Roberts Gorden CRV-B-6 Outside Air Supply, Non-Pressurized, Duct Sizing, Duct Design Rules

	SECTION 10: OUTSIDE AIR SUPPLY
SECTION 10: OUTSIDE AIR SUPPLY
The CRV-Series system is approved for use with an	blower motor has a pressure switch interlock that
outside air system. Halogenated hydrocarbons or	must be used. Wire this switch in series with the
other corrosive chemicals in the air can be drawn into	pump pressure switch. When using an outside air
the equipment and seriously damage the system	blower with a ROBERTS GORDON® System Control
components. Avoid the use of such chemical	or ROBERTS GORDON® ULTRAVAC™ control or
compounds near the air inlet to the heaters.	relay transformer, a separate load relay package is
IMPORTANT: If the building has a slight negative	required. Wire the control for the relay in parallel with
pressure or contaminants are present in the air, an	the pump. The outside air blower must have a
outside combustion air supply to the heaters is	separate 20A, 120V power supply. See Page 38,
strongly recommended.	Figure 21 for outside air blower internal wiring
All joints and seams in the air supply system must be	requirements.
airtight. Attach the filter housing to the burner	10.2 Non-Pressurized
assembly using the wing nut provided.
	For a non-pressurized outside air supply, a 4" (O.D.)
10.1 Pressurized
	single wall pipe duct may be attached to the burner
See Page 39, Figure 23 for a typical layout of a
	and end vent. For length and duct sizing
pressurized air supply system.	requirements, see duct design rules in Figure 19. To
For pressurized outside air supplies, the outside air	prevent condensation, insulate the outside air duct.
FIGURE 19: Duct Sizing
Outside Air System Design Requirements:

Blower Performance (90707501):

112 Flow Units

One outside air blower is required per each EP-100 or EP-200 series pump and two outside air blowers may be required for each EP-300 series pump. Outside air blowers cannot be shared between two separate CRV- Series systems.

Duct Design Rules:

- System should be designed so that the blower is positioned closest to the highest flow requirements (end vents).

- When a duct is carrying more than 40 flow units, it must be at least 6" (15 cm) diameter.

Pressurized Systems

-6" (15 cm) diameter duct must not exceed 120' (36 m) total per system.

-4" (10 cm) diameter duct must not exceed 120'

(36 m) per radiant branch. Non Pressurized

-6" (15 cm) diameter duct must not exceed 90' (27 m) maximum 100 flow units

-4" (10 cm) diameter duct must not exceed 90' (27 m)

-Elbows are equivalent to 10' (3 m) of duct length.

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