There are two types of pilot light systems. A continuous Pilot Light (or continuous pilot ignition- CPI) and Millivolt, also known as a standing pilot light, is when the pilot light stays on at all times.. Intermittent Pilot Light, or IPI (Intermittent Pilot Ignition) will, as the name suggests, turn your pilot light on intermittently as the gas is turned on to ignite your fireplace. Most new systems will provide you with these different options when it comes to lighting your unit.

Millivolt vs. Electronic Ignition

Millivolt systems require you to manually light the pilot light. With this system, the pilot light is always left on. If you turn it off during the warm months, you will need to relight it when you’re ready to use it again.

New systems are often equipped with electronic ignition, which provides CPI and IPI. IPI was designed largely as an energy-saving measure, because the pilot light does not use gas when it’s not on. When you use IPI mode, the electronic module will ignite the pilot light when the thermostat says it’s time to turn on the fireplace, or when you manually turn it on.

The system has a sparker. The sparker ignites the pilot light. There’s a flame sensor that detects the pilot light flame, and gives the system the go ahead to allow the fuel into the burner. Electricity is needed to operate the sparker. Many units have a battery pack so the sparker will work in the event of a power outage.

It takes the fireplace a little longer to come on when you use IPI. There’s also a greater chance of malfunction. Generally speaking, the more often something is used, the greater the chance it will stop working properly due to wear and tear.

CPI mode operates using the same system as IPI. However, the pilot light remains on when the fireplace shuts off. This allows for faster operation, and has many other benefits.

The Benefits of Continuous Pilot Mode

Should you leave your pilot light on? Should you leave it on during the winter, or all year round? There are several advantages to leaving your fireplace in CPI mode, even during the summer months.

The benefits of CPI include:

  • Maintains draft
  • Prevents moisture in your fireplace
  • Keeps your chimney cap clear of snow
  • Improves reliability
  • Enables it to function during a power outage

Maintains Draft

A draft is a bad thing in most areas of your home in the winter months, but is essential to the proper functioning of your fireplace. If your chimney is too cold, it will not provide an adequate draft. This is essential for operating your fireplace, but also for other things in your home. A proper draft will pull in air that is used for combustion. If you have a gas water heater, furnace, or boiler, the byproducts of these appliances are vented through your chimney.

The system is designed to keep heat in your home, which is important for efficiency. However, you’ll also need enough warmth in the chimney to create draft. Why does temperature matter? Because warm air rises. If there’s not enough draft, it reduces efficiency. A pilot light provides the warmth the system needs.

Prevents Moisture in Your Fireplace

Moisture can build up and cause problems in your fireplace without a pilot light, especially in cold damp weather. When you start your fireplace, you may notice condensation on the glass. Over time, condensation can cause corrosion. Sulfur can also build up due to condensation. If you notice a white film on the glass, it should be cleaned. Today’s systems have electrical components that can be sensitive to moisture. Leaving your pilot light on provides enough heat to keep the area dry and burn away the condensation.

Keeps Your Chimney Cap Clear of Snow

A chimney cap performs a few important functions. It keeps rain, snow, and debris from getting into your chimney while allowing the gasses to escape. If the chimney cap becomes blocked by snow, the chimney can’t ventilate properly. This can cause it to not work properly or a back draft that allows harmful gasses into your home. A continuous pilot light provides enough heat to melt snow and prevent it from blocking the chimney cap.

Increases Reliability

A continuous pilot light can decrease the need for chimney and fireplace maintenance. Natural gas has an additive that gives it a distinctive smell, called Mercaptan. Even with the pilot light off, a faint smell will remain. Spiders are attracted to the scent, and often spin webs in chimneys and fireplaces. This can cause significant issues that require chimney maintenance. When the pilot light is lit, the chimney is no longer an attractive home for spiders.

It also decreases wear and tear on your unit, and never leaves you wondering if it will start.

Fireplace Can Be Used in a Power Outage

The pilot light requires electricity to light. If the pilot light is off when the power goes out, your fireplace won’t function. When you use CPI, the pilot light is always on, and your fireplace will function during a power outage. If you encounter a winter storm that knocks out your power, this can be the difference between riding the storm out at home or needing to seek warmer shelter. Newer systems often have a battery backup capable of lighting the pilot light, but simply leaving your pilot light on is the most reliable method for ensuring your system will start when you need it.

Should You Run CPI All Year?

All things have their positives and negatives. The most often mentioned downside of continuous pilot mode is that it uses natural gas to keep it on. However, the cost of running your fireplace in continuous mode is $4-$6 per month. The cost of running it during the summer months when you aren’t using your fireplace is around $30. The cost of running continuous pilot mode for an entire year is around $60. When you consider all the benefits, it’s a very small price to pay.

Some benefits of CPI hold true only for the winter months, but some are applicable all year round. It’s important to prevent moisture in your chimney all year round. Cold can contribute to the buildup, but it can easily happen during humid summer months or a rainy spring as well.

Spiders and animals find chimney’s an attractive home year-round. If you turn your pilot light off for the summer, you may be greeted with spider webs that can cause an unpleasant scent when you start your fireplace. They can also damage or block important sensors or circuits in your system.

There’s also the convenience of your fireplace being ready for use anytime you desire. In many areas, cooler weather isn’t always confined to a particular season, so you may want to occasionally light your fireplace outside of the traditionally cooler months. It can also provide a light source during summer power outages. Keeping your fireplace in CPI mode means you can start it anytime, even if there’s no power.

Continuous pilot mode has plenty of benefits and minimal downside. It can help prevent many common problems and make using your fireplace more convenient. However, it’s not a replacement for regular fireplace and chimney maintenance. Keeping a maintenance schedule and using CPI can keep your fireplace running great for years to come.