Nortek MB7EM 3-PHASE Series, Installation Instructions Manual

5

Downflow Applications:

 Position the blower over the duct and 

secure together with sheet metal screws.

Return Air Connections

The return air must be delivered to the blower by duct(s) secured 

to the casing, running full size and without interruption. Tape or 

seal all seams if required by local code.

Upflow & Horizontal Applications:

 Position the blower over the 

duct and secure together with sheet metal screws.

Downflow Applications:

 To attach the supply air duct, bend 

the furnace flanges outward 90° with a pair of wide duct pliers. 

Position the duct on top of the cased coil and secure together 

with sheet metal screws.

Acoustical Duct Work

•  Certain installations may require the use of acoustical lining 

inside the supply duct work. Acoustical insulation must be in 

accordance with the current revision of the Sheet Metal and 

Air Conditioning Contractors National Association (SMACNA) 

application standard for duct liners. Duct lining must be UL 

classified batts or blankets with a fire hazard classification of 

FHC-25/50 or less.

•  Fiber duct work may be used in place of internal duct liners if 

the fiber duct work is in accordance with the current revision 

of the SMACNA construction standard on fibrous glass ducts. 

Fibrous duct work and internal acoustical lining must be NFPA 

Class 1 air ducts when tested per UL Standard 181 for Class 

1 ducts.

•  Damping ducts, flexible vibration isolators, or pleated media-

style filters on the return air inlet of the air handler may be 
used to reduce the transmission of equipment noise eminating 
from the air handler. These treatments can produce a quieter 
installation, particularly in the heated space. However, they 
can increase the pressure drop in the duct system. Care 
must be taken to maintain the proper maximum pressure rise 
across the air handler, temperature rise and flow rate. This 
may mean increasing the duct size and/or reducing the blower 
speed. These treatments must be constructed and installed in 
accordance with NFPA and SMACNA construction standards. 
Consult with local codes for special requirements. For best 
sound performance, be sure to install all the needed gaskets 
and grommets around penetrations into the air handler, such 
as for electrical wiring.

Air Filters

 WARNING:

Never operate the air handler without a filter 

or with doors removed. Dust and lint can build 

up on internal components, resulting in loss of 

efficiency, equipment damage, and possible fire.

MB7 Series air handlers are not equipped with a filter rack; 

however, it is strongly recommended that a filter be located in 

the return air duct system. Installing the filter and replacing it 

every 3 months will increase air quality throughout the home.

Unconditioned Spaces

All duct work passing through unconditioned space must 

be properly insulated to minimize duct losses and prevent 

condensation. Use insulation with an outer vapor barrier. Consult 

your Distributor for the recommended type and thickness of 

insulation for your area as required by local codes.

Condensate Drainage

 CAUTION:

The air handler must be level to ensure proper 

condensate drainage. An unlevel installation may 

result in structural damage, premature equipment 

failure, or possible personal injury.

•  To ensure proper condensate drainage, the unit must be 

installed in a level position within 1/4 inch over the height, 

width, and depth of the unit. The best system performance will 

be obtained if the unit is located in a centralized position with 

respect to the air distribution system. Refer to the Installation 

Instructions supplied with the Cased Coil for proper condensate 

drain connections.

•  If the air handler is located in or above a living space where 

damage may result from condensate overflow, an auxiliary 

drain pan should be installed under the unit. A separate drain 

line should extend from the pan to a conspicuous point and 

serve as an alarm indicating that the primary drain is restricted. 

As an alternative to a separate drain line, an approved water 

level indicator or float switch device should be used to shut 

down the unit in the event water is detected in the auxiliary 

pan.

•  During system checkout, inspect the drain line and connections 

to verify proper condensate drainage.

•  Methods for disposing of condensate vary according to local 

codes. Refer to local codes or authority having jurisidiction for 

restrictions and proper condensate disposal requirements.

AIR HANDLER INSTALLATION

The MB7 Series air handler is shipped ready for vertical upflow 

installation and is approved for attic, basement, alcove/closet 

or crawlspace installation with zero clearance to combustibles. 

They may also be applied in downflow or horizontal left and right 
discharge applications. See 

Table 1, (page 4)

 for required 

installation clearances. 

This appliance is approved only for 

indoor use.
NOTE:

 For shipping purposes, the front and rear joining brackets 

are located in the unit’s heater box. Remove these two items 

from the heater box before beginning.
•  The unit must be leveled at installation and attached to a 

properly installed duct system.

•  The surface that the air handler is mounted on must provide 

sound physical support of the unit.

• The air handler must be installed so that all electrical 

components are protected from water.

•  If a louvered door is installed across the front of this unit, the 

appliance must be mounted flush or behind front edge of 

finished wall.

•  Modular air handlers are intended to be mated with specific 

C6 & C7 cased coils. Reference the Technical Specifications 
for coil mating combinations.

Upflow Installation

MB7 series air handlers are shipped from the factory ready for 

upflow configuration as shown in 

Figure 1 (page 6)

. Return 

air must must enter from the bottom of the unit.

1. Remove the bracket above the door of the cased coil. Retain 

the screws for later use. 

NOTE: 

Before mating the modular 

unit with the cased coil, clean the mating surfaces on both