Domestic Water Supply; Pressure Relief Pipe Work - Bosch Worcester Greenstar HIU E Installation And Maintenance Instructions Manual

Pre-installation requirements
4.3

Domestic water supply

Use in hard water areas
Normally there is no need for water treatment to prevent scale formation
as the maximum temperature of the DHW heat exchanger is limited by
the electronic control.
In areas where temporary water hardness exceeds 200 ppm,
consideration may need to be given to the fitting of a scale prevention
device. In such circumstances, the advice of the local water authority
should be sought.
Showers/bidets:
• Ensure that the shower is suitable for use with mains water pressure.
• If a shower head can be immersed in water or comes closer than
25mm from the top edge of a bath or shower tray spill over level then
an anti-siphon device must be fitted to the shower hose.
• Bidets with direct hot and cold mains water can be used (with the
approval of the local water authority) and must be the over rim
flushing type with shrouded outlets to prevent the fitting of hand held
sprays.
Water mains pressure
• Minimum inlet pressure to achieve nominal DHW flow rate
– 58.6kW units - 2.0 bar
– 39.1kW units - 1.5 bar
• Maximum mains fed water pressure 10 bar.
– If necessary fit a pressure reducing valve.
• Where the mains water supply has a non-return, back flow
prevention valve fitted, a mini expansion vessel should be connected
to the mains water inlet pipe between the non-return valve and the
appliance.
NOTICE: Risk of damage to household appliances!
Non-return, back flow prevention devices (including
those associated with water meters) fitted to the mains
water supply can cause a pressure build up which could
damage the appliance and other household appliances.
▶ Fit a mini expansion between the non-return valve,
back flow prevention device.
4.4

Pressure relief pipe work

WARNING: Risk of scalding!
Injury if discharge pipe is not routed correctly.
▶ The pressure relief valve is a safety device for the
appliance and if activated may discharge boiling
water or steam through the relief valve drain pipe.
▶ Care should be taken when siting the outlet pipe so
that it does not cause an obstruction or discharge
above a window, entrance or other public access
where it could cause a hazard.
Refer to figure 9
• The pressure relief drain pipe [1] and [3] from the appliance should
be at least 15mm diameter copper pipe and run downwards to a safe
point of discharge, away from any electrical equipment or other
hazard, preferably to an external drain or soak away.
• Pipe [1] should be finished with a partial bend, near the outlet to face
the external wall (as shown) to help prevent freezing.
18
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2
3
4
Fig. 9 Pressure relief pipe-work external routing
[1] Outlet facing external wall
[2] External wall
[3] Outlet to external drain
[4] External drain
Internal PRV discharge
The PRV discharge pipe may terminate internally to a safe position such
as a waste pipe or soil pipe, provided that the following conditions are
met:
• The material used must be capable of taking the maximum
temperature provided by the District Heating primary flow.
• The discharge must be directly or indirectly visible and will not
discharge onto the occupants of the premises or onto any electrical
wiring or components. An example of "directly" is a tundish and
"indirectly" an audible indication of pressure loss.
• There is a continual fall towards the discharge point from the HIU.
• Where a tundish is used, a suitable trap is installed to protect against
foul smells entering into the living areas, whilst ensuring no undue
resistance to the discharge. An example would be a washing machine
trap with upstand.
• For the higher district flow temperatures above 85 °C, It is
recommended to use the Hotun Hiflo tundish manufactured by RA
Tech UK. Guidance on this product can be found at http://
hutun.co.uk.
– We would also recommend that the Hotun Shield is used in
conjunction with the Hotun Hiflo on HIU installations. The Hotun
Hiflo tundish can also be used for providing a visual indicator
which will allow connection of a PRV directly into internal waste
pipes or soil stacks.
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6720646608-123.1Wo
6 720 808 928 (2017/06)