MAINFOLD PRESSURE “U” TUBE CONNECTION
Outlet
Pressure
Tap
Tubing
Gas Valve
3.5 IN (0.87 kPa)
Water
Column
Gas
Pressure
Shown
FIGURE 43: Reading Gas Pressure
Observing Burner Operation
1.Observe burner to make sure it ignites. Observe color of flame. On natural gas the flame will burn blue with appreciably yellow tips. On Propane gas a yellow flame may be expected. If flame is not the proper color call a qualified service technician for service.
2.Let furnace heat until blower cycles on.
3.Turn thermostat down.
4.Observe burner to make sure it shuts off.
5.Let the furnace cool and blower cycle off.
Should overheating occur, or the gas supply fail to shut off, shut off the manual gas valve to the furnace and allow burner to run until furnace cools down and blower shuts off before shutting off the electrical supply.
If any abnormalities are observed when checking for correct operation, such as burner failing to ignite or to turn off, sooty flame, etc., call your nearest authorized service technician as shown in the Service Center List included in the home owner envelope with the furnace.
If Furnace Fails to Operate Properly
1.Check setting of thermostat - and position of HEAT/COOL switch if air conditioning is installed. If a
2.Check to see that electrical power is ON.
3.Check to see that the switch on the gas control valve is in the full ON position.
4.Make sure filters are clean, return grilles are not obstructed, and supply registers are open.
5.Be sure that furnace flue piping is open and unobstructed.
If the cause for the failure to operate is not obvious, do not attempt to service the furnace yourself. Call a qualified service agency or your gas supplier.
ADJUSTMENT OF TEMPERATURE RISE
The temperature rise, or temperature difference between the return air and the supply (heated) air from the furnace, must be within the range shown on the furnace rating plate and within the application limitations shown in Table 8 “ELECTRICAL AND PERFORMANCE DATA”.
The supply air temperature cannot exceed the “Maximum Supply Air Temperature” specified in these instructions and on the fur- nace rating plate. Under NO circumstances can the furnace be allowed to operate above the Maximum Supply Air Temperature. Operating the furnace above the Maximum Supply Air Temperature will cause premature heat exchanger failure, high levels of Carbon Monoxide, a fire hazard, personal injury, property damage, and/or death.
The temperature rise, or temperature difference between the return air and the heated supply air from the furnace, must be within the range shown on the furnace rating plate and within the application limitations as shown in Table 8.
After about 20 minutes of operation, determine the furnace temperature rise. Take readings of both the filter door and the heated air in the ducts. Increase the blower speed to decrease the temperature rise; decrease the blower speed to increase the rise.
Do not energize more than one motor speed at a time or damage to the motor will result.
PERFORMANCE CHECK
1.After the desired input has been obtained,
2.After the burner has been in operation for at least 20 minutes, assuring combustion chamber and heat exchanger are fully warmed, take combustion analysis flue gas samples in the flue pipe.
All adjustments below must be made with the following instructions:
a.Draft Gauge
b.O2 or CO2 Analyzer
c.CO Tester
d.Water Column Gauge
NOTE: ALWAYS USE RELIABLE COMBUSTION TEST INSTRU- MENTS. BEING PROFICIENT IN THE USE OF THESE INSTRU- MENTS AND INTERPRETING THE DATA IS NECESSARY FOR SAFE, RELIABLE AND EFFICIENT BURNER OPERATION.
IT IS ESSENTIAL TO MAKE CERTAIN THAT THE PRODUCTS OF COMBUSTION DO NOT CONTAIN CARBON MONOXIDE, CO.
The most common causes of CO are flame impingement on cool sur- face and insufficient primary air, both of which could be caused by over firing. The only answer is to reduce the firing rate or increase the pri- mary air.
36 | Unitary Products Group |