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seacern 11-15-2010 03:43 PM

Dryer about burnt house down, why didn't breaker flip?
 
My house was built in 1997. The dryer has a three prong outlet with the "L" prong. I put a load of clothes in on Saturday night. Thank god in about five minutes I decided to have a beer before going to bed. Smoke was pouring out around the wall outlet. It appears that one leg (black) was loose and arcing. The heat had melted away a third of the receptacle, burnt the hot wire insulation back about 1.5 inches, and burnt around the blade on the dryer plug.

Why didn't the 30amp breaker trip?

Jim Port 11-15-2010 03:54 PM

Breakers trip due to too much current attempting to flow on the circuit. You had the rated current flowing thru a loose connection. The current did not increase from the normal operating levels.

A house as new as yours should have had a 4 wire receptacle installed.

seacern 11-15-2010 04:09 PM

I assume the fourth prong is the ground wire. The ground on this circuit is coiled in the back of the box. Should I buy a four prong replacement receptacle for the melted one and replace the wiring harness on the dryer. The dryer is only six months old.

What is the advantage of a four prong over a three prong?

a7ecorsair 11-15-2010 04:47 PM

Who installed the receptacle on the wall and who connnected the dryer?

Red Squirrel 11-15-2010 05:53 PM

Sounds like it may have been a defective plug or bad install.

An arc fault breaker (AFCI) would probably have tripped, but not a regular breaker. I don't know how well a dryer or any motorized appliance would work on an AFCI though.

SubSailor 11-15-2010 07:06 PM

Quote:

Originally Posted by Red Squirrel (Post 534879)
Sounds like it may have been a defective plug or bad install.

An arc fault breaker (AFCI) would probably have tripped, but not a regular breaker. I don't know how well a dryer or any motorized appliance would work on an AFCI though.


I wouldn't imagine anything motorized would work well on an AFCI since they generate arcs in the motor.

hardwareman 11-15-2010 09:05 PM

I've seen this a hundred times, dryers do not come with cords attached, it is up to the home owner or seller to put the cord on the appliance. whomever put your cord on did not tighten the screws on the receptacle block tight enough causing the cord and the wires to over heat and melt

seacern 11-15-2010 09:42 PM

Guys, there seems to be a little confusion.

The house was built in 1997. I bought the house in June, 2010. The wired receptacle for the dryer looks original to the home. It's in a utility/pantry area off the kitchen. Yes it has a three prong outlet with the top prong in the shape of an "L".

Lowes delivered the new dryer in June.

Yes, Lowes personal installed the correct wiring harness to match the three prong receptacle.

No, it doesn't look like Lowes did anything wrong. The arcing didn't occur where the wiring harness connected to the dryer.

The arcing happened inside the plastic duplex wall box where the 220v circuit attached to the three prong dryer receptacle.

I am assuming that the problem was arcing due to the black wire not being securely tightened.

Why did it happen now, after 13-years????

Who knows?

The house did sit empty for two years. It was a distress sale.

I found that a newly installed hot water heater had been wired faulty with an direct hot to ground connection. When I connected the pull-out disconnect, sparks flew and the main 200 amp service breaker flipped.
After rewiring the hot-water heater, everything worked fine.

The real estate agent had hired a "do-all" type guy to secure the home and do the minimum must be repaired items to sell the home.

Maybe the dryer plug was broken and the same "electrician" replaced the broken plug as wired the heater.

My, why didn't the breaker trip question has been answered.

How about the three versus four prong question. Should I replace the melted receptacle with a four prong. If so, why. What safety features does the ground wire offer. As I stated above, the ground wire is coiled in the back of the duplex box unused.

dmxtothemax 11-15-2010 09:42 PM

Because even at less than 30amps,
Electricity can cause high heat,
Lets say only 20amps was flowing,
30 x 120 = 3600w.
Just think what 3600 watts of heat can do,
And thats still well within the safey range of the breaker.

Quote:

Originally Posted by seacern (Post 534785)
My house was built in 1997. The dryer has a three prong outlet with the "L" prong. I put a load of clothes in on Saturday night. Thank god in about five minutes I decided to have a beer before going to bed. Smoke was pouring out around the wall outlet. It appears that one leg (black) was loose and arcing. The heat had melted away a third of the receptacle, burnt the hot wire insulation back about 1.5 inches, and burnt around the blade on the dryer plug.

Why didn't the 30amp breaker trip?


McSteve 11-15-2010 10:23 PM

As long as you need to replace the drier outlet anyway, and you have a ground wire available, you should use a four-prong outlet. You would then change the cord on the drier to a 4-prong cord, and remove the neutral-to-ground jumper on the drier.

It used to be common to wire driers using the neutral as an equipment ground, but it hasn't been legal in new construction for a while now.

The problem as I understand it is that the frame of the drier is connected to the neutral, which ordinarily should have a zero volt potential relative to ground. However, if the neutral connection to the drier breaks or comes loose, the current through the timer and motor will be trying to flow through any available path back to the panel. If you touch the frame of the drier, you can become that path and get shocked.

I believe there are other reasons as well, but that's just off the top of my head.

michaelcherr 11-16-2010 08:02 AM

Stated correctly above.
Use 4 prong it will help you never get shocked. Electricity takes path of least resistance haveing that ground wire ensures you are not that path.

Jim Port 11-16-2010 08:17 AM

Quote:

Originally Posted by michaelcherr (Post 535143)
. Electricity takes path of least resistance haveing that ground wire ensures you are not that path.

Electricity takes all paths to ground. The percentage varies based on the resistance of each path.


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