10.7.6 -
Installation
The water supply of each desuperheater is arranged in parallel.
The water connections on the desuperheater water inlets and
outlets must not cause any mechanical local constraint at the heat
exchangers. If necessary, install flexible connection sleeves.
Install water flow control and balancing valves at the heat
exchanger outlet. Water flow control and balancing can be done
by reading the pressure drop in the heat exchangers. This pressure
drop must be identical on all of them with the total water flow rate
given by the “Electronic catalogue” selection program.
Refer to the pressure drop curves below to perform the adjustment
of the balancing valves before starting up the installation. It is
possible to fine-tune the variable water flow control for each
desuperheater when the unit is running at full load, attempting to
obtain outlet water temperatures which are completely identical
on each circuit.
Desuperheater
(plate heat exchanger pressure drop curves)
1
10
100
0.1
1
10
Heat
exchan
ger
press
ure
drop,
kPa
Heat exchanger water flow rate, l/s
Heat exchanger water flow rate, l/s
Heat
exchanger
pressure
drop,
kPa
1
2
3
4
1 Circuit with 1 compressor
2 Circuit with 2 compressors
3 Circuit with 3 compressors
4 Circuit with 4 compressors
Operation of the pump (see typical diagram - item 20 of chapter
10.7.5) of the desuperheater water circuit can be linked to:
1- The start-up of the first compressor of the unit : terminal block
37/38
2- The heat water need : Output DO-01 terminal block n°491/492
of the EMM board (option 156)
A dedicated flow switch (item 29) can also be installed to generate
an alarm if there is a problem with the pump (customer control
system).
The volume of the desuperheater circuit water loop must be as
low as possible so that the temperature can increase rapidly when
the unit is started up. The minimum entering water temperature
at the desuperheater is 25°C. A three-way valve (item 31) may be
necessary with a controller, as the sensor controlling the minimum
temperature requires water at the inlet.
The desuperheater water loop must include a damage limitation
accessory in case of a fire and an expansion tank. When selecting
these, consider the water loop volume and the maximum
temperature (120°C) when pump operation is stopped (item 20).
10.7.7 -
Operating range
Cooling mode
Minimum Maximum
Water heat exchanger (evaporator)
Entering water temperature at start-up
(1)
°C
6.8
(1)
30
Leaving water temperature during operation °C
5
15
Entering water temperature at shut-down
°C
-
60
Desuperheater
Entering water temperature at start-up
(2)
°C
25
60
Leaving water temperature during operation °C
30
80
Entering water temperature at shut-down
°C
3
60
Air heat exchanger (condenser)
Entering air temperature
(3)
°C
0
46
Available static pressure
Pa
0
0
Heating mode
Minimum Maximum
Water heat exchanger (condenser)
Entering water temperature at start-up
°C
8
45
Leaving water temperature during operation °C
20
50
Entering water temperature at shut-down
°C
3
60
Desuperheater
Entering water temperature at start-up
(2)
°C
25
60
Leaving water temperature during operation °C
30
80
Entering water temperature at shut-down
°C
3
60
Air heat exchanger (evaporator)
Entering air temperature
°C
-10
35
Available static pressure
Pa
0
0
Note:
Do not exceed the maximum operating temperature.
(1) For an application that requires operation below 6.8°C, contact Carrier.
(2) The entering water temperature at start-up must not be lower than 25°C. For
installations with a lower temperature a three-way valve is necessary.
(3) For operation down to -20°C the unit must be equipped with option 28 (winter
operation). In addition the unit must either be equipped with the frost protection
option or the water loop must be protected by the installer by adding a frost
protection solution.
Maximum outside temperatures:
During storage and transport of the
30RQM/30RQP units the minimum and maximum temperatures must not exceed
-20°C and +48°C. It is recommended to observe these temperatures during
transport by container.
10.7.8 -
Control configuration with the desuperheater
option
This configuration allows the user to enter a setpoint that is relative
to the minimum condensing temperature (default = 30°C) to
increase the heating capacity reclaimed at the desuperheaters,
if required. The percentage of the reclaimed heating capacity
compared with the total capacity rejected by the air heat exchanger
increases in proportion to the saturated condensing temperature.
For the control of the setpoint of the minimum saturated condensing
temperature please refer to the Pro-Dialog control manual for the
30RQM/30RQP units.
Other parameters directly affecting the effective capacity reclaimed
at the desuperheater are principally:
-
The unit load rates, that decide whether the unit
operates at full load (100%) or part load (depending on the
number of compressors per unit circuit).
-
The water entering temperature in the desuperheater and
depending on the unit heating or cooling opera-ting mode:
•
In heating mode the water heat exchanger entering water
temperature
•
In cooling mode the air heat exchanger entering air
temperature.
10 - OPTIONS
53
Summary of Contents for Carrier 30RQM 160
Page 63: ......
