AquaStar 170 VP manual Description Of Operation Of Aquastar, Water Path, Gas Flow Path

DESCRIPTION OF OPERATION OF AQUASTAR 170

WATER PATH

Cold water entering the Cold Water Inlet passes through a nylon mesh Water Filter Screen (#21) which filters out dirt and debris. Water then passes through the Water Flow Restrictor (#8) which prevents water flow from exceeding 4.25 gallons per minute. The flow control is there to help ensure that water does not flow through the heat exchanger faster than the burners can heat it. The restrictor can be removed if needed.

From the Flow Restrictor the water flows to #3, the Water Valve. The only way out of the water valve is through a small hole, the venturi. Water squirting through the venturi creates a pressure buildup on the high pressure side of the diaphragm chamber. The water pressure is lower on the other side of the venturi hole. A small tube transfers this reduced pressure to the low pressure side of the diaphragm chamber.

The pressure differential moves the diaphragm which exerts force on the Push Rod (#24). At 1.1 gallons per minute, the pressure differential becomes sufficient to overcome the spring pressure of the Gas Flow Valve (#7) opening the gas valve.

The water then moves through the Heat Exchanger (#1) where it absorbs approximately 80% of the heat from the burners. The balance of the heat is exhausted with the flue gases. Located midway through the Heat Exchanger, a Water Temperature Probe (#17) senses water temperature. It works with the Gas Flow Valve (#6) to regulate the amount of gas to the burners.

Before the water leaves the AquaStar, it passes two energy CutOff Switches (ECO-#19). These are safety devices which cause other gas controls to shut off all the gas if the Heat Exchanger overheats.

GAS FLOW PATH

The appliance Gas Regulator (#23) at the inlet to the heater ensures that gas pressure fluctuations don’t over-pressure the heater. The Manual Gas Flow Shut- off Valve (#14) provides a quick gas shut off right on the heater.

The E.C.O.s are integrated with the pilot light. An Electro-Magnet in the Gas Valve ensures that gas flows to the burner only when there is a pilot light to ignite it. The Pilot Knob (#15) shuts gas off to the burners while you light the pilot. You must hold the Pilot Knob in at the single flame position long enough for it to heat the Thermocouple (#12).

The water activated gas valve (#7) opens and shuts in response to water flow. On heaters fueled with LP Gas, a Slow Ignition Device (#4) gradually increases gas flow for ignition. The Natural Gas models have no such device because Natural Gas is delivered at a much lower pressure.

The Thermocouple (#12) produces a very small amount of electricity (0.03 volts) when it is exposed to a flame. This electricity is just enough to hold open the spring- loaded Electromagnet Gas Flow Shut-off Valve (#13). If the thermocouple is not hot enough, the spring closes the valve. Pushing #15 in the single flame position, allows gas to flow to the pilot. Gas can’t go to the burners until the pilot has been lighted and the knob has been turned to the three flame position and released.

If a malfunction causes the Heat Exchanger to get too hot, the E.C.O.s (#19) interrupt the electrical circuit between the thermocouple and electromagnet. This safety feature shuts off the gas to both burners and the pilot. Manual relighting is required once the problem is corrected.

The Thermostatic Gas Flow Modulator (#5) works with the Water Temperature Probe (#17) to modulate the amount of gas delivered by the thermostatically controlled Gas Flow Valve, (#6). Initially the water in the Heat Exchanger is cold, the Gas Flow Valve allows a full flow of gas to the Burners (#2). Then depending on the flow rate, inlet water temperature and/or the Thermostatic Temperature Selector (#20), the Gas Flow Valve (#6) adjusts gas flow anywhere from 0 to 165,000 Btu's.

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