180R9288_AQ109686503100en-001301 | 35
© Danfoss | 2023.12
Operation guide
Installation, Operation and Maintenance Manual for PAHT 20-90 pumps
7.4
Closed-system design (not
applicable for PAHT 256-308)
A
Inlet line:
Dimension the inlet line to obtain
minimum 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 monitoring 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
1
2
3
4
6
6
7
8
5
9
10
11
