Bosch Bosch 17e Installation Guide download pdf (Page 3)

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The "Primary Circulation" Circuit - causes water to flow through the gas

heating process. The Primary Circulation Pump sources its water from

the Accumulator cylinder or the mains supply or both.

(This will depend on the flow rate through the mains pressure circuit).

Because heated water is always discharged to the Accumulator the

delivered temperature is very stable. Diagram 2 shows the Mains

Pressure + Primary circuits.

b) The "Secondary Circulation" Circuit (this is only required where

there is a need for secondary pipework reticulation i.e. hot water flow

is maintained in a loop through all outlets). In these installations the

secondary return is connected to the hot water primary flow pipe to

ensure the hot water that is circulating does not short circuit the mix

into heated water. Diagram 3 shows the Mains Pressure + Primary +

Secondary circuits.

Notes for the following Water flow circuit diagrams :

Applications

In applications where hot water supply is direct and non-recirculated,

such as some motels, laundrettes, hospitals and sports club

showers; the mains pressure and primary circuits provide a simple

system capable of very high delivery and heat transfer.

In applications where hot water is to be circulated past the outlets,

such as some motels, apartments and very large homes; the

secondary circulating pump and circuit provides immediate hot water

delivery at each outlet with this minor addition to the system. Usually

made in-situ, this circuit is additional to the Integrated Package and is

not provided in the Bosch-Everlast Integrated Package.

Tempering or Thermostatic mixing valves

In accordance with Australian Standard AS 3500.4, it is

recommended that where required a temperature control device or

mixing valve be fitted between the water heater and bathrooms and

ensuites to reduce the risk of scalding. This is achieved by

controlling water temperature to below 50 degrees C. The locations

as shown on the Water flow circuit diagrams are where required at

point of use in the mains pressure circuit.

To ensure there is no conflict with thermostat set temperature of

the COMBO system, they are not associated with the primary or

secondary circulation circuits.

Expansion Relief Valve.

A 750 – 850 kPa expansion relief valve is recommended in the

Primary Circulation Circuit which is transferring heated water into

the Accumulator. The valve allows for expansion of water in the

primary piping loop during the heating cycle. Discharge may

occur during heating and is normal.

Pressure and temperature relief valve (PTR)

A Pressure Relief Valve is located on the Hot Water Outlet

connection of each Bosch Heater Unit in accordance with AG

102, to prevent pressure damage to the heat exchanger.

The COMBO Accumulator cylinder features dual 20 mm PTR

ports. Two 850 kPa PTR valves are provided to meet

requirements in accordance with AG 102 Sec 2.7.10. State

Regulations may require the installation of two PTR valves and/or

PTR valves in the piping manifold configuration. If only one PTR

valve is required, the second provides safe redundancy or a

blanking plug may be substituted. The PTR valve pressure

setting should always be 850 kPa.

Pressure limiting valve

A 500 - 600 kPa Pressure Limiting valve must be fitted, to

ensure correct function of the system in conjunction with

the PTR valve / Expansion Relief valve.

As shown in the Water Flow Circuit Diagrams, isolating valves for

ease of service, line strainers and non return valves are

recommended as good installation practice and to ensure

protection of pumps from contamination or damage in the event

of water system pick up of contaminants.

Installation must comply with Australian Standard AS 3500.4 -

National Plumbing Code, and any local authority regulations.

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Bosch Bosch 17e Installation Guide Page 3

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