Annual servicing is the sort of thing people skip because nothing appears to be wrong. That is precisely the point of it — the failures worth preventing are the ones that have not happened yet.
Here is what is actually involved, so you can judge it rather than take it on faith.
The safety half
Combustion and venting. A gas furnace burns fuel and must send the products of that combustion outside. The technician checks that the venting is intact, correctly sloped, unobstructed and properly terminated. Blocked or damaged venting is how combustion gases end up indoors.
The heat exchanger. Inspected for cracks. This is the component that keeps combustion gases separate from the air circulating through your home, and a crack in it is the most serious fault a furnace can have. Finding one during a routine service is exactly the outcome the service exists for.
Gas connections. Checked for leaks at the appliance.
Safety controls. The limit switches, pressure switches and flame sensing that shut the furnace down when something is wrong. These are tested rather than assumed — a safety device that has failed silently provides no protection at all, and you would never know until the day it was needed.
Those four are why this is not optional maintenance in the way that, say, cleaning your gutters is.
The reliability half
Burners cleaned, because deposits cause uneven combustion and rough starts.
Flame sensor cleaned — the single most common cause of a furnace lighting and immediately shutting down.
Ignitor inspected. Ignitors fail with age, and a technician can often see one that is close.
Blower cleaned and inspected. A dirty blower wheel moves less air, which reduces heat output and makes the motor work harder.
Electrical connections checked and tightened. Vibration loosens terminals over years, and loose connections cause intermittent faults that are miserable to diagnose in a failure.
Airflow and temperature rise measured. The difference between the air going in and the air coming out tells the technician whether the system is moving the right amount of air. Wrong temperature rise means either a restriction or a sizing problem, and it shortens equipment life.
Condensate drainage, on high-efficiency units, which produce water as a by-product of their efficiency. A blocked condensate drain will shut a furnace down and can leak.
Filter checked and replaced or advised.
The warranty part
Most manufacturers require documented annual maintenance for the warranty to remain valid. If your furnace fails within the warranty period and there is no service record, the claim can be refused.
That is a straightforward financial argument. The cost of servicing over the warranty period is generally less than one denied major repair.
When to book it
Before the heating season, in the shoulder period of late summer to early autumn.
Two reasons. Any fault found can be fixed before you depend on the system, rather than during the week you cannot be without heat. And technicians are available — once the first cold snap arrives, everyone who has been ignoring their furnace calls at once, and a service booking competes with genuine no-heat emergencies.
Doing it together
If your hot water tank is due for attention as well, having both looked at in the same visit is more efficient than two separate ones. The same applies to a gas fireplace, which has its own annual servicing requirement and is easy to forget entirely.
What you should get afterwards
A written record of what was checked and what was found — including the things that were fine. That record is your warranty documentation, and it is also how you notice, next year, that something has changed.
If your furnace has never been serviced or you cannot remember the last time, that is a reason to book, not a reason to keep waiting.
Vancouver, Burnaby, Richmond, Coquitlam, Port Coquitlam, New Westminster. 604-865-7979.
Related: Furnace maintenance and tune-ups · Furnace repair · Gas fireplace installation and service
