A.O. Smith HYB-90N, Installation And Operating Manual

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36 www.hotwater.com 316888-001 Rev. 00 dRaFt Jun 28 245
CONSTANT OUTPUT TEMPERATURE CONTROL
While the temperature regulation in the previous section
describes the features of temperature monitoring and
regulation, your water heater goes beyond the on/off
control implied there and implements a gas, air and water
fl ow modulation scheme to provide a constant water
delivery temperature from the heat engine for the duration
of the call for heat.
Heat Needed during Normal Operation
The amount of heat needed is based on the amount
of water
fl owing through the heater and the amount of
temperature rise that needs to be generated to meet your
demands. The system will calculate the amount of heat
needed.
The temperature regulation will prevent the inlet
temperature from reaching the temperature set-point.
Detection of Failure to Maintain Desired Constant
Temperature
This check can be used to detect a failure of the stage
2 gas valve. In this case, an insuf
fi cient amount of heat
would be applied. This check can also serve to diagnose
failures or mis-wiring of the water
fl ow restriction valve. If
the valve fails to restrict the fl ow of water, the system may
not be able to suf fi ciently heat the water passing through
the heat engine.
A failure to maintain the desired constant temperature is
determined by the outlet water temperature remaining 15
degrees lower than the set-point for one minute while the
fl ame is established. If this condition is detected while in
the heating state for normal modes, an Alert message is
provided to the display panel.
START UP CONDITIONS
Smoke/Odour
It is not uncommon to experience a small amount of
smoke and odour during the initial start-up. This is due to
burning off of oil from metal parts, and will disappear in
a short while.
NOTE: If there is a discharge from the temperaturepressure
relief valve, refer to the “THERMAL EXPANSION”
section of this manual.
NOTE: Do not plug the temperature-pressure relief
valve.
Strange Sounds
Possible noises due to expansion and contraction of some
metal parts during periods of heat-up and cool-down do not
necessarily represent harmful or dangerous conditions.
Condensation causes sizzling and popping within the
burner area during heating and cooling periods and should
be considered normal. See “CONDENSATE” section.
OPERATIONAL CONDITIONS
Smelly Water
In each water heater there is installed at least one anode
rod (see parts section) for corrosion protection of the tank.
Certain water conditions will cause a reaction between this
rod and the water. The most common complaint associated
with the anode rod is one of a “rotten egg smell” in the hot
water. The smell is a result of four factors which must all
be present for the odour to develop:
a. A concentration of sulfate in the supply water.
b. Little or no dissolved oxygen in the water.
c. A sulfate reducing bacteria which has accumulated
within the water heater (this harmless bacteria is
nontoxic to humans).
d. An excess of active hydrogen in the tank. This is caused
by the corrosion protective action of the anode.
Smelly water may be eliminated or reduced in some
water heater models by replacing the anode(s) with one
of less active material, and then chlorinating the water
heater tank and all water lines. Contact the local water
heater supplier or a quali
fi ed service agency for further
information concerning an Anode Replacement Kit and
this chlorination treatment.
If the smelly water persists after the anode replacement
and chlorination treatment, we can only suggest that
chlorination or aeration of the water supply be considered
to eliminate the water problem.
Do not remove the anode leaving the tank unprotected.
By doing so, all warranty on the water heater tank is
voided.
“Air” In Hot Water Faucets
HYDROGEN GAS: Hydrogen gas can be produced in a
hot water system that has not been used for a long period
of time (generally two weeks or more). Hydrogen gas is
extremely flammable and explosive. To prevent the
possibility of injury under these conditions, we recommend
the hot water faucet, located farthest away, be opened for
several minutes before any electrical appliances which
are connected to the hot water system are used (such as
a dishwasher or washing machine). If hydrogen gas is
present, there will probably be an unusual sound similar
to air escaping through the pipe as the hot water faucet is
opened. There must be no smoking or open
fl ame near
the faucet at the time it is open.