How to Wire an A/C Unit Wiring an A/C unit involves installing a double-pole, 240-volt circuit breaker in the main service panel, running a 240-volt cable to the A/C's location, installing a safety-disconnect switch there, and then running weatherproof flex from the switch to the A/C's terminal box. This isn't an especially difficult project but it will involve applying for an electrical wiring permit from your the building department, working with the NEC (National Electrical Code,) and using some basic applied math. The most difficult part of this project will be routing the cable from the service panel to the safety-disconnect switch. This may involve fishing the cable through finished walls and floors/ceilings. Locate the nameplate on the A/C unit and note the specifications for the "Continuous Duty Full Load Current" and/or the "Branch Circuit Selection Current." Calculate the minimum required Ampacity (Ampacity refers to the maximum current that a conductor of a given size can carry safely) for the branch circuit conductors by multiplying the "Continuous Duty FLC (Full Load Current)" or the "Branch Circuit SC (Selection Current,)" whichever is greater by 1.25, per NEC Article 440.32.

Compare the computed value with the values given in NEC Table 310.16, column one. If the computed value falls between two listed values, select the wire size with the next higher rating. Calculate the minimum rating for the safety disconnect switch by multiplying the "Continuous Duty FLC" or the "Branch Circuit SC," whichever is greater by 1.15 per NEC Article 440.12(A)(1.) If this minimum rating falls between two standard ratings, select the next higher rated switch. Calculate the minimum circuit breaker rating by multiplying the larger of the two current ratings by 1.25 per NEC Article 210.20(a). Compare this value with the values given in NEC Article 240.6. If the computed value falls between two standard ratings, select the higher rated circuit breaker. Apply for your wiring permit. Don't start the wiring until the permit arrives. Wiring the A/C Unit Mount the safety disconnect switch next to the A/C unit. Route the type UF cable between the service panel and the safety-disconnect switch.

Install a cable connector in one of the safety switch's bottom knockouts. Remove 12 inches of the cable's outer jacket and secure the cable in the connector by tightening the clamping screws. Route the red and black circuit conductors to the top of the switch, strip off ¾ inches of insulation, and attach them to the main switch lugs.top five ac units Attach the white circuit neutral conductor and the green/bare-grounding conductors to the switches neutral and grounding bars, respectively.switch on ac unit Install liquid tight connectors in the switch and the A/C terminal box and make up the flex.ac unit central air Secure the flex to the switch and attach the red and black conductors to the bottom lugs on the switch. Attach the neutral conductor and the system-grounding conductor as you did above in step 8.

Attach the flex to the terminal box and make up those connections by attaching the conductors to the appropriately marked terminals. Remove the cover to the service panel and install the double-pole breaker. Install a cable connector and the cable in the service panel. Connect the red and black circuit conductors to the circuit breaker terminals. Connect the neutral and ground conductors to the service panel's neutral and grounding bars. Only one wire per screw or your installation will fail inspection. Call the local government building department for inspection. EC&M Journal Sizing a circuit breaker. EC&M Journal Code Calculations Article 440 Air Conditioning and Refrigerating Equipment An air conditioning system uses the outside condensing unit to force liquid refrigerant through a metering valve, found in the inside unit's... Wiring an AC electric motor is not particularly difficult if the manufacturer's manual is available. But if the manual cannot be found,...

Air conditioner units come in many types such as a window mounted unit, a central air system or units that are called... How to Install a Split AC Unit; How to Wire an Outlet Split Switch; How to Size Wire for a Central Air Conditioner. An air conditioning unit typically has two separate labels. Air conditioning units, while fully protected on the outside by a plastic or metal casing, are a complex web of wires and... Check the wiring once again to make sure all the connections are ... The run capacitor on an air conditioning unit is... Wiring an electrical alternating current (AC) switch involves some planning and forethought, but is not a difficult procedure. Safety needs to be... Air conditioning condensing units communicate with the furnace via two thermostat wires. The two wires are encased in insulation to make one... It takes no special skills to install a new breaker into your home's main electrical panel. Circuit breakers are not interchangeable or...

How to Install an Air Conditioner. Install the mounting brackets that came with the air conditioner unit (be sure to follow... HVAC condenser units allow people to be comfortable in their homes. Using refrigerant, they pull the heat and humidity out of the... How Do I Install the Disconnect Box for an Air Conditioning Unit? How to Connect Wiring to an AC Compressor How to Repair a Thermostat Wire Connecting to an Air Conditioner Unit How to Wire from a Main Breaker to a Sub-Panel How to Install an Electric Disconnect Switch Use of Type UF Cable for AC Unit Is Type UF cable permitted to be used as the supply from an AC disco to the unit without any support when installed outdoors? I can't seem to find any sop where this is OK, please let me know. Re: Use of Type UF Cable for AC Unit Most of the time when we are installing these units we use " liquid tight " for the application and install conductors rated for wet locations. Now I will have to admit many electricians just sleeve 10-2 NM inside the pipe which I am sure could raise a entirly new debate.....

However, because of the risk of damage we install " liquidtite" and pull UF cable within it......Sure some will say you should pull individual conductors of like THWN and so on.....which is probably the best.....but in the real world I do not believe we have been turned down for a short 2-3' UF sleeved within Liquidtight.....I like it better than people sleeving NM Cable within it because NM is not rated for the wet location existant in conduit. Ok...can you run UF to the AC unit from the disconnect.....hmmm.....Is it subject to physical damage?....Probably....another note is UF should be sized based on 60 degree ratings as listed in table 310.16 If you sleeve it...support it 12" from the enclosure. NFPA 70 (NEC) Code Making Panel 5 and 17 Committee Member NEC Code Questions - Visit http://masterthenec.boards.net/ �Promise me you'll always remember: You're braver than you believe, and stronger than you seem, and smarter than you think.� -RIP Dad, Love You!.

Disclaimer - All my posts on this forum are of my own personal opinion and represent Electrical Code Academy, Inc.Sad thing is "Liquid Tight " is not protection from Physical Damage either really........but AHJ's have never really had a issue with it. Either way....of the choices.....I would write up the UF as being exposed to damage...... I am guessing that means it was a bootleg job. Is this common around your area? May be right or could have more serious problems of an HVAC nature, like a bad charge. Bootlegged connections and runs abound here out the wahzoo. I routinely find a handyman has installed wiring to an AC unit. They have been known to run NM, UF outside (literally coming out of the soffit down to the unit, no NM clamps) I found one not long ago the fella had run the NM from inside the Air handler closet down through the line set chase out to the outdoor unit. It was bright yellow too for all the world to see. Another time I found someone had used green garden hose for a "sorta" liquidtight FMC to run cable (again NM) out to their shed.

Its like anything goes here if you can get away with it. The best case might be an HVAC guy moonlighting who just didn't have any sealtite on the truck Worst case would be a stolen unit installed by a handyman working out of his trunk. I would also be looking at shortcuts they took in the ductwork and other issues "How to install outdoor wiring" This article states that the NEC requires #12 for all residential wiring.... When did this change ? Are you refering to that comment line in the article you posted which I have re-posted below: "The National Electrical Code now requires No. 12 gauge wire for all residential electrical wiring."We are buying # 14 AWG everyday...and just for the record I am NOT one of those who believe every plug in the house should be 12 AWG...sure it has more capacity....but if you KNOW what you are doing and size it correctly...14 AWG is fine... I am not aware of any stoppage of # 14 AWG....atleast not in the CODE book I use...thehehehe

But I can say that 90% of Electricians (in Massachusetts) installing wiring in new construction today, utilize 12 AWG. could be quite possible, however in VA or atleast in the area's I deal with....14 AWG is used with no problems and has been in use since 1928 when NM Cable was introduced. I do not have a problem wiring 14 AWG for bedrooms and general lighting...and guess what...I have done 1,000's of homes....no reports of random tripping yet.....tehehehhe If the client requests 12 AWG we most certainly will run it, they have to also be aware of the additional charge for wire and labor associated with running more 12 AWG wire.for those who say that is not a big difference in labor...they obviously have not done alot of houses in 12 AWG....Kitchens are bad enough...but the entire house....murder in mid-winter.... I dont have a problem with it either way...Both work fine to me as it ends up being on the shoulders of the electrician to wire the branch circuits correctly and break up the wiring to reduce any potential for Voltage Drop....remember 50' is still a long way...considering all the factors envolved like panel placement and so on....