P-K THERMIFIC
®
Gas-Fired Boiler
41
3.10.3.4 Gas Pressure Adjustment
See rating label for the minimum and maximum inlet gas pressure of the boiler. Each boiler is furnished
with two plugged taps in the gas train for test gauge connections. One tap is located at the main gas
cock for measuring the inlet gas supply pressure. The supply pressure during main burner operation
must be greater than the minimum indicated on the rating label: 5” W.C. for natural gas, (4” W.C. for low
pressure option), 7” W.C. for propane. The second tap is located downstream from the last main gas
control where the gas line enters the back of the cabinet and is used for measuring the manifold gas
pressure.
Fuel adjustments are made first at Hi fire and second at low fire. Hi fire gas pressure adjustments are
made at the gas pressure regulator while the boiler is operating in hi fire. Low fire combustion
adjustments are made second, with the valve actuator in the Low fire position. Low fire gas is set at the
factory and cannot be adjusted.
Gas Pressure Regulator
To adjust Hi Fire using the gas pressure, first connect appropriate pressure-
sensing device (manometer) at the manifold tap, then remove cap from
regulator. Turn adjusting screw clockwise to increase pressure, counter-
clockwise to decrease pressure. The manifold gas pressure indicated on the
“Factory Firetest” label (affixed on the back of the cabinet) should be used to
achieve the proper firing rate of the individual boiler. Replace cap after
adjustment.
If a replacement Lo-Hi-Lo actuator is required, follow the actuator
manufacturer’s instructions and pre-set the low fire setting of the actuator to
the same position as the original actuator. This must be performed by
qualified service personnel.
3.10.3.5 Adjust the combustion for local conditions
The final adjustment for the combustion is
performed using a combustion analyzer. The
analyzer probe should be inserted into the hole in
the boiler vent outlet collar (shown right). The
analyzer should be placed at the outlet, before the
barometric damper or any other vent devices.
Put boiler in High fire. Adjust the gas pressure
using main gas regulator adjusting screw to achieve
an analyzer reading of 7.5% O
2
(allowable range is
6.5% to 8.0% O
2
). Measure the stack draft. Verify
that stack draft is between -0.02” W.C. and -0.1”
W.C.
Put the boiler in low fire (Lo-Hi-Lo only), adjust the air pressure (as shown in Section 3.10.3.3) using the
low fire set screw to achieve an analyzer reading of 7.5% O
2
. Record all readings on the field fire test
report and send to Harsco Industrial, Patterson-Kelley.
Increase
Decrease
Summary of Contents for P-K THERMIFIC N700
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Page 56: ...P K THERMIFIC Gas Fired Boiler 56 6 1 2 2 Lo Hi Lo Sealed Combustion Diagram 1500 1700 2000...
Page 58: ...P K THERMIFIC Gas Fired Boiler 58 6 1 3 2 Factory Installed Low Water Cut Off Diagram...