Baxi Potterton Gold FSB 30 HE manual Sealed Systems Fig

	3 Litre
Air	Top Up Bottle
	(if required)
Vent

	Pressure	Filling
Safety		Point
	Gauge
Valve
		Pump
	Expansion		Radiator
			Circuit
	Vessel
Boiler
	System Drains at
	Low Point

Max Boiler Flow

Fig. 13 Temp = 82° C

Method of determining minimum expansion

vessel volume for sealed systems.

		Multiply Total
Vessel Charge	Initial System	Water Content Of
Pressure (Bar)	Pressure (Bar)	System By (Litres)
	0.5	0.067
0.5	1.0	0.112
	1.5	0.207
	2.0	0.441
1.0	1.0	0.087
	1.5	0.152
	2.0	0.330
1.5	1.5	0.125
	2.0	0.265

Table. 1	Example :-	System Volume = 75 litres
		Vessel Charge Pressure = 1.0 bar
		Initial System Pressure = 1.5 bar
	Then :-	75 x 0.152 = 11.4 litres

Expansion Vessel Volume

NOTE

Where a vessel of the calculated size is not obtainable then

the next available larger size should be used.

Stop	Double
	Check	Stop
Valve	Valve	Valve
Mains
Inlet
	Temporary	CH
	Hose
		Return
Fig. 14

6.0System Details

6.7Sealed Systems (Fig. 13)

1.SAFETY VALVE - A safety valve complying with the requirements of BS 6750 Part 1 must be fitted close to the boiler on the flow pipe by means of a horizontal or vertically upward connection with no intervening valve or restrictions and should be positioned to facilitate testing. The valve should be pre-set and non-adjustable to operate at a pressure of 3 bar (45 Ibf/in2). It must be arranged to discharge any water or steam through a pipe to a safe outlet position.

2.PRESSURE GAUGE - A pressure gauge of minimum range 0-4 bar (0-60 Ibf/in2) with a fill pressure indicator must be fitted to the system, preferably at the same point as the expansion vessel in an easily visible position.

3.EXPANSION VESSEL - An expansion vessel complying with the requirements of BS 4814 must be fitted to the system by means of a connection close to the inlet side of the circulating pump in accordance with the manufacturers instructions, the connecting pipe being unrestricted and not less than 15mm (1/2 in) nominal size. The volume of the vessel should be suitable for the system water content and the nitrogen or air charge pressure should not be less than the system static head (See Table. 1).

Further details of sealed system design can be obtained from BS 5449 and the British Gas publication entitled 'Specifications for Domestic Wet Central Heating Systems'.

4.FILLING POINT - A filling point connection on the central heating return pipework must be provided to facilitate initial filling and pressurising and also any subsequent water loss replacement / refilling. The sealed primary circuits may be filled or replenished by means of a temporary connection between the primary circuit and a supply pipe provided a ‘Listed’ double check valve or some other no less effective backflow prevention device is permanently connected at the inlet to the circuit and the temporary connection is removed after use. The filling method adopted must be in accordance with all relevant water supply regulations and use approved equipment.

Your attention is drawn to, for GB: Guidance G24.2 and recommendation R24.2 of the Water Regulations Guide. for IE: the current edition of I.S. 813 “Domestic Gas Installations”.

5.MAKE UP SYSTEM - A method of replacing water lost from the system should be provided either by means of a make up vessel of not more than 3 litres (5 pints) capacity, mounted above the highest point of the system, or by re-pressurisation of the system.

6.VENTING - A method of venting the system during filling and commissioning must be provided by fitting automatic air vents or by venting manually.

7.HOT WATER STORAGE - The hot water storage vessel must be of the indirect coil type.

8.COMPONENTS - All components used in the system must be suitable for operation at 110°C (230°F) and at the pressure allowed by the safety valve.

14© Baxi Heating UK Ltd 2011