Bryant 580J*08--14D appendix GAS Heating System, Control Circuit, Fuel Types and Pressures

Troubleshooting Supply Fan Motor Overload Trips

The supply fan used in 580J units is a forward-curved centrifugal wheel. At a constant wheel speed, this wheel has a characteristic that causes the fan shaft load to DECREASE when the static pressure in the unit-duct system increases and to INCREASE when the static pressure in the unit-duct system decreases (and fan airflow rate increases). Motor overload conditions typically develop when the unit is operated with an access panel removed, with unfinished duct work, in an economizer-open mode, or a leak develops in the duct system that allows a bypass back to unit return opening.

Condenser Fan Motor Protection

The condenser fan motor is internally protected against overtemperature.

Control Circuit, 24-V

The control circuit is protected against overcurrent conditions by a circuit breaker mounted on control transformer TRAN. Reset is manual.

GAS HEATING SYSTEM

General

The heat exchanger system consists of a gas valve feeding multiple inshot burners off a manifold. The burners fire into matching primary tubes. The primary tubes discharge into combustion plenum where gas flow converges into secondary tubes. The secondary tubes exit into the induced draft fan wheel inlet. The induced fan wheel discharges into a flue passage and flue gases exit out a flue hood on the side of the unit. The induced draft fan motor includes a Hall Effect sensor circuit that confirms adequate wheel speed via the Integrated Gas Control (IGC) board. Safety switches include a Rollout Switch (at the top of the burner compartment) and a limit switch (mounted through the fan deck, over the tubes). (See Fig. 30 and 31.)

INDUCED-
DRAFT
MOTOR	ROLLOUT
MOUNTING
	SWITCH
PLATE
BURNER	FLUE
SECTION	EXHAUST
INDUCED-	VESTIBULE
DRAFT MOTOR	PLATE
MANIFOLD
PRESSURE
TAP
GAS	BLOWER
VALVE	HOUSING
	C09153

Fig. 30 - Burner Section Details

Limit Switch

and Shield

C08284

Fig. 31 - Limit Switch Location

Fuel Types and Pressures

Natural Gas

The 580J unit is factory-equipped for use with Natural Gas fuel at elevation under 2000 ft (610 m). See section Orifice Replacement for information in modifying this unit for installation at elevations above 2000 ft (610 m).

Gas line pressure entering the unit’s main gas valve must be within specified ranges. (See Table 5.) Adjust unit gas regulator valve as required or consult local gas utility.

Table 5 – Natural Gas Supply Line Pressure Ranges

UNIT MODEL	UNIT SIZE	MIN	MAX
580J	All	4.0 in. wg	13.0 in. wg
		(996 Pa)	(3240 Pa)

Manifold pressure is factory-adjusted for NG fuel use. (See Table 6.) Adjust as required to obtain best flame characteristic.

Table 6 – Natural Gas Manifold Pressure Ranges

UNIT	UNIT	HIGH	LOW	RANGE
MODEL	SIZE	FIRE	FIRE
580J	All	3.5 in. wg	1.7 in. wg	2.0--- 5.0 in. wg (Hi)
		(872 Pa)	(423 Pa)	(498--- 1245 Pa)

Liquid Propane

Accessory packages are available for field-installation that will convert the 580J unit to operate with Liquid Propane (LP) fuels. These kits include new orifice spuds, new springs for gas valves and a supply line low pressure switch. See section on Orifice Replacement for details on orifice size selections.

Fuel line pressure entering unit gas valve must remain within specified range. (See Table 7.)

580J

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