IDEAL INDUSTRIES HE24, HE18, HE12, HE15 manual Sealed System Requirements

GENERAL

7 SEALED SYSTEM REQUIREMENTS - continued

4.Expansion Vessel

a.A diaphragm type expansion vessel must be connected to a point close to the inlet side of the pump, the connecting pipe being not less than 15 mm (1/2" nominal) size and not incorporating valves of any sort.

b.The vessel capacity must be adequate to accept the expansion of the system water when heated to 110oC (230oF).

c.The charge pressure must not be less than the static water head above the vessel. The pressure attained in the system when heated to 110o C (230o F) should be at least 0.35 bar (5 Ib/in2) less than the lift pressure of the safety valve.

For guidance on vessel sizing refer to the table in Frame 8.

For further details refer to BS. 5449, BS. 7074:1 and the British Gas Corporation publication 'Material and Installation Specifications for Domestic Central Heating and Hot Water'. For IE refer to the current edition of I.S.813.

5.Cylinder

The cylinder must be either of the indirect coil type or a direct cylinder fitted with an immersion calorifier which is suitable for operating on a gauge pressure of 0.35 bar (5 Ib/in2) in excess of the safety valve setting. Single feed indirect cylinders are not suitable for sealed systems.

6.Make-up Water

Provision must be made for replacing water loss from the system, either:

a.From a manually filled make-up vessel with a readily visible water level. The vessel should be mounted at least 150 mm (6") above the highest point of the system, and be connected through a non-return valve to the system, fitted at least 300 mm (12") below the make-up vessel on the return side of the domestic hot water cylinder or radiators.

or

b.Where access to a make-up vessel would be difficult by pre-pressurisation of the system. Refer to 'Filling', below.

7.Mains Connection

There must be no direct connection to the mains water supply or to the water storage tank supplying domestic water, even through a non-return valve, without the approval of the local water authority.

8.Filling

The system may be filled by one of the following methods:

a.Through a cistern, used for no other purposes, via a ball valve permanently connected directly to a service pipe and/or a cold water distributing pipe.

The static head available from the cistern should be adequate to provide the desired initial system design

pressure. The cold feed pipe from the cistern should include a non-return valve and a stop valve with an automatic air vent connected between them, the stop valve being located between the system and the automatic air vent. The stop valve may remain open during normal operation of the system if automatic water make-up is required.

b.Through a self-contained unit comprising a cistern, pressure booster pump (if required) and, if necessary, an automatic pressure reducing valve and flow restrictor. The cistern should be supplied through a temporary connection from a service pipe or cold water distributing pipe.

This unit may remain permanently connected to the heating system to provide limited automatic water make-up. Where the temporary connection is supplied from a service pipe or distributing pipe which also supplies other draw-off points at a lower level then a double check valve shall be installed upstream of the draw-off point.

c.Through a temporary hose connection from a draw-off tap supplied from a service pipe under mains pressure. Where the mains pressure is excessive a pressure reducing valve shall be used to facilitate filling.

The following fittings shall form a permanent part of the system and shall be fitted in the order stated:

A stop valve complying with the requirements of

BS. 1010, Part 2 (the hose from the draw-off tap shall be connected to this fitting).

A test cock.

A double check valve of an approved type.

•Thoroughly flush out the whole of the system with cold water, without the pump in position.

•With the pump fitted, fill and vent the system until the pressure gauge registers 1.5 bar (21.5lb/in2). Examine for leaks.

•Check the operation of the safety valve by manually raising the water pressure until the valve lifts. This should occur within ± 0.3 bar (± 4.3lb/in2.) of the preset lift pressure.

•Release water from the system until the initial system design pressure is reached.

•Light the boiler and heat the system to the maximum working temperature. Examine for leaks.

•Turn off the boiler and drain the system while still hot.

•Refill and vent the system.

•Adjust the initial pressure to the required value.

Sizing procedure for expansion vessels: The volume of the expansion vessel (litres) fitted to a sealed system shall not be less than that given by the table on the following page, multiplied by a factor of 0.8 (for flow temperatures of less than 83o C).

12 icos - Installation & Servicing