Checking The Water Volume And Expansion Vessel Pre-Pressure - Rotex RKHBRD011AAV1 Guia De Instalacion

Checking the water volume and expansion vessel
pre-pressure
The unit is equipped with an expansion vessel of 12 litre which has a
default pre-pressure of 1 bar.
To assure proper operation of the unit, the pre-pressure of the
expansion vessel might need to be adjusted and the minimum and
maximum water volume must be checked.
1 Check that the total water volume in the installation, excluding
the internal water volume of the unit, is 20 l minimum.
In most applications this minimum water volume will have a
satisfying result.
In critical processes or in rooms with a high heat load
though, extra water volume might be required.
When circulation in each space heating/radiator loop is
controlled by remotely controlled valves, it is important that
this minimum water volume is kept even if all the valves are
closed.
Example
C1
1 11 2 3 11 4
5
1 Outdoor unit
2 Indoor unit
3 Refrigerant heat
exchanger
4 Water heat exchanger
5 Compressor
6 Pump
7 Shut-off valve
8 Collector (field supply)
9 By-pass valve
(field supply)
2 Using the table below, determine if the expansion vessel pre-
pressure requires adjustment.
RKHBRD011~016AAV1+Y1
Indoor unit for air to water heat pump system
4PW55786-1
A B
6 7 7 8 9 10
M3
T3
M2
T2
M1
T1
10 Radiator (field supply)
11 Electronic expansion
valve
C1 Remote controller
M1...M3 Individual motorized valve
to control loop radiators
(field supply)
T1...T3 Individual room
thermostat (field supply)
A Installation space
B Living room
3 Using the table and instructions below, determine if the total
water volume in the installation is below the maximum allowed
water volume.
Installation
65°C ≤270 l
height
(a) 80°C ≤180 l
difference
No pre-pressure adjustment
≤7 m
required.
Actions required:
• pre-pressure must be
increased, calculate
according to "Calculating
the pre-pressure of the
>7 m
expansion vessel"
• check if the water volume
is lower than maximum
allowed water volume
(use graph below)
(a) Installation height difference: height difference (m) between the highest
point of the water circuit and the indoor unit. If the indoor unit is located at
the highest point of the installation, the installation height is considered 0 m.
Calculating the pre-pressure of the expansion vessel
The pre-pressure (Pg) to be set depends on the maximum
installation height difference (H) and is calculated as below:
Pg=(H/10+0.3) bar
Checking the maximum allowed water volume
To determine the maximum allowed water volume in the entire circuit,
proceed as follows:
1 Determine for the calculated
corresponding maximum water volume using the graph below.
2 Check that the total water volume in the entire water circuit is
lower than this value.
If this is not the case, the expansion vessel inside the indoor unit is
too small for the installation.
2.5
2
1.5
1
0.5
0.3
0.0
0 20 50 100 150 200
maximum water volume [l]
= pre-pressure
= maximum water volume
= increase pre-pressure vessel volume
= decrease pre-pressure vessel volume
Example 1
The indoor unit is installed 5 m below the highest point in the water
circuit. The total water volume in the water circuit is 100 l.
In this example, no action or adjustment is required.
Example 2
The indoor unit is installed at the highest point in the water circuit.
The total water volume in the water circuit is 380 l.
Water volume
65°C >270 l
80°C >180 l
Actions required:
• pre-pressure must be
decreased, calculate
according to "Calculating
the pre-pressure of the
expansion vessel"
• check if the water volume
is lower than maximum
allowed water volume
(use graph below)
Expansion vessel of the unit
too small for the installation.
pre-pressure (Pg) the
250 300 350 400 450
Installation manual
11