Hot Rod Forum banner

wiring compressor

9K views 78 replies 19 participants last post by  grouch 
#1 ·
I just purchased a compressor with a 15amp 240 v motor.
I have 2 separate 110v circuits close to the compressor.
Can I use the hot leg from each of these circuits to supply 220v?
Logically it sounds correct, but I am not an electrician.
Thanks,
Bob
 
#28 ·
more electrical

My son is and electrical contractor- and master electrician. Now I ask him what are the new rules in the 'NEC. As stated in previous posts wire size depends on the wire distance from the breaker to the load and overload calculation... An electric dryer has 110 volt control-timer and the rotation motor is 110 volts which doesn't have and much starting power requiremenrts
 
#29 ·
The maximum wire size is governed by one of three things. 1) If the load is a motor load like a compressor which has a high current start out of proportion to the running current, 2) the distance between the circuit breaker and the load causes voltage drop, or 3) if you have a certain plug configuration as is your case. A 10 gauge wire will not support a 50 amp circuit.

You need to install the correct sized wire and circuit breaker.
 
#32 ·
roger1 said:
You say you installed a 50Amp outlet.
That may be the wrong one for your dryer.

I have never seen an electric residential dryer that wasn't 30 Amps.

50 Amp will require #8 and 30 Amp requires #10.
The outlet is actually for a welder rated at 20A. What I did was run a line using 10gage from the new garage outlet to a junction box near the dryer. In the junction box I spliced in a dryer cord having the correct pin type for an existing dryer outlet. When I want to use the welder I unplug the dryer and plug in my new garage line. The dryer line is 10gage with a 30A breaker near the outlet. So in effect what I have is an extension running from the dryer outlet. I ran it this way because the main panel is full.
 
#33 ·
I did it too

In the early 50's my step dad bought a welder for the ranch.. the only 220 outlet was for the elect stove so we just made a big extersion cord and brought the welder up to the house. a 200ft walk to old blacksmith shop if you needed another tool. In my new shop my son is an electrical contractor and he installed a 200 amp 42 circuit panel and a 100 amp sub panel... every major tool has it's own dedicaataed circuit. and when I was building it I said what's this outlet box for and he said someday you will buy a plasma cutter and it goes right here. I still have about a dozen spaces in the sub panel...the lights don't go dim when the air comp kicks in. when someone is weldiing or using one of the big saws.
 
#34 ·
you guys are killin me! scott, as long as you cannot possibly run both the dryer and your whatever at the same time you will be fine they way you have it.

aluminum wire is still used in every new house. for range wire, for your service entrance conductors, both from the transformer and down your service mast. just not for anything else however.

#8 gauge wire can only handle 50A if it is copper and you are using it at 100% of it's rated capacity, not 125% as in if it's for a motor. it's probably easier to find #6 copper romex than #8 anyway.

the size of your circuit is determined by one and only one item: the overcurrent device, ie the breaker. whether or not you will burn your house down is up to you and the size of wire you want to use. try table 310.16 in the NEC and if you have a load that is a motor or on for over 3 hours at a time mulitply your load by 125% (1.25) to size your circuit.

if you put a new dryer (with a 4 prong plug having a nuetral) to an older 3 prong outlet, you will be using a 3 prong cord/plug. the nuetral and ground will have provisions to be tied together inside the dryer at the cord connection. and i have recently found out that yes indeed, both the light, computer AND the motor turning the drum, run on 120V. only the heating elements run on 240.

all circuit conductors are req'd to be run in the same raceway or cable. EMT is considered a grounding conductor with approved couplings/connectors so no need for a grounding conductor (green wire). except from the box to the cord/recep.
what else did you guys post here:
the two hots do have to be under the same breaker. however two 120V (single pole) breakers can be tied together with an approved handle tie if you put them next to each other. if you were hard up for temporary purposes only you could take the hot from two 120v circuits and make 240 happen, but if and only if the hots came from different phases in the panel.
you guys scare me with this one. hire somebody that knows what they are doing.
i used to frequent a dyi forum for electrical work, but i realized i was probably doing more harm that good. i STRONGLY recommend against you laymen doing ANY electrical work at all. some people think that if they can use a screwdriver and have a dyi book that they are electricians. y'aarrrr!!! :nono:
 
#35 · (Edited)
aluminum wire

Aluminum wire requires all equipment and connectors be approved for aluminium . Al is soft and the old connectors would allow the wire to losen then spark ...then mabe a fire. Electricians now coat aluminum connections with a special anti- oxidant compound... Leave it to a Pro ... Keep my son and step son working ! ! !
 
#36 ·
bullheimer said:
i used to frequent a dyi forum for electrical work, but i realized i was probably doing more harm that good. i STRONGLY recommend against you laymen doing ANY electrical work at all. some people think that if they can use a screwdriver and have a dyi book that they are electricians. y'aarrrr!!! :nono:


I could not agree more! I have in the past said that these threads about wiring compressors (or most anything) can be just plain dangerous and should be left to a pro or at least checked out by a pro before turning on the power. I am not a licensed electrician but I did learn the basics of wiring by spending many years installing equipment. I have seen a heck of a lot of DIY installations with problems ranging from just would not run to damage to the equipment and all of these fellows had asked advice from someone else. The biggest problem I see with "long distance" advice on wiring is the safety concerns, several times I have seen compressors wired by a DIYer that was improperly grounded and when the hazard was pointed out every single time the response was "but it runs just fine" :rolleyes: I think that probably anyone here could do a proper job of wiring AFTER a bit of instruction but guys electricity is nothing to teach yourself because it is VERY unforgiving to mistakes and has no conscience at all!
 
#37 ·
bullheimer said:
you guys are killin me! scott, as long as you cannot possibly run both the dryer and your whatever at the same time you will be fine they way you have it.

bullheimer...........lol............no doubt...........in my case, I have been doing my own electrical work for about 30 years and I have had some of my work inspected by the town (both rough and finished). I have done mostly 120v including wiring in new circuits. I put a dedicated 240v line for baseboard heat in my own garage. The 240v extension I just did is in my fiances house. One thing I am very careful about is workmanship and I know the ramifications of knicking the copper wire when stripping the end for a connection. I am fully aware that the governing factor for wire size is primarily the breaker rating although the length of the run needs to be considered too. And, you are correct............I can only run either the dryer or, something else on the extension but not both at the same time.

Thanks for the tips :thumbup:
 
#39 ·
bluesman2333 said:
I personally would not wire a dryer and an air compressor recept on the same circuit, even if the intention is to not run them at the same time. . They are dedicated loads and as such, need separate circuit breakers and wiring to the recepts.
I agree wholeheartedly with this.
Do it right!

If somehow you caused a fire by doing it wrong and an investigation turned up what you did, I wouldn't be surprised if the insurance company would try to get out of paying your claim. Plus, why put safety to risk? Someone could get hurt.
 
#41 ·
bluesman2333 said:
I personally would not wire a dryer and an air compressor recept on the same circuit, even if the intention is to not run them at the same time. . They are dedicated loads and as such, need separate circuit breakers and wiring to the recepts.
Maybe I read post #32 wrong. I read it that one is unplugged and the other is plugged in as needed.
 
#43 ·
bullheimer said:
aluminum wire is still used in every new house. :
I think you might want to check electric codes. I think they are National, although in Illinois aluminum wiring has been banned for at least a decade and probably longer. It may not be a National standard, but I know in many states you won't find ANY new houses built with that wiring. I doubt that insurance can even be gotten for a home with that wire, here it ALL had to be replaced because of fire potential,as the connection would loosen from heat expansion ,the heat created form the loose connections caused too many fires and is no longer accepted.I'll post what year that was when I locate my electrical code book.
 
#44 ·
woodz428 said:
bullheimer said:
aluminum wire is still used in every new house. :
I think you might want to check electric codes. I think they are National, although in Illinois aluminum wiring has been banned for at least a decade and probably longer. It may not be a National standard, but I know in many states you won't find ANY new houses built with that wiring.
Some important context is lost in the above partial quote of bullheimer's comment, IMO.
bullheimer said:
aluminum wire is still used in every new house. for range wire, for your service entrance conductors, both from the transformer and down your service mast. just not for anything else however.
[Bold added].

Every new house in my area has aluminum service drop conductors. The range wiring seems to depend upon the electrician. None have aluminum conductors anywhere else in the house. This matches bullheimer's statements very closely.
 
#45 ·
On the projects I do it usually specs that aluminum wire shall not be used in sizes smaller than #8 awg. Even then they need to be in a compression adapter before inserting it into the termination. The NEC does allow both feeders and branch circuits to be in aluminum but I personally wouldn't do it.

Years ago, aluminum wire was used because of the cost benefit, but it was discovered that people were not stripping it properly nor were they putting it under cl/au terminals. This caused loose connections and then fires.

Although insurance can be problematic on houses wired in aluminum, you can get insurance on them. If cared for properly, as in retorquing connections and using noalox, you can have a safe installation on branch circuits.

Example of compression adapter: http://www.wescodirect.com/direct/Products/ProductListDetail.aspx?pik=141622&productId=141622
 
#47 ·
1ownerT said:
Maybe I read post #32 wrong. I read it that one is unplugged and the other is plugged in as needed.
That is correct and I emphasize again thatonly one of two plugs can be in the existing dryer receptical.[/B]...........either the dryer lead or.......the lead for the garage line extension. Think of this way.......it would be similar to having two dryers side by side.........I could only have one plugged in at a time. The receptical for the dryer is correct for the dryer and has a different pin configuration than the 240v receptical in the garage.
 
#48 ·
scotzz said:
That is correct and I emphasize again thatonly one of two plugs can be in the existing dryer receptical.[/B]...........either the dryer lead or.......the lead for the garage line extension. Think of this way.......it would be similar to having two dryers side by side.........I could only have one plugged in at a time. The receptical for the dryer is correct for the dryer and has a different pin configuration than the 240v receptical in the garage.


The problem is that you will be using a compressor that is a 220V 20 Amp on a 30 Amp breaker.
Not good to do.
 
#50 ·
I reread the extra context that you felt was missing..now in your and Bullheimers area that may be the case...however the comment wasn't about new houses in his or your area it was EVERY new house. I just happen to know that locally that is NOT true. It is unacceptable locally, that would eliminate EVERY new house. It is not allowed in any service, I don't care whether it is entrance or range service it is NOT allowed. I also made sure that I stated that I wasn't sure whether it was a National or local. So it apparently isn't National, but I am more than aware of local ordinances, several of my good friends are master electricians as well as my son-in-law. That's the main reason I suggest checking your local building codes. Since this is really an International forum some things aren't universally applied. I know that Rods/Custom builds are pretty easy to register here in Illinois, I do it regularly, but I wouldn't even want to try it in Ca., or some other states....Ca. is the most notorious that's why I mentioned it specificly. I have no personal opinion on the Al. wiring,I do know that inspectors can be tough. So it's always better to be informed of local standards. NOW, as a caveat, some stuff done by the homeowner on their own, doesn't require certain things...like a licensed electrician...but, I think stuff like wiring standards still have to be met.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top