SECTION IX: START-UP AND
ADJUSTMENTS
The initial
All electrical connections made in the field and in the factory should be checked for proper tightness.
When the gas supply is initially connected to the furnace, the gas piping may be full of air. In order to purge this air, it is recommended that the ground union be loosened until the odor of gas is detected. When gas is detected, immediately retighten the union and check for leaks. Allow five minutes for any gas to dissipate before continuing with the
GAS PIPING LEAK CHECK
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in serious injury, death or property damage.
Never test for gas leaks with an open flame. Use a commercially available soap solution made specifically for the detection of leaks to check all connections. A fire or explosion may result causing property damage, personal injury or loss of life.
Burner ignition may not be satisfactory on first startup due to resid- ual air in the gas line or until gas manifold pressure is adjusted. The ignition control will make three attempts to light before locking out.
It is recommended that when the gas supply is first connected to the furnace, the ground union be loosened until the odor of gas is detected. When gas is detected, immediately tighten the union and check for gas leaks. Allow five minutes for any gas to dissipate before continuing with the startup procedure. Be sure that proper ventilation is available to dilute and carry away any vented gas.
With furnace in operation, check all of the pipe joints, gas valve connec- tions and manual valve connections for leakage using an approved gas detector, a
The furnace and its equipment shutoff valve must be disconnected from the gas supply during any pressure testing of that system at test pres- sures in excess of 1/2 PSI (3.45 kPa).
The furnace must be isolated from the gas supply piping system by closing the equipment shutoff valve during any pressure testing of the gas supply system.
IGNITION SYSTEM SEQUENCE
1.Turn the gas supply ON at external valve and main gas valve.
2.Set the thermostat above room temperature to call for heat.
3.System
a.The induced draft blower motor will start and come up to speed. Shortly after inducer
b.After this warm up, the ignition module will energize (open) the main gas valve.
c.After flame is established, the supply air blower will start in about 30 seconds.
CALCULATING THE FURNACE INPUT (NATURAL GAS)
Burner orifices are sized to provide proper input rate using natural gas with a heating value of 1030 BTU/Ft3 (38.4 MJ/m3). If the heating value of your gas is significantly different, it may be necessary to replace the orifices.
NOTE: DO NOT set manifold pressure less than 3.2 in wc or more than
3.8in wc for natural gas at sea level. If manifold pressure is outside this range, change main burner orifices.
NOTE: If orifice hole appears damaged or it is suspected to have been redrilled, check orifice hole with a numbered drill bit of correct size. Never redrill an orifice. A
DO NOT bottom out gas valve regulator adjusting screw. This can result in unregulated manifold pressure and result in excess over- fire and heat exchanger failures.
Verify natural gas input rate by clocking meter.
1.Turn off all other gas appliances and pilots.
2.Run furnace for a minimum of 3 minutes in heating operation.
3.Measure time (in sec) for gas meter to complete 1 revolution and note reading. The 2 cubic feet dial provides a more accurate mea- surement of gas flow.
4.Refer to Table 9 for cubic feet of gas per hour.
5.Multiply cubic feet per hour by heating valve (BTU/cu ft) to obtain input.
If clocked rate does not match the input rate from the unit nameplate. follow steps in next section to adjust the manifold pressure. Repeat steps 2 - 5 until correct input is achieved.
Be sure to relight any gas appliances that were turned off at the start of this input check.
28 | Johnson Controls Unitary Products |
