
Calculation of minimum water content and flow rates
To achieve perfect operation, the machine needs water content achievable using the following formula:
CHILLER:
OPTIMAL V= Q
ev
/20
MINIMUM V= Q
ev
/35
HEAT PUMP
OPTIMAL V= Q
cond
/7
MINIMUM V= Q
cond
/20