Shared Neutral Current Additive 120/208?

Joined
9 Dec 2013
Messages
5
Reaction score
0
Location
California
Country
United Kingdom
I'm remodeling my kitchen and am bringing it up to code. My service is 120/208. I wired up my first multiwire circuit. I decided to read neutral current flow with a clamp on ammeter to make sure everything was cool. I had a 1 amp load and a 2 amp load on the two hots. I expected to see something less than 2 amps on the neutral but was surprised to see the full 3 amps. The hots are fed from opposite busses. Can anyone help me figure this one out?


Thanks,

Don
 
Sponsored Links
Sponsored Links
Joined
9 Dec 2013
Messages
5
Reaction score
0
Location
California
Country
United Kingdom
Then your clamp meter is wrong.

What loads are these?

Refrigerator at 1 amp and 3/8" drill motor at 2 amps. I was using a cheap off brand clamp on ammeter but it doesn't seem that would be the culprit here. I might have to increase load and test again.
 
Joined
18 Jul 2004
Messages
8,516
Reaction score
406
Location
Devon
Country
United Kingdom
You could run into odd readings at low loads, and also with inductive/capacitive loads too. Many cheapy clamp meters are no good at low currents. There are also harmonic currents to consider.
 
Joined
9 Dec 2013
Messages
5
Reaction score
0
Location
California
Country
United Kingdom
You could run into odd readings at low loads, and also with inductive/capacitive loads too. Many cheapy clamp meters are no good at low currents. There are also harmonic currents to consider.


After more thorough testing I am even more troubled.

Quick recap: My service 120/208, hot to hot is 208.

With an 8.5 amp toaster oven on one circuit and 11 amps on the other circuit which feeds the fridge (about 1 amp) and space heater (temp) my neutral current reads 19.2 amps. I'm using an Amprobe ACD-15 Pro clamp on ammeter. This condo has been wired with mostly MWBCs ever since it was built from what I can tell. Have the neutrals been overloaded the whole time?! I'd really like to get on the feed to my panel which is just a subpanel but I just don't have the room.



Thanks,

Don
 
Joined
9 Dec 2013
Messages
5
Reaction score
0
Location
California
Country
United Kingdom
I'm both embarrassed and happy to say that after further troubleshooting I discovered that the outlet we wired temp for testing was miswired and being fed by the wrong circuit. This led to all loads being on the same leg. I was a little lazy in my initial troubleshooting and made too many assumptions. One assumption was that there was a problem in the first place.

I think the initial problem I saw with the 3 amp neutral was simply due to low inductive loading along with meter creep.

Final Reads Ignoring Fridge (<1 amp) which is always on:

CKT 1 on 2 off - In=9.1A
CKT 1 off 2 on - In=11.9A
Both CKTs on - In=12.0A

Thanks for the replies.
 
Sponsored Links
Top