A multiple installation of 27 litre gas water heaters on a single manifold is possible, using a parallel plumbing
arrangement, where large volumes of hot water are required. It is good practice, but not essential, to install
the water heaters in an Equa-Flow® plumbing arrangement. The installation may operate on a dead leg
system or a circulated flow and return system.
If a circulated flow and return system is installed, the circulator must be sized and set to provide a minimum
flow rate of 3.0 L/min through the circulated hot water flow and return system and be either thermostatically
and / or timer controlled. The circulator must not be set to operate continuously, i.e. 24 hours per day.
The cold (or solar preheat) water and hot water manifolds must be designed to balance the flow from each
water heater. To achieve this, there are basic installation requirements and principles which must be
1. The maximum number of water heaters in a bank should be 6. Only one bank can be installed.
2. The water heaters must be of the same model.
3. The cold (or solar preheat) water line, cold (or solar preheat) and hot headers and hot water line must be
sized to meet the requirements of both AS/NZS 3500.4 and the application. The gas line must be sized
to meet the requirements of AS/NZS 5601 and the application.
Minimum header pipe sizes at the installation are:
Cold (or solar preheat) and hot header pipe size
Note: Water and gas supply pipe sizes to the installation may be required to be larger than the minimum
pipe sizes at the installation to meet the requirements of the Standards and the application.
The recommended branch line size for the cold (or solar preheat) and hot water and gas pipes is DN20.
4. A full flow gate valve or ball valve and if required a pressure limiting valve must be installed on the cold
water line to the system. A non-return valve or stop tap must not be installed.
Note: The gate valve or ball valve and pressure limiting valve are not required if this is an in-series gas
booster installation to a solar water heater.
5. A full flow gate valve or ball valve (not a stop tap) must be installed on both the inlet and outlet branches
of each water heater. A non-return valve must not be installed.
6. An isolation valve must be installed on the gas branch of each water heater.
7. An adjustable pressure reducing valve (PRV) (RMC model SYR 312 / 20) must be installed on the cold
(or solar preheat) branch to all but the first water heater.
Each PRV is to be adjusted so that each subsequent water heater is staged to operate only after the
required hot water flow rate increases by intervals of 13 litres per minute (refer to “Pressure Reducing
Valve Commissioning Procedure” on page 29).
8. Non-return valves or pressure limiting valves must not be installed on the branch lines to the water
9. It is good plumbing practice for all fittings, valves and branch lines to be matched sets all the way along
10. Sufficient space must be left to enable access, servicing or removal of any water heater.
The water heaters can be installed side by side with minimal clearance between them. The AGA has
approved the installation of the water heaters with an exemption from the 300 mm minimum clearance
requirements between flue terminals, as stated in AS/NZS 5601, clause 22.214.171.124.
A second rating label is attached to the inside of the front cover of each water heater. This can be
referenced to determine details of the water heater.