John Wood Commercial - 300-400K BTU - Manual (Page 50)

50
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 36 and Supply gas regulator on page 13. Ensure all
requirements and installation instructions are maintained.
manifold gas pressure adjustment
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.
Ensure the "dynamic" supply gas pressure is above the
minimum requirements in Table 3 on page 13 before any
adjustments are made to the manifold gas pressure. Attempts
to adjust manifold gas pressure during periods of low supply
gas pressure could result in overfiring when the supply
gas pressure returns to normal. See Supply gas Pressure
Adjustment on this page.
If necessary, adjust the manifold gas pressure as follows:
1. Follow the instructions for Initial Start up on page 49
to connect manometers to the supply and manifold gas
pressure taps and to start the water heater.
2. remove the manifold gas pressure regulator cover screw,
see Figure 56.
3. using a small flat tip screw driver turn the adjustment screw
clockwise to increase manifold gas pressure and counter
clockwise to decrease manifold gas pressure.
note:
Turn the manifold gas pressure adjustment screw
in small increments (no more than 1/4 turn) and allow the
manifold gas pressure to stabilize for several minutes
before making further adjustments.
4. replace the gas pressure regulator cover screw.
5. Cycle the burner on and off several times to check operation.
6. Compare the actual manifold gas pressure reading recorded
above to the required minimum/maximum values given
in Table 3 on page 13. Adjust manifold gas pressure as
necessary, see the instructions that follow.
7. record the supply gas pressure when the 24 VAC gas Valve
is energized and the Main burner is ignited. This is a “dynamic”
gas pressure reading; while the water heater is firing.
8. Compare the actual supply gas pressure reading recorded
above to the required minimum/maximum values given
in Table 3 on page 13. Adjust supply gas pressure as
necessary, see the instructions that follow.
ON
OFF
HONEYWELL
MANIFOLD GAS
PRESSURE REGULATOR
COVER SCREW
24 VAC GAS VALVE TOP VIEW
ALL 300,000 NATURAL AND PROPANE, AND 400,000 BTU/HR PROPANE MODELS
MANIFOLD GAS
PRESSURE TAP
1/8’ NPT PLUG
INLET OUTLET
GAS CONTROL
KNOB
figure 56
supply gas pressure adjustment
Fire and Explosion Hazard
Turn off gas lines during installation.
Contact a qualified installer or service
agency for installation and service.
Excessive gas pressure to gas valve can
cause serious injury or death.
Do not use water heater with any gas
other than the gas shown on the rating
label.
Supply gas pressure shall be measured while the water heater is
not firing (static pressure) AND while the water heater is firing at
full capacity (dynamic pressure).
If the supply gas pressure to the water heater is not between
the required minimum and maximum values given in Table 3 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 3 on page 13 with all gas fired
appliances connected to a common gas main firing at full capacity.