Johnson-controls TG9S*MP User Manual download pdf (Page 28)

364861-UIM-B-0708

28 Johnson Controls Unitary Products

SECTION IX: START-UP AND

ADJUSTMENTS

The initial start-up of the furnace requires the following additional

procedures:

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 start-up

procedure. Be sure proper ventilation is available to dilute and carry

away any vented gas.

GAS PIPING LEAK CHECK

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 non-corrosive leak detection fluid or other leak detection

methods. Take appropriate action to stop any leak. If a leak persists,

replace the faulty component.

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 start-up will occur as follows:

a. The induced draft blower motor will start and come up to

speed. Shortly after inducer start-up, the hot surface igniter

will glow for about 17 seconds.

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/Ft

(38.4 MJ/m

). 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

3.8 in 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 burr-free and squarely aligned orifice hole is

essential for proper flame characteristics.

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.

All electrical connections made in the field and in the factory should

be checked for proper tightness.

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.

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.

Be sure to relight any gas appliances that were turned off at the

start of this input check.

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Johnson-controls TG9S*MP User Manual Page 28

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