Ariston 250I Instructions For Installation, Use, Maintenance - Page 13

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250I WITH TYPICAL BOILER CONNCETION

TPRV & PRV DISCHARGE

The discharge from the cylinder TPRV and combination PRV must

be plumbed to the tundish and should not be used for any other

purpose. The tundish must be vertical and fitted within 750mm of the

pressure relief valve and must be located with the Nuos. The tundish

must be in a position visible to the occupants, and positioned away

from any electrical devices. The discharge pipe from the tundish

should terminate in a safe place where there is no risk to persons in

the vicinity of the discharge, and be made of a suitable material in line

with Building Regulation G3 (preferably metal). The tundish must not

be located near or above electrical components, switches or junction

boxes.

TPRV & PRV DISCHARGE PIPES – TO GULLY

The discharge pipes from safety devices (tundish) must be installed

to fully comply with Part G3 of the Building Regulations (latest edition).

The following text, and diagram 1 are reproduced from G3 Building

Regulations 2010 (as amended) Draft.

BUILDING REGULATIONS G3

(The following text is reproduced from the Building Regulations. It is

included here for reference only).

These are a statutory document and take priority over all other reg-

ulations and recommendations. The installation of an unvented hot

water system of over 15 litres is classified as a "Controlled Service"

and Regulation G3 applies. To meet the requirements of the regula-

tion, installation of an unvented system should be undertaken by a

"competent installer". All installations of unvented hot water storage

systems having a capacity of more than 15 litres should be notified

to the relevant Local Authority by means of building notice 10 or by

the submission of full plans. It is important to note that it is a criminal

offence to install an unvented hot water storage system over 15 litres

without notifying the Local Authority

DISCHARGE PIPES FROM SAFETY DEVICES

Discharge pipe D1

1. Safety devices such as temperature relief valves or combined

temperature and pressure relief valves should discharge either

directly or by way of a manifold via a short length of metal pipe (D1)

to a tundish.

2. The diameter of discharge pipe (D1) should be not less than the

nominal outlet size of the safety device, e.g. temperature relief

valve.

3. Where a manifold is used it should be sized to accept and dis-

charge the total discharge from the discharge pipes connected to it.

4. Where valves other than a temperature and pressure relief valve

from a single unvented hot water system discharge by way of the

same manifold that is used by the safety devices, the manifold

should be factory fitted as part of the hot water storage system

unit or package.

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

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

possible to, and lower than, the safety device,with no more than

600mm of pipe between the valve outlet and the tundish (see

Diagram 1).

Note: To comply with the Water Supply (Water Fittings) Regula-

tions, the tundish should incorporate a suitable air gap.

6. Any discharge should be visible at the tundish. In addition, where

discharges from safety devices may not be apparent, e.g. in dwell-

ings occupied by people with impaired vision or mobility, consid-

eration should be given to the installation of a suitable safety

device to warn when discharge takes place,e.g. electronically op-

erated.

Discharge pipe D2

7. The discharge pipe (D2) from the tundish should: a. have a vertical

section of pipe at least 300mm long below the tundish before

any elbows or bends in the pipework (see Diagram 1); and b. be

installed with a continuous fall of at least 1 in 200 thereafter.

8. The discharge pipe (D2) should bemade of: a. metal; orb. oth-

er material that has been demonstrated to be capable of safely

withstanding temperatures of the water discharged and is clearly

and permanently marked to identify the product and performance

standard (e.g. as specified in the relevant part of BS 7291-1:2006

Thermostatic pipes and fittings for hot and cold water for domestic

purposes and heating installations in buildings General require-

ments).

9. The discharge pipe D2 should 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 9m

long, i.e. for discharge pipes between 9m and 18m the equiva-

lent resistance length should be at least two sizes larger than the

nominal outlet size of the safety device; between 18 and 27m at

least 3 sizes larger, and so on; bends must be taken into account

in calculating the flow resistance. See Diagram 1, Table 3.1 and the

worked example.

Note: An alternative approach for sizing discharge pipes would

be to follow Annex D, section D.2 of BS 6700:2006 + A1:2009

Specification for design, installation, testing and maintenance of

services supplying water for domestic use within buildings and

their curtilages.

13 / EN