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Sterling QVSD-400 - User Manual

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INSTALLATION INSTRUCTIONS AND SERVICE MANUAL
STERLING SEPARATED COMBUSTION
GAS-FIRED INDOOR DUCT FURNACE
(S) SCDFM-4
J30-05374
HVAC PRODUCTS
260 NORTH ELM ST., WESTFIELD, MA 01085
TEL: (413) 564-5540 FAX: (413) 562-5311
www.sterlinghvac.com
MODELS: QVSD-100 thru 400
01/11
FOR YOUR SAFETY
The use and storage of gasoline or other fl ammable vapors and liquids in open containers in
the vicinity of this appliance is hazardous.
FOR YOUR SAFETY
If you smell gas:
1. Open windows.
2. Don’t touch electrical switches.
3. Extinguish any open fl ame.
4. Immediately call your gas supplier.
Model No.
Serial No.
ATTENTION: READ THIS MANUAL AND ALL LABELS ATTACHED TO THE UNIT CAREFULLY BEFORE
ATTEMPTING TO INSTALL, OPERATE OR SERVICE THESE UNITS! CHECK UNIT DATA PLATE FOR TYPE OF GAS
AND ELECTRICAL SPECIFICATIONS AND MAKE CERTAIN THAT THESE AGREE WITH THOSE AT POINT OF
INSTALLATION. RECORD THE UNIT MODEL AND SERIAL No.(s) IN THE SPACE PROVIDED. RETAIN FOR FUTURE
REFERENCE.
APPROVED FOR USE IN CALIFORNIA
INSTALLER'S RESPONSIBILITY
Installer Please Note: This equipment has been test fi red and inspected. It has been shipped
free from defects from our factory. However, during shipment and installation, problems such
as loose wires, leaks or loose fasteners may occur. It is the installer's responsibility to
inspect and correct any problems that may be found.
RECEIVING INSTRUCTIONS
Inspect shipment immediately when
received to determine if any damage
has occurred to the unit during
shipment. After the unit has been
uncrated, check for any visible
damage to the unit. If any damage is
found, the consignee should sign
the bill of lading indicating such
damage and immediately file claim
for damage with the transportation
company.
Install, operate and maintain unit in accordance with manufacturer's
instructions to avoid exposure to fuel substances or substances from incomplete
combustion which can cause death or serious illness. The state of California
has determined that these substances may cause cancer, birth defects, or other
reproductive harm.
Improper installation, adjustment, alteration, service or maintenance can
cause property damage, injury or death. Read the installation, operating and
maintenance instructions thoroughly before installing or servicing this equipment.

Table of Contents

Questions and Answers

  • S
    Sara ClarkSep 6, 2025
    Why is my Sterling QVSD-400 power ventor motor turning on and off?
    • B
      brendacarsonSep 6, 2025
      If the power ventor motor on your Sterling Furnace turns on and off while the burners are operating, it could be due to several reasons. First, ensure the ventor relay heater terminals are connected per the diagrams. A defective ventor relay switch could also be the problem, requiring replacement of the ventor motor. Additionally, the motor protector might be cycling on and off, so check the motor amps against the motor nameplate rating and check the voltage, replacing the power ventor motor if defective. Finally, ensure the motor is properly oiled.
  • C
    Colleen KlineAug 22, 2025
    Why is my Sterling Furnace not igniting?
    • A
      Ana MccormickAug 22, 2025
      The Sterling Furnace might fail to ignite due to several reasons. First, ensure all manual gas valves are open and that the unit has power, replacing the fuse or turning on the power supply if necessary. Verify the thermostat is calling for heat by turning it up. Check the limit switch with a continuity tester, replacing it if open. Inspect the thermostat or transformer wiring at the gas valve, consulting wiring diagrams. If these steps don't resolve the issue, the gas valve, thermostat, transformer, or ignition control may be defective and require replacement. Also, ensure all wiring connections are tight, referring to the diagrams.
  • T
    Tabitha PierceSep 3, 2025
    What to do if my Sterling QVSD-400 is not producing enough heat?
    • J
      James TaylorSep 3, 2025
      If your Sterling Furnace isn't producing enough heat, consider the following: The gas input might be incorrect. The heater might be undersized, especially if the heated space has been enlarged. In this case, have a heat loss calculation performed and compare it to the heater's output (80% of input). Your gas supplier or installer can provide this information, and if the heater is undersized, consider adding additional heaters. A malfunctioning thermostat could also be the issue, requiring replacement. Also, check for proper air movement through the heat exchanger and check the voltage to the fan motor. Clean the power ventor motor and adjust dampers accordingly.
  • B
    Brandon GillSep 2, 2025
    What causes a Sterling QVSD-400 to deliver cold air on start-up?
    • R
      Rachel LeeSep 2, 2025
      If your Sterling Furnace is delivering cold air on start-up, it is likely due to the fan relay heater element being improperly wired. To fix this, check and tighten all wiring connections per the diagrams. Ensure that the thermostat wires tagged “W” and “G” are connected together, unless special thermostats are used; if so, refer to the thermostat wiring diagram.
  • A
    Alicia MillerSep 1, 2025
    What causes a Sterling QVSD-400 flame to lift from burner ports?
    • X
      xdavisSep 1, 2025
      A flame lifting from the burner ports in your Sterling Furnace could be due to: A pressure regulator set too high, requiring you to reset the manifold pressure. A defective regulator, which means you should replace the regulator section of the combination gas valve or the complete valve. A burner orifice that is too large, requiring you to check with your local gas supplier for the proper orifice size and replace it if needed.
  • C
    Cynthia WaltonAug 30, 2025
    What causes rapid burner cycling in a Sterling Furnace?
    • D
      Danielle BanksAug 30, 2025
      Rapid burner cycling in a Sterling Furnace can stem from several causes. Check for loose wire connections at the gas valve or thermostat and tighten them. The thermostat heat anticipator might be set too high, requiring adjustment for longer cycles. The unit could be cycling on a high limit, so check for proper air supply across the heat exchanger. A poorly located thermostat or drafts on the pilot can also cause this issue, so relocate the thermostat and eliminate drafts. Finally, a defective ignitor control or high limit could be the cause, necessitating replacement of the ignitor. If the high limit is suspected, temporarily jumper the high limit switch terminals 1 and 2; if the burner operates normally, replace the switch.
  • N
    Nicole GallowayAug 29, 2025
    How to fix a Sterling QVSD-400 with yellow tip flame?
    • M
      Marissa Lewis DDSAug 29, 2025
      If your Sterling Furnace has a yellow tip flame (excluding permissible yellow tipping on propane gas), it could be due to several reasons: insufficient primary air, clogged burner ports, misaligned orifices, a clogged draft hood, dust or lint at the air mixer opening and around the air shutter, or insufficient combustion air. To address this, first, open the air shutter. Then, clean the main burner ports. If that doesn't work, replace the manifold assembly. Also, clean the draft hood and check for any dust or lint at the air mixer opening and around the air shutter. Finally, inspect for obstructions in the combustion air inlet cap and piping.
  • C
    Chelsea JohnsonAug 27, 2025
    Why is my Sterling Furnace making a noisy flame?
    • H
      herbert72Aug 28, 2025
      A noisy flame in your Sterling Furnace can be due to several reasons. First, there might be too much primary air, in which case you should close the air shutter. It could also be a noisy pilot, requiring a reduction in pilot gas. An irregular orifice causing a whistle or resonance would necessitate replacing the orifice. Lastly, excessive gas input could be the culprit, requiring you to reset the manifold pressure. If resetting the manifold pressure doesn't solve the issue, consider replacing the regulator section of the combination gas valve or the complete valve, or check with your local gas supplier for the correct orifice size and replace it if necessary.
  • J
    Jessica DavisAug 27, 2025
    What to do if my Sterling Furnace burner won't turn off?
    • D
      David BrownAug 27, 2025
      If the burner in your Sterling Furnace won't turn off, consider these steps: Relocate the thermostat away from drafts. If that doesn't work, replace the thermostat. Check the wiring diagrams to ensure proper thermostat or transformer wiring at the gas valve. Inspect for short circuits, such as staples piercing the thermostat wiring, and correct them. If these steps don't resolve the issue, the gas valve might be defective or sticking and needs replacement. Also, check for excessive gas supply pressure.
  • A
    Amanda JohnsonAug 25, 2025
    Why is my Sterling QVSD-400 Furnace power ventor motor not running?
    • K
      Kristopher HallAug 25, 2025
      If the power ventor motor on your Sterling Furnace isn't running, first check and tighten all wiring connections according to the diagrams. Ensure the thermostat wires tagged “W” and “G” are connected, unless special thermostats are in use. If the wiring is correct, the motor overload protector or the motor itself may be defective, requiring replacement. Also, check the power ventor relay by ensuring 24V is present across terminals 1 and 3 on the fan relay. If it is, jumper terminals 2 and 4; if the motor then runs, the relay is defective and needs replacement. If 24V is not present, check the wiring diagrams.

Summary

Installers Responsibility

Inspection and Correction of Issues

Installer is responsible for inspecting and correcting any problems that may occur during shipment or installation.

Receiving Instructions

Shipping Damage Inspection and Claims

Instructions to inspect the unit for shipping damage and file claims with the transportation company.

General Safety Information

Safety Terminology Definitions

Explains hazard alert symbols and terms used in the manual for safety.

Unit Specifications

Physical Dimensions and Gas Inlet

Provides key physical dimensions, gas inlet sizes, and weight for different unit models.

Performance Data

Airflow and Temperature Rise Metrics

Lists input/output ratings, airflow capacities, and temperature rise for various unit sizes.

Installation Clearances

Minimum Clearance Requirements

Details minimum safe distances from combustible materials and for service access.

Special Installation Locations

Outlines installation requirements for aircraft hangars and public garages.

Installation Procedures

Ductwork and Airflow Design

Covers recommended ductwork designs and airflow adjustment for optimal unit performance.

Suspension and Mounting

Provides guidance on proper suspension points and ensuring secure mounting of the unit.

Electrical Connections

Power Supply and Wiring Standards

Details power supply requirements, adherence to electrical codes, and grounding procedures.

Thermostat Installation and Settings

Instructions for thermostat mounting, wiring, and setting the heat anticipator for optimal control.

Wiring Diagrams

Honeywell Ignition System Diagram

Illustrates the wiring for units utilizing the Honeywell ignition system.

Johnson Ignition System Diagram

Illustrates the wiring for units utilizing the Johnson ignition system.

Combustion Air Piping

Combustion Air Piping Installation Requirements

Details installation requirements for combustion air piping, including codes, pipe materials, and length limits.

Exhaust Venting

Exhaust Venting Installation Requirements

Covers installation requirements for exhaust venting, including codes, pipe materials, and termination guidelines.

Gas Piping

Pipe Sizing and Selection

Provides formulas and tables to calculate and select the appropriate gas pipe size based on input and length.

Pipe Installation

Gas Supply and Pressure Requirements

Details standards for installing gas piping, including pressure testing and required gas pressures.

Burner Components

Burner Drawer Parts Identification

Identifies common parts found in the burner drawer assembly.

Gas Input Rate

Input Rate Calculation

Explains the process for calculating the gas input rate using gas meter readings and BTU content.

Pressure Adjustments

Pilot and Manifold Pressure Settings

Provides procedures for adjusting pilot and manifold gas pressures for optimal operation.

Unit Operation

Initial Lighting Procedure

Step-by-step instructions for safely lighting the unit for the first time.

Primary Air Shutter Adjustment

Describes how to adjust the primary air shutter for proper burner flame characteristics.

Maintenance Procedures

Periodic Service Routine

Outlines a routine inspection and service schedule for maintaining the unit.

Power Venter Assembly

Component Identification and Notes

Identifies components and provides notes on assembly and flue size requirements.

Troubleshooting Guide

Flame and Gas Odor Issues

Addresses troubleshooting steps for flame appearance issues and gas odor detection.

Ignition and Condensation Problems

Provides solutions for ignition problems and condensation of water vapor.

Cycling and Ventor Operation Issues

Troubleshoots issues related to rapid burner cycling, noisy power ventor, and pilot ignition problems.

Ventor and Heat Output Issues

Troubleshoots issues related to power ventor operation and insufficient or excessive heat output.

Spark, Pilot, and Safety Switch Issues

Resolves problems with spark, pilot operation, and hi-limit switch tripping.

Replacement Parts and Warranty

Ordering Parts and Warranty Terms

Details how to order replacement parts and the terms of the product's limited warranty.

Sterling QVSD-400 Specifications

General IconGeneral
BrandSterling
ModelQVSD-400
CategoryFurnace
LanguageEnglish

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