Equipment Overview; Principal Of Operation - Jet MAXI D125 Operation & Maintenance Manual

Equipment Overview

The function of this pressurisation unit is to provide a means of automated water top-up to sealed heating and
cooling systems. The equipment is designed to provide periodic water top-up to compensate for minor losses in
system pressure (e.g. slow leaks, air venting, etc.).
This equipment is not designed to cope with sudden losses of system pressure (e.g. manual
draining) or major water losses (e.g. large leaks). The equipment is also not intended to be used
for water boosting applications.

Principal of Operation

The following schematic shows the internal arrangement of a pressurisation unit:
The pressurisation unit is fitted with a break tank (1) which is filled from the mains water supply (2) via a float
operated valve (3). The break tank is fitted with an overflow (4) in case the break tank overfills, and a weir
overflow (5) in case the primary overflow fails.
The pressurisation unit is connected into the heating system (6) via an isolation valve (7).
The pressure sensor (8) monitors the system pressure.
If the pressure sensor detects a drop in pressure, the pump (9a) will pump water from the break tank into the
system. Once the required pressure has been reached, the pump will stop.
On twin pump models, a second pump (9b) is provided. The two pumps will run in a duty/standby configuration
(i.e. the active pump will alternate with each pump start).
The pump(s) are fitted with non-return valves (10a, 10b) to prevent backflow.
A drain valve (11) is provided for draining down the unit and for commissioning purposes.
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Rev 8.1 Oct-15 Page 6 / 42