- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
This is a story of what not to do and why....
I had installed 4 recessed cans by adding them to 2 existing cans in the kitchen. Sounds easy enough.... When I got home that evening I got a call from my customer who said the EMF's in her kitchen were above .6 milGauss (I think).
My first question was a dumb one because when I asked how she knew this she said she had a Gauss meter. Of course, who doesn't. Born with a brain smaller than my mouth I barely knew what a gauss meter was.
Apparently after much conversation I learned that the reading was at .2 ( a tolerable level) but shot up to .6 when I added the 4 cans. As I unscrewed each bulb the EMF's would simultaneously drop. Unfortunately, I had no idea what causes EMF's. I did some research and found out there are basically three areas in the wiring that could lead to high levels of EMF. Of course, microwaves, etc have emf's but you have to get close to read them. We were reading the emf's at table height from the lights in the ceiling. I will state the reason I know.
1) If the neutral and ground come in contact after the load,
2) If two circuits enter a multiganged switch box and the neutrals are tied together (we all have done that at some point in our lives) and,
3) the neutral running separately from the load.
My Discovery
I quickly checked the cans I installed and the existing ones to make sure there was no connection between neutrals and ground. There weren't --so I ruled out #1.
There were two multiganged boxes in the kitchen with 3 way switches and some single poles. There was only one circuit feeding both multigang boxes in the kitchen. So- #2 was ruled out.
Then I noticed that the previous electrician (20 years earlier) had run a two wire cable between the 3 way switches as travelers. The 3 ways were feed from one box and switched from the other. The neutral was picked up in the second box from the other feed (same circuit). On a whim I disconnected the travelers and hook the switch as a single pole and the emf's dropped to zero. Since the neutral was traveling a different path (through the second feed cable) it created the emf's.
The easy fix since my customer never used the other 3 way was to keep it disconnected. I almost felt smart after that one.:smile:
I had installed 4 recessed cans by adding them to 2 existing cans in the kitchen. Sounds easy enough.... When I got home that evening I got a call from my customer who said the EMF's in her kitchen were above .6 milGauss (I think).
My first question was a dumb one because when I asked how she knew this she said she had a Gauss meter. Of course, who doesn't. Born with a brain smaller than my mouth I barely knew what a gauss meter was. Apparently after much conversation I learned that the reading was at .2 ( a tolerable level) but shot up to .6 when I added the 4 cans. As I unscrewed each bulb the EMF's would simultaneously drop. Unfortunately, I had no idea what causes EMF's. I did some research and found out there are basically three areas in the wiring that could lead to high levels of EMF. Of course, microwaves, etc have emf's but you have to get close to read them. We were reading the emf's at table height from the lights in the ceiling. I will state the reason I know.
1) If the neutral and ground come in contact after the load,
2) If two circuits enter a multiganged switch box and the neutrals are tied together (we all have done that at some point in our lives) and,
3) the neutral running separately from the load.
My Discovery
I quickly checked the cans I installed and the existing ones to make sure there was no connection between neutrals and ground. There weren't --so I ruled out #1.
There were two multiganged boxes in the kitchen with 3 way switches and some single poles. There was only one circuit feeding both multigang boxes in the kitchen. So- #2 was ruled out.
Then I noticed that the previous electrician (20 years earlier) had run a two wire cable between the 3 way switches as travelers. The 3 ways were feed from one box and switched from the other. The neutral was picked up in the second box from the other feed (same circuit). On a whim I disconnected the travelers and hook the switch as a single pole and the emf's dropped to zero. Since the neutral was traveling a different path (through the second feed cable) it created the emf's.
The easy fix since my customer never used the other 3 way was to keep it disconnected. I almost felt smart after that one.:smile:
