CONSTANT OUTPUT TEMPERATURE CONTROL

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 flow 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 flowing 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 insufficient amount of heat would be applied. This check can also serve to diagnose failures or mis-wiring of the water flow restriction valve. If the valve fails to restrict the flow of water, the system may not be able to sufficiently 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 flame 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/Odor

It is not uncommon to experience a small amount of smoke and odor 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 temperature- pressure 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 odor 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 qualified 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 flame near the faucet at the time it is open.

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A.O. Smith HYB-90N Constant Output Temperature Control, Detection of Failure to Maintain Desired Constant Temperature