34 | 180R9289 | AQ109686503106en-001102
© Danfoss | 2023.01
Operation guide
Installation, Operation and Maintenance Manual for PAHT 256-308 pumps
7.4 Closed-system design (not applicable
for PAHT 256-308)
A
Inlet line:
Dimension the inlet line to obtain mini-
mum pressure loss (large flow, minimum
pipe length, minimum number of bends/
connections, fittings with small pressure
losses and restrictions).
B
Inlet filter:
Install the filter (1) in front of the tank (2).
Please consult the Danfoss filter data sheet
for guidance on how to select the right
filter.
C
Monitoring pressure switch:
Install the monitoring pressure switch (3) in
front of the filter (1). Set the maximum inlet
pressure to 2 barg (29.0 psig). The monitor-
ing pressure switch will stop the pump (5) if
inlet pressure is higher than 2 barg (29.0
psig), indicating that the filter element
must be changed.
D
Monitoring temperature switch:
Install the monitoring temperature switch
(4) in the tank. Set the temperature value
according to technical data, item 4. The
monitoring temperature stops the pump if
inlet temperature is higher than the set
value.
E
Hoses:
Always use flexible hoses (6) to minimize
vibrations and noise.
F
Inlet pressure:
In order to eliminate the risk of cavitation
and other pump damage, pump inlet
pressure must be maintained according to
specifications described in item 4, technical
data.
G
Non-return valve (7):
Should be installed after the outlet to
prevent pump backspin, which may ruin
the pump.
H
Pressure relief valve:
As the Danfoss PAHT pump begins to
create pressure and flow immediately after
start-up regardless of any counter pressure,
a pressure relief valve (8) should be
installed to prevent system damage.
I
System water filling:
To ensure proper filtration of new water
(10) supplied to the system, always use the
filling valve (9).
J
Minimum level switch:
Install the minimum level switch (11) above
the outlet of the reservoir. The level switch
must stop the pump if the water in the
reservoir is below the switch, which
indicates that the reservoir is empty.
Reservoir
PI
System
PI
M
PI
System
PI
M
1
2
3
4
5
5
7
6
1
2
3
4
6
6
7
8
5
9
10
11
Data sheet
