Standard Pressurisation Unit - Grundfos PHT-N130 Installation And Operating Instructions Manual

5.1 Standard Pressurisation Unit (PHT-N/D/F models).
The following schematic shows the arrangement of the PHT-N/D/F pressurisation models:
Fig. 2 – PHT-N/D/F Schematic
The pressurisation unit is connected into the sealed system (System 1) through the System 1
Connection(6.
The System 1 Isolation Valve(7) provides a point to isolate the unit from the system.
The System 1 Drain Valve(8) provides a point to drain down the unit and/or system and for
commissioning purposes.
The System 1 Pressure Transmitter(AI1) measures the pressure in System 1.
The PHT unit can be configured with one or two pumps (P01 and P02) which when energised, will
transfer water from the Break Tank into System 1 to increase the pressure as required.
The pumps run in a duty/standby configuration where only one pump runs at a time (the duty
pump). The duty pump will always be the pump with the least accumulated total run time. This is a
measure to spread the wear evenly between the two pumps.
In single pump units Pump 1(P01) permanently acts as the duty pump.
A Current Sensor(AI5) (not shown on schematic), measures the electrical current consumption of
Pump 1(P01) and Pump 2(P02) to detect faults in the pumps.
A System 1 Fault Output(DO1) (not shown on schematic) is used to interlock the boiler or chiller on
System 1 to disable it if the system pressure falls outside of safe operating limits.
A General Fault Output(DO2) is provided to signal any fault presented by the unit.
Three additional outputs are provided which can be customised to signal a range of specific faults
or functions, Programmable Output 1(DO6), Programmable Output 2(DO7) and Programmable
Output 3(D08).
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The pressurisation unit is fitted
with a Break Tank(1) which is filled
from the Water Supply(2), via a
Float Valve(3). The break tank is
fitted with a Drain Overflow(4) in
case the Break Tank overfills, and a
Weir Overflow(5) in case the Drain
Overflow becomes blocked.
A Low Water Float Switch(DI1) is
fitted to detect a low water
condition.
A High Water Float Switch(DI2)
(optional extra) is fitted to detect
overfilling of the tank.