Installation Manual

51
Figure 53
CHECKING THE FIRING RATE
If ring rate adjustment is required follow these instructions to
determine the actual ring rate of the water heater:
NOTE: The heaters covered by this manual are capable of
modulating their ring rate. The ring rate should be checked
with the heater operating at it's full ring rate.
1. Ensure there are no other gas red appliances connected to
the gas meter ring during this test.
2. Contact the gas supplier to determine the heating value, in
Btu per cubic foot, of the gas supply.
3. Start the water heater and ensure it is ring.
4. Locate the gas meter serving the water heater.
5. Time how long (in seconds) it takes for one cubic foot of gas
to be used while the water heater is ring with a stop watch.
6. Use the formula below to “clock” the gas meter and determine
the actual ring rate of the water heater based on the heating
value (Btu per cubic foot) of the gas supply:
x H = Btu/hr
3600
T
x 1050 = 300,000 Btu/hr (87.9 kW)
3600
12.6
Example:
• 3600 = seconds in one hour.
• T = time, in seconds, to burn one cubic foot of gas.
• H = heating value of gas in Btu per cubic foot.
• Btu/hr = actual ring rate of the water heater.
NOTE: 1050 Btu per cubic foot is a standard value for natural
gas. Standard propane gas Btu content is 2500 Btu per cubic
foot. Btu values may change in certain areas and at high
elevations. Check with the local gas utility company.
TO TURN OFF GAS
1. Change the Operating Set Point to the lowest temperature setting,
see Operating Set Point And Differential Adjustment on page 45.
2. When the water heater has completed its shut down sequence
and enters the standby mode, turn the water heater’s on/off
switch to the “off” position. When in the "off" position the switch
only removes electrical power from the gas valve and blower
so that water heating is disabled. The display, CCB, and other
electrical components will still be energized and the display will
read "Water Heating Disabled".
3. Close the Main Gas Shutoff Valve, see Figure 48 on page 38.
If the supply gas pressure to the water heater is not between
the required minimum and maximum values given in Table 4 on
page 13 adjust the supply gas regulator as necessary. Adjust
the supply gas regulator(s) per the regulator manufacturer’s
instructions to achieve the required “static” and “dynamic”
supply gas pressure.
Multiple Appliance Installations:
In multiple water heater installations or in installations
where the installed water heater(s) share a common gas
supply main with other gas fired appliances; the supply gas
pressures shall be measured at each water heater with all
gas fired appliances connected to a common main firing at
full capacity.
On multiple water heater installations the supply gas line
regulators shall be adjusted to provide gas pressure to each
water heater within the minimum and maximum supply pressure
requirements listed in Table 4 on page 13 with all gas red
appliances connected to a common gas main ring at full
capacity.
NOTE: A pressure drop of more than 1.5” W. C. (0.37 kPa)
when the Main Burner ignites is an indication of an inadequate
supply of gas and can lead to ignition failure, rough starts and/
or rough operation. If a drop of more than 1.5” W. C. (0.37
kPa) in supply gas pressure occurs when the Main Burner
ignites, ensure the supply gas lines and regulator(s) are
properly sized and installed. See the requirements for Supply
Gas Regulator and Supply Gas Line on page 13. See Supply
Gas Line Installation on page 38 and Supply Gas Regulator on
page 13. Ensure all requirements and installation instructions
are maintained.
Fire and Explosion Hazard
Gas and carbon monoxide detectors are
available.
Overfiring could result in fire or
explosion.
Under no circumstances should the
input exceed the rate shown on the
water heater’s rating label.
Breathing Hazard - Carbon Monoxide Gas
Breathing carbon monoxide can cause brain damage or
death. Always read and understand instruction manual.
Under no circumstances should
the input exceed the rate shown
on the water heater’s rating label.
Overfiring could result in damage to
the water heater and sooting.
Gas and carbon monoxide detectors
are available.