Running Electrical Wires Through Furniture?

[John Stevens]

This question is inspired by the beautiful desk Jason Tuinstra built. A couple months ago I sketched some similar designs for a table that would house a stereo receiver and CD player in "drawer-like" compartments, with the power wire and speaker wires run through a hollow, tapered leg. I figured a power cord could be safely run through a wooden column, because it's done in wooden lamps. However, I don't know beans about electricity or fire safety, and I don't want my furniture to create a fire hazard.

What design standards should be followed when routing electrical wires through wooden columns (such as a lamp or a table leg) in order to avoid creating a risk of an electrical fire?

Thanks in advance for your help.

[Keith Christopher]

A couple of things to consider. You have to make sure it's a UL listed wire and it can handle the current draw from what is plugged into it. I would also recommend installing some metal tubing in the leg just to be safe.

[Andrew Ault]

Avoid bending the wire sharply and ensure that it does not pass over sharp edges.

[Don Frambach]

I would work out some sort of a "strain relief" as the cord exits the furniture so that it can't bend sharply.

[Don Baer]

I would work out some sort of a "strain relief" as the cord exits the furniture so that it can't bend sharply.

You took the words right out of my mouth. Actually it is required by code.
They will insure that if someone trip on the cord t wont stress the wire.
This is an example of a strain relief. Not exactly what I was looking for but you'll get the idea.

http://www.abbatron.com/photos/hdw_css_wsre_photo.gif

[Guy Baxter]

John -
I’m no expert, but I think it would be prudent to hard-wire a current limited power strip inside your desk. Most power strips have a built-in circuit breaker of 15A or less. This would prevent a future owner of your desk from using the outlet as an extension cord to his bandsaw, cabinet saw, and arc welder. Or maybe his son takes it to college and uses the outlet to power his mega-watt guitar amp in the dorm room. Either scenario could lead to an interesting heat exchange between the insulated wire and the wooden table leg. Most lamps have just one bulb (<300W) which limits the current to roughly 3A max.
Just my 2 cents worth.
GB

[Joe Pelonio]

John,

I agree with Guy on the power strip, and further I would say to have a hole in the back large enough for the plug to fit thru. Otherwise you will have to remove the molded plug and put on a new one to get it thru the leg, thus absolving the power strip manufacturer from liability and putting it instead onto you, should something happen. There should be grommets available as you see those large holes with plastic grommets in the back wall of computer desks all the time. I have learned that when you manufacture something that's electrical even with UL listed parts the item itself is not UL approved without them testing it. For that reason when I made a bottom-lit stained glass top table I decided to keep it rather than sell it and assume liability. If you are planning to make more of these for people that you don't know, your best bet is to have a hole ready but have them do their own power strip. You know how people love lawsuits these days.

[Jamie Buxton]

John, I've run cables through hollowed legs. It works like a champ, and doesn't make your beautiful furniture have this ugly tail of cables trailing down to the floor.

If the legs are long, boring a long hole can be an issue. I've ripped the stock in half, put dados on the inside faces, glued the stock back together, and then shaped the leg. In many kinds of wood, you really can't tell the joint is there.

I don't have much worry about running all the cables through a common bore. After all, if the cables were just in the usual snarl in the back of a cabinet, they'd be in the same close quarters as if they're running through a leg.

I'm also comfortable about threading a power cable through a hole only as big as the cable, and then putting a plug on the end of it. Even for wood guys, installing a plug on the end of a piece of zipcord shouldn't be too challeging. You might also consider installing cable to feed an FM antenna to your stereo.

A strain relief might be nice, but I can't guess what "code" requires it. When folks say "code", they generally mean building code. However, building codes don't regulate furniture, so I'm stumped. Actually, if the leg is long, the friction in the bored hole may act as a strain relief.

[Jason Tuinstra]

John, I wish I could say that I put a lot of time and attention into this detail, but I didn't - simply because I didn't think that there were any issues. I used a cord from an unused extension cord with four outlets. It was black, just what I wanted, and I could keep the molded end. I then used a powerstrip with the same gague wire, and soldered off the old wire and soldered on the new wire. Closed it up, and I was good to go. I really don't know how this could possibly be dangerous. I'm no electrical expert, though I am the son of an electrician, but I think it's fairly logical to say that this is safe and in no way going to start a fire or anything else. I shared your concern at first, but after I thought about it, I figured my concern was unfounded as long as I made sure that the connections were soldered and the cord was sound.

Now get to work on this project and show us some pictures!

[Randy Meijer]

Here is the problem guys. When electricity moves through a wire, heat is generated. Generate too much heat and the wire burns up. Amperage ratings of electrical conductors is essentially controlled by how hot they can get with out creating a problem(causing a fire). If you have an extension cord laying out on the lawn supplying your weedeater, the heat in the cord is passed through the insulation and off onto the air.....no problem....the cord never gets too hot. On the other hand, if that cord is running with several others through a hole bored in a 4x4 wood post, there is nowhere for the heat to go so it builds up in side the wood post.....to much heat and the insulation will fail and a fire may result. This is why the capacity of electrical conductors is down rated when carried in conduit.... heat build up.

The chances of catching your furniture on fire because the cable through your hollow wooden leg is suppying juice for a table lamp and a computer is pretty remote; but suppose someone decides to plug in one of those 1800 watt space heaters on a cold day to keep their feet warm and maybe you used a slightly undersized conductor in your piece of furniture?? It could be a problem. I'd give some very careful consideration to running electrical conductors through areas totally enclosed by wood.

[John Hart]

I agree with Keiths suggestion that a metal conduit integrated into the leg is a pretty safe idea....and that Randy's concern that the circuit may get overloaded some day in a way that you had not originally planned (space heater) should be of paramount concern...but let me throw another wrench in there.... Running power and speaker wire in the same tight space will cause "crosstalk" between the cables and may cause a 60HZ hum in your speakers. Just a thought.

[Dave Richards]

There are some excellent points regarding safety being brought up here. I would like to add one more thing. Don't count on the circuit breaker in the power strip to protect anythiing. I've seen a number of them fail to operate properly.

I think it would be wise to add a separate breaker or an inline fuse to the supply right before the power strip. Adding a GFCI woulld be a good idea as well but that's not for fire concerns.

[Andy Hoyt]

The cable enters and exits the wood leg through one continuous tunnel. Would it be safe to say that any heat build-up would exit the tunnel on the uphill side just like the cable does. Oversized tunnel would obviously help.

[Jamie Buxton]

If you want to build your stereo cabinet to support an 1800 watt space heater, go ahead. Me, I'd build it to support a stereo. Stereos, despite the vastly inflated power numbers in the advertising, typically consume less than 100 watts. The temperature rise of the power cord is darn difficult to feel, and is not likely to be an issue inside a wooden leg.

I'm uncomfortable with the suggestion of putting the power cable in a metal conduit. If there are burrs on the ends of the conduit, they might cut through the cable's insulation. In contrast, a wooden conduit poses no hazard to the insulation. That is, if you're concerned about protecting the cable, the wood is better than the metal.

Crosstalk between cables is a rare, though possible, issue on the input side of amplifiers. The very small crosstalk signal gets amplified by the amp to the point that it can be perceived. Crosstalk into a cable on the output side of an amp -- that is, the speaker cables -- isn't a problem.

[Byron Trantham]

As an "after the fact" wiring solution, you might look at Rockler. They have a huge selection of wire management devices.

[Randy Meijer]

...Running power and speaker wire in the same tight space will cause "crosstalk" between the cables and may cause a 60HZ hum in your speakers.

I would think that running shielded cables for the speakers and amplifier should take care of that problem???