AC Unit Rated at 18.3 amps on 20 amp Breaker

Reply

  #1  
Old 02-26-14, 06:44 PM
G
Member
Thread Starter
Join Date: Dec 2013
Posts: 108
Received 0 Votes on 0 Posts
AC Unit Rated at 18.3 amps on 20 amp Breaker

My 7 year old house's outdoor a/c unit trips the breaker now and then. Its on a 20 amp dual breaker. Seems kind of tight. Do they make a 25 amp breaker? The a/c unit says 25 max breaker..
 
Sponsored Links
  #2  
Old 02-26-14, 06:57 PM
Justin Smith's Avatar
Member
Join Date: Dec 2010
Location: Cressona, Pa, USA
Posts: 2,546
Received 0 Votes on 0 Posts
What size wire is it on? A 25A breaker needs #10 wire.
 
  #3  
Old 02-26-14, 07:01 PM
G
Member
Thread Starter
Join Date: Dec 2013
Posts: 108
Received 0 Votes on 0 Posts
Thanks Justin. I am not sure. How do I tell the wire number..
 
  #4  
Old 02-26-14, 07:03 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,638
Received 83 Votes on 73 Posts
Is the MCA and MOPD listed on the unit label? I suspect you should have a 30 amp breaker for the unit to start, but it may work with a 25 amp breaker.

What size wire is it on? A 25A breaker needs #10 wire.
Not necessarily. The wire size and overcurrent protection is determined by the unit specs. The breaker is not sized to protect the wire size with most motor or compressor circuits, but sized slightly larger to allow the motor to start.

It would help to know the manufacturer and model number.
 
  #5  
Old 02-26-14, 07:07 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 15,144
Received 83 Votes on 71 Posts
Justin, AC wiring and OCP are different than regular branch circuit sizing. The information from the dataplate is used. It will say the minimum circuit ampacity and the maximum overcurrent protection size.
 
  #6  
Old 02-26-14, 07:27 PM
G
Member
Thread Starter
Join Date: Dec 2013
Posts: 108
Received 0 Votes on 0 Posts
Thanks guys. I have an electrician from home warranty company coming on Friday. What do you think I should tell him I want...

I have a York..
[ATTACH=CONFIG]27443[/ATTACH]
 
Attached Images  
  #7  
Old 02-26-14, 07:42 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,638
Received 83 Votes on 73 Posts
It's a 3 ton unit, MCA is 18.3. #12 wire is fine, but if this were a new unit I'd run #10. Circuit breaker should be 25 amp maximum.
 
  #8  
Old 02-28-14, 09:18 AM
G
Member
Thread Starter
Join Date: Dec 2013
Posts: 108
Received 0 Votes on 0 Posts
Hey Guys, electrician was here. He did an amp test at the breaker. When my AC compressor kicks on, it pulls 13 amps. When it is running steady it pulls 9amps. He just replaced the existing 20 amp breaker with a new 20amp breaker cause he did not have a 25 in his truck.

So 13 amp at start up. How in the world is my 20 amp breaker tripping?
 
  #9  
Old 02-28-14, 09:23 AM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,597
Received 13 Votes on 11 Posts
So 13 amp at start up. How in the world is my 20 amp breaker tripping?
Weak breaker. Replaced a lot of them on the window A/C circuits in an apartment building I did maintenance for. The springs inside maybe due to constant heat from heavy continuous load become weaker.
 
  #10  
Old 02-28-14, 10:18 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 15,144
Received 83 Votes on 71 Posts
The startup current on a motor or compressor can be several times what the run current is.
 
  #11  
Old 02-28-14, 06:03 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,638
Received 83 Votes on 73 Posts
A new 20 amp breaker might solve the problem. If not, change it to a 25 amp breaker.
 
  #12  
Old 03-01-14, 05:37 AM
A
Member
Join Date: Mar 2010
Location: USA
Posts: 4,067
Received 75 Votes on 69 Posts
Loss of Freon in the AC system can cause erratic operation including unexpectedly larger current draw that can trip the breaker.

Double check the AC unit's running current, starting current, suggested circuit amperes rating (wire size and breaker), and maximum circuit amperage rating. You are permitted to wire it into a circuit up to the maximum amps rating. You should have a circuit at least of the suggested amps rating. You can get breakers that specifically don't trip that quickly, for use on circuits that handle AC units or other motorized tools or appliances with high starting current.

Sometimes, wire size can be smaller than a given breaker rating normally requres when the circuit is dedicated for and hard wired to a specific appliance. See the appliance specs or instructions.
 
  #13  
Old 03-02-14, 07:44 AM
W
Member
Join Date: Jan 2014
Location: USA
Posts: 699
Received 0 Votes on 0 Posts
I always size the wire and Circuit Breaker to the max fuse / HVAC CB rating . No call backs .

If all works well , leave it as is .

If you do end up needing a 25 amp CB , have some one order it or order one online . Or use a 30 amp 2 pole fusible disconnect at the unit and fuse it at 25 amps , which you can find . Feed with a 2 pole 30 amp CB & # 10 wire .

But , often the problem is some one is diddling with the tstat , off - on . This forces the compressor to try to start against high head pressure . Install a 5 or 7 minute electronic time delay relay in the coil circuit of the condenser contactor .

God bless
Wyr
 
  #14  
Old 03-02-14, 02:02 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,638
Received 83 Votes on 73 Posts
If you do end up needing a 25 amp CB , have some one order it or order one online
Most supply houses around here have started stocking 25 amp breakers. Regardless, they aren't hard to get.
 
Reply
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


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: