HAMWORTHY HEATING LTD
4
WEYMOUTH
500001112/C
4.0 OPERATION OF THE PRESSURISATION UNIT
Figure 5 Schematic Layout of the Standard and Advanced Units.
4.1 Unit Operation.
A drop in system pressure due to, for example, loss of water, will cause the pump to maintain the pressure. As
the level of water in the tank reduces a ball valve allows new water into the tank
.
When the pump pressure switch
is satisfied the pump stops
4.2 Safety Functions (Advanced only):
The advanced unit is fitted with two extra pressure switches . A pressure above the high pressure limit set on the
unit will switch over the SPDT high pressure switch and a pressure below the low pressure limit set on the unit will
switch over the SPDT low pressure switch.
The switches can be connected to boiler safety circuits as shown in the wiring diagram supplied with the unit and
displayed inside the unit’s cover.
5.0 GENERAL REQUIREMENTS
5.1 Related Documents.
Pressure Systems and Transportable Gas Containers Regulations 1989.
It is the law that pressure system appliances are installed by competent persons in accordance with the above
regulations. Failure to install appliances correctly could lead to prosecution. It is in your own interest and that of
safety, to ensure that this law is complied with.
The installation of the pressurisation unit and expansion vessel MUST be in accordance with the relevant require-
ments of the Pressure System Regulations, Building Regulations, IEE Regulations and the bylaws of the local
water undertaking.
It should also be in accordance with any requirements of the local authority and the relevant recommendations of
the following documents:-
Applicable standards and documents are:
BS 7074 Application, selection and installation of expansion vessels and ancillary equipment for sealed water systems.
BS 6644 Installation of Gas Fired Hot Water Boilers 60 kW to 2 MW
BS 6880 Parts 1,2&3: Code of practice for low temperature hot water heating systems of output greater than 45 kW.
BS 6759 Part 1 (ISO 4126): Specification for safety valves for steam and hot water.
BS 3456 (CEE10 Part 1, CEE11 Part 1): Safety of Household and similar electrical appliances.
HSE Guidance note PM5: Automatically controlled steam and hot water boilers.
