# How many Amps in a Garage. AND how to maintain consistent lighting from an outlet (no flickering)

I have two questions that hopefully someone more experienced than me can answer.

Background: I am doing a claymation in a garage and need to set up a lighting system that requires (a.) lots of wattage and (b.) constant voltage so lighting stays extremely consistent [doesn't get dim or flicker despite other people using outlets].

The garage is connected to about 20 other garages in an apartment complex, so it is not a typical house hold garage.

Question 1: (A.) There is one outlet on the garage ceiling. How many amps would you assume is connected to this outlet (20? 50? 100?) It may be impossible to know but perhaps there is a standard amount of amps that apartment garages need to have. I figure it would have to be more than 20 because if 4 garages are opened at the same time, the breaker would trip.

(B.) How many watts could I draw from this one outlet?

(C.) How can I find out how many amps are in the garage? Where would the circuit breaker be to find it?

Question 2: The lights I have set up go dim periodically (perhaps when others open their garage). How do I maintain constant light? (Voltage stabilizer, online ups?) I'm not sure what those are, but what is my best option to make sure those lights are always a consistent brightness?

• A good UPS is probably your best option for consistent voltage, unless you can run low-voltage lights from a regulated supply (EG 12v DC using a car battery + float charger).
– John U
Jul 4, 2013 at 11:20
• Assuming the electrical wiring was performed by professionals and checked by an engineer, the best way to know the maximum current you can draw is to check the circuit breaker from where comes the power for your outlet. If there are more than one, then you can distribute the load between the outlets that are connected to each one. But anyway your best solution is still that one given by @JIm Dearden
– fceconel
Jul 4, 2013 at 17:31
• Since the garage outlet is probably a common-area outlet, you might want to check with with your landlord to see if you're even allowed to plug into it for personal use before you invest much money in this project. Some apartments will not let you use common-area power at all, or only for incidental personal use. (i.e. plugging in a vacuum cleaner to clean your car is ok, setting up a 1500 watts of lighting for a video studio is probably not). They may not let you use the garage opener outlets for any reason since tripping a breaker may lock other residents out of their garages. Dec 12, 2013 at 21:06

More current! What are you using for lighting - arc lamps?

As an animator and photographer myself I'd want to run the lighting as cool as possible. There are some great LED lights out there (or you could build your own). For small stages I've even used LED torches for highlights.

LEDs also have the advantage of running from a regulated DC supply (which gets around your droop problem). You can control intensity (PWM) and color temperature control (LEDs come in all sorts of colors).

Modern digital cameras (video and still) operate quite happily in lower light conditions giving well saturated color.

Just on a Health and Safety point

(1) Drawing a higher current than the wiring was designed to take greatly increases the risk of fire. You really do not want to cause a fire. The fact that your lights dim means that the system is straining to cope with normal demand.

(2) Hot lights can also cause fires. Especially with various artist's materials being used (bits of paper, paint etc.)

• It's easy to exceed the maximum available current from an outlet using incandescent lamps. You can buy a dual lamp, dual filament 1400W worklamp for \$99 -- add in another 500W worklamp and you're over the limit. High power incandescents tend to be cheaper than the equivalent LED and Fluorescent alternatives. Dec 12, 2013 at 21:28

In my opinion, the best option for you is also the most efficient: Use LED based set lighting. The LED based lights use power regulators to generate the 3V needed for each individual LED "lamp," and those regulators (typically switching buck controllers) are usually very tolerant to fluctuations in power. LEDs also have excellent life spans, don't typically change color over time (or with voltage!) and won't heat up your space like Xenon/Halogen/whatever old-style lamps will. There won't even be any appreciable waiting time for warm-up like there is with old-school photo lamps.

And you'll save on electricity.

LED systems can easily light an entire scene with perhaps 200 Watts of power, so 2A of draw out of a single outlet.

## Can't create energy unfortunately...

The voltage drops because of Ohm's Law. In your case:

Voltage droop in power line = square-root of power used times the resistance in the power line

If you see the lights dim occasionally, at those moments, there is too much load on the line.

Your only solution, conceptually, is to add more energy to the system.

### UPS

A UPS stands for "Uninterruptible Power Supply". There are two basic types:

1. A true UPS in which power from the wall is converted and applied to a storage device, like a battery, and then the storage device is used to power anything connected to it's outlets.

2. An SPS ("Standby Power Supply") connects it's outlets to the power line directly and simply switches to a battery after it detects the power line is no longer providing sufficient power.

True UPS's work because the power always comes from their internal reserve with or without external power. SPS's detect-and-switch, which causes a bunch of problems in your scenario:

1. There is a distinct switching transient that will result in brightness change
2. It does not switch (by design) on power line transients
3. Output (AC) power is typically of poor quality, which will manifest in a different effective light intensity

Unfortunately, true UPS's are very expensive and, given your interest in maximum outlet power ratings, I suspect that you will need a massive UPS to keep up with your power needs.

Virtually every "UPS" you find in the consumer electronics space is actually an SPS.

### Generator

I would recommend that you just go completely off-grid and make your own power if you are so sensitive to light level. A 2.2kW capable generator runs around \$600 (US).

### Inverter

You might also consider using a DC-to-AC inverter to use a bank of car batteries for this purpose.

## Good luck!

Sounds like an interesting project!

# 1(A)

In the US most general lighting circuits are rated for 15 amperes, though general receptacle outlets are typically either 15 or 20 amperes.

# 1(B)

Calculating the wattage a circuit can safely supply is done using a simple formula.

`Voltage * Current * Safety Factor = Wattage`

80% is a common safety factor used to insure circuits are not constantly loaded to 100%

`120V * 15A * 80% = 1440W`
`120V * 20A * 80% = 1920W`

# 1(C)

There is almost no way to answer this through the internet. In a house you could likely follow the service conductors, and eventually locate the service panel. In an apartment building, the panel can be more difficult to find. In the US (or maybe only some states), the panel has to be accessible to the tenants. Because of this, the panel is commonly located either in each apartment or a common area.

# 2

An Uninterrupted Power Supply (UPS) might be able to supply a more steady flow, though you may still get a big of dimming or flicker depending on the unit.

Completely depends on the building, and the area. There wouldn't be a specific answer. That said, standard wiring will be for between 10 and 20 amps.

The best way to know is finding the electrical box that applies to your garage. If the circuit is only for your garage, then the fuse or breaker will tell you how many amps you can pull. If it covers more than one garage, then it will be atleast the maximum of that fuse, shared with whatever anyone else is using at the time. Wattage is a function of Voltage and Amperage, so again, it depends on what the circuit is built for.

As for the lights going dim, heavy current draw from garage motors will cause the voltage to sag down. Not much you can do without a generator or independent circuit.

It's difficult to say without a picture of the plug which could tell us a lot (what part of the world you are in, amperage, etc.) I will assume that you are in the US and guess that your outlet is 120V at 15A. It's possible you have a 20A circuit though given the garage setting. Again, we would need more information. Best thing to do would be to check the plug for its rating and examine the breaker it is connected to for its rating. If the assumption is correct (120V @ 15A) you could pull 1800W from this outlet. I am guessing that the apartment complex does not intend for you to use this outlet and it's solely there for the garage door opener (hence a single outlet above). You probably won't find the breaker box for this reason.

Your circuit is obviously tied to others garages and so how much current you can squeeze before tripping the breaker is not as trivial as what I outlined above. For example, Joe next door might be charging his brand new electric car in his garage. His car along with your lighting could be enough to trip the breaker alone... which will leave a few of your neighbors upset that they can't park their car in their garage. :)

Unfortunately I can't think of a way to maintain a consistent brightness on the cheap. Others may chime in here. Essentially what's happening is your neighbor fires up their garage door opener which causes excess current to flow on the branch resulting in a voltage drop. This voltage drop is visible to you as flicker.

• I'd think a LAMP outlet (light socket?) would be on a lot less than a 15A fuse, and that this amount of studio lighting would be better powered from a wall socket rather than a lighting circuit. Just taking a wild guess though as the question is unclear.
– John U
Jul 4, 2013 at 11:18
• @JohnU - he seems to be talking about a ceiling mounted receptacle that is used to plug in an electric garage door opener. His apartment building may not have any accessible wall outlets. In the USA, a typical lighting circuit would be 15A, while a wall or ceiling receptacle would be on a 15A or 20A circuit. Dec 12, 2013 at 21:37

There are some pretty nifty power conditioners out there that might actually do sufficient voltage regulation for your needs. Furman products spring to mind. The good ones are pricey. I'll refer you to their educational video page at http://www.furmansound.com/page.php?div=01&id=TECH