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Heating / December 18, 2018

3 Common Problems that Affect Gas Furnace Manifolds

Despite being one of the most heavily used home appliances when cold weather rolls around, gas furnaces hold up admirably against general wear and tear. Yet problems may still occur that compromise the ability of a furnace to adequately heat your home. A gas furnace contains numerous components, any one of which can develop a debilitating problem.

One vital yet overlooked component is the manifold. The manifold acts as a crucial point of connection between the gas valve and the burner assembly. If you would like to learn more about the problems that afflict manifolds, keep reading.

What Could Cause Gas Pressure to Drop?

This article outlines three symptoms of low gas pressure to your furnace you might experience as a homeowner.

  1. Incorrect Pressure
  2. Insect Infestation
  3. Corrosion

What is a gas furnace manifold?

The manifold functions as the intermediary between the furnace’s gas valve and the actual burner inside the combustion chamber. The burner consists of a series of open tubes that contain an internal nozzle known as a spud.

Incorrect Pressure

In order for the burner to work efficiently, the gas pressure coming from the manifold must be carefully regulated.

The ideal pressure level depends on a number of factors.

  • The fuel source plays a key role, with natural gas and propane requiring different pressures.
  • Likewise, the size and capacity of the furnace affect the necessary pressure.

Symptoms of Low Gas Pressure to Furnace

What happens when there is incorrect furnace gas pressure?

  • Low pressure leads to rough ignition and overall poor combustion.
  • High pressure, on the other hand, can lead to overfiring the heat exchanger which will accelerate the amount of wear and tear placed on the heat exchanger. This could also trigger the furnace’s high limit control. When that happens, the furnace shuts down to avoid overheating — even if your house hasn’t finished warming up completely.

What should gas pressure be for a furnace?

A professional HVAC technician can measure and adjust the pressure of your gas manifold if necessary. In most cases, a gas furnace should have a manifold pressure of around 3.5 inches of water, or 3.5 WC (water column) for short. The ideal pressure setting can also be found on the rating plate

Insect Infestation

You likely only need to run your furnace 3-5 months of the year depending upon what area of San Diego you live. The rest of the time, the furnace sits idle. Unfortunately, this downtime gives unwanted pests plenty of opportunities to take up residence inside of your furnace and its components.

While birds and rodents can create problems inside your duct system, your furnace itself remains more prone to insect infestations. Should these insects build their nests inside your furnace’s manifold, the resulting debris may create problems once winter rolls around, creating blockages that negatively affect flow and pressure.

Your chances of dealing with insect problems go up if you choose to turn off your gas furnace’s pilot light in the summer. A non-functioning pilot orifice provides the perfect point of entry for unwanted critters.

Keeping your pilot light on throughout the summer will cost you far less than having to have your burner assembled and manifold disassembled for a thorough cleaning.

Corrosion

Over time, a gas furnace manifold may develop corrosion that inhibits the proper flow of gas. Such corrosion forms naturally as the result of the combustion gas reaction, which allows water vapor to condense as the furnace cools down after a heating cycle.

Likewise, excessive soot buildup also hastens the rate of rust formation. Fortunately, in a well-maintained furnace, the manifold should experience relatively little corrosion compared to other components.

Always hire a professional to inspect and tune up your system prior to each winter. The technician can remove any existing corrosion to reduce the likelihood of the problem growing out of control.

Need Your Furnace Inspected or Repaired?

The manifold plays a huge role in the overall working of your furnace.  If your furnace is not acting properly and might be in need of repair, contact us or book an appointment for our specialists in San Diego to come to take a look.

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