Friday, February 18, 2011

Electric Dryer Confusion


Submitted by: Nick Markowitz
Electrical Contractor

For many years all 240-volt Electric dryers were wired using a 3 wire 30-amp cord set.
2 hot wires and 1 combined neutral and ground wire that was originally started during WWII during the copper shortage.
Unless the dryer was being used in a mobile home in which case a 4-wire cord set was to be used. In the 1999 NEC code all dryers were to start using 4 wire cord sets in new electrical installations because modern dryers have many more 120 devices in them that requires using a separate ground wire instead of a combined ground neutral wire, and 3 wire sets were still allowed were only 3 wires had been run in older residences.
The problem was that most new dryers automatically come set up for 4 wire service.
So when you install a new dryer into the older 3 prongs set up you have to move a jumper wire so that the dryer is properly grounded.
But this is not happening and many electrocutions and fires can be traced directly back to dryers not being properly grounded.
Take the recent incident were one of my customers asked me to go to one of his employee’s apartment to correct a dryer plug, which had burned and melted.
First off the wrong 3-wire receptacle was installed for dryer use a 50 amp Range plug was installed instead of a 30 amp dryer plug. This instantly caused a problem as dryers are
Designed so only a30 amp plug wire properly attaches to the back of the dryer. So you end up with wires getting scraped and not properly attached. But
The immediate problem which caused the fire was the fact that who ever installed the dryer receptacle used over sized aluminum wire and did not tighten it properly and did not use the proper anti oxidant to prevent corrosion.
When the tenant went to use the dryer the loose connection caused the wiring to heat
And the receptacle caught fire. The breaker should have tripped when the hot-wire of the dryer made contact with the case of the dryer but did not because the tenant improperly hooked up the dryer. Which was wired for 4 wires use. He did not move the jumper to the correct position. There fore he had no ground. Luckily the smoke detector went off and damage was minimal.
When I asked him why he did not follow the wiring directions, which would have shown him the correct way to hook up the dryer. He told me the dryer was a floor model that had no instructions with it. Plus the salesman assured him that all he had to do was hook up the 3 wires. Needless to say I called the store and reamed the management for giving electrical advice when they had no business doing so. I also reminded the management that they were fully liable had there been serious damage for giving the bad advice and I also reminded them that Pa. Consumer Law requires that full instructions which come with an appliance must be given to a new appliance owner.
Although this 4 wire rule for dryers has been on the books since 1999 the correct way to install dryers is still not filtering down to all the handyman types and in store sales and stock persons as to how to correctly install the wiring .So do not worry you will never be out of work as a Firefighter.

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