Armstrong World Industries ACUM185 General Electrical System, Conductor Sizing Connection

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4. ELECTRICAL SYSTEM		haust piping becomes extremely hot during operation and
There are a number of different generator systems and		remains hot for a long time after shutdown. For that reason,
		the following precautions are necessary:
typical loads in the context of electrical systems. Most sys-		• Avoid contact with hot engines, exhaust manifolds,
tems, unless they contain automated switch gear, have a
means of disconnect between the generator and the			exhaust piping and mufflers. Any of these can cause
load.	This is typically a transfer switch or discon-		severe burns.
nect.	Ensure the contacts on the switch are rated for the	• Where piping must pass through combustible walls or
size of your system.			ceilings, special precautions must be taken to prevent
4.1.	GENERAL ELECTRICAL SYSTEM		fire or heat damage such as using heat thimbles
			through walls and ceilings.
When mounting electrical panels, a 3 foot clearance is re-
quired and the use of an emergency light to illuminate the		5.2.	GENERAL RULES FOR EXHAUST SYSTEM
unit during operation is typically required. Power for the		When installing an exhaust system for a generator, the fol-
emergency light should be from both the primary utility and
the generator. This is highly recommend so that in the event		lowing rules should be considered:
of a malfunction there is a light source to see to work on the		• Exhaust piping should be of wrought iron or steel hav-
unit.	Refer to your local building and electrical codes to		ing adequate strength and durability.
ensure compliance.
		• Exhaust fittings may be of cast iron. A 9 inch spacing
4.2.	CONDUCTOR SIZING CONNECTION		(10 inches (250mm) recommended) from the exhaust
			pipe and walls is also required by most local codes.
This information is dependent upon your generator output
		• Low points in horizontal runs of piping should be pro-
and intended load. When connecting cables to the genera-
tor, make connections at the generator first. Make the con-			vided with condensation traps, as well as condensation
			drains.
nections at the load last. Failure to do so may constitute a
		• Piping and mufflers must be properly supported and
fire or safety hazard.
All ampacities are typically calculated at 75 o C (Celsius)			connected.
		• A flexible length of exhaust pipe is required between
(167 o F(Fahrenheit) in the conductor size charts. Building			the engine exhaust manifold and rigid exhaust piping.
wire conductors should be rated at 90oC(194oF) to allow for
		• Exhaust piping must be terminated safely outside a
different ambient temperatures that these conductors may
pass through.			structure that houses a generator, in such a way that
All conductors are typically required by electrical code to be			hot gases and sparks will be discharged harmlessly
			and will not blow against any combustible surface or
copper. The recommended conductor sizes are based on			material.
maximum current. Ampacities are found in NEC Article 310,		• Exhaust piping must not terminate under loading plat-
Table 310-16. Conductor resistances are found in NEC Ta-			forms, structures, or near any opening in a building.
ble 8 "Conductor Properties".
		• Where necessary, exhaust piping must be guarded
4.3.	CONNECTING THE GENERATOR		and/or insulated to prevent burns.
Please the refer to the electrical drawing of the unit and		• Provide a clearance of at least 9 inches (229mm)(10
your transfer switch documentation for information related.			inches (250mm) recommended) between exhaust
Leave the installation only to a trained personnel and don’t			piping and any combustible material.
		• Keep exhaust piping well clear of fuel tanks, fuel lines,
forget to observe the local laws and permit requirements.
			etc.
Errors during the installation may damage the equipment		5.3.	RAIN CAP
and electrical devices connected to the unit and may create		A rain cap is recommended on the end of the exhaust pipe.
fire and electrocution risks.		The rain cap is attached to the end of the pipe and opens
		due to the pressure from the exhaust discharge force. The
5. EXHAUST SYSTEM
		rain cap protects the exhaust system from the environment
5.1.	GENERAL (EXHAUST SYSTEM)	when the system is not running.
Generator engines give off deadly carbon monoxide gas
through their exhaust systems.		5.4.	SPARK ARRESTOR
Carbon monoxide gas, if breathed in sufficient concentra-
		Use of a spark arrestor is required by the U.S. Department
tions, can cause unconsciousness or death. Exhaust gases
must be piped safely away from any room or enclosure that		of Forestry if located on lands under their jurisdiction. The
houses a generator and to a well ventilated area where		spark arrestor is recommended in areas where combustible
people will not be endangered.		materials may ignite such as dry grass, leaves, or other
Besides the possibility of carbon monoxide poisoning, ex-		combustible materials.
AR-EXP-CUMMINS-07-00			OWNERS MANUAL