Hi, I just moved to a new house and the dryer hookup box has two cables coming into it. (i.e. there are 2black, 2white(neutural), and 2 ground wires) . Both of the cables have 30amp breaker each. Can anyone give me words of advice how to make the connections for a 4 prong hookup. Thank you in advance
normally theres only one cable feeding box.
turn breaker off, check entire home for anything not powering on
According to :
This was wired incorrectly from the get-go. It looks as if the person who used it used two separate 120V (with ground) circuits to make one 240V one, and promptly didn't bother using the ground.
Code violation amongst other things (separate breakers, multiple cables for the same circuit). Further, I have my doubts whether the cable is in fact properly rated for the ampacity you're pulling from it - if they were stupid enough to wire it the way you have it now, I wouldn't put it past them to use undersized wire _too_.
Without a very close look at the circuit (eg: wire size, where the breakers are, tiebars etc), I recommend you call in an electrician to figure this mess out. I'm not going to tell you how to make the existing double-cable mess "work". Because it's dangerous, perhaps _very_ dangerous, and they probably screwed it up in other ways that you haven't realized yet.
Correctly done for a modern code 4 prong hookup, this circuit _should_ have a single 10gauge 4 conductor cable (black, red, white and bare), connected to a dual breaker (two breakers connected together with a tiebar). Which means pulling a new cable.
_If_ the existing cable size was right, and you replaced that breaker with a dual, you could abandon one of the cables and make it a 3 wire connection. But I don't recommend that, despite the fact that it's still code legal (renovation grandfathering) in the US.
It ain't legal, period, in Canada. Hasn't been since at least WWII. If you try to install a dryer onto an existing circuit, it MUST be converted to 4-wire. No exceptions whatsoever.
someone may have tapped the 240 for another outlet like perhaps a lttle used welder or other infrequent load. i must admit doing that.... being out of breaker slots.... the 2 loads are never on at the same time...
theres also a chance someone doubled up the number of cables to save buying heavier wire.
really need to know more....
likely not safe but if it feeds say a now unused 240 outlet for welding and the conductors are heavy enough it wouldnt be a big thing
Are the breakers 120v or 240v? (are the breakers single or double?)
In general, older houses will often have 3 wires for 240v; 2 hots and a ground. You cannot use a 4 prong hookup, but must follow the dryer's instructions for a 3 prong hookup. The "danger" is that if the ground connection is broken, the frame is potentially hot, which is not a great idea around water. But there are millions like it (including mine) and I have never heard of anyone getting hurt.
However, I can't imagine why you have two cables going to your box. Possibly someone "made" /3 cable by using the two blacks as hots, and a white as a neutral. If that is true, they will be going to two 120v breakers or 1 240v breaker.
If that is the case, and they go to a 240v breaker, and they pass through all the same holes, then there is nothing particularly unsafe about it. It is a code violation and will leave the next guy as confused as you are now, but it is not inherently unsafe; if they go to a 240v breaker and go through all the same holes.
If it is actually a "new" house, you should complain to the builder. If it is "new to you" house, wasn't there already an outlet attached?
Thank you for your replies!
The breakers are not connected to each other. They are 30Amp each.
Both of the cables are 10/2
The cables are coming from different places, and I am not sure but I think on of them is coming from the dishwasher. I am truly confused!
The breakers are 120v, right? In principle you could replace one of the breakers with a 240v breaker and wire the dryer up with a 3 prong outlet, but it would be a code violation. Existing installations are grandfathered, but you cannot make a new one.
Either find a 120v dryer, install a 12/3 cable, or violate code.
It would unsafe to use cables that do not run together; do not consider doing that.
The breakers are required to be ganged (tied together) so that they are both ON or OFF together. This means that they must be adjacent to each other.
You are also required to have a neutral (white wire) and a ground wire (bare or green). Older installations allowed for the neutral to also serve as the ground, hence, older dryers had 3 hole receptacle outlets. New work dryer outlets are 4 holes.
In the US, you buy your dryer with either a 3-wire, or 4 wire dryer cord, which must be installed properly. (Cords are sold separately)
10 gauge is the correct wire gauge for a 30A dryer circuit. Make sure that there is also a ground wire, and preferably a neutral (white) wire, in additon.Beachcomber
According to snipped-for-privacy@aol.com :
Then both wires would be connected to both breakers.
Big no-no. You're not allowed to double up conductors ot increase ampacity. Nor are you allowed to do this with conductors smaller than about #2.
Paralleling conductors is almost never useful in a residential setting, and is only permissible in order to reduce voltage drop. Each conductor _must_ be sized large enough to carry the full amps by itself.
I made up a 150' extension cord to carry a max of 14a. I doubled up #14 cables to reduce VD because that is what the store going out of business had at 80% off. Now code doesn't apply to an extension cords, but would the concept pass code for wiring since the single conductors are capable of carrying the load alone?
No, it just says you can't parallel small conductors
According to Toller :
Yes, except for the fact that #14 is too small to be paralleled under NEC. I think the minimum size is #2.
This sort of thing is usually reserved for industrial equipment.
310.4 Conductors in Parallel. Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, ...
If you are located in the US and the circuit has been in place for a decade or more then the three wire cable is legal. You would follow the manufacturers directions for converting the dryer to a three wire connection. You still have to figure out which cable is the feed from the panel and were the other cable goes.
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