Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

Circuit breaker pops on AC compressor when power goes out?

Circuit breaker pops on AC compressor when power goes out?

Reply

  #1  
Old 08-03-06, 05:05 AM
Member
Thread Starter
Join Date: Feb 2003
Location: USA
Posts: 119
Circuit breaker pops on AC compressor when power goes out?

Once the power comes back on, the breaker trips. I reset the breaker and all is well until the next power outage/recovery. Is it just that I need a new circuit breaker? Is it possible that I need a higher amp breaker (it's 30 amps now).
 
Sponsored Links
  #2  
Old 08-03-06, 05:22 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
How soon did the power come on after going off? If it was pretty quick then the system didn't have time to equalize before trying to start back up and being under a load like that it will trip a breaker. If that's the case you either need to get a digital stat with built in time delay or you need to buy a time delay and install it in the outdoor unit. This will keep it from trying to restart for 5 - 10 minutes after power is restored.
 
  #3  
Old 08-03-06, 06:52 AM
Member
Join Date: Aug 2004
Location: NA
Posts: 1,065
Once the power comes back on, the breaker trips. I reset the breaker and all is well until the next power outage/recovery. Is it just that I need a new circuit breaker? Is it possible that I need a higher amp breaker (it's 30 amps now).
Your breaker is most likely correct in size and normally you would never increase a breaker size. You can do so on A/c if the nameplate states a max. breaker size and it is greater in amps than the one installed. You may never increase the breaker above the maximum nameplate breaker size.

Is this problem something that has recently started happening or has the unit always had this problem?

Roger
 
  #4  
Old 08-03-06, 06:57 AM
Member
Join Date: Feb 2006
Location: USA
Posts: 929
Some of the older systems had a capacitor that had a resistor wired between the terminals that drained the cap when power was removed. If you have this then what you are seeing is normal. Your capacitor would need to be charged prior to the compressor coming on. The fix for this would be a delay on make time delay.
 
  #5  
Old 08-03-06, 08:53 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
mattison hit the nail
 
  #6  
Old 08-03-06, 08:59 AM
scott e.'s Avatar
Member
Join Date: Jun 2003
Location: Anderson, IN
Posts: 412
Originally Posted by Roger
Your breaker is most likely correct in size and normally you would never increase a breaker size. You can do so on A/c if the nameplate states a max. breaker size and it is greater in amps than the one installed. You may never increase the breaker above the maximum nameplate breaker size.

Is this problem something that has recently started happening or has the unit always had this problem?

Roger
Only if you don't exceede the ampacity of the wiring. Since most installers don't upsize their conductors, I doubt that a breaker upgrade is possible without rewiring.
 
  #7  
Old 08-03-06, 09:28 AM
Member
Join Date: Aug 2004
Location: NA
Posts: 1,065
Not true...on motor circuits using hermetic design you are allowed to upsize breakers above wire ampacity in order to get the compressor started if it wont start otherwise. The ampacity of the wire is sized to the specifications of the a/c unit nameplate and an appropriate breaker is installed. If the compressor wont start then you are allowed to upsize the breaker. You may not however exceed the max. breaker size stated on the nameplate.
This is true with all motors but you need to understand the rules of NEC 430 and 440.

You can also have breakers much higher in amp rating than the conductors serving arc welders.

Roger
 
  #8  
Old 08-03-06, 08:19 PM
WFO
WFO is offline
Member
Join Date: Feb 2004
Location: usa
Posts: 247
Originally Posted by jwhite
mattison hit the nail
Absolutely!
Most reclosers on the power line have anywhere from an instantaneous reclose to a couple of seconds. In either case, the compressor is trying to re-start with a lot of head pressure (which would normally bleed off given time). If it isn't tripping under normal conditions, don't look for a problem that isn't there.
 
  #9  
Old 08-03-06, 10:48 PM
Member
Join Date: Aug 2004
Location: NA
Posts: 1,065
For my education how long are we talking between power off to restoring power to prevent this tripping of the breaker due to compressor head pressure. I've heard of hard start capacitors but I dont believe that is applicable with this problem or is it?
 
  #10  
Old 08-04-06, 02:00 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
Depending on the size of the system, two to five minuts time delay is common to avoid this.
 
  #11  
Old 08-04-06, 04:15 AM
Member
Thread Starter
Join Date: Feb 2003
Location: USA
Posts: 119
Originally Posted by mattison
How soon did the power come on after going off? If it was pretty quick then the system didn't have time to equalize before trying to start back up and being under a load like that it will trip a breaker. If that's the case you either need to get a digital stat with built in time delay or you need to buy a time delay and install it in the outdoor unit. This will keep it from trying to restart for 5 - 10 minutes after power is restored.
This makes the most sense in my situation. It doesn't happen everytime the power goes out/on...but typically if the compressor is running at the time and the outage is short...it trips the breaker. There is no delay so under a load it trips. My heat pump has a delay and never has the problem. Sounds like the digital thermostat is the easiest fix!
The house is only 5 years and has been going on for years.

Thanks guys!
 
  #12  
Old 08-04-06, 04:48 AM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
Another possibility is that when the utility comes back on line, its voltage is not quite stable for some time. Your compressor may be suffering from under voltage conditions imposed by the utility prior to steady state operation.
 
  #13  
Old 08-04-06, 04:53 AM
Member
Thread Starter
Join Date: Feb 2003
Location: USA
Posts: 119
Originally Posted by HandyRon
Another possibility is that when the utility comes back on line, its voltage is not quite stable for some time. Your compressor may be suffering from under voltage conditions imposed by the utility prior to steady state operation.
What could I do to rectify that situation? Also...I have a heat pump that never suffers from this.
 
  #14  
Old 08-04-06, 04:58 AM
Member
Thread Starter
Join Date: Feb 2003
Location: USA
Posts: 119
Originally Posted by bverdon
This makes the most sense in my situation. It doesn't happen everytime the power goes out/on...but typically if the compressor is running at the time and the outage is short...it trips the breaker. There is no delay so under a load it trips. My heat pump has a delay and never has the problem. Sounds like the digital thermostat is the easiest fix!
The house is only 5 years and has been going on for years.

Thanks guys!
Well...I just checked th manual of my thermostat...it has a 5 minute delay. But...it states that the 5 minute delay is in effect when the thermostat turns the system off. Are there thermostats that are smart enought to recognize when power is removed from the system?
 
  #15  
Old 08-04-06, 06:12 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
The easier solution is to install a "delay on break" timer. This inexpensive device will recognize when power to the contactor coil is lost (whether from a power failure or from the thermostat ending its call for cooling) and prevent it from turning back on for five minutes (or whatever time you adjust it to, although five minutes is fine). The wiring is simple. Search google or e-bay for "delay on break," or see if a local supply house will sell you one. You'll want to get this taken care of, as you said it happens freqently. Restarting the system before the pressures have equalized (which takes a few minutes after the system is turned off) is hard on the compressor.
 
  #16  
Old 08-04-06, 07:04 AM
Member
Thread Starter
Join Date: Feb 2003
Location: USA
Posts: 119
Originally Posted by eclipse
The easier solution is to install a "delay on break" timer. This inexpensive device will recognize when power to the contactor coil is lost (whether from a power failure or from the thermostat ending its call for cooling) and prevent it from turning back on for five minutes (or whatever time you adjust it to, although five minutes is fine). The wiring is simple. Search google or e-bay for "delay on break," or see if a local supply house will sell you one. You'll want to get this taken care of, as you said it happens freqently. Restarting the system before the pressures have equalized (which takes a few minutes after the system is turned off) is hard on the compressor.
Sounds like the ticket. Where does it get installed? Sounds like something I could do myself...
 
  #17  
Old 08-04-06, 07:10 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
Normally, it would be installed in the electrical compartment of the outdoor condensing unit, although I suppose you could install it in the air handler/furnace as well.
 
  #18  
Old 08-04-06, 09:41 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
Originally Posted by bverdon
Well...I just checked th manual of my thermostat...it has a 5 minute delay. But...it states that the 5 minute delay is in effect when the thermostat turns the system off. Are there thermostats that are smart enought to recognize when power is removed from the system?
Most thermostat timers are reset on loss of power, and have to time out on power up. I dunno why yours would be different.


The easiest way to go will be to find a thermostat that will do the trick. or just figure out how to set your existing one up so that it will.

If you do go with the Delay On Make timer that would be needed, you need to be sure of where you are putting it into the circuit At The Condensing Unit.
 
  #19  
Old 08-04-06, 11:00 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
Originally Posted by jwhite
If you do go with the Delay On Make timer that would be needed, you need to be sure of where you are putting it into the circuit At The Condensing Unit.
Is there any particluar advantage to using a delay on make versus delay on break? It seems to me that with a delay on break, system operation generally will track thermostat operation, while using a delay on make means that the system waits the ca. 5 minutes upon the call for cooling.
 
  #20  
Old 08-04-06, 11:10 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
A delay on break timer would be running immediatly at power start up. That is the OPs problem.
 
  #21  
Old 08-04-06, 11:13 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
eclipse. the problem that you stated about a delay on each call for cooling is why I say to not use timers in the CU and instead get the right thermostat for the job.

The T stat will have min times, but start immediatley if the timer has already timed out.

Of coarse I could design a timer ciriut that would work just as well, but the t stat would be cheeper.
 
  #22  
Old 08-04-06, 11:27 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
Originally Posted by jwhite
A delay on break timer would be running immediatly at power start up. That is the OPs problem.
Yes, but wouldn't a momentary power failure would provide the break to start the time delay?
 
  #23  
Old 08-04-06, 11:41 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
Originally Posted by eclipse
Yes, but wouldn't a momentary power failure would provide the break to start the time delay?
Delay on break means that the relay contacts close on startup and when the timer runs out they open. Thus after a power failure they would be on immediatly, then after a time turn off.

Delay on make means that on power up the timer starts first, and after that time the contacts close starting the load.

You would be correct if only the signal circuit was lost, but on total power loss the timers will go back to start.

Some of the best info on these types of products come from dealers. Here is a good web site with great info on how these timers work. http://www.kele.com/olcat/RC15/RTE-V.PDF
 
  #24  
Old 08-04-06, 11:56 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
I get it now. Thanks.
 
  #25  
Old 08-04-06, 12:29 PM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
Wait -- I don't get it. The timers I've seen have only two terminals. They are simply inserted in series into one side of the incoming 24V to the contactor coil. How can it tell the difference between a signal loss and total power loss?
 
  #26  
Old 08-04-06, 12:58 PM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
two terminal timers can only be on delay. they can never be off delay.

off delay requre the use of a second singnal circuit.
 
  #27  
Old 08-04-06, 01:09 PM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
Google "ICM 203" and look at the second item (indented under the first). It is a two terminal delay on break. What am I missing here?
 
  #28  
Old 08-04-06, 01:30 PM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
send me that link.. then I can see what you are talking about.
 
  #29  
Old 08-04-06, 01:33 PM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
What you are missing is the operating instructions. Please read them carefully.
 
  #30  
Old 08-04-06, 01:44 PM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
What you are missing is the OP problem. When power glitches the CU trips out instead of staring . Probably due to high head pressure. The solution is a time delay on the start.

A delay on break timer will start right away, then time out, then let go. Notice the part about start right away. That will trip the breaker again and that is the OP problem.

It was cool that you could find one that uses a trickel voltage and does not need a seperate power source to operate. Good job.

The fact that you still are not understanding why it will not work for the OP tells me that you do not understand basic electricity.
 
  #31  
Old 08-04-06, 01:57 PM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Eclipse is from Cleveland. That's why he don't get it. "Just kidding" I'm from Cincy. Foot ball season is coming up and the Cincy Cleveland game is one that I make sure and go to.


Here is all that is needed. It's 2 wire hook up and takes like 5 minutes to install.
http://www.famousparts.com/icdeonbrti.html
 
  #32  
Old 08-04-06, 02:01 PM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
but, a delay on break timer will be in the on position when first power up.

so, explain to me in detail how that will help the OP.
 
  #33  
Old 08-04-06, 02:56 PM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Either will work. A delay on make starts it's count as soon as power is restored. A delay on break starts its count as soon as power is lost. Either way the compressor won't start untill the time delay times out.

I usually use a delay on make for staging purposes so on start up I'm not starting two compressors at once.
 
  #34  
Old 08-04-06, 03:51 PM
Member
Join Date: May 2006
Posts: 253
In residential a delay on break is more comfortable/practical. Do you really want unconditioned air blowing for 5 minutes every time your unit cycles on?

Delay on break will keep the unit from coming on again until the specified time has elapsed.
 
  #35  
Old 08-05-06, 03:04 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
Looks like you guys are right about that timer. I had not been thinking about mechanical timers. This is a good solution to the OP problem. just put it inline with the condenser start wire at the unit. Usually the yellow hooked to Y1. If there is a Y2 then two timers would be needed.
 
  #36  
Old 08-07-06, 05:55 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
The one that Mattison posted the link to (thanks) is precisely the one I was referring to. I am fully aware that normally a delay on break will reset its timer upon being energized, which wouldn't help the OP (or anyone else whose breaker was tripping because of excessive current draw on restart due to high head pressure). But it seemed to me that the timer that I (admittedly awkwardly by giving a Google dearch rather than a link) referred to addresses that situation. But the comment that I do not understand basic electricity was purely gratuitous. Believe me, I do.
 
  #37  
Old 08-07-06, 07:13 AM
Member
Join Date: May 2006
Posts: 253
Originally Posted by eclipse
The one that Mattison posted the link to (thanks) is precisely the one I was referring to. I am fully aware that normally a delay on break will reset its timer upon being energized, which wouldn't help the OP (or anyone else whose breaker was tripping because of excessive current draw on restart due to high head pressure). But it seemed to me that the timer that I (admittedly awkwardly by giving a Google dearch rather than a link) referred to addresses that situation. But the comment that I do not understand basic electricity was purely gratuitous. Believe me, I do.
A delay on break will reset its timer upon being DE-energized. T-stat cycles off time delay begins. If t-stat calls for cooling before the time has elapsed the contactor will not pull in until the time has passed.

They both do the same thing in regards to high head. They allow it time to equalize. They just do it at different points in the cycle.
 
  #38  
Old 08-07-06, 07:19 AM
Member
Join Date: Apr 2001
Location: Cleveland, Ohio
Posts: 336
De-energized; yep, that's what I meant. My bad.
 
  #39  
Old 08-07-06, 08:06 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Eclipse: I'm sure you probably know more about electric than I would ever know. I just know HVAC and controls.
 
  #40  
Old 08-08-06, 09:16 AM
hornetd's Avatar
Member
Join Date: Aug 2001
Location: Maryland
Posts: 695
Heating Air Conditioning Refrigeration circuits sizing & Protection

Originally Posted by scott e.
Only if you don't exceed the ampacity of the wiring. Since most installers don't upsize their conductors, I doubt that a breaker upgrade is possible without rewiring.
At the risk of sounding quarrelsome I must point out that the wire is sized by the circuit selection ampacity rather than the size of the Over Current Protective Device (OCPD). The circuit selection ampacity is found on the name plate of the motor compressor unit of the air conditioning system. The OCPD provides fault protection to the branch circuit. The overload protection is provided by the built in overload detecting mechanism in the motor compressor unit. In motor circuits in general and Heating Air Conditioning and Refrigeration circuits in particular the general rules for the ampacity of conductors are modified by the specific equipment articles of the code. It is not unheard of to find number twelve conductors protected by forty ampere fuses or circuit breakers in these applications. As long as the size of the circuit matches or exceeds the size given on the name plate and the OCPD matches or is less than the value on the name plate all is well.
 

Last edited by hornetd; 08-08-06 at 09:26 AM.
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
Display Modes
'