Bus Conversions dot Com Bulletin Board
April 19, 2014, 07:08:23 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: New ownership began September 1st 2012!  Please send any comments to info@busconversions.com
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1] 2 3   Go Down
  Print  
Author Topic: Is my new rooftop A/C unit bad? (tripped breaker)  (Read 2254 times)
belfert
Hero Member
*****
Offline Offline

Posts: 5306




Ignore
« on: July 13, 2013, 06:00:59 AM »

I finished installing a new Atwood 15K BTU rooftop A/C last night.  It ran fine for an hour or two.  I started up the generator to make sure all three would run on the generator and they did.  After about half an hour the breaker tripped for the Atwood A/C unit.  Temps were only around 82 degrees and the sun was almost down so no real sun load.

Is this a sign my new rooftop A/C unit is bad if it trips the breaker at only 82 degrees?  I have 12 gauge wire running to it and the breaker is 20 amp.  My other two A/C units have run at 104 degrees outside (and tremendous sun load) without tripping the breaker.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
Len Silva
Hero Member
*****
Offline Offline

Posts: 4076


Angle Parked in a Parallel Universe


WWW

Ignore
« Reply #1 on: July 13, 2013, 06:08:12 AM »

If you don't have a clamp on ammeter to measure the current, I would replace the breaker.  Relatively cheap way to troubleshoot and likely culprit.
Logged


Hand Made Gifts

Ignorance is only bliss to the ignorant.
robertglines1
steam nut
Hero Member
*****
Offline Offline

Posts: 3929





Ignore
« Reply #2 on: July 13, 2013, 06:10:43 AM »

If the breaker in ? has been tripped a bunch it could be weak link. Just a observation.  They tend to get that way.   FWIW.
Logged

Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
luvrbus
Hero Member
*****
Offline Offline

Posts: 11518




Ignore
« Reply #3 on: July 13, 2013, 06:13:05 AM »

They draw more than the 13 amps they advertize more like 16 to 17 about the same as a Coleman,it will blow cold air our friends have 2 in a S&S and were on 15 amp breakers it didn't work   
« Last Edit: July 13, 2013, 06:25:06 AM by luvrbus » Logged

Live each day like it was your last,one day it will be
belfert
Hero Member
*****
Offline Offline

Posts: 5306




Ignore
« Reply #4 on: July 13, 2013, 06:26:18 AM »

I'm going to check for the amp draw later today.  It would be cheap enough to get a new breaker although I've very rarely blown a breaker.  I just rearranged all the breakers in the panel yesterday to accommodate the new A/C unit.  I was trying to balance the load for when I run off a 240 volt circuit.  (My generator is 120 volt and feeds both legs.)

I wouldn't expect any 15K BTU rooftop to work on a 15 amp breaker.  All of my breakers are 20 amp (or larger as necessary).
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
HighTechRedneck
Global Moderator
Hero Member
*****
Offline Offline

Posts: 2916


BCM Editor


WWW
« Reply #5 on: July 13, 2013, 06:40:21 AM »

Since they ran fine on shorepower but tripped breaker on generator power, you might check the voltage with the full load of all three running, with compressors engaged, and other typical loads on.  If your generator can't maintain 120V under that load, then the amps would go up as the volts go down.
Logged
bevans6
Hero Member
*****
Offline Offline

Posts: 4342


1980 MCI MC-5C




Ignore
« Reply #6 on: July 13, 2013, 07:38:19 AM »

Remember that the maximum continuous current for a 20 amp breaker is 16 amps.  Over that and it is supposed to trip after an hour or so particularly if it's installed in a hot location.  I have read of 100% rated breakers being available.  I was going to mention checking the voltage but got beat to it!   Grin

Brian
« Last Edit: July 13, 2013, 07:51:07 AM by bevans6 » Logged

1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
TomC
Hero Member
*****
Offline Offline

Posts: 6515





Ignore
« Reply #7 on: July 13, 2013, 09:02:17 AM »

Sounds stupid, but make sure the black wire coming from the breaker is tight. Vibration from running down the road can loosen it up causing heat and resistance. I installed a computer fan in my breaker box cabinet to cool it in summer. Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Sam 4106
Hero Member
*****
Offline Offline

Posts: 645





Ignore
« Reply #8 on: July 13, 2013, 12:33:43 PM »

Tom,
It isn't just a loose black wire that can cause resistance, a loose neutral (white) wire can  cause it too. I would be good to check all the wires in the panel for looseness.

Good luck, Sam
Logged

1976 MCI-8TA with 8V92 DDEC II and Allison HT740
wg4t50
Hero Member
*****
Offline Offline

Posts: 669





Ignore
« Reply #9 on: July 13, 2013, 01:00:15 PM »

Correct,  most 20 amp breakers are dual purpose, meaning both magnetic and thermally tripped.
Yes a 20 amp is actually 16 amp at most in a cool area. They can become maddening on a hot day with a large load that warms them up.
Dave M
Logged

MCI7 20+ Yrs
Foretravel w/ISM500
belfert
Hero Member
*****
Offline Offline

Posts: 5306




Ignore
« Reply #10 on: July 13, 2013, 01:34:32 PM »

The A/C was just wired up yesterday as it is now so I am pretty sure nothing is loose.  The breaker could be bad perhaps.  We are going to check the amp draw right now.

I haven't run it long enough on shore power to see if it trips the breaker on shore power too.  It just happened to be running off the generator when the breaker tripped.  I cannot run three A/Cs off shore power at home as I only have a 30 amp circuit.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
belfert
Hero Member
*****
Offline Offline

Posts: 5306




Ignore
« Reply #11 on: July 13, 2013, 02:31:41 PM »

I measured the amp draw on the new A/C and it is under 12 amps, but the outside temp is 75 degrees right now.  I am running the A/C units all full blast to try to replicate the issues from yesterday.  I even opened all of the windows to keep the A/C units running.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
wg4t50
Hero Member
*****
Offline Offline

Posts: 669





Ignore
« Reply #12 on: July 13, 2013, 03:41:15 PM »

Does the breker trip within a few seconds or a longer time, if longer, you should detect with your fingers the breaker getting hot.  If quick trip, would check the wiring again.
Dave M
Logged

MCI7 20+ Yrs
Foretravel w/ISM500
Sam 4106
Hero Member
*****
Offline Offline

Posts: 645





Ignore
« Reply #13 on: July 13, 2013, 05:19:17 PM »

Brian,

Just for giggles, if you connected the 12 ga wire from your 20 amp breaker to the air conditioner wires with wire nuts, and you reused the old wire nuts or too large new wire nuts, check those joints. They may be loose. Never re use wire nuts because the coil inside them can stretch and not make a firm connection. It is also a good idea to twist the wire ends together with a pliers and trim the ends even before putting the new wire nuts on. You get more contact between the wires that way. A few tricks I learned from my retired electrical contractor neighbor.

Good luck, Sam
Logged

1976 MCI-8TA with 8V92 DDEC II and Allison HT740
belfert
Hero Member
*****
Offline Offline

Posts: 5306




Ignore
« Reply #14 on: July 13, 2013, 07:42:12 PM »

This is a third brand new rooftop so I ran brand new wire for it.  Atwood does not provide a junction box for the AC wiring so I used good quality butt connectors to connect their stranded wire to my stranded wire.

I have no idea if the breaker got hot as it only happened once.  I tried to make it happen, but then my generator broke and I spent the rest of the evening fixing that.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
Pages: [1] 2 3   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!