Installation manual
10
EKHBH/XE008AA3V3
Indoor unit for air to water heat pump system
4PW48441-1B
Checking the water volume and expansion vessel pre-
pressure
The unit is equipped with an expansion vessel of 10 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
A minimum water volume is required to prevent that the water
temperature drops too much during defrost (low ambient
temperature).
If the water volume is too low, two problems can occur:
1 The water temperature drops too much during defrost and
defrost stops to protect the plate heat exchanger against
freezing.
2 The compressor does not start up after the defrost cycle
because the water temperature is too low.
In both cases the backup heater will operate instead of the
compressor to increase the water temperature.
When the water temperature is high enough, the backup heater
stops and the compressor restarts.
The minimum required water volume in the system is 20 l.
However, to minimize emergency backup heater operation it is
highly recommended to have a water volume of 40 l.
2
Using the table below, determine if the expansion vessel pre-
pressure requires adjustment.
3
Using the table and instructions below, determine if the total
water volume in the installation is below the maximum allowed
water volume.
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 pre-pressure (Pg) the
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.
If the heating load is higher than the backup heater
capacity, the water temperature can not increase. In
this case refer to
"Re-start at low outdoor ambient
Repeated forced defrost stops can in some cases
cause severe ice build-up on the outdoor unit. This will
lead to reduced unit performance.
When circulation in each space heating 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
1
Outdoor unit
8
By-pass valve
(field supply)
2
Indoor unit
3
Heat exchanger
FHL1..3 Floor heating loop
(field supply)
4
Pump
5
Shut-off valve
T1..3
Individual room
thermostat (field supply)
6
Collector (field supply)
7
Shut-off valve
M1..3
Individual motorised
valve to control loop
FHL1 (field supply)
FHL1
FHL2
FHL3
M1
T1
M2
T2
M3
T3
5
4
3
2
1
7
6
8
Installation
height
difference
(a)
(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.
Water volume
≤
280 l
>280 l
≤
7 m
No pre-pressure adjustment
required.
Actions required:
•
pre-pressure must be decreased,
calculate according to
the pre-pressure of the expansion
vessel"
•
check if the water volume is lower
than maximum allowed water volume
(use graph below)
>7 m
Actions required:
•
pre-pressure must be increased,
calculate according to
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
= maximum water volume
0.3
0.5
1
1.5
2
2.5
100
50
0
20
150
200
250
300
350
400
450
maximum water volume [l]
pre-pressure [bar]
Summary of Contents for EKHBHE008AA3V3
Page 29: ...NOTES NOTES ...
Page 30: ...4PW48441 1B Copyright Daikin ...
