Daikin SERHQ032BAW1, Инструкция по установке и эксплуатации

Страница: 14 / 76

5 Preparation
Installer and user reference guide
14
SERHQ020~0 SEHVX20~64BAW
Split packaged air-cooled water chiller
4P508020-1A – 2018.01
▪ The maximum water piping temperature is 50°C according to
safety device setting.
▪ Always use materials which are compatible with the water used in
the system and with the materials used in the unit. (The unit piping
fittings are made of brass, the plate heat exchangers are made of
stainless steel 316 plates brazed together with copper and the
optional pump housing is made of cast iron.)
▪ Select the piping diameter in relation to the required water flow
and available external static pressure (ESP) of the pump. See the
following table for the recommended water piping diameter.
Capacity class Water piping diameter
20+32 1-1/4"
40+64 2"
NOTICE
It is strongly recommended to install an additional filter on
the water circuit. Especially to remove metallic particles
from the field water piping, it is advised to use a magnetic
or cyclone filter which can remove small particles. Small
particles can damage the unit and will not be removed by
the standard filter of the unit.
5.4.2 Formula to calculate the expansion vessel
pre-pressure
The pre-pressure (Pg) of the vessel depends on the installation
height difference (H):
Pg=0.3+(H/10) (bar)
5.4.3 To check the water volume and expansion
vessel pre-pressure
The unit has an expansion vessel of 12 litre with a default pre-
pressure of 1 bar.
To make sure that the unit operates properly:
▪ You must check the minimum and maximum water volume.
▪ You might need to adjust the pre-pressure of the expansion
vessel.
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)