Plugging into the electric dryer outlet
It's been a while since I last asked a question on this forum & I did try to see if the topic had been covered through lots of searches, but nothing turned up. As electric cars gain in popularity, ...
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theoldwizard1 wrote:RoyB wrote:No~Shock~Zone
Here is a neat photo marked up to shows the comparison...
Learn something new every day ! Well, in this case, something OLD ! I never knew there were 2 different versions ! Both of those plugs/outlets are "deprecated" and have not been used in new construction in several years.
Those are not both dryer outlets. The one on the left is a standard 30A RV outlet (NEMA TT-30), used exclusively for RVs. The one on the right is the old standard dryer outlet (NEMA 10-30) where the neutral serves as the chassis ground. The neutral wire for it should be full-sized, the same as the two hot wires. The 10-50 connection is an old standard for electric ranges that similarly has a neutral but no separate safety ground. Both of these are not permitted in new construction, but are not at all uncommon in existing houses...including DrewE's house.
The adapter for an RV (or whatever) would simply bridge the neutral connection to both the neutral and ground positions on the 50A connection (a NEMA 14-50). It would function fine, though of course the current on either leg would be limited to 30A by the 30A circuit feeding the dryer outlet. Should the neutral line fail, the chassis of the RV (or dryer) would not grounded and would float to potentially dangerous voltages depending on the relative loading of the two legs. You'd also have the usual wild voltages due to imbalances that you typically get with a broken neutral on a 120/240V circuit, so it would be a bad day all around.
The dryer outlet should also not be confused with a NEMA 6-30 (which looks quite different, with two horizontal blades lined up with each other and a U-shaped ground pin) which is a "pure" 240V plus safety ground connection that has no neutral. It is used for things like large air conditioners and 240V power tools. I think there under some circumstances the safety ground is permitted to be undersized as it is not normally a current carrying conductor.
