GFCI tripping when cordless rings

Status
Not open for further replies.

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Well haven't had to many problems with GFCI's for some time but got a call the other day that customer plugged in a new cordless phone/answer machine into one of the GFCI's in the kitchen and when it rang tripped the GFCI.

I have read about ham radios, etc that when transmitting can cause the trip but are there any small cube style EMI/RFI plug in filters that would solve the problem? My search doesn't yield many results.

Any other thoughts?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150215-0943 EST

Try putting an isolation transformer between the GFCI and the cordless AC power input. A small control transformer can be tried.
See http://www.alliedelec.com/catalog/pf.aspx?fn=1006.pdf P-6412 is a 35 VA unit at about $30. P-6406 is 50 VA with an electrostatic shield.

The Bell Telephone ring signal from an ordinary circuit is AC and probably somewhat over 100 V. I suspect that there is some input or coupling circuit inside the cordlees that in some fashion couples some of that ring signal into one of the AC input wires.

An experiment with an isolation transformer is a way to help identify the cause.

.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
I could try that, but I'm sure the customer is not going to want to see some honky transformer with cords hanging around.
I'm surprised that with issues like this someone doesn't have a listed product (or is there? share if you know any.) for such use such as a small cube style plug in like some surge arresters that wouldn't look to bad.
Are the specifics just to wide spread for a single product to achieve attenuation of RF interfering with GFCI's?
 

sparkyrick

Senior Member
Location
Appleton, Wi
Well haven't had to many problems with GFCI's for some time but got a call the other day that customer plugged in a new cordless phone/answer machine into one of the GFCI's in the kitchen and when it rang tripped the GFCI.

I have read about ham radios, etc that when transmitting can cause the trip but are there any small cube style EMI/RFI plug in filters that would solve the problem? My search doesn't yield many results.

Any other thoughts?

Try plugging into the same GFCI with an extension cord and move the phone away from the receptacle and see if it stops tripping. Perhaps the radio signal from the phone in close proximity to the GFCI is causing it to trip
dunno.gif
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150215-1155 EST

mopwr:

I did not suggest an isolation transformer as the ultimate solution. I don't believe you have an RFI problem, but rather I suspect an unbalanced current into the AC wire pair to the cordless phone when the ring signal is present. Thus, I expect the GFCI is doing its intended job.

My solution would be to use a non-GFCI source.

.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
I told the homeowner to try that yesterday and report back if it corrects the problem.
Athough still looking for a nice little listed solution for this delemna. Because I'm sure he wants to keep the phone base plugged in at that location. Of course they could try a different phone still a crappy thing to tell someone.
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
150215-1155 EST

mopwr:

I did not suggest an isolation transformer as the ultimate solution. I don't believe you have an RFI problem, but rather I suspect an unbalanced current into the AC wire pair to the cordless phone when the ring signal is present. Thus, I expect the GFCI is doing its intended job.

My solution would be to use a non-GFCI source.

.

All cordless phones run on low voltage supplied from a small class 2 "wall wart" transformer. I can't see how anything inside the phone base could cause and imbalance as far as the GFCI is concerned. You could short the secondary conductors together or connect them to ground and the GFCI is not going to care.

I'm thinking maybe they have some cheap Chinese designed GFCI's and they are reacting to RFI from the phone.
 

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Many wall wart supplies do not have an internal transformer. Phone ring signal is up to 90V, 20 Hz. Easy to visualize how 5 mA could couple onto the white wire, which would trip a GFCI. 5 mA = 90/18kohms; numerous possibilities, such as degraded MOV from past lightning strikes with a high MOV leakage current, etc. Hard to know without the exact phone circuit diagram.
 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Not quite apples to oranges but a few months ago we bought new phones for home. Landline. One base with three cordless. The old base has always been next to the kitchen counter top TV. New one needed to be moved to the basement because the TV would lose reception when the wart was plugged in. Antenna not cable. I suspect the mfg process is not up to snuff even if it is brand name. Junk.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Not quite apples to oranges but a few months ago we bought new phones for home. Landline. One base with three cordless. The old base has always been next to the kitchen counter top TV. New one needed to be moved to the basement because the TV would lose reception when the wart was plugged in. Antenna not cable. I suspect the mfg process is not up to snuff even if it is brand name. Junk.

I have to agree with you!
Look at some LED lights when turned ON knock out radio stations. Some claim to be FCC compliant but seem to be hard pressed to not interfere with things.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Many wall wart supplies do not have an internal transformer. Phone ring signal is up to 90V, 20 Hz. Easy to visualize how 5 mA could couple onto the white wire, which would trip a GFCI. 5 mA = 90/18kohms; numerous possibilities, such as degraded MOV from past lightning strikes with a high MOV leakage current, etc. Hard to know without the exact phone circuit diagram.

My thoughts of the MOV being degraded had entered my mind. Don't know if one would call a Leviton GFCI a Chinese piece of junk.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150215-2949 EST

mopowr:

The Leviton GFCIs I have tested and analyzed are quite immune to false triggering. However, their board layout could be improved. This change, shortening a trace to the SCR gate, might reduce a type of false triggering I could produce from turning off an inductive load. It was not easy to generate the false triggering.

To trip the GFCI it is necessary to trigger the small SCR that energizes the trip coil.

.
 

GrayHair

Senior Member
Location
Nashville, TN
Swithing power supplies

Swithing power supplies

Not quite apples to oranges but a few months ago we bought new phones for home. Landline. One base with three cordless. The old base has always been next to the kitchen counter top TV. New one needed to be moved to the basement because the TV would lose reception when the wart was plugged in. Antenna not cable. I suspect the mfg process is not up to snuff even if it is brand name. Junk.

I also use an antenna and have problems with switching power supplies causing pixelation and lock-up; this didn't happen with my old HD TV. Switching power supplies seem inherently "noisy", some wiping out certain ham bands.

With no load on my laptop power supply, there is no interference. But when my laptop is charging, the TV locks-up. This only happens on high-VHF channels (6 thru 13); UHF channels (14 and up) are not effected. There is a low-VHF translator in this market but I don't receive it.

Regards!
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I also use an antenna and have problems with switching power supplies causing pixelation and lock-up; this didn't happen with my old HD TV. Switching power supplies seem inherently "noisy", some wiping out certain ham bands.

With no load on my laptop power supply, there is no interference. But when my laptop is charging, the TV locks-up. This only happens on high-VHF channels (6 thru 13); UHF channels (14 and up) are not effected. There is a low-VHF translator in this market but I don't receive it.

Regards!
Remember that with digital TV broadcasting the channel number is no longer related to the actual broadcast frequency. In many cases the conversion took a low or high VHF numbered station and moved its frequency into the UHF spectrum.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
150215-2949 EST

mopowr:

The Leviton GFCIs I have tested and analyzed are quite immune to false triggering. However, their board layout could be improved. This change, shortening a trace to the SCR gate, might reduce a type of false triggering I could produce from turning off an inductive load. It was not easy to generate the false triggering.

To trip the GFCI it is necessary to trigger the small SCR that energizes the trip coil.

.

Thanks for the insight!
Customer told me today it happened when he called his land line from his cell phone in the same room. So now I wonder if it's related to the base unit or the cell phone? Maybe I'll just change the GFCI to another brand if it continues to be an issue.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150216-2133 EST

mopowr:

I doubt the cellphone has anything to do with the problem.

Leave the cordless base unit in its present position, but run an extension to the base unit from some other outlet that is not connected to the load terminals on the problem GFCI. Then run the cellphone experiment.

Next take the base unit to a different GFCI outlet and plug into that outlet. Rather than move the base unit use the extension cord to connect to the different GFCI. I expect that different GFCI to trip on the ring signal.

.
 

GrayHair

Senior Member
Location
Nashville, TN
Channel moves for DTV

Channel moves for DTV

Remember that with digital TV broadcasting the channel number is no longer related to the actual broadcast frequency. In many cases the conversion took a low or high VHF numbered station and moved its frequency into the UHF spectrum.

Oh I'm very familiar with ATSC's virtual channel versus actual RF channel. The interference I described only happens on 2 channels and both are high-VHF; no issues on UHF. Initially, one local VHF station went UHF, one stayed high-VHF, one moved from low-VHF to high-VHF and one stayed low-VHF. The rest were already UHF. The station that stayed low-VHF later moved to UHF due to reception problems.

Regards!
 

electricalist

Senior Member
Location
dallas tx
For sure i would plug it into a different gfci and test it then i would try to figure out how the gfci is sharing a neutral with an oposing phase... Disconnect the load side.
 
Status
Not open for further replies.
Top