Internal Breaker Keeps Tripping

Reply

  #1  
Old 05-12-19, 06:05 AM
Member
Thread Starter
Join Date: May 2019
Posts: 13
Internal Breaker Keeps Tripping

Good morning!

I have a 3 year old Lennox system. The unit was working fine (In heat mode) and then a few days ago we noticed that the Honeywell smart thermostat was off. That unit does not have batteries and is powered with the 24vac from the unit. I went down to investigate and noticed the 3amp breaker inside the unit had tripped. I reset it and everything came back online and was working fine. A few hours later the breaker had tripped again. This time the blower fan was stuck on and since the controller was not powered there was nothing to turn it off. I had to kill power to the unit. I can keep resetting the breaker and everything comes back online and then down the road a few hours it trips again.

The controller board in the unit displays a code when running and there are no indications of an error in the controller board. Before I call for backup I thought I would consult the professionals here for advice. I have attached some relevant pictures.

Thanks in advance for your help.

Name:  l1.jpg
Views: 89
Size:  108.3 KB

Name:  l2.jpg
Views: 93
Size:  56.4 KB

Name:  l3.jpg
Views: 82
Size:  80.5 KB
 

Last edited by PJmax; 05-12-19 at 10:28 AM. Reason: reoriented/resized pictures
Sponsored Links
  #2  
Old 05-12-19, 06:33 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 3,619
Hi, I assume the yellow wire jammed into that switch is the door switch, is there a wiring Dia. You can post? That breaker appears to be on the line side .
Geo
 
  #3  
Old 05-12-19, 10:29 AM
Member
Thread Starter
Join Date: May 2019
Posts: 13
I didn't see a wiring diagram anywhere. They did leave the manual. Would It be in there?

Is the wire jammed in the door switch an issue? I assume not. There is a typical 120v switch really close to that breaker on the outside of the unit so you are likely correct that it's on the line side of things.

Is it likely the control board is drawing too much power and tripping the breaker or would it be the fan motor or something else? It is a variable speed fan motor.
 
  #4  
Old 05-12-19, 10:57 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
That 3A breaker is more than likely in the 24v transformer line.
Lennox tech service is n/a this weekend.

If it only trips in A/C mode..... it could be a defective reversing valve, contactor coil or with the addition of your stat is pushing the system just over the limit.

Did you check the back of the blower door for info ?
 
  #5  
Old 05-12-19, 03:28 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
It's only tripping in the heat mode. A/c has not been on since last summer. We'll be making the switch here shortly.

If the 3amp breaker is only on the 24vac line could a fault in the thermostat be causing the problem? The controller board definitely loses power when the breaker trips. The indicator giving status goes out.

Is it worth it to replace the thermostat before calling out a tech? Once the breaker is reset everything functions normally.
 
  #6  
Old 05-12-19, 03:41 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
OK. I was wrong. There is a wiring diagram. I also checked the voltage on the 24v transformer and it's running 27.8v. See new pics.

There also seems to be an old transformer (likely reused?) hanging from the new one and another attached to the fan.

Name:  l4.jpg
Views: 71
Size:  422.0 KB

Name:  l5.jpg
Views: 70
Size:  105.2 KB

Name:  l6.jpg
Views: 69
Size:  83.4 KB
 

Last edited by PJmax; 05-12-19 at 03:53 PM. Reason: resized pictures
  #7  
Old 05-12-19, 03:46 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
The circuit breaker is CB8 on the diagram and is in the transformer 24v line.... 27.8v is ok.
Doubtful it's the board. More likely to be a wiring short in the thermostat line.
No likely to be a defective thermostat.

That lovely hanging transformer is probably for powering the humidifier.
Trace where the attached cable goes.
 
  #8  
Old 05-12-19, 04:27 PM
Member
Join Date: Nov 2012
Location: USA
Posts: 3,619
Hi, post #1 heat is working fine, post # 5 itís only tripping in heat mode???
What am I missing? Has anything been added to the system that maybe causing this?
The 24 volt circuit is mostly safety switches, gas valve , contactor for condenser.
Try this, restore the circuit breaker and set the Stat to call for heat, does the breaker trip?
Geo
 
  #9  
Old 05-12-19, 08:08 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
Yes, that extra transformer is probably the humidifier.

​​​​​​To clarify, I reset the internal Breaker, the thermostat and control board power up and the system turns on and functions properly, but only for a little while. At some point after, sometimes a few hours, sometimes a few minutes and the breaker will trip again and it shuts down the thermostat and control board. If the Blower was on when the breaker trips it stays on until I kill power to the whole unit.

Are you implying there could be a short between the control board and the thermostat cable? How could I check that?
 
  #10  
Old 05-13-19, 12:07 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
The board runs on 24v which is why it also goes dead when that breaker trips.

In order to see what is drawing excessive power..... you'd need to put an ammeter in the 24v line..... near the transformer. You need to see what the circuit is drawing normally (standby) and then in heating mode.
 
  #11  
Old 05-13-19, 03:59 AM
Member
Thread Starter
Join Date: May 2019
Posts: 13
I will try to do that tonight. Thanks.
 
  #12  
Old 05-13-19, 04:09 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 3,619
My thought was to see if the breaker tripped on a call for heat, possibly a bad gas valve drawing to much current, the Amp meter is a good call but if it runs for awhile before it trips it maybe hard to see anything, try cooling and let it run and see what happens.
Geo
 
  #13  
Old 05-13-19, 10:55 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
It could ultimately be a defective circuit breaker. That's where the current meter comes in handy.
A 3A breaker could hold rated current for a short while before tripping.
 
  #14  
Old 05-13-19, 06:14 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
Well, I went to place my fluke 73iii in line with the breaker and won't you know it both the 10amp and 300mA fuses in my meter are blown. I'll have to try again tomorrow. I will check it with both cooling and heat modes if I can. I'll try to stay until it trips.
 
  #15  
Old 05-13-19, 06:17 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
Pjmax you mentioned a Lennox tech line. Is that something I can call or is it only for professionals?

Here is a thought. Around the same time this started happening we lost a gfci outlet in the kitchen. It just died. Could there have been a power surge or something that took it and this breaker or something else out?
 
  #16  
Old 05-13-19, 06:21 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
The tech area I was trying to access was for manuals online.

When you re-fuse your meter...... only use the 10A setting.
You don't have an actual short. At least not one that is always there. It is either coming intermittently or the circuit draw is coming close to 3A. We could keep guessing but that doesn't get us anywhere.
 
  #17  
Old 05-14-19, 04:45 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
OK. So I ran the unit in both heat and cool mode. See attached pictures. In heat mode the breaker tripped at 0.5amps and on cool it tripped at 0.6amps. It happened within a minute of the system kicking on.

The 3rd picture is of the fuse. I looked it up and it's a thermal fuse. Clearly it's tripping way below the 3amp level. Should I replace this as a starting point?

I found this on Amazon that seems to be a direct replacement. Is it worth a shot before hiring a repair service

https://www.amazon.com/TE-CONNECTIVI...gateway&sr=8-2
 
Attached Images    
  #18  
Old 05-14-19, 11:15 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
It's a circuit breaker. You can use the one you linked to or you could replace it with a fuse. I carry fuseholders and fuses with me when I service systems. You can splice it in place of the circuit breaker. The fuses and fuseholder can be obtained from any auto parts store. You'd use an ATC-3A fuse.

Name:  atc.jpg
Views: 41
Size:  14.7 KB

 
  #19  
Old 05-15-19, 04:01 AM
Member
Thread Starter
Join Date: May 2019
Posts: 13
OK. That works. Does it seem like this is the likely culprit?
 
  #20  
Old 05-15-19, 04:30 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 3,619
Hi, I would think if it tripped that quick itís more like a short, wonít hurt to try the fuse though.
Geo
 
  #21  
Old 05-16-19, 11:25 AM
Member
Join Date: Jun 2018
Location: USA
Posts: 2
One more thing to look at

If your control wires have been tied to a pipe with a cable tie or something similar, it can over time actually pinch the insulation to such a point where the hot wire can short to either the pipe its tied to or one of the other control wires and would trip the breaker . I have run into this situation. Cut the cable ties, replace the control cables and loosely tie them. If not try disconnecting all loads from control circuit and then reconnect one at a time until it trips.
 
  #22  
Old 05-16-19, 04:24 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 50,124
Likes Received: 76
In heat mode the breaker tripped at 0.5amps and on cool it tripped at 0.6amps.
It happened within a minute of the system kicking on.
If you were there watching the meter and it didn't spike up and then trip.... the breaker is tripping prematurely. It's tired.
Typically a wiring problem would be there instantly..... not a minute later.
Also typical for there to be a short to the condenser but rarely to the furnace.
 
  #23  
Old 05-16-19, 07:01 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
OK. Well breaker didn't work. I pulled the thermostat off the wall and powered the unit and it didn't trip anything. Plug the thermostat back in and it trips immediately. So does this imply thermostat or cable as the culprit?

Can I start removing the wires from the thermostat to the unit one at a time? Should I go buy a short length of new thermostat cable and thermostat and test that out?
 
  #24  
Old 05-16-19, 08:16 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
New update. Since the breaker didn't seem to fix it I bought a short line of thermostat cable and a cheap thermostat. Hooked it up and the system is not tripping. I'm going to let this run for a while and then if that's good I'll hook it up to the other thermostat tomorrow and verify whether the issue is the cable or the thermostat.
 
  #25  
Old 05-18-19, 12:14 PM
Member
Thread Starter
Join Date: May 2019
Posts: 13
Friends,

Thank you so much for your help. I've replaced the thermostat wire and everything seems to be up and running like it should be!
 
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