Daikin SEHVX20BAW, Инструкция по установке и эксплуатации

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4 Preparation
Installation and operation manual
9
SERHQ020~0 SEHVX20~64BAW
Split packaged air-cooled water chiller
4P508019-1C – 2018.04
Minimum water volume
Model Minimum total water volume (l)
20 76
32 110
40 152
64 220
INFORMATION
In critical processes, or in rooms with a high heat load,
extra water might be required.
INFORMATION
The temperature step difference can be modified using
settings [A‑02] and [F‑00]. This has an impact on the
minimum water volume required when the unit operates in
cooling.
By default, the unit is set to have a water temperature
difference of 3.5 K which allows it to operate with the
minimum volume mentioned in the previous table.
However, if a smaller temperature differential is set, as in
the case of process cooling applications where
temperature fluctuations must be avoided, a larger
minimum water volume will be required.
To ensure proper operation of the unit when changing the
values of setting [F‑00] (for cooling mode), the minimum
water volume has to be corrected. If this volume exceeds
the range allowed in the unit, an additional expansion
vessel or a buffer tank must be installed in the field piping.
Example:
To illustrate the impact on the system when modifying the setting
[F‑00], we will consider a unit with a minimum allowable water
volume of 66 l. The unit is installed 5 m below the highest point in
the water circuit.
Assuming that the setting [F‑00] is changed from 5°C (default value)
to 0°C. From the below table we see that 5°C corresponds to a
temperature differential of 3.5 K and 0°C to 1 K, which is actually the
lowest value we can set.
[F‑00] value (°C) Temperature differential (K)
0 1
1 1.5
2 2
3 2.5
4 3
5 3.5
6 4
7 4.5
8 5
9 5.5
10 6
11 6.5
12 7
13 7.5
14 8
15 8.5
The water volume correction factor according to the curve shown in
the below graph is 3.5; this means that the minimum volume will be
3.5 times larger.
Correction factor curve for minimum water volume
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
a
b
a Water volume correction factor
b Temperature differential (K)
When multiplying 64 l by the correction factor, we get 224 l, which
will be the minimum water volume allowed in the installation if a
temperature differential of 1 K is used.
Now it is very important to check that for the height difference of the
system, the volume in the system is less than the maximum allowed
value at that pre-pressure (Pg). If we take a look at the curve, for
1 bar of pre-pressure, the maximum volume allowed is 350 l.
The total volume in the system will definitely be larger after adding
the internal volume of the unit. In this case, some pre-pressure can
be applied or an additional expansion vessel or buffer tank must be
installed in the field piping.
The default value of pre-pressure (Pg) is for a height difference of
7 m.
If the height difference of the system is lower than 7 m AND the
volume in the system is less than the maximum allowed value at that
pre-pressure (Pg) (see graph), then NO pre-pressure (Pg)
adjustment is required.
Maximum water volume
Use the following graph to determine the maximum water volume for
the calculated pre-pressure.
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250 300 350 400 450 500 550 600
A
B
33
b
a
a Pre-pressure (bar)
b Maximum water volume (l)
A System
B Default
If the total water volume in the entire circuit exceeds the maximum
allowed water volume (see graph), an additional expansion vessel
must be installed in the field piping.
4.4 Preparing electrical wiring
4.4.1 Safety device requirements
The power supply must be protected with the required safety
devices, i.e. a main switch, a slow blow fuse on each phase and an
earth leakage protector in accordance with the applicable legislation.
Selection and sizing of the wiring should be done in accordance with
the applicable legislation based on the information mentioned in the
table below.