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ADJUSTMENT OF MANIFOLD GAS PRESSURE -
ADJUSTMENT OF MANIFOLD GAS PRESSURE -
ADJUSTMENT OF MANIFOLD GAS PRESSURE -
ADJUSTMENT OF MANIFOLD GAS PRESSURE -
GR MODELS ONLY
GR MODELS ONLY
GR MODELS ONLY
GR MODELS ONLY
This furnace is designed to operate on NATURAL GAS or PRO-
PANE GAS ONLY. Do Not Burn any other Fuel in this furnace.
Burning any fuel except NATURAL GAS or PROPANE GAS can
cause premature heat exchanger burnout, high levels of carbon
monoxide, excessive sooting, a fire hazard, personal injury, prop-
erty damage and /or death.
An overpressure protection device, such as a pressure regulator,
must be installed in the gas piping system upstream of the furnace
and must act to limit the downstream pressure to the gas valve so it
does not exceed 0.5 PSI (14" w.c. (3.48 kPa). Pressures exceeding
0.5 PSI (14" w.c. (3.48 kPa) at the gas valve will cause damage to
the gas valve, resulting in a fire or explosion or cause damage to
the furnace or some of its components that will result in property
damage and loss of life.
Turn gas off at the ball valve or gas cock on gas supply line
before the gas valve. Find the pressure ports on the gas
valve marked Outlet Pressure Tap and Inlet Pressure Tap.
The inlet and manifold gas pressure may be measured by connecting a
"U" tube manometer to the gas valve with a piece of tubing. Follow the
appropriate section in the instructions below. Refer to Figure 29 for a
drawing of the locations of the pressure ports on the gas valve.
Read the inlet gas pressure
Connect the positive side of the manometer to the Inlet Pressure Tap on
the gas valve. Do not connect any tubing to the negative side of the
manometer, as it will reference atmospheric pressure. Refer to Figure
30 for connection details.
1.
Turn gas and electrical supplies on and follow the operating
instructions to place the unit back in operation.
2.
The inlet gas supply pressure must be taken at the port marked
Inlet Pressure Tap.
3.
Using a 3/32" (0.2 cm) Allen wrench, remove the set screw by
turning it counter clockwise. Install a 1/4" barbed X 1/8" MPT fitting
in the pressure port.
4.
Push one end the 1/4" (0.9 cm) ID flexible tubing over the barbed
fitting so the barbed fitting is inside the tubing.
5.
Connect the other end of the tubing to a "U" tube manometer.
6.
Once the correct gas inlet pressure has been established, turn the
gas valve to OFF and turn the electrical supply switch to OFF; then
remove the flexible tubing and the barbed fitting from the gas valve
pressure tap, insert the tap plug, and tighten the pressure tap plug
using the 3/32" (2.4 mm) allen wrench.
7.
Turn the electrical and gas supplies back on, and follow the oper-
ating instructions to place the furnace back in operation. With the
burners in operation, check for gas leakage around the gas valve
pressure port for leakage using an approved non-corrosive gas
leak detection fluid, or other non-flammable leak detection
method.
Read the manifold gas pressure
Connect the positive side of the manometer to the Outlet Pressure Tap
on the gas valve. Do not connect any tubing to the negative side of the
manometer, as it will reference atmospheric pressure. Refer to Figure
30 for connection details.
1.
The manifold pressure must be taken at the port marked Outlet
Pressure Tap.
Unitary Products Group
2.
Using a 3/32" (0.2 cm) Allen wrench, remove the set screw by
turning it counter clockwise. Install a 1/4" barbed X 1/8" MPT fitting
in the pressure port.
3.
Push one end the 1/4" (0.9 cm) ID flexible tubing over the barbed
fitting so the barbed fitting is inside the tubing.
4.
Connect the other end of the tubing to a "U" tube manometer.
5.
Adjust manifold pressure by adjusting gas valve regulator screw
for the appropriate gas per Table 14.
6.
Refer to Figure 29 for location of pressure regulator adjustment
cap and adjustment screws on main gas valve.
7.
After the manifold pressure has been adjusted, re-calculate the
furnace input to make sure you have not exceeded the specified
input on the rating plate. Refer to "CALCULATING THE FURNACE
INPUT (NATURAL GAS)".
8.
Once the correct BTU (kW) input has been established, turn the
gas valve to OFF and turn the electrical supply switch to OFF; then
remove the flexible tubing from the gas valve pressure tap barbed
adapter. Remove adapter and install the tap plug. Tighten the
pressure tap plug using the 3/32" (2.4 mm) Allen wrench.
9.
Turn the electrical and gas supplies back on, and follow the oper-
ating instructions to place the furnace back in operation. With the
burners in operation, check for gas leakage around the gas valve
pressure port for leakage using an approved non-corrosive gas
leak detection fluid, or other non-flammable leak detection
method.
TABLE 14: Nominal Manifold Pressure - GR Models
Nominal Manifold Pressure
Natural Gas
Propane (LP) Gas
O
INLET
F
F
WRENCH
BOSS
SUPPLY
PRESSURE
ON/OFF SWITCH
TAP
(shown in OFF position)
FIGURE 28: Gas Valve - GR Models Only
IMPORTANT: The cap for the pressure regulator must be removed
entirely to gain access to the adjustment screw. Loosening or tightening
the cap does not adjust the flow of gas.
IMPORTANT: If gas valve regulator is turned in (clockwise), manifold
pressure is increased. If screw is turned out (counter clockwise), mani-
fold pressure will decrease.
NOTE: The regulated outlet pressures, have been calibrated at the fac-
tory. Additional pressure adjustment should not be necessary. If adjust-
ment is necessary, set to the specifications in Table 17. After
adjustment, check for gas leakage.
The manifold pressure must be checked with the screw-off cap for
the gas valve pressure regulator in place. If not, the manifold pres-
sure setting could result in an over-fire condition. A high manifold
pressure will cause an over-fire condition, which could cause pre-
mature heat exchanger failure. If the manifold pressure is too low,
sooting and eventual clogging of the heat exchanger could occur.
Be sure that gas valve regulator cap is in place and burner box to
gas valve pressure reference hose is connected.
166753-UIM-C-0706
3.5" w.c. (0.87 kPa)
10.0" w.c. (2.488 kPa)
ELECTRICAL
CONNECTIONS
OUTLET
ON
OUTLET
(MANIFOLD)
PRESSURE TAP
MAIN REGULATOR
ADJUSTMENT
23
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