Job Hazard Analysis: Furnace installation

A general example for this task. Your JHA should reflect your crew, equipment and site — review it with a competent person before work starts.

Steps, hazards and controls

1. 1. Walk the job, set up the work area, and plan the carry path

   • Trips and falls on stairs, clutter, cords, and dim basement lightingMedium
     • Ask the homeowner to clear a path from the door to the furnace before the crew carries anything.
     • Set up LED work lights at the furnace and on the basement stairs.
     • Run extension cords along walls and tape them down where people walk.
     • Wear slip-resistant work boots.
   • Existing gas smell, CO, or damaged wiring found at the old furnaceHigh
     • Turn on a personal CO monitor and walk the area with a combustible gas detector before starting.
     • If you smell gas or the detector alarms, stop, get everyone out, and call the gas utility from outside.
     • Note any scorched wiring, rusted gas fittings, or old wrapped duct insulation and tell the supervisor before touching it.

2. 2. Shut off and lock out power and gas to the old furnace

   • Electric shock from the 120V furnace circuit or a mislabeled breakerHigh
     • Turn off the furnace service switch and the breaker in the panel.
     • Put your lock and tag on the breaker so nobody turns it back on.
     • Test for voltage at the furnace junction box with a non-contact tester and a meter before touching wires.
     • Use insulated screwdrivers and pliers.
   • Gas release when disconnecting the old gas lineHigh
     • Close the furnace gas shutoff valve and tag it before loosening any fitting.
     • If the valve will not close fully, shut gas at the meter and call the supervisor.
     • Cap or plug the open gas line right away.
     • No open flames, smoking, or sparking tools near the gas line.

3. 3. Disconnect and remove the old furnace

   • Cuts from sharp sheet metal edges, screws, and cut ductMedium
     • Bend over or tape sharp edges on cut plenums and duct.
     • Wear cut-resistant gloves when handling sheet metal.
   • Back strain and crushed hands carrying the furnace on stairsMedium
     • Use an appliance dolly with straps on stairs.
     • Strip off the blower and doors first to lighten the load.
     • Carry with two people, call out each move, and keep hands clear of door frames.
   • Dust, mold, and possible asbestos on old duct wrap or furnace partsMedium
     • Do not cut, tear, or sweep suspect white or gray duct wrap; stop and call the supervisor for testing.
     • Use a HEPA vacuum instead of dry sweeping.
     • Wear an N95 or better respirator when dust is present.

4. 4. Set the new furnace and connect plenums and ductwork

   • Lacerations and eye injuries from snips, drills, and cut-off toolsMedium
     • Check cords, guards, and bits on drills and cut-off tools before use.
     • Clamp sheet metal to the bench instead of holding it by hand.
     • Wear safety glasses and cut-resistant gloves.
   • Falls from a stepladder while hanging duct or a plenum overheadMedium
     • Use a 6-ft fiberglass stepladder fully opened and locked on a level floor.
     • Do not stand on the top step or top cap.
     • Keep your belt buckle between the rails and have a second worker hand up materials.

5. 5. Connect the gas piping and leak test

   • Gas leak, fire, or explosion from a bad fitting or flex connectorHigh
     • Install a new approved flex connector, sediment trap, and shutoff valve; do not reuse the old connector.
     • Use pipe dope or tape rated for gas.
     • Open the gas slowly and test every joint with leak solution and the gas detector.
     • Keep a charged ABC fire extinguisher within reach.
   • Hand injuries from pipe wrenches slippingLow
     • Use two wrenches to back up fittings and pull toward you, not push.
     • Wear work gloves.

6. 6. Install the PVC or metal vent and condensate drain

   • Flammable vapors and skin or eye irritation from PVC primer and cementMedium
     • Read the SDS and label before using primer and cement.
     • Open a window or run a fan to move fresh air through the work area.
     • Keep cans closed when not in use and away from water heater and furnace pilot flames.
     • Wear nitrile gloves and safety glasses.
   • Carbon monoxide entering the home from a poorly sealed or wrongly pitched ventHigh
     • Follow the manufacturer's vent size, length, slope, and termination clearances.
     • Fully seat and glue every joint and support the pipe at the required spacing.
     • Have a second tech inspect the full vent run before startup.
   • Drill kickback and dust when coring through a rim joist or wallMedium
     • Use a hole saw with a side handle and brace the drill.
     • Check for wires and pipes in the wall before drilling.
     • Wear safety glasses and hearing protection.

7. 7. Wire the furnace, remove lockout, and start up with combustion testing

   • Electric shock when connecting line voltage or restoring powerHigh
     • Make all wire connections with power still locked out and the ground wire connected first.
     • Close all covers, count the crew, and tell everyone before removing your lock.
     • Only the worker who placed the lock removes it.
   • Carbon monoxide or gas buildup during first firingHigh
     • Keep your personal CO monitor on during startup.
     • Check gas pressure and test flue gas with a combustion analyzer per the manufacturer.
     • If CO is high or the burner rolls out, shut off gas and power and find the cause before restarting.
     • Confirm a working CO alarm is in the home and tell the homeowner if it is missing.

8. 8. Clean up and haul out the old furnace and scrap

   • Cuts and trips from sheet metal scrap and debrisLow
     • Pick up sheet metal scraps as you go and put them in a bucket or box.
     • HEPA vacuum the work area before leaving.
     • Wear cut-resistant gloves.
   • Back strain and crush injuries loading the old furnace into the truckMedium
     • Use a dolly and the truck's liftgate or ramp.
     • Lift with two people and strap the load before driving.