Intertherm M1B Series, Installation Instructions Manual

8

FuRnacE InstallatIon

notE: 

These Installation procedures are suggested for 

typical furnace installations. Since each installation is 

different, the sequence of instructions may differ from 

the actual installation. Only qualified HVAC technicians 

should install this furnace.
The installer must be familiar with and comply with all 

codes and regulations applicable to the installation of 

these heating appliances and related equipment. In 

the absence of local codes, the installation must be in 

accordance with the current provisions of one or more of 

the following standards.

•  Federal  Manufactured  Home  Constructions  &  Safety 

Standard (H.U.D. Title 24, Part 3280.707[a][2])

•  American National Standard (ANSI-119.2/NFPA-501C) 

for all recreational vehicle installations.

•  American National Standard (ANSI-Z223.1/NFPA-54) 

and/or CAN/CSA B149 for all gas-fired furnace models.

•  American  National  Standard  (ANSI-Z95.1/NFPA-31) 

and/or CSA B139 for all oil-fired furnace models.

•  American National Standard (ANSI-C1/NFPA-70) and/or 

CSA 22.1 Canadian Electric Code Part 1 for all electrical 

field wiring.

•  Units have been researched under standards UL 307A 

& B, UL727-1999, ANSI Z21.47b/CSA 2.3b-2008, and 

CSA B140.10.

General Information

•  The furnace must be leveled at installation and attached 

to a properly installed duct system. 

Do  not  use  the 

back  of  the  furnace  for  return  air. 

See 

page  7

 for 

circulating requirements.

•  The  furnace  must  be  installed  so  that  all  electrical 

components are protected from water.

•  The dimensions of the room or alcove must be able to 

accommodate the overall size of the furnace and the 

installation clearances listed in 

Table 1, (page 6)

and 

Figure 1 (page 6)

•  The  furnace  must  be  installed  upstream  from  a 

refrigeration system.

•  The  M1  Series  gas  and  M5  Series  oil  furnace  is 

certified for use on wood flooring or supports, but must 

be installed on top of a duct connector. This factory 

supplied accessory must be installed in the floor cavity 

and attached to the supply air duct before the furnace 

is installed.

locating & cutting Duct openings

Floor cut-outs and fuel line holes must be carefully located 

to avoid misalignment of the furnace, and vent piping. 
To locate standard ducts see 

Figure 6 (page 9)

. For 

round ducts, see 

Figure 7

.

1. Measure 10” from the rear wall or alcove and mark the 

centerline of the cut-out on the floor.

2. Using the centerline as a starting point, draw the rest 

of the duct cut-out to the dimensions shown in 

Figure 

6

 or 

Figure 7

.

3. Cut out the floor opening 1/16” larger than the actual 

cutout drawn. This will allow some clearance when 

installing the duct connector.

4. Measure from the top of the floor down to the top of the 

supply air duct to obtain the depth of the floor cavity. 

notE: The depth of the floor cavity shown as “X” in 

Figure 9 (page 9)

 will determine the correct duct 

connector.

5. Determine which duct connector to use from Table 3 

(page 9).

6. Measure and drill gas hole and cut out for cooling coil 

(if applicable). See 

Figure 6

 or 

Figure 7

.

Standard Duct Connector Installation

The standard duct connector is designed for use on ducts 

12” in width. However ducts narrower than 12” may not 

allow sufficient clearances for this type of installation. For 
an alternate installation method, see 

page 9

.

1. Center  the  duct  connector  in  the  floor  opening  with 

bottom tabs resting on top of the supply air duct.

2. Mark the cut-out area on the supply air duct by tracing 

around the connector tabs of the duct connector. See 

Figure 8 (page 9)

.

3. Remove the duct connector and cut out the marked 

area of the supply air duct 1/4” larger the actual cutout 

drawn.

4. Install the duct connector back in the floor opening with 

the bottom tabs extending into the supply air duct.

5. Install the mounting plate under the back side of the 

duct connector as shown in 

Figure 8

. Align the screw 

holes in both components.

6. Secure the duct connector and the mounting plate to 

the wood floor with appropriate size screws.

7. Bend the connector tabs on the bottom of the duct 

connector upwards and as tight as possible against 

the supply air duct.

8. Bend both tabs up 90° on the mounting plate. See 

Figure 10 (page 10)

.

9. Seal all connections with industrial grade sealing tape 

or liquid sealant.

notE: 

Requirements for sealing ductwork vary 

from region to region. Consult with local codes for 

requirements specific to your area.