All installations and services must be performed by qualified service personnel.
C. Measuring And Adjusting Heat Input Rate
DO NOT exceed input rating stamped on furnace nameplate or manufacturer's
recommended burner manifold pressure for orifice size used.
Observe the following precautions when measuring:
A. Burner manifold pressure with a pressure gauge.
1. Close the gas valve (turn the gas control knob to the OFF position) BEFORE removing the:
a. burner manifold pressure tap plug to connect the manometer (or calibrated pressure
gauge)
b. manometer, or gauge, and replacing the pressure tap plug.
2. Shut off the gas supply at the appliance service (manual gas shutoff) valve (or for LP
gases, shut off the gas at the storage tank service valve) BEFORE removing the:
a. gas valve inlet pressure tap plug
b. manometer, or gauge and replacing the inlet pressure tap plug.
3. Perform a gas leakage test at the gas valve inlet and burner manifold pressure tap plugs.
B. Gas flowrate by clocking gas meter.
1. To determine the amount of flow, through the gas meter, due to the operation of the
furnace.
a. Turn off all other appliances and extinguish their pilot flames, if equipped, or
b. Deduct the gas consumption of all other operating appliances from the total meter
reading.
2. Convert the gas flowrate to the heat input rate (in BTUH) as described in step 10 (in the
following section) and compare the value to the heat input rating on the furnace
nameplate.
40
