America's Best Wall & Remote Mount NFPA 496 Building Pressurization Units

Model Number Matrix

The Model Number Segments below specify standard features and options for our Window Mount Explosion Proof Air Conditioner and Heat Pump Units.

Helpful information is provided just below each Segment and applicable Model Number Selection Notes at the bottom of this page.

As always, please feel free to contact a Bebco Sales Associate for assistance!

Typical Model Number:


1 – Case Style & Material

IC Seal-Welded Galvanneal Steel
ISSeal-Welded 304 Stainless Steel
IXSeal-Welded 316 Stainless Steel

Bebco Model WDP and RDP Whisper Drive™ Building Pressurization Units are offered in three case styles with a urethane paint finish. Custom housing finishes may also be selected under Segment 6 to satisfy your unique and particular applications. Case Style IC designates a 14-gauge seal-welded galvannealed steel housing and Case Styles IS and IX designate a 14-gauge seal-welded 304 or 316 grade stainless steel housing.

Selection of a case style should be based upon the environmental conditions at your installation site, and a proper choice will ensure years of durable service. Please contact a Bebco Sales Associate if you prefer assistance regarding this selection!

2 – Configuration *1

WDPWall Mount Dual Blower Building Pressurization Unit
RDPRemote Mount Dual Blower Building Pressurization Unit

Model WDP Whisper Drive™ Units mount through a framed cutout in the exterior wall of the room or building to be pressurized and Model RDP Whisper Drive™ Units may be mounted on an exterior wall or roof. Selection depends upon the preference for the fully integrated installation convenience of the Model WDP Unit, versus available wall space considerations or a preference to integrate pressurization with an HVAC Unit. Bebco Sales Associate are standing by to provide further information, as required.

3 – Fan Blade Size

1212” Diameter Fan Blades / 21 Sq Ft Openings, Maximum
1616” Diameter Fan Blades / 31 Sq Ft Openings, Maximum
2020” Diameter Fan Blades / 55 Sq Ft Openings, Maximum
2424” Diameter Fan Blades / 75 Sq Ft Openings, Maximum

As the leading Standard for pressurization in American, NFPA 496 requires a velocity of 60 feet per minute through all openings capable of being opened. Bebco Model WDP and RDP Whisper Drive™ Building Pressurization Unit sizing is therefore based upon their maximum air flow rates, which then derive the maximum area of permissible openings in a room or building.

Typically, most pressurized buildings and rooms only feature doors, but operable windows and other similar items must also be considered with exception only to equipment access doors that are properly labeled and sealed during normal operations. In addition, the integrity of all doorway gaskets and other factors of building construction may affect the unit’s performance. Please ask a Bebco Sales Associate for more information regarding these critical aspects that affect proper unit size selection.

4 – Area Rating *2

D1Class I, Division 1, Groups C & D
D2Class I, Division 2, Groups C & D

Bebco Model WDP and RDP Whisper Drive™ Building Pressurization Units are available with UL Listings for use in either Class I, Division 1 or 2, Group C & D Hazardous Classified Locations. The distinguishing difference between these options includes our Primary and Secondary Motor ratings and the type of conduit or rated cabling that must be utilized to connect them to your power source, alarm system and optional remote control safety devices.

The location for any building to be pressurized is classified by the Authority Having Jurisdiction (AHJ) or Facility Safety Manager, which is typically determined by compliance to NFPA 497, a guide for the classification of Hazardous Classified Locations. If you are not sure which option to select, Bebco Sales Associates can offer pricing for both ratings, until proper determination is made.

5 – Remote Control Inputs *3

AHard Wired ESD & ECO Inputs
BIntrinsically Safe ESD & ECO Inputs
CIntrinsically Safe ESD Input
DIntrinsically Safe ECO Input

As a unique, advanced feature, Bebco Model WDP and RDP Whisper Drive™ Building Pressurization Units are available with Emergency Shutdown and Control Override Controls in hard-wired or intrinsically safe versions. When specified for WDP Units, an optional pre-wired junction box is added to simplify unit installation. When specified for Model RDP Units, hard wired terminals are provided in the remote-control station or a separate junction box with intrinsically safe barriers is supplied for installation in a location of your preference.

These inputs can be wired to emergency operators and combustible gas detectors to manually or automatically prevent or evacuate the entry or release of combustible vapors within your pressurized room or building. Bebco offers all of these devices as accessories to our Model WDP and RDP Units, and Bebco Sales Associates can also provide typical shutdown circuit wiring diagrams and support to guide you through the process of considering and selecting the best configuration of remote-control inputs and remote-control accessories to meet your safety requirements.

6 – Housing Finish *4

GANSI 61 Gray Sprayed Urethane
SWhite Sprayed Urethane
TANSI 61 Gray Epoxy Powder Coated
PWhite Epoxy Powder Coated
UCustom Finish

Do you have a unique application that requires a custom finish or color? Bebco Model WDP & RDP Whisper Drive™ Housings are offered with a 3-6 mil thick white urethane standard finish or a custom finish based upon your specification of paint type, brand, color and application method.

Regardless of which option you select, standard or custom coatings are applied on all sides of all finished parts, which are then assembled after curing, so no metallic surface is uncoated, regardless of its interface with other metallic or non-metallic parts. Ask a Bebco Sales Associate for more information regarding this valuable optional feature!

Please contact us for information regarding any aspect of unit customization.

We’ll be pleased to review all aspects of this unique product and strive to meet any special requirements!


  1. All Units require a 208-240 VAC Single Phase 50-60 Hertz 20 Amp Power Sources. Please contact us for other power options.
  2. Custom Ratings for Group B, Class II or Class III Areas are available. Please contact a Bebco Sales Associate regarding these options.
  3. Hard Wired Inputs are lug terminals in junction box mounted within WDP Housings or in RDP Remote Control Station Enclosures.
  4. Please specify custom housing finish in writing at time of order.