Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-07-2009, 06:45 PM   #1
Member
 
Join Date: Oct 2008
Posts: 67
Rewards Points: 75
Default

air conditioner question


I have (2) # 10 orange wires going to the central airconditioning unit from (2) 40amp breakers. First of all, these should be 30amps breakers correct due to the size of wires? And why is there 2? Doesn't there need to be a neutral?

howard.wheaton is offline   Reply With Quote
Old 03-07-2009, 07:10 PM   #2
Licensed Pro
 
Join Date: Mar 2007
Location: SC
Posts: 1,544
Rewards Points: 1,000
Default

air conditioner question


AC unit is 240 only, so no neutral is needed. Hermetically sealed compressors (AC) use a little different rules, so the 40A breaker on #10 wire is OK.

__________________
"Life is hard. Life is harder when you're stupid." John Wayne
HouseHelper is offline   Reply With Quote
Old 03-07-2009, 09:36 PM   #3
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,618
Rewards Points: 1,030
Default

air conditioner question


As stated above, an A/C unit doesn't need a neutral, just the 2 hots.

The nameplate usually states a minimum circuit ampacity. This determines the wire size. It also states a maximum breaker or fuse size. The wire size is usually 'too small' for the breaker, but perfectly legal and safe.

The reason is because the A/C unit is self-protected against overloads, so it cannot overload the wire. It can however, develop a short-circuit. This is the sole function of the breaker; to protect against short-circuits and ground faults.

The reason the breaker needs to be larger than normal is because the compressor contains a motor. All motors draw much more current when starting than they do when running. (Usually about 6 times as much). A 'normal' size breaker might see this starting surge current as a fault and trip when there isn't a problem.

About the only places that a breaker can be larger than the wire is A/C units, motors, and welders. There are a few others, but you'll never find them in residential wiring.

Rob
micromind is offline   Reply With Quote
Old 03-08-2009, 09:19 AM   #4
Master Electrician
 
JohnJ0906's Avatar
 
Join Date: Mar 2007
Location: Baltimore, MD
Posts: 332
Rewards Points: 250
Default

air conditioner question


Quote:
Originally Posted by howard.wheaton View Post
I have (2) # 10 orange wires going to the central airconditioning unit from (2) 40amp breakers. First of all, these should be 30amps breakers correct due to the size of wires? And why is there 2? Doesn't there need to be a neutral?
Is this one or 2 units?
__________________
John from Baltimore
One Day at a Time
"Experience is what you get when you were expecting something else"
"The bitterness of low quality lingers long after the sweetness of low cost is forgotten"
JohnJ0906 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Basement Renovation Question KUIPORNG Remodeling 234 08-26-2008 08:19 AM
hrv question indep HVAC 3 07-17-2008 10:39 PM
Basement vapor barrier question rob7young Remodeling 2 04-13-2008 09:10 AM
New service Question Onytay Electrical 1 10-24-2007 05:47 AM
One furnace question and one thermostat question lh0628 HVAC 4 10-11-2007 10:17 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.