Clothes Dryer Hose issue

[William Merritt]

I am a retired inspector. I reached an age where is was not safe to go on roofs, attics and in crawl spaces. However, I still enjoy keeping up with what is going on in the inspection world. I had a strange thing happen the other day as I was cleaning our clothes dryer vent. The flexible vent hose (one that is approved for electrical and gas dryers) was connected to the wall unit that exits to the outside through a poured concrete wall. As I was about to attach the vent hose to the back of the dryer I touched the dryer case with the spring steel wire in the vent hose and got an electrical arc. A breaker didn't trip. The dryer was plugged in so I unplugged it, finished the connection and plugged the dryer back in with some reluctance. Anyone want to tell me what was or is going on? Thanks, WHM

[Jerry Peck]

The flexible vent hose (one that is approved for electrical and gas dryers) ...
.
As I was about to attach the vent hose to the back of the dryer I touched the dryer case with the spring steel wire in the vent hose and got an electrical arc.

First, what you are describing sounds like one of those white (or gray) plastic dryer vent connectors with the steel spring wire in it ... and those are not approved for use on any clothes dryer.

Second, does your clothes dryer have a 3-prong (3-wire) or 4-prong (4-wire) cord/plug/wiring?

If 3-prong, then the cabinet of the clothes dryer is carrying neutral current and fault current through the neutral conductor as there is no true grounding conductor - and it sounds like you have some neutral/fault current which should not be there (the 240 volt clothes dryer is likely all 240 volts, including the timer, which means there should not be any neutral current - unless there was a fault somewhere).

That little arc will not trip the breaker, could kill you, but not trip the breaker - which is why the newer (from 1993 or 1996 I think it was) wiring was 4-wire.

Oh, also, most of the dryers wired with 3-wire circuits should not have been allowed to have been wired that way as that exception which allowed that was a very narrow exception which only allowed 3-wire circuits when the circuit originated at the service equipment, not from a downstream panel (even though many areas allowed 3-wire circuits for them for many decades from panels which were not service equipment).

[Billy Stephens]

I am a retired inspector. I reached an age where is was not safe to go on roofs, attics and in crawl spaces. However, I still enjoy keeping up with what is going on in the inspection world. I had a strange thing happen the other day as I was cleaning our clothes dryer vent. The flexible vent hose (one that is approved for electrical and gas dryers) was connected to the wall unit that exits to the outside through a poured concrete wall. As I was about to attach the vent hose to the back of the dryer I touched the dryer case with the spring steel wire in the vent hose and got an electrical arc. A breaker didn't trip. The dryer was plugged in so I unplugged it, finished the connection and plugged the dryer back in with some reluctance. Anyone want to tell me what was or is going on? Thanks, WHM

Unplug the 240 Volt Appliance and Do Not Use! Call the appliance Repairman for Repair / Replacement.
*aka Hot wire in contact with metal housing.

[John Kogel]

Jerry is correct, if the wiring is old 3-wire, it should be upgraded. Have an electrician check it out if you can't get in there yourself.

The spark could have simply been a static charge caused by dry air and friction. But it is indicating that the cabinet is not properly grounded, and was only grounded when you touched it with the wire.

If the wiring is 4-wire, have the connections at the wall outlet checked. #8 wire is stiff and can pop out of the receptacle if a screw is loose in there.

The breaker needs to see current over 30 amps before it will snap off. Your spark was probably less than that, but ... I believe as little as 1/10th of an amp is enough to stop your heart. Have it fixed ASAP.

[William Merritt]

First, what you are describing sounds like one of those white (or gray) plastic dryer vent connectors with the steel spring wire in it ... and those are not approved for use on any clothes dryer.

Second, does your clothes dryer have a 3-prong (3-wire) or 4-prong (4-wire) cord/plug/wiring?

If 3-prong, then the cabinet of the clothes dryer is carrying neutral current and fault current through the neutral conductor as there is no true grounding conductor - and it sounds like you have some neutral/fault current which should not be there (the 240 volt clothes dryer is likely all 240 volts, including the timer, which means there should not be any neutral current - unless there was a fault somewhere).

That little arc will not trip the breaker, could kill you, but not trip the breaker - which is why the newer (from 1993 or 1996 I think it was) wiring was 4-wire.

Oh, also, most of the dryers wired with 3-wire circuits should not have been allowed to have been wired that way as that exception which allowed that was a very narrow exception which only allowed 3-wire circuits when the circuit originated at the service equipment, not from a downstream panel (even though many areas allowed 3-wire circuits for them for many decades from panels which were not service equipment).
This is a 4-wire hook up and the vent is the aluminum foil looking flex tubing. To futher confuse things I put a VOM on it and the dryer case is grounded. Now I am really confused

[John Kogel]

William, how long is the dryer vent hose? Is it possible a static charge had built up on the hose?
You see, I was wondering how the hose connection to the concrete wall was providing a good enough ground, although it could if rebar in the concrete was in contact or if some other factor. From what you say, the spark appears to have jumped from the hose to the grounded dryer cabinet. At least that is a possibility.

[Billy Stephens]

This is a 4-wire hook up and the vent is the aluminum foil looking flex tubing. To futher confuse things I put a VOM on it and the dryer case is grounded. Now I am really confused

Unplug the appliance and call the repairman.

[Jerry Peck]

This is a 4-wire hook up ...

If this is a newly installed clothes dryer, check to make sure the bonding jumper has not been installed between the neutral terminal and ground.

Check the wiring in the dryer receptacle with the dryer unplugged, do you have 240 volts and 120 volts between the correct receptacle slots?


... and the vent is the aluminum foil looking flex tubing.

Not allowed by most manufacturers either as it is a mylar type of plastic with that aluminum coating on it. Still is a fire hazard as it is really no difference than the white plastic ones.


To futher confuse things I put a VOM on it and the dryer case is grounded.

Was that with the dryer vent connector connected or not connected? Check it with that dryer vent connector removed (you will want to remove and replace that mylar stuff with either rigid metal or flexible metal connector any way, so removing it to make this check gets you half way there. :)

[Mike Borchardt]

Unplug the dryer, disconnect the dryer vent hose, connect your VOM between the dryer vent and the vent connection to the outdoors, plug the dryer in and take note of any voltage on the VOM. This may verify if it was static discharge or an actual wiring issue. :o

[michael Rodney]

I am a little confused also.

I presume the dryer is in regular use....that is why it was necessary to clean the vent. So if a hot wire was in contact with the metal chassis of the dryer, why did not some one get a shock at some point? After all, the dryer is being used.

Next could it be static electricity? May be I guess. Not sure how big the spark was though.

You said the chassis grounded, confirmed by a VOM test. If it is grounded and on a 4 wire circuit, then maybe it is static.

In either event and to be safe, have it checked by a repair guy. Make sure he understand what the problem you are reporting.

[William Merritt]

Unplug the dryer, disconnect the dryer vent hose, connect your VOM between the dryer vent and the vent connection to the outdoors, plug the dryer in and take note of any voltage on the VOM. This may verify if it was static discharge or an actual wiring issue. :o
Thanks for the suggestion! Will do.