120/208 AFCI Question

Status
Not open for further replies.
One of my electricians did a panel and arc-fault upgrade on a condo complex that has a 120/208 system. The owner has a range that uses a 120v warming burner. The range is fed with a 4-wire and is terminated properly. Anytime the warming burner is turned on, it trips all arc faults on one phase. It looks as though it is tripping on the same phase that this warming burner is pulling its 120 from and if we swap the legs feeding the range, it will then trip all arc faults on the opposing phase. We are using Cutler Hammer CH breakers with diagnostics and are getting the code for a series arc. I have to admit, this one has me scratching my head. I am assuming that the warming burner is creating an imbalance which is changing the sign wave enough to mimic an arc, but I really don't know and have no ideas on a remedy. Any thoughts?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The neutral current from the 120V element could be causing problems if the range wiring bonds neutral to ground or uses a single wire and has a ground connection via structure. But that should show GF fault code.
Possibly the thermostatic control is mimicking an arc signature and that signal is hitting the other branches through coupling by high neutral or hot VD?
Or there is actually a series arc in the neutral. :)
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
The neutral current from the 120V element could be causing problems if the range wiring bonds neutral to ground or uses a single wire and has a ground connection via structure. But that should show GF fault code.
Possibly the thermostatic control is mimicking an arc signature and that signal is hitting the other branches through coupling by high neutral or hot VD?
Or there is actually a series arc in the neutral. :)

Good question, how does the unit know if such a condition is in the "protected" portion of the circuit when any current "signature" should exist and/or can be introduced at any point all the way back to the source? And even then if in the supply neutral why not trip breakers on the other line as they share the same neutral? Must have to do with how much imbalance and where it is present at that time?

I will refrain from my thoughts on AFCI in general:roll:
 

edlee

Senior Member
I had a similiar problem a few years back with an electric dryer tripping seemingly unrelated single-pole AF breakers. I found a loose connection in the dryer receptacle outlet, the neutral or ground (don't remember which) so I tightened it up. The tripping stopped.

It didn't make any sense to me at all, but then that's what we get with AF devices!
 

JFletcher

Senior Member
Location
Williamsburg, VA
Will a 2p 240V (split phase) AFCI work on 2p 208V? Found an Eaton manual for 2p AFCI:

"2. Install circuit breaker on a single phase 120/240 VAC 60 Hz power supply system."
 

kwired

Electron manager
Location
NE Nebraska
Will a 2p 240V (split phase) AFCI work on 2p 208V? Found an Eaton manual for 2p AFCI:

"2. Install circuit breaker on a single phase 120/240 VAC 60 Hz power supply system."
I think this has been asked here somewhat recently, IIRC it depends on actual design of the unit in question.

GFCI breakers (with neutral) OTOH seem to mostly all have 120 volt control circuit and will work on either system.
 

JFletcher

Senior Member
Location
Williamsburg, VA
I think this has been asked here somewhat recently, IIRC it depends on actual design of the unit in question.

GFCI breakers (with neutral) OTOH seem to mostly all have 120 volt control circuit and will work on either system.

Yep:

http://forums.mikeholt.com/showthread.php?t=172497

Post 10 and 16.

Looking up "AFCI breakers for 208V" doesnt give much...

Must be a problem with voltage or phase angle.
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
The 208V issue would only be a problem with 2 pole AFCI's The op is having issues with single pole AFCI's.
 

JFletcher

Senior Member
Location
Williamsburg, VA
The 208V issue would only be a problem with 2 pole AFCI's The op is having issues with single pole AFCI's.

OP stated 4-wire. Regardless of the warming burner being 120V, it is coming from a 2p breaker.

...

Upon second read, it is ambiguous. I dunno if it's one or two pole, or if a 2p AFCI would trip with a 120V load.

Do ranges have to be AFCI protected? I wasnt aware of any 240V/208V loads that had to be.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Will a 2p 240V (split phase) AFCI work on 2p 208V? Found an Eaton manual for 2p AFCI:

"2. Install circuit breaker on a single phase 120/240 VAC 60 Hz power supply system."
If that is in the instructions, then it would be UL's position that the instruction is a 110.3(B) instruction and that AFCI device could not be used on a 3 phase system or even a single phase system derived from a 3 phase system.
 

kwired

Electron manager
Location
NE Nebraska
OP stated 4-wire. Regardless of the warming burner being 120V, it is coming from a 2p breaker.

...

Upon second read, it is ambiguous. I dunno if it's one or two pole, or if a 2p AFCI would trip with a 120V load.

Do ranges have to be AFCI protected? I wasnt aware of any 240V/208V loads that had to be.

OP does not have an AFCI on the range, but when the 120 volt warming burner on that range is operating it causes troubles with the other single pole AFCI's in the dwelling. He does have a 208/120 supply, whether that is a contributing factor to the problem, IDK.

Curious if it only trips AFCI's in this unit or if it effects other units as well?
 
OP stated 4-wire. Regardless of the warming burner being 120V, it is coming from a 2p breaker.

...

Upon second read, it is ambiguous. I dunno if it's one or two pole, or if a 2p AFCI would trip with a 120V load.

Do ranges have to be AFCI protected? I wasnt aware of any 240V/208V loads that had to be.

The range is fed with a standard bi-metal 2-pole breaker. The AFCI breakers that are tripping are all single pole breakers all on the same phase. I have checked for poor connections in the panel and at the range receptacle and everything is tight.
 
OP does not have an AFCI on the range, but when the 120 volt warming burner on that range is operating it causes troubles with the other single pole AFCI's in the dwelling. He does have a 208/120 supply, whether that is a contributing factor to the problem, IDK.

Curious if it only trips AFCI's in this unit or if it effects other units as well?

We only have access to this one unit, however the homeowner has good relationships with her neighbors and no similar complaints have been relayed to us.
 
Status
Not open for further replies.
Top