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6 8
PLUMBING CONNECTION
WINTER 2015
HOT WATER INSTALLATION CHECKS
POINT 1
The current water heating market is blessed with
numerous choices and solutions available for the
consumer’s hot water needs and expectations.
The end result of water heating system options all relate
to heat exchange in one way or another. For example,
heat exchange through a primary flue baffle of a mains
pressure gas storage system or the same process through a
continuous flow gas model.
Listed are significant water temperatures via the Rheem
Hot Water Manual that relate to the delivery of heated
water and the variations that need to be considered when
recommending a water heating solution for your next job.
POINT 2: PRESSURE LIMITING/REDUCTION
Where water supply pressures exceed the maximum
indicated allowances, a means of reducing line pressure is
an essential part of the correct installation of a gas, solar or
electric water heating system.
This may be achieved by means of either a pressure
limiting valve or a pressure reduction valve.
Whichever valve is used, it should be placed on the cold
water supply to the whole house in order to maintain equal
cold and hot water pressures. This requirement is also
necessary for the adequate performance of most tempering
valves and thermostatic mixing valves.
In such cases, however, a larger valve is needed than when
connected only to the water heater cold supply connection.
A description of the two types of valves is as follows...
LIMITING VALVE
The pressure limiting valve remains open until the
upstream pressure approaches the valve pressure setting.
With inlet pressures above this, the valve acts as a reducing
valve to keep the outlet pressure around this level.
Pressure limiting valves are made in a range of sizes, the
most common being 15mm, 20mm and 25mm.
For continuous flow water heaters, it is recommended to
use an RMC PSL type pressure limiting valve, as this model
valve does not display non-return characteristics typical in
PS type valves.
INSTALLATION OF LIMITING VALVES
The following needs to be applied:
∫ Where approved by local water supply authorities, the
pressure limiting valve may be placed on the cold water
JON PALFREY
LISTS THREE POINTS OF RELEVANCE WHEN CONSIDERING THE INSTALLATION REQUIREMENTS OF
THE NEXT WATER HEATING SYSTEM YOU SELECT AND INSTALL.
HOT WATER CLINIC
JON PALFREY
TABLE 17.11: SIGNIFICANT WATER TEMPERATURES
Temperature
Event
0°C
Freezing point of water at sea-level
4°C
Temperature below which water reduces its density
(weight)
8°C
Approximate minimum ambient water temperature
in Australia (Melbourne - winter, used in sizing water
heaters for Victoria)
13°C
1. Approximate average water temperature
in Melbourne 2. Approximate minimum water
temperature in Sydney
20°C - 45°C
Temperature range in which Legionella bacteria
flourish
24°C
Approximate maximum ambient water temperature
in Australia
38°C - 40.5°C Bathing temperature for children and infants
40°C - 43°C
Bathing temperature for adults
50°C
Maximum supply temperature to bathrooms and
Ensuites for new installations in Australia
55°C and
above
Temperature range in which Legionella bacteria
cannot survive
55°C - 60°C Washing up temperature
60°C
Thermostat setting for booster elements in Rheem
Solar, Heat Pump and Dual Element water heaters
60°C
Normal setting for domestic gas water heaters
65°C
Maximum setting for Rheem domestic gas thermostats
70°C
Maximum setting for Rheemglas electric thermostats
75°C
1. Factory setting for Rheem Heavy Duty electric
water heater thermostats 2. Maximum setting for
Optima electric thermostats
77°C
Temperature required in the sink for sanitising purposes
82°C
Maximum thermostat setting for thermostats in
Rheem Heavy Duty water heaters
82°C - 92°C Temperature at which the energy cut-off device will
operate on fixed setting thermostats
87°C- 90°C High limit thermostat setting on Rheem 621,631265
and 621,631275 water heaters
87°C - 95°C Temperature at which the energy cut-off device will
operate on adjustable thermostats
93°C - 95°C Temperature at which a TPR valve subjected to
normal working pressure will start to discharge
98.5°C Nominal thermostat setting for Rheem Lazer boiling
water units
100°C Boiling point of water at sea-level