Thomas & Betts FE, BE Clearances and Combustion Air contd, Suspending the Heater, Suspension

6.Clearances and Combustion Air (cont'd)

Model			Required Clearances (inches and mm)
Size		Top	Flue	Sides	Bottom	Rear
			Collector
25-400	6"(152)		6"(152)	18"(457)	12"(305) *	24" (610)**

*When supplied with optional downturn nozzle, bottom clearance is 42"(1067mm). For service purposes, on standard units, bottom clear- ance exceeding minimum (12" or 305mm) is not required but may be desirable.

**For servicing purposes only, rear must remain full open.

All fuel-burning equipment must be supplied with the air that enters into the combustion process and is then vented to the outdoors. Suffi- cient air must enter the equipment location to replace that exhausted through the heater vent system. In the past, the infiltration of outside air assumed in heat loss calculations (one air change per hour) was assumed to be sufficient. However, current construction methods uti- lizing more insulation, vapor barriers, tighter fitting and gasketed doors and windows or weather-stripping, and mechanical exhaust fans may now require the introduction of outside air through wall openings or ducts.

The requirements for combustion and ventilation air depend upon whether the unit is located in a confined or unconfined space. An "un- confined space" is defined as a space whose volume is not less than 50 cubic feet per 1000 BTUH of the installed appliance. Under all condi- tions, enough air must be provided to ensure there will not be a nega- tive pressure condition within the equipment room or space. For spe- cific requirements for confined space installation, see Paragraph 7.

WARNING: These power-vented unit heaters are designed to take combustion air from the space in which the unit is installed and are not designed for connection to outside combustion air intake ducts. Connecting outside air ducts voids the warranty and could cause hazardous operation. See Hazard Levels, Page 2.

7.Combustion Air Requirements for a Heater Located in a

Confined Space

Do not install a unit in a confined space without providing wall open- ings leading to and from the space. Provide openings near the floor and ceiling for ventilation and air for combustion as shown in Figure 1, depending on the combustion air source as noted in Items 1, 2, and 3 below the illustration.

Figure 1 - Confined Space: A space whose volume is less than 50 cubic feet per 1000 BTUH of the installed appliance input rating

Add total BTUH of all appliances in the confined space and divide by figures below for square inch free area size of each (top and bottom) opening.

1.Air from inside the building -- openings 1 square inch free area per 1000 BTUH. Never less than 100 square inches free area for each open- ing. See (1) in Figure 1.

2.Air from outside through duct -- openings 1 square inch free area per 2000 BTUH. See (2) in Figure 1.

3.Air direct from outside -- openings 1 square inch free area per 4000 BTUH. See (3) in Figure 1.

NOTE: For further details on supplying combustion air to a confined space, see the National Fuel Gas Code ANSI Z223.1a (latest edition ).

8. Suspending the Heater

Before suspending the heater, check the supporting structure to be used to verify that it has sufficient load-carrying capacity to support the weight of the unit.

Net Weight (lbs and kg)

Model					Size
Type		25	50	75	100	125	165	200	250	300	400
Fan	lbs	76	83	92	101	132	154	175	209	226	281
	kg	34	38	42	46	60	70	79	95	103	127
Blower	lbs	97	104	118	130	180	206	240	278	301	395
	kg	44	47	54	59	82	93	109	126	137	179

NOTE: If the installation includes an optional stepdown transformer kit (Option CF or CG), the stepdown transformer bracket is part of the heater suspension and must be installed prior to hanging the heater. Follow the instructions on the installation sheet included with the op- tion kit.

A fan-type unit heater is equipped with standard two-point suspen- sion. A 3/8-16 threaded hanger bracket assembly is located on each side of the heater. If a fan-type unit has been ordered with optional, factory-installed, four-point suspension (Option BJ6), it will have two threaded hanger brackets on each side.

A blower-type heater is equipped with standard four-point suspen- sion. Two 3/8-16 threaded hanger bracket assemblies are located on each side of the unit. Each hanger bracket assembly is designed for threaded rod attachment.

For both "standard" and "optional" suspension point dimensions, see Dimension Tables in Paragraph 3. (Note: If installing Option CK19 hanger kit, suspension points change; see Figure 4B.)

WARNING: Suspend the heater only from the threaded hanger brackets. Do not suspend from the heater side panel.

When the heater is lifted for suspension, the bottom must be protected. If the wooden crate bottom has been removed, the bottom of the heater will have to be supported with plywood or other appropriately placed material. If the bottom is not supported, the bottom access panel could be damaged. Also, when lifting a blower unit, support the blower and motor to prevent the unit from tipping.

All blower models have legs that support the blower assembly during shipping. After

the unit is sus- pended, these legs should be removed.

Be sure that the threaded hanger rods are locked to the heater as

shown in FigureFigure 2 -

2.Suspension

Form 436, Page 6