Furnace Services

JC & JC HVAC Mechanical Contractors repairs, replaces and maintains gas and electric forced-air furnaces for homes and businesses across Silver Spring, Bethesda, Washington, DC and the wider DC Metro area. If your furnace is short cycling, blowing cool air or locking itself out, contact our team and a licensed technician will come out to find the cause.

A furnace is a specific machine, and it fails in specific ways. This section of our site is about forced-air furnaces only: the cabinet in your basement, closet or attic that burns natural gas or uses electric resistance coils to warm air, then pushes that air through your ductwork with a blower. If your home heats with hot water radiators, a heat pump or a mix of equipment, our broader heating services page is the better starting point.

What does a furnace technician actually work on?

A furnace technician works on the parts that create and move heat in a forced-air system: the gas valve, ignitor, flame sensor, inducer motor, pressure switch, heat exchanger, blower, limit switches, control board, filter rack and venting.

Each of those parts has a job in a strict sequence. When the thermostat calls for heat, the control board starts the inducer motor to clear the combustion chamber. A pressure switch confirms the draft. The hot surface ignitor glows, the gas valve opens, burners light, and the flame sensor proves there is a flame within a few seconds. Only after the heat exchanger warms up does the blower start sending heated air to your rooms. If any step fails its check, the board shuts the sequence down and usually records a flash code.

That chain of safety checks is why furnace work rewards a methodical technician. A furnace that "won't heat" can be suffering from a dirty flame sensor, a cracked inducer housing, a plugged condensate trap or a filter so loaded that the high-limit switch keeps tripping. The symptom is the same. The fix is completely different.

Gas furnace or electric furnace: which one is in your home?

Gas furnaces are fed by Washington Gas, and electric furnaces and air handlers with electric heat strips run on Pepco power. Single-family homes, rowhouses and condos can have either type.

Gas furnaces

Gas furnaces come in two broad families. Standard-efficiency models, rated around 80 AFUE, vent hot exhaust up a metal flue or masonry chimney. High-efficiency condensing models, rated 90 AFUE and up, pull so much heat from the exhaust that its water vapor condenses into liquid, so they vent through PVC pipe and need a condensate drain. Knowing which one you have tells a technician where to look first.

Electric furnaces

Electric furnaces have no burners, no flue and no combustion risk. They use heavy resistance elements switched on in stages by sequencers or relays. They are simple and quiet, but they draw a lot of current, so worn relays, burned wire connections and tripped breakers are the usual trouble spots.

Our furnace services

We split furnace work into two core services so you can find the information that fits your situation.

Furnace installation and replacement

When a furnace is near the end of its working life, unsafe, or simply the wrong size for the house, we handle the full replacement: load calculation, equipment selection, venting, gas and electrical connections, and startup testing. As the licensed contractor, we pull the permits the job requires and meet the inspector. Read more on our Furnace Installation & Replacement page.

Furnace repair and service

For a furnace that will not light, will not stay lit, runs without heating or keeps throwing error codes, our technicians test each stage of the sequence and repair the failed part. See Furnace Repair & Service for how each failure is diagnosed and repaired.

How do you know your furnace needs attention?

Your furnace needs a technician when it changes behavior: new noises, shorter or longer run cycles, cool air from the vents, a blinking status light, a rising gas bill, or any carbon monoxide alarm.

Watch for these specific warning signs:

• The burners light, then shut off within a few seconds and try again
• A clicking or humming from the cabinet with no flame
• A loud bang or whoosh when the burners ignite, which can point to delayed ignition
• Water pooling under a high-efficiency furnace or dripping from an attic unit
• Rooms far from the furnace staying cold while nearby rooms overheat
• Yellow, lazy or lifting burner flames instead of steady blue ones
• Soot or scorch marks near the burner compartment
• A carbon monoxide detector sounding, even once

Some of these are nuisance problems. Others, like delayed ignition, soot and CO alarms, are safety problems that should not wait for a convenient day.

Why does carbon monoxide safety matter with a gas furnace?

A gas furnace produces carbon monoxide as part of combustion, so the heat exchanger, venting and draft must keep every bit of exhaust separated from the air your family breathes.

The heat exchanger is a sealed metal chamber. Burner flame and exhaust stay inside it, and house air passes over its outside surface. Years of heating and cooling cycles stress that metal, and cracks or rust-through can develop, especially in a furnace that has run hot because of poor airflow. Venting problems matter just as much: a disconnected flue, a blocked chimney or a crushed PVC vent can push exhaust back into the home.

During furnace service we inspect the heat exchanger, check draft and vent connections, and measure combustion so problems are found by instruments rather than by a CO alarm. If you ever smell gas, leave the house and call Washington Gas from outside. If a CO alarm sounds, get everyone outdoors and call 911, then call us for the furnace.

How often should a furnace be serviced?

A gas furnace should be inspected and cleaned once a year, ideally in early fall, and the filter should be checked every month or two during the heating season depending on its type and your household.

Annual service is not a cleaning visit with a fresh filter and nothing else. A proper furnace tune-up includes cleaning and testing the flame sensor, checking the hot surface ignitor's resistance, confirming the inducer motor and pressure switch work correctly, measuring gas pressure at the manifold, checking temperature rise against the furnace's rated range, inspecting the heat exchanger, and verifying that every limit and rollout switch opens when it should. On condensing furnaces we also clean the condensate trap and flush the drain.

Electric furnaces need less combustion work but still benefit from a yearly check of element circuits, sequencers, wire connections and blower operation. Filters matter for every furnace. A one-inch filter in a busy household with pets can load up in a few weeks, while a deeper media filter lasts much longer. When filters go too long between changes, the blower struggles, the heat exchanger runs hot, and the high-limit switch begins to cycle the burners off.

What to expect during your visit

A furnace visit starts with your description of the problem, moves through a step-by-step test of the heating sequence, and ends with a clear explanation of the repair or replacement options before any work starts.

Our technician will check the thermostat call, read any control board codes, inspect the filter and blower, watch a full ignition cycle, measure temperature rise across the furnace, and look over the venting and gas connections. If a part has failed, we explain what it does and why it failed, so the same thing does not happen again next month. If the furnace is unsafe to run, we will tell you plainly and shut it down rather than leave you with a hazard.

Every repair and installation is backed by our 1-Year Workmanship Warranty, and we offer 24/7 emergency service for no-heat calls in the middle of a cold snap.

Related services

Furnaces share duct systems, thermostats and sometimes venting with other equipment in your home. Our heat pump services cover dual-fuel setups where a heat pump handles mild weather and the furnace takes over in deep cold. Homes with radiators or baseboard heat are covered under boiler services, and dirty or leaky ducts that starve a furnace of airflow are handled through air duct cleaning.

Keep your furnace ready for the next cold snap

A furnace that is cleaned, tested and adjusted before winter is far less likely to fail on the coldest night of the year. Ask about our VIP Comfort Club maintenance plan, and financing is available when replacement makes more sense than another repair. Call (301) 509-2475 or request furnace service online and our family-owned team will get your heat back on.