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DESCRIPTION OF OPERATION OF AQUASTAR 80/125 MODELS
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 3.25 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 moves up to #3, the
Water Flow Sensor. This entire unit is also known as the
Water Valve Assembly. The spring pressure of the
Venturi Piston (#23) diverts most of the water flow into the
diaphragm chamber. The only way out of the diaphragm
chamber is through a smaller 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 (#25). At 3/4 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 Heat Exchanger it passes the
Overheat Sensor Switch (#19). This is a safety device
which causes other gas controls to shut off all the gas
if the Heat Exchanger overheats.
GAS FLOW PATH
The appliance Gas Regulator (#24) 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 gas shut-off safety devices 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
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 Overheat Sensor Switch (#19) interrupts 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 25,000 /125,000 Btu's
(Model 125) and 25,000/77,500 (Model 80).
Special “S” version heaters have the ability to further
modulate gas flow so that the effective output approaches
0. This permits the AquaStar 80/125 vpS to work
effectively and safely with pre-heated water.