If properly maintained, furnaces can last up to twenty years before they need to be replaced. Of course, the actual lifespan of a furnace, like any appliance, depends on the amount of work that it does and the amount of maintenance that it receives. Over time, your furnace will begin to exhibit certain signs that mean that you'll have to look at purchasing and installing a new unit.
Understanding these signs means that you'll avoid using an inefficient and ineffective furnace for an extended period of time:
Reduced Heat Production
Perhaps the most obvious sign, if your furnace is no longer producing any heat or is producing less heat than it was previously, it is not working properly. The issue may be a minor one, like clogged ductwork, or a major one, such as damaged machinery and parts within the furnace itself. A HVAC professional should examine your furnace to determine the cause of the problem.
Increased Energy Bills
If your energy bills increase without a proportional change in your energy usage during the winter months, your furnace may be using more energy to produce the same amount of heat. A loss in efficiency means that your furnace is no longer operating as it should be, and either needs to be repaired or replaced.
If your furnace makes banging, squeaking, or any other unusual noises when you turn it on, it may be about to break down. These sounds are usually representative of damaged parts within the furnace, and mean that the unit itself is not operating as it should be, resulting in poor heating and inefficient energy usage.
If you begin to experience drafts in rooms that were previously well heated, your furnace may not be working properly. However, this could also be caused by dust and debris buildup in your duct work, which is still a problem but is much cheaper and quicker to fix. Have a HVAC professional examine your furnace and ductwork to pinpoint what the issue is and the best way to fix it.
Burner Flame Color
If the burner flame on your furnace changes color from blue to yellow, there may be carbon monoxide in your home, which represents a serious health threat. You should call a professional immediately to examine your furnace and determine if carbon monoxide has leaked into your home. If it has, you'll have to replace the furnace itself, as carbon monoxide can be lethal.
If you have other questions or need more help, try contacting a professional furnace repair company to help address your concerns.