The instructions provided with each system contain valuable information on the installation and service of the system in the field. (Photo courtesy of Jim Bergmann.)
You have just graduated from vocational school. Your new employer is hooking you up with some new tools and you just learned about 401(k) plans. Today you are riding with Joe, the senior installation technician. One minute with Joe and you know he’s the ultimate professional. His uniform is military fit, and his truck is neat and clean and more organized than the shop at school. With notebook and pencil in hand, you are ready for your first day as a professional installation technician.

The van pulls into the customer’s driveway, and as Joe looks over to you, his eyes drill a laser beam into your brain.

“Son, this is the most important advice that I can give you, so listen carefully,” he says. Your ears perk up. Instinctively, you know Joe’s advice will one day make your bank account go ballistic.

“Get an installation guide for every piece of equipment that we install,” says Joe. “Read the guides from cover to cover. Follow them like your career depended on it — because one day it will.”

Today we will look at the topics covered in a furnace installation guide.


Safety is the first mindset you take to a jobsite, and it is usually covered in the first section of the installation guide. This section will talk about the furnace in relation to the building systems that you will connect to: gas, electrical, vent, control, drain, ductwork, and combustion air. The location of the installed equipment and its proximity to building components is also a safety concern. And, finally, the equipment itself has to be considered. Adjusting gas pressures, electrical connections, insulation, and internal circuitry all require safety awareness.

Connections And Dimensions

This section contains line drawings of the equipment showing top, bottom, and side views. Connection points for supply and return air, gas, electrical, and condensate are illustrated along with their dimensions. This is very important information for the preplanning process of the job. You want to make sure you bring the correct material to the jobsite.

Ductwork System

Information in this section is concerned with adapting the equipment to the ductwork system. Considerations include:

  • Transmission of vibration and noise.

  • Filter location.

  • Location of return air connection.


    The manufacturer will tell you to follow local code requirements. In the absence of local codes, you will be instructed to follow national codes. In addition to adhering to gas, wiring, flue, and plumbing codes, the local authority will most often refer back to the very instructions you are using to install the furnace.

    Location And Clearances

    Where you place the equipment is important. Concerns include access to the ductwork and combustion and ventilation openings. Accessing the furnace for general service is also a concern. It is also important to determine whether or not the atmosphere around the equipment is corrosive.

    Gas Piping

    Instructions will show tables for proper sizing along with the correct installation of manual shutoff valves, unions, and the drip leg. Along with the minimum and maximum allowable gas pressures there are instructions for verifying if the furnace is burning the correct amount of fuel according to the nameplate. (This is typically called clocking the meter.)

    Electrical Connections

    This section shows the electrical connection points between the power supply, thermostat, and equipment. The field wiring of accessory equipment like humidifiers is also included here.

    Condensate Drain

    These directions show what material to use, internal routing instructions for multiposition furnaces, and unconditioned space installation.

    Combustion And Ventilation Air

    This section covers minimum requirements for combustion air along with the correct entry points into the mechanical room.


    Instructions for venting will include the correct:

  • Venting material.

  • Size and length of the vent.

  • Routing of the vent.

  • Vent clearance requirements.

  • Fastening and hanging material.

  • Inlet air installation.

    Lighting Instructions

    This section covers step-by-step procedures for starting up the equipment.

    Adjustments And Safety Checkout

    This section provides directions for adjustments to airflow, temperature rise, and blower timing, along with steps to verify proper operation of the safeties and limits.

    Sequence Of Operations

    Starting with a call for heat at the thermostat, this section covers the exact order in which the furnace components operate to produce a run cycle.

    Communicating With The Customer

    User information is in this section. The professional installation technician covers usage details here with the homeowner. This is an excellent time for the technician to educate the homeowner on the benefits of annual maintenance and service agreements.

    That first day with Joe was over 30 years ago. Within one week you had all of the installation instructions you could get your hands on. You read every one. And you continued to read every new one that came out. Oftentimes you heard other technicians complaining about their rate of pay. A little spark would flicker inside; you’d smile and remember Joe’s advice. You never had such a complaint.

    Rothacker is a member of the National Comfort Institute’s Advisory Board and a National Comfort Team Founding Member. For questions or comments on the Tech Page, contact Rothacker at

    Publication date: 04/21/2003