Bosch WORCESTER GREENSTORE Operations Instructions download pdf (Page 14)

INSTALLATION

6 720 645 752 (2012/05)14

3.6.5 DHW EXPANSION VESSEL

B Connect the expansion vessel using the hose supplied to the cold

water inlet control group.

For DHW systems with a large volume:

B Check whether the expansion vessel supplied (18 or 25 litres) is

adequate and if required, install an additional expansion vessel in

parallel to the one supplied, ensuring the air charge of each is

identical.

3.6.6 INSTALLING THE DISCHARGE PIPE WORK FROM THE

SAFETY VALVES SUPPLED

B Locate the cold water inlet control group so that any water flowing

from the expansion relief valve will be drained together with any water

discharged from the temperature and pressure relief valve.

B Route the discharge pipework in accordance with part G3, schedule 1

of the Building Regulations (the following includes the most important

requirements of the Building Regulations).

B Install the tundish vertically in direct proximity to the cylinder

(maximum distance between safety valves and tundish 600 mm).

B The discharge pipe work must be of a material capable of

withstanding the potential temperatures and pressures.

B The following applies for the discharge pipe work downstream of the

tundish:

– Minimum 300 mm vertical drop before the first bend.

– Must be at least one pipe size larger than the inlet of the tundish.

– Route the discharge pipe work with a constant fall.

3.6.7 DISCHARGE ARRANGEMENT

Fig. 9 Diagram of a typical discharge pipe arrangement (extract from

Building Regulation G3)

A Safety device (e.g. temperature relief valve)

B Metal discharge pipe (D1) from temperature relief valve to

tundish

C Discharge pipe (D2) from tundish with continuous fall

D Fixed grating

E Trapped gulley

FTundish

Position the inlet control group so that the discharge from both the two

safety valves can be joined together via a 15 mm end feed Tee. Connect

the Tundish and route the discharge pipe. The discharge pipework must

be routed in accordance with Part G3 of schedule 1 of the Building

Regulations. The information that follows is not exhaustive and if you are

in doubt you should seek advice.

The two safety valves will only discharge water under fault conditions.

When operating normally water will not be discharged.

The tundish should be vertical, located in the same space as the

unvented hot water storage system and be fitted as close as possible and

within 600 mm of the safety device e.g. the temperature relief valve.

The discharge pipe (D2) from the tundish should terminate in a safe

place where there is no risk to persons in the vicinity of the discharge

and:

• Be at least one pipe size larger than the nominal outlet size of the

safety device unless its total equivalent hydraulic resistance exceeds

that of a straight pipe 9 m long i.e. discharge pipes between 9 m and

18 m equivalent resistance length should be at least two sizes larger

than the the nominal outlet size of the safety device, between 18 and

27 m at least 3 sizes larger, and so on. Bends must be taken into

account in calculating the flow resistance. Refer to Fig. 9, Table 6 and

the worked example.

An alternative approach for sizing discharge pipes would be to follow

BS6700 Specification for design installation, testing and

maintenance of services supplying water for domestic use within

buildings and their curtilages.

• Have a vertical section of pipe at least 300 mm long, below the

tundish before any elbows or bends in the pipework.

• Be installed with a continuous fall.

• It is preferable for the discharge to be visible at both the tundish and

the final point of discharge but where this is not possible or practically

difficult there should be clear visibility at one or other of these

locations. Examples of acceptable discharge arrangements are:

– Ideally below the fixed grating and above the water seal in a trapped

gulley.

– Downward discharges at a low level; i.e. up to 100 mm above

external surfaces such as car parks, hard standing, grassed areas

etc. are acceptable providing that where children play or otherwise

come into contact with discharges, a wire cage or similar guard is

positioned to prevent contact whilst maintaining visibility.

– Discharges at a high level; e.g. in to metal hopper and metal down

pipe with the end of the discharge pipe clearly visible (tundish

visible or not) or onto a roof capable of withstanding high

temperature discharges of water and 3 m from any plastic guttering

systems that would collect such discharges (tundish available).

– Where a single pipe serves a number of discharges, such as in

blocks of flats, the number served should be limited to not more

than 6 systems so that any installation can be traced reasonably

easily. The single common discharge pipe should be at least one

pipe size larger than the largest individual discharge pipe to be

connected. If unvented hot water storage systems are installed

where discharges from safety devices may not be apparent i.e. in

dwellings occupied by blind, infirm or disabled people,

consideration should be given to the installation of an electronically

operated device to warn when discharge takes place.

WARNING: Risk of scalding!

Hot water can lead to severe scalding.

B Route the discharge pipe work so that any discharged

hot water or steam cannot create a risk.

300 mm

minimum

B The discharge will consist of scalding water and

steam. Asphalt, roofing felt and non-metallic

rainwater goods may be damaged by such

discharges.

B It is not acceptable to discharge straight into a soil

pipe.

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Bosch WORCESTER GREENSTORE Operations Instructions Page 14

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