The ONT power supply unit in a Verizon installation is a small box that plugs into a standard electrical outlet and its sole purpose is to provide electricity to the Optical Network Terminal (ONT), the device that converts the fiber optic signal for your internet, TV, and phone services. Without this power supply, your ONT cannot operate, which means all of your Verizon FiOS services would be down.
What is the ONT power supply unit in a Verizon installation?
In simple terms, the ONT power supply unit (PSU) acts as the bridge between your home's electrical system and the ONT. It takes the standard alternating current (AC) from your wall outlet and converts it into the direct current (DC) that the ONT needs to function. This small, often wall-mounted box is a critical piece of hardware because the ONT itself does not have a power cord that plugs directly into the wall; it relies entirely on this dedicated power supply. The unit typically has a small LED light on it; when lit, it indicates that the adapter is receiving power and working correctly. This is the first thing to check if you suspect a power issue with your FiOS connection.
Why the power supply unit has a battery
Many people are surprised to learn that the ONT power supply unit often contains a backup battery, but its function is frequently misunderstood. This battery backup exists for one specific reason: to keep your Verizon voice service (including 911 calls) operational during a power outage. It does not power your internet or TV service during an outage. This is a crucial distinction because it means if the power goes out, you will lose your Wi-Fi and television, but you may still have a working home phone for a limited time. Depending on your specific installation, Verizon may have provided one of three types of backup units: the standard Battery Backup Unit (BBU), the PowerReserve, or the Battery Storage Unit (BSU). Each serves the same fundamental purpose but with different capacities and battery configurations.
Understanding your battery backup runtime
Knowing how long your backup will last in an outage can help you plan. The runtime depends entirely on which unit you have installed. For a standard BBU, a fully charged 12V battery provides up to 8 hours of backup power for voice services. If your installation uses the PowerReserve unit, which is used with an ONT configured with a Power Adaptor, you can expect at least 24 hours of backup power for basic voice service, powered by 12 D-cell alkaline batteries. For homes with higher voice line requirements (typically three or more lines), the Battery Storage Unit (BSU) can be added. When a BSU is combined with an existing BBU and uses two fully charged 12-volt 8Ah sealed lead acid batteries, it can provide up to 24 hours of backup power. This information is useful for understanding how long you can make calls during an extended outage before the battery is depleted.
What a beeping power supply unit means
If your ONT power supply unit starts beeping, it is trying to tell you something important. A beeping BBU or BSU indicates one of two conditions: a low or exhausted battery, or a loss of commercial power. The beeping is an audible alarm designed to alert you that the backup battery is being used or has failed. If you have a standard BBU and want to silence the alarm, you can press and hold the "Alarm silence" button for 10 seconds. This will stop the beeping temporarily, but remember, the underlying issue (low battery or power loss) still needs to be addressed. If the beeping is due to a power outage, the alarm will continue until the battery is depleted or the power is restored.
Replacing the batteries in your unit
Eventually, all backup batteries will need to be replaced. When that time comes, it is essential to use the correct type of battery for your specific unit. For a standard BBU, you will need a 12-volt 7.2Ah sealed lead acid battery. If you have a BSU, it requires 12-volt 8Ah sealed lead acid batteries. For the PowerReserve unit, you must use D-cell alkaline batteries; rechargeable or lithium batteries are not compatible and should not be used. Proper disposal of old batteries is also important. You should never throw them in the regular trash. Resources like Call2Recycle can help you find a drop-off location near you to ensure the old batteries are disposed of in an environmentally safe manner.
Installation and placement basics
The installation of the ONT power supply unit is not a DIY project. It requires professional installation by a Verizon technician, who will ensure the unit is set up correctly. During installation, the technician will need to place the unit near a standard electrical outlet. It is important that the outlet is in good working condition and that you avoid using extension cords or power strips, as these can interfere with the unit's performance. Additionally, the technician will select a location that is well-ventilated to prevent overheating. The PSU and the ONT itself generate heat during normal operation, so good airflow around the unit is necessary to ensure reliable performance and to prevent the unit from getting excessively hot to the touch.
