
260 North Elm St., Westfield, MA 01085
(413) 564-5540 Fax: (413) 562-5311
www.sterlinghvac.com
DESCRIPTION
The Sterling “XF/XC” Series Convertible Venting Type Tubular
Gas-Fired Unit Heater offers a highly efficient, extremely durable
alternative to the traditional clam shell design. These propeller
and blower type units combine the latest tubular heat exchanger
and in-shot burner technology with the quality and reliability you
have come to know from Sterling. Units are available in sizes 100
to 400 MBH and have been certified by ETL as providing 83%
thermal (combustion) efficiency.
CONVERTIBLE VENTING - STANDARD OR SEPARATED COMBUSTION
Notably, the Sterling “XF/XC” unit heater is designed so it can
be installed in either standard or separated combustion venting
configurations without requiring modification to the unit itself.
Located on the rear cover panel of each unit, combustion air
inlet collars are left open in a standard combustion venting
configuration. When set up for separated combustion, combustion
air piping is connected to the inlet collars so that the burners, spark
ignitor, and flue system are enclosed within the unit, allowing
the entire combustion process to remain unaffected by the
atmosphere in the space where the heater is located. Separated
combustion venting configurations should be used where dusty,
dirty or mildly corrosive conditions exist, or where high humidity
or slightly negative pressures prevail.
ADDITIONAL VENTING FLEXIBILITY
The Sterling “XF/XC” unit heater is ETL certified in accordance with
categories I and III venting requirements. This certification allows units
to be vented both vertically and horizontally using either single wall or
double wall venting materials. Available as an accessory option, Sterling
offers a Combustion Air Inlet Kit that allows for concentric venting of
both combustion and exhaust air systems through one termination.
TUBULAR HEAT EXCHANGER
The Sterling tubular heat exchanger has been designed to provide
maximum and uniform heat transfer. The low pressure drop
associated with this design enables heated air to be evenly distributed
to the conditioned space. This curved, non-welded serpentine design
experiences less thermally induced stress making it highly durable for
significantly longer service life. All Sterling tubular heat exchangers
are constructed of heavy duty 20-gauge aluminized steel. Optional
409 stainless steel heat exchangers are also available.
DIRECT SPARK IGNITION SYSTEM & CONTROL ACCESSIBILITY
Sterling “XF/XC” units utilize a direct spark pilotless ignition of the
burner, providing fast heat delivery. This highly reliable and efficient
ignition system incorporates an integrated electronic control
board to regulate the system sequence of operation, including
an externally mounted LED indicator for simple troubleshooting.
Designed with the service person in mind, ignition and fan controls
are located in one centrally located control panel.
XF/XC SERIES
Unit Size 100 125 150 175 200 250 300 350 400
PERFORMANCE DATA†
Input - BTU/Hr. 100,000 125,000 150,000 175,000 200,000 250,000 300,000 350,000 400,000
Output - BTU/Hr. 83,000 103,750 124,500 145,250 166,000 207,500 249,000 290,500 332,000
Flue Size Diameter* - in 5 5 5 5 5 5 6 6 6
Gas Inlet, Natural/LP Gas - in 1/2 1/2 1/2 1/2 1/2 3/4 3/4 3/4 3/4
XF PERFORMANCE/DIMENSIONAL DATA
Free Air Delivery - CFM 1,600 2,200 2,400 2,850 3,200 3,450 5,000 5,600 5,800
Air Temperature Rise 47°F 42°F 47°F 46°F 47°F 54°F 45°F 47°F 51°F
Full Load Amps at 120V 6.4 6.9 6.9 8 8 8 11.6 13.8 13.8
MOTOR DATA: Motor HP 1/10 1/4 1/4 1/3 1/3 1/3 1/4 (2) 1/3 (2) 1/3 (2)
Motor Type (ODP) SP PSC PSC PSC PSC PSC PSC PSC PSC
RPM 1,050 1,050 1,050 1,050 1,050 1,050 1,050 1,050 1,050
Amps @ 115V 4.2 4.7 4.7 5.8 5.8 5.8 9.4 11.6 11.6
DIMENSIONAL DATA - inches
Overall Unit Height 33-3/4 33-3/4 33-3/4 33-3/4 33-3/4 33-3/4 34 34 34
Overall Unit Width 25-1/4 25-1/4 25-1/4 37-1/4 37-1/4 37-1/4 55-1/4 55-1/4 55-1/4
Overall Unit Depth 43-1/2 43-1/2 43-1/2 43-1/2 43-1/2 43-1/2 44-3/4 44-3/4 44-3/4
XC PERFORMANCE/DIMENSIONAL DATA
Free Air Delivery - CFM 1,181 1,476 1,771 2,067 2,362 2,953 3,501 4,134 4,724
Air Temperature Rise 65°F 65°F 65°F 65°F 65°F 65°F 65°F 65°F 65°F
Outlet Velocity - FPM 370 463 555 395 451 564 422 498 570
MOTOR DATA: Motor HP 1/4 1/2 1/2 3/4 3/4 1 1 1-1/2 1-1/2
Motor Type ODP** SPH SPH SPH SPH SPH Cap. Start Cap. Start Cap. Start Cap. Start
RPM 1,725 1,725 1,725 1,725 1,725 1,725 1,725 1,725 1,725
Amps @ 115V†† 5.1 7.2 7.2 11.6 11.6 13 13 18.2 18.2
DIMENSIONAL DATA - inches
Overall Unit Height 33-3/4 33-3/4 33-3/4 33-3/4 33-3/4 33-3/4 34 34 34
Overall Unit Width 25-1/4 25-1/4 25-1/4 37-1/4 37-1/4 37-1/4 55-1/4 55-1/4 55-1/4
Overall Unit Depth 49-3/4 49-3/8 49-3/8 56-1/8 56-1/8 56-1/8 53-3/8 56-1/8 56-1/8
† Ratings shown are for unit installations at elevations between 0 and 2,000 ft (0 to 610m). For unit installations in U.S.A. above 2,000 ft. (610m), the unit input must be field
derated 4% for each 1,000 ft. (305m) above sea level; refer to local codes, or in absence of local codes, refer to the latest edition of the National Fuel Gas Code, ANSI Standard
Z223.1 (N.F.P.A. No. 54).
For installations in Canada, any reference to deration at altitudes in excess of 2,000 ft. (610m) are to be ignored. At altitudes of 2,000 ft. to 4,500 ft. (610 to 1372m), the unit must
be field derated to 90% of the normal altitude rating, and be so marked in accordance with the ETL certification. See unit installation manual for field deration information.
†† See installation manual for ODP motor full load amp values at non-standard voltages.
* Flue collar is factory supplied with unit; to be field installed per included instructions.
** LEGEND: SPH = SPLIT PHASE CAP. START = CAPACITOR START ODP = OPEN DRIP PROOF
XF & XC