Sizing Expansion Vessels; Water Circulation Pump Characteristics - Mitsubishi Electric ecodan EHPX-Serie Installationshandbuch

4
Installation

sizing Expansion Vessels

Expansion vessel volume must fit the local system water volume.
To size an expansion vessel both for the heating and cooling circuits the following
formula and graph can be used.
When the necessary expansion vessel volume exceeds the volume of an built-in
expansion vessel, install an additional expansion vessel so that the sum of the
volumes of the expansion vessels exceeds the necessary expansion vessel
volume.
* For installation of an EHSC-*M*EB model, provide and install an expansion
vessel in the field as the model does not come fitted with an expansion vessel.
ε × G
V =
P ¹ + 0.098
1 −
P ² + 0.098
Where;
V : Necessary expansion vessel volume [L]
ε : Water expansion coefficient
G : Total volume of water in the system [L]
P ¹ : Expansion vessel setting pressure [MPa]
P ² : Max pressure during operation [MPa]
Graph to the right is for the following values
ε : at 70 °C = 0.0229
P ¹ : 0.1 MPa
P ² : 0.3 MPa
*A 30% safety margin has been added.

Water Circulation Pump Characteristics

Pump speed can be selected by main controller setting (see <Figure 4.3.4 -
4.3.7>).
Adjust the pump speed setting so that the flow rate in the primary circuit is appro-
priate for the outdoor unit installed (see Table 4.3.1). It may be necessary to add
an additional pump to the system depending on the length and lift of the primary
circuit.
<Second pump >
If a second pump is required for the installation please read the following care-
fully.
If a second pump is used in the system it can be positioned in 2 ways.
The position of the pump influences which terminal of the FTC4 the signal cable
should be wired to. If the additional pump(s) have current greater than 1A please
use appropriate relay. Pump signal cable can either be wired to TBO.1 1-2 or
CNP1 but not both.
Option 1 (Space heating only)
If the second pump is being used for the heating circuit only then the signal cable
should be wired to TBO.1 terminals 3 and 4 (OUT2). In this position the pump can
be run at a different speed to the hydrobox's in-built pump.
Option 2 (Primary circuit DHW and space heating)
If the second pump is being used in the primary circuit between the hydrobox and
the outdoor unit (Package system ONLY) then the signal cable should be wired to
TBO.1 terminals 1 and 2 (OUT1). In this position the pump speed must match
the speed of the hydrobox's in-built pump.
Note: Refer to 5.2 Connecting inputs/outputs.
Expansion vessel sizing
25
20
15
10
5
0
0 50 100 150
System water volume [L]
<Figure 4.3.3>
Outdoor heat pump unit
Packaged PUHZ-W50
PUHZ-W85
PUHZ-HW112
PUHZ-HW140
Split PUHZ-RP35
PUHZ-RP50
PUHZ-RP60
PUHZ-(H)RP71
PUHZ-(H)RP100
PUHZ-(H)RP125
PUHZ-RP140
PUHZ-SW40
PUHZ-SW50
PUHZ-SW75
PUHZ-SW100
PUHZ-SW120
PUHZ-SHW80
PUHZ-SHW112
PUHZ-SHW140
<Table 4.3.1>
* If the water flow rate is less than 7.1 L/min, the flow switch will be activated.
If the water flow rate exceeds 27.7 L/min, the flow speed will be greater than 1.5 m/s,
which could erode the pipes.
200 250 300 350 400
Water flow rate range [L/min]
7.1 - 14.3
10.0 - 25.8
14.4 - 27.7
17.9 - 27.7
7.1 - 11.8
7.1 - 17.2
8.6 - 20.1
10.2 - 22.9
14.4 - 27.7
17.9 - 27.7
20.1 - 27.7
7.1 - 11.8
7.1 - 17.2
10.2 - 22.9
14.4 - 27.7
20.1 - 27.7
10.2 - 22.9
14.4 - 27.7
17.9 - 27.7
20