Return Air Requirements - Suburban SF-20 Installation Instructions Manual

RV such as slide out, pop-up etc. always insure that the appliance cannot
be operated by setting the thermostat to the positive "OFF" position and
shutting off all electrical and gas supply to the appliance. Never operate
furnace with vent covered.
CAUTION: This furnace was shipped from the factory set up for the gas
connection to be made at the right rear of the unit as illustrated in Figure
1. If you wish to make gas connection through the top of cabinet, you must
remove furnace from cabinet and turn gas inlet fitting 90° CLOCKWISE.
DO NOT TURN FITTING COUNTER-CLOCKWISE, this will loosen fitting and
result in a gas leak.
WARNING! Hold manifold firmly when turning elbow to prevent any
force from being inserted on the valve and to prevent any leaks from
developing. Be sure to check all fittings for leaks including the inlet and
outlet on the valve before reinstalling furnace into cabinet. Correct all
leaks immediately. NOTE: The furnace must be in operation to properly
check for leaks.
NOTE: These furnaces must be installed and vented as described in this manual
so that the negative pressure created by the air circulating (return air) fan cannot
affect the combustion air intake or venting of any other appliance. It is imperative
that the products of combustion be properly vented to the atmosphere and that
all combustion air supplied to burner be drawn from the outside atmosphere.
(See Installing Vent Assembly.)
NOTE: Do not install the furnace with the vent facing toward the forward end of
the coach.
IMPORTANT: If this furnace is to be connected to a common duct system also
serving a cooling unit, a manual or automatic damper is required to prevent
any cold conditioned air from circulating back into the furnace. Cold air passing
over the furnace combustion chamber during the operation of the cooling unit
can result in the formation of condensation inside the furnace combustion
chamber. This condensation may promote corrosion and premature failure of
the combustion chamber.
NOTE: These furnaces shall be installed so the electrical components are
protected from water.
These furnaces are design certified for propane/LP gas only. Do not attempt to
convert to natural gas.
Gas supply pressure for purposes of input adjustment:
Minimum - 11" W.C.* Maximum - 13" W.C. *
(W.C.* - Water Column).
In the U.S.A., the installation of the furnace must be in accordance with local
codes and regulations. In the absence of local codes and regulations, refer to
the latest edition of:
1. Standard for Recreational Vehicles NFPA 1192.
2. National Fuel Gas Code ANSI Z223.1.
3. Furnace must be electrically grounded in accordance with the latest edition of
the National Electrical Code NFPA 70.
In Canada, the furnace must be installed in accordance with:
1. Standard CSA Z240.0.2-08 Recreational Vehicles.
2. CSA Standard Z240.6.2-08 C22.2 NO.148-08 Electrical Requirements for
Recreational Vehicles.
3. Standard Z240.4.2-08 Installation Requirements for Propane Appliances and
Equipment in Recreational Vehicles.
4. CAN/CGA-B149 Installation Codes.
5. Any applicable local codes and regulations.
This unit is equipped with an electric igniter device that has an energy
consumption of .1 amp @ 12 volts D.C.
WARNING! Extension tubes cannot be used. If you try to extend the vent,
it will result in improper installation which could cause unsafe furnace
operation.
There are three (3) methods described below for installing the furnace.
Regardless of the method you choose, we require an opening be provided in
the exterior of the trailer or motor home for free, unobstructed removal of the
furnace. This exterior, removable panel or wall section of the trailer or motor
home must be a minimum of 17-3/4 x 8.
It is important that adequate return air be provided to assure normal heating and
operation of the furnace. Failure to provide the minimum return air will cause
erratic furnace cycling. Refer to the chart shown below for minimum return air
requirements.

Return Air Requirements

Model Minimum Free (unobstructed) Area
SF-20/25/30/35
SF-42
*May be reduced to 88 sq. in. min. if 5 ducts are used.
NOTE: Return air must be from within the living area of the coach.
NOTE: RV's that have a wall of separation to a cargo area (Toy Box) to transport
internal combustion engine vehicles must not have return air openings from this
area.
A. INSTALLATION DIRECTLY AGAINST OUTER PANEL OF COACH
(See Figure 1) (Panel supplied by installer)
Maximum wall thickness for this type installation is 2".
1. Locate the furnace near lengthwise center of the coach.
2. Choose a location for installation out of the way of wires, pipes, etc., which
might interfere with the installation. Adhere to the minimum clearances from the
cabinet to combustible construction as listed in Table 2. Refer to Figure 3 for
illustration of furnace clearances.
3. When an appliance is installed directly on carpeting, tile or other combustible
material, other than wood flooring, the appliance shall be installed on a metal or
wood panel extending the full width and depth of the appliance. If preferred, the
carpeting, tile or combustible materials, other than wood may be cut away the
full length and depth of the appliance plus the appliance minimum clearances to
combustibles. (See Table 2.)
4. Cut an opening through the inner wall. This will allow the rear of the furnace
to be installed against the outer panel of the coach.
5. Locate center lines for exhaust and intake, as shown in Figure 1.
6. Cut two 2-1/4" diameter holes through the outer panel of the coach. (See
Figure 1.)
7. Put furnace in place, making sure that rear of the furnace cabinet is as close
to outer panel of the coach as possible and still assure proper vent tube overlap.
(See Installing Vent Assembly.)
8. Secure furnace to the floor using the two (2) holes provided in the furnace
cabinet. (See Figure 4).
9. Be sure furnace is secured within furnace cabinet. (See Figure 4).
10. Install vent assembly. (See instructions for installing vent.)
B. INSTALLATION NOT AGAINST OUTER PANEL OR SKIN AND "X"
DIMENSION GREATER THAN 1 ½"
(See Figure 2) (Exterior panel supplied by installer)
Maximum wall thickness for this type installation is 2".
1. Locate the furnace near lengthwise center of the coach.
2. Choose a location for installation out of the way of wires, pipes, etc, which
might interfere with the installation. Adhere to the minimum clearances from
cabinet to combustible construction as listed in Table 2. Refer to Figure 3 for
illustration of furnace clearances.
3. When an appliance is installed directly on carpeting, tile or other combustible
material, other than wood flooring, the appliance shall be installed on a metal or
wood panel extending the full width and depth of the appliance. If preferred, the
carpeting, tile or combustible materials, other than wood may be cut away the
full length and depth of the appliance plus the appliance minimum clearances to
combustible. (See Table 2.)
4. Determine "X" dimension as shown in Figure 2. The tubes supplied with
the furnace will accommodate an installation range for "X" from o-1 ½". If "X"
dimension is greater than 1 ½", then special vent tubes as charted in Figure 2
must be ordered.
2
55 Sq. In.
142 Sq. In.*
TABLE 1