John Wood Indirect Water Heaters - Manual (Page 5)

To Assure Relief Valve Operation
(Every 12 months):
Manually open the relief valve to flush any lime deposits that
may have developed. CAUTION! Water can be extremely
hot. Make certain the seat closes properly. Let it snap shut.
See Figure 3.
Cathodic Protection
Your water heater has been equipped with an anode that
protects the tank from corrosion. As the anode works, it
slowly dissolves over time and may need to be replaced. If
the anode is less than 10mm (3/8 in.) in diameter, or has
any exposed bare core, it must be replaced. Depending on
water conditions, an anode can last from one to ten years.
Many localities treat their water, which can have significant
effect on the life of your heater. Water conditioning, such as
over-softening, can accelerate the rate at which the anode
is consumed. Rapid depletion can leave a heater unprotect-
ed causing a premature failure. As with any water heater, it
is good practice to check the anode annually to see if it
needs replacing. Operating a water heater without an
actively working anode will void the warranty. Failure to
maintain the anode may result in premature failure of the
heater.
To Prevent Corrosion Of The Tank
(Every 12 months):
1. Turn the electrical supply to the water heater "OFF".
2. Close the cold inlet supply valve.
3. Open a hot water tap supplied by the heater. (CAU-
TION: Water will be hot).
4. Remove enough water to empty the piping system.
5. Using a 1 1/16" socket remove anode, inspect and
replace if required. The anode is centrally located in the
top of the heater.
6. To refill the heater, see 'Filling' section.
Pressure Build-Up In A Water System
During the heating cycle of the water heater the water
expands, creating a pressure build-up in the water system.
The water supply meter may contain a check valve or back-
flow preventer. This will create a closed water system. A
temperature and pressure relief valve must be installed on
the water heater (150 PSI maximum pressure setting, see
temperature and pressure relief valve.) To prevent this “T &
P VALVE” from discharging hot water, the loss of energy
and to reduce the possible build-up of lime in the “T & P
VALVE” there are two recommendations:
1. Install an expansion tank on the cold water supply line.
For every 50 U.S. gallons of stored water the expansion
tank must have a minimum capacity of 1.5 U.S. gallons.
or
2. Install a 125 PSI Pressure relief (only) valve in the cold
water supply line. Make sure that the discharge of this
valve is directed to a drain to prevent water damage and
ensure that it is protected from freezing.
WARNING: Failure of the internal heating coil could cause
an over pressurization of heating system boiler and a dis-
charge of water from the boiler pressure relief valve.
Temperature and Pressure
Relief Valve
Manual Relief Valve
Discharge line to drain
Figure 3 T&P Valve Test
– 5 –