System design
Electrical Planning for Church AV
Quick answer
A 20 amp circuit carries only 16 amps, or 1,920 watts at 120 volts, because the code treats anything running three hours or more as a continuous load and limits it to 80 percent of the breaker. A Sunday service with setup and rehearsal is a continuous load.
Electrical planning is the part of a church AV project that volunteers cannot do and that nobody wants to pay for, and it is where the failures are most expensive. Undersized circuits trip during services. Shared circuits put the audio system on the same wiring as the HVAC and the kitchen, which produces hum and voltage sag nobody can trace. And work done without a licensed electrician creates liability that outlives everyone involved in the decision.
This page is planning guidance so that your conversation with an electrician is productive and so the budget is right the first time. It is not instructions for doing the work. Everything that touches building wiring belongs to a licensed electrician working to your local code.
On this page
The continuous load rule, which governs everything
The National Electrical Code treats a load running three hours or more as continuous, and limits a continuous load to 80 percent of the circuit breaker rating. A church service with setup, rehearsal and the service itself comfortably exceeds three hours, so church AV is a continuous load and the 80 percent limit applies.
The consequences are arithmetic. A 15 amp circuit carries 12 amps, which at 120 volts is 1,440 watts. A 20 amp circuit carries 16 amps, which is 1,920 watts. A 30 amp circuit carries 24 amps, which is 2,880 watts. Those are the numbers to plan against, not the breaker labels, and a design that loads a 20 amp circuit to 2,300 watts because "the breaker is 20 amps" is both non-compliant and going to trip.
Plan to the derated figure and then leave headroom on top of it. A rack loaded to 1,900 watts on a 20 amp circuit is technically at the limit and practically has no room for the next device, the vacuum cleaner somebody plugs in, or the inrush when everything powers on at once. Size your circuits with the power draw calculator and aim to land well inside the limit.
What church AV equipment actually draws
The key insight is that amplifiers do not draw their rated output. Program draw is roughly a fifth of rated output for class D and a third for class AB.
A complete church audio rack typically draws around 1,000 to 1,300 watts on program material, which fits within the 1,920 watt continuous limit of a single 20 amp circuit.
| Device | Rated | Typical continuous draw | Notes |
|---|---|---|---|
| Class D amplifier, 1,000 watts | 1,000 W | About 200 W | Roughly one fifth of rated output on music |
| Class AB amplifier, 1,000 watts | 1,000 W | About 330 W | Roughly one third of rated output on music |
| Digital mixing console | Varies | 100 to 200 W | Steady draw, largely independent of level |
| Wireless receiver | Varies | About 15 W each | Four receivers is about 60 watts |
| Loudspeaker processor | Varies | About 30 W | Negligible, but it adds up across a rack |
| Powered loudspeaker, 2,000 watt peak | 2,000 W peak | About 400 W | Class D, and peak rating is not continuous output |
| Projector, installation class | Varies | 300 to 500 W | Often the largest single AV load in the building |
| PTZ camera over Ethernet | Varies | About 15 W each | Drawn from the network switch, not a wall outlet |
Figures are planning estimates based on the standard program draw ratios for amplifier classes and typical device specifications. Confirm against the nameplate rating of the specific equipment you buy, and give the totals to your electrician rather than treating them as a design.
How many circuits does a church AV system need?
Most church audio systems fit on one dedicated 20 amp circuit, which surprises people who expect a rack of amplifiers to need far more. Total the continuous draw using the ratios above, divide by 1,920 watts, and round up. A rack with two 1,000 watt class D amplifiers, a console, four wireless receivers and a processor comes to roughly 800 watts, which is comfortably inside one circuit.
Where multiple circuits become necessary is when video joins in. An installation projector at 300 to 500 watts, a video rack, computers and monitors add up quickly, and the sensible arrangement is a separate circuit for video anyway. Powered loudspeakers on stands each need an outlet near them, which is a distribution problem as much as a capacity one.
The most important requirement is not capacity at all, it is that the AV circuits are dedicated. An audio system sharing a circuit with fluorescent lighting, an HVAC unit, a kitchen appliance or a dimmer pack will pick up noise and voltage sag from those loads, and no amount of equipment quality fixes it. Ask for dedicated circuits for AV, fed from the same panel, and treat that as a requirement rather than a preference.
Grounding, hum, and the fault nobody can find
The classic church audio fault is a hum that rises with the fader, appears when the video system is connected, or arrives when a guitar amplifier is plugged in. Almost always it is a ground loop: two pieces of equipment connected by an audio cable are also connected to building ground at two different points, and the small voltage difference between those points drives current through the audio cable shield.
The correct fixes are, in order: feed all AV equipment from the same electrical panel so ground references match, break the loop at the signal level with a transformer isolated direct box such as the Radial ProDI at $134.99, or use an isolation transformer on the offending path. The incorrect fix, which is common and dangerous, is lifting the safety ground on a power cord with an adapter. That removes the protective earth that keeps a faulty device from putting mains voltage on a microphone somebody is holding. Never do it.
Isolated ground receptacles are sometimes specified for AV and are genuinely useful in some buildings, but they are an electrician design decision rather than something to demand by default. What to ask for is dedicated circuits from a common panel, properly bonded, with the AV loads separated from motors, dimmers and heating.
Planning the electrical work, step by step
- Total the continuous draw of everything AV. Use one fifth of rated output for class D amplifiers, one third for class AB, and nameplate figures for everything else. Include the projector, any powered loudspeakers, the video rack and the streaming computer. This total is the single most useful thing you can hand an electrician.
- Divide by the derated circuit limit, not the breaker rating. Use 1,920 watts for a 20 amp circuit and 1,440 for a 15 amp circuit, because AV is a continuous load limited to 80 percent of the breaker. Round up, then add a circuit of headroom if the budget allows, because the next purchase always needs an outlet.
- Ask for dedicated AV circuits from a common panel. Dedicated means nothing else is on them, and a common panel means all AV equipment shares a ground reference, which prevents most hum problems before they exist. Separate the AV circuits from lighting dimmers, HVAC and kitchen loads specifically.
- Locate the outlets where the equipment actually is. Rack location, each powered loudspeaker position, the projector mount, each camera position, the mix position and the platform. Walk the building and mark them, because an outlet twenty feet from where it is needed produces a permanent extension lead across a walkway.
- Have a licensed electrician design and install it. Circuit design, panel work, conduit, new outlets and anything in the building fabric must be done by a licensed electrician to local code, and inspected where your jurisdiction requires it. Hand over your load totals and outlet locations and let them design it.
- Protect the rack with a conditioner and a sequencer. A power conditioner provides surge protection and rack lights. A sequencer powers equipment up in order and shuts the amplifiers down first, which prevents the thump through the loudspeakers and protects the drivers when a volunteer flips one switch.
- Verify under real conditions before you sign off. Run the full system at service level with the HVAC running and the lighting at service settings, and check for hum, dimming or breakers warming. Faults that appear only when the air handling starts or the stage lights come up are exactly the ones that will otherwise be discovered during a service.
Lighting dimmers and the noise they inject
Worth its own mention because it catches so many churches. Older phase control dimmers chop the mains waveform to dim a lamp, and that chopping radiates electrical noise into anything nearby, including audio cable running alongside the dimmer feed. The result is a buzz that varies with the dimmer setting, which is diagnostic: if the noise changes when the house lights are dimmed, the lighting is the source.
The fixes are physical separation of audio and lighting cable runs, feeding audio and lighting from different circuits, and where possible replacing phase control dimming with modern drivers. Crossing power and audio cable at right angles rather than running them parallel reduces coupling substantially, and that costs nothing at installation time and is nearly impossible to change afterwards. Keep audio runs in their own conduit or on their own side of the building, and plan it before anyone pulls cable.
Sources
- National Electrical Code continuous load rule limiting a circuit to 80 percent of the breaker rating
- Amplifier program draw at approximately one fifth of rated output for class D and one third for class AB
- Standard audio system grounding practice on common panel feeds and transformer isolation
- Radial Engineering published specifications for transformer isolated direct boxes
Frequently asked questions
How many watts can a 20 amp circuit carry for church AV?
Sixteen amps, or 1,920 watts at 120 volts. The code treats anything running three hours or more as a continuous load and limits it to 80 percent of the breaker rating, and a service with setup and rehearsal exceeds three hours. Plan to 1,920 watts rather than 2,400, and leave headroom inside that for future equipment.
Does a church sound system need its own circuit?
Yes, dedicated circuits are strongly recommended and usually cheap to provide during any electrical work. Sharing a circuit with HVAC, fluorescent lighting, dimmers or kitchen equipment introduces noise and voltage sag that no equipment upgrade will fix afterwards. Ask for dedicated AV circuits fed from a common panel so ground references match.
Why does our sound system hum when the video is connected?
Almost certainly a ground loop, where audio and video equipment reach building ground at different points and the voltage difference drives current through the audio cable shield. Fix it by feeding all AV from the same panel and by using a transformer isolated direct box or isolation transformer on the offending path. Never lift a safety ground to solve it.
Is it safe to lift the ground on a power cord to stop hum?
No, and this is one of the few genuinely dangerous shortcuts in church AV. The safety ground is what prevents a faulty device from putting mains voltage on equipment somebody is touching, including a microphone held by a person standing on a concrete floor. Break the loop at the signal level with an isolation transformer instead.
How much power does a rack of amplifiers really use?
Much less than the rated output suggests, because music is mostly quiet with brief peaks. Class D amplifiers draw roughly a fifth of rated output and class AB about a third, so a rack containing 4,000 watts of class D amplification draws around 800 watts on program material and fits comfortably within a single 20 amp circuit.
Can our volunteers add outlets for the AV system?
No. Anything that touches building wiring, including adding outlets, running new circuits and panel work, must be done by a licensed electrician working to local code and inspected where required. Volunteers can plan loads, mark locations and pull low voltage cable where code allows, but the electrical work itself is not volunteer territory.
Researched, not professional advice. This page is compiled from published manufacturer specifications, operator manuals, FCC rules, published standards and owner-review consensus, not hands-on testing. Sound system design, rigging loudspeakers overhead, and any electrical work are jobs for a qualified professional: have flown loudspeakers and their attachment points signed off by a structural engineer or a certified rigger, and have all wiring done by a licensed electrician to your local code. Wireless microphone rules change, so confirm the current FCC position before buying. As an Amazon Associate we earn from qualifying purchases.