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MEASURING TECHNIQUES
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Ohm (resistance)
measurements are taken, with all power turned off to the heater,
on the heating elements and the temperature sensors. Continuity checks can
be done on the control wires, high limit switch, level detector circuit and
leak detector circuit. Refer to
Component Testing Table for details. The multi-meter should be
dialed to ohms, on the appropriate scale to measure up to 20 ohms for the
elements and on the appropriate scale to measure up to 500 ohms for the
temperature sensors. The two multi-meter probes need to be placed on both
connection terminals of the device in order to correctly measure the
resistance (ohms). Refer to the
Component Testing Table for the normal ohm readings of the elements
in the various models. If no ohm reading or a decimal ohm value is read for
any of these devices, then it is likely the device or it’s connecting
control wire to the control board is open and needs to be corrected or
replaced. However, the ohm meter must be checked again for proper dial
setting and scale to be sure the reading was correct.
Below are to photos illustrating the use an ohm meter, or multi-meter, used
to measure ohms (resistance) through a temperature sensor and a heating
element. This check helps determine the values of these components as well
as continuity.
Amp (current)
measurements are taken while all of the power is on and the
heater is running to determine if power is getting through from the board to
the elements. Also, this check may also help determine, and lead to further
checking for, an open heating element, a disconnected element wire, flow
rate exceeding the heater’s capacity, or simply no power to the circuit
being checked. The check is done by dialing the amp meter to read on the 100
amp scale.
 First
the amp meter is clamped around a single red or black element wire traveling
from the board to the element. With the heater running for a wide open flow,
each heating element wire should read at or below the maximum amp rating of
the circuit supply (See Component
Testing Table for ratings). If the reading is zero amps, then
further checks should be done to determine that the incoming power wires are
in phase, the circuit breaker is turned
on, the power wires are tight at the lugs, the heating elements are good and
the wires are tightly connected on top of the heating element. If it is
determined as a result of these checks that there is no amp flow getting
through from the board to one or more the heating elements, the control
board could be malfunctioning and need replacing.
Run hot water at a faucet with normal flow and measure the amperage as
described above. If the amperage is modulating (jumping up and down) within
the same range on each element wire, then the flow rate is within the
heater’s capacity. If the amperage is steady and constant at the maximum amp
rating for each element, then the flow rate may be exceeding the heater’s
capacity.
Flow rates can easily be measured at a
faucet, if necessary, by using a common one-gallon bucket or a similar
container of known liquid capacity. Flow rates of new vanity faucets and
kitchen faucets are rated for 2.5 gallons per minute. Mop sink faucets are
high flow fixtures and are rated at 4 gpm or greater. If in doubt, the
approximate flow rate can be determined by simply turning on the faucet in
question to full flow, and timing how long it takes to fill the one gallon
bucket. If it takes 20 seconds to fill the one gallon bucket, then the flow
rate is 3 gallons per minute or 3 gpm. If it takes 15 seconds to fill the
bucket, then the flow rate is 4 gpm. Simply divide 60 seconds (which is one
minute) by the recorded time to fill the bucket to arrive at the flow rate.
Temperature readings of the inlet and
outlet water to the heater can be determined with a common cooking or baking
thermometer. The inlet water temperature should be measured at the nearest
faucet to the heater, by simply turning on the cold water (not the hot) and
placing the thermometer into the flow. For best results, let the water run
for approximately one to two minutes before taking the reading. This allows
purging of any ambient temperature water sitting in the lines. Inlet water
temperatures can vary depending on geographical location and the type of
water system, to the building.
The outlet or hot water output temperature of the heater needs to be
measured at a faucet downstream from the heater. Also, a reading should be
taken at the outlet pipe above the heater to verify that there is no mixing
of hot and cold at the faucet or in the plumbing between the heater and the
faucet. The thermometer can be placed on the metal connection above the
outlet fitting (not on the plastic outlet fitting itself) to obtain a
reading, or simply feel the pipe to determine if the heater is producing hot
water. If the outlet pipe of the heater is hot, but the faucet downstream
from the heater is not producing hot water (provided enough time was allowed
to purge the lines of standing cold water), then there may be the need to
check the plumbing lines or the faucet for possible ratio adjustments,
mixing or simply for incorrect line connections.
Temperature adjustments can be made at
the heater using the adjustable thermostat knob that is located on the left
side of the control board (the protective heater cover must be removed to
expose the control board). Typically, the factory calibrates the setting to
the 3 o’clock position to provide approximately 120 degree F output
temperature.
Caution; For new construction, most
local building codes require that the maximum domestic hot water
temperatures do not exceed 120 degrees F, to reduce the risk of
scalding. Due to these liability issues, it is recommended to leave the
temperature at the factory setting.
Most dishwashers have heating coils to heat the water to an effective
cleaning temperature. The soap used for dishwashers and washing machines is
designed to kill the bacteria. Therefore, it is not recommended to turn up
the heater output temperature for dishwashers and washing machines.
Heaters used for standard applications, such as for domestic hot water, have
a temperature range that can be adjusted with the thermostat knob from about
90 to 130 degree F. Turning the knob to the right (clockwise), increases the
temperature output and turning the knob to the left (counterclockwise),
decreases the output temperature of the heater.
IT’S IMPORTANT TO REMEMBER THAT TANKLESS WATER HEATERS PROVIDE A
CONTINUOUS FLOW OF HOT WATER AT THE DESIRED TEMPERATURE. THERE IS NO REASON
TO OVERHEAT THE WATER, WHICH CAUSES EXCESS MINERAL DEPOSITS IN ANY WATER
HEATER, JUST SO THAT YOU CAN ADD COLD WATER TO COOL IT DOWN. TAKE ADVANTAGE
OF THE BENEFITS OF YOUR TANKLESS WATER HEATER AND OPERATE IT AT AS LOW A
TEMPERATURE AS YOU WISH TO USE FOR YOUR NORMAL HOT WATER REQUIREMENTS.
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