Switchable Oulet

[Gregory C. Scheer, Jr.]

Today I inspected a home. Most rooms had a switchable outlet (outlet mounted upside down). In the three bedrooms the switchable outlet had 120 VAC on the top plug and only 98-99VAC on the switchable outlet. The others in the home were fine; on when on, and off when off. I'm thinking there's a wiring problem. Have you seen this? One last commonality--the bedroom's switchable is on a slider-rheostat type of wall switch.

[Marc D. Shunk]

Switched receptacles are prohibited from being served by dimmers. That's your problem.

[Gregory C. Scheer, Jr.]

I didn't know that. Thanks. Even so, could it be the wiring of the dimmer that is allowing the lower voltage?

[Paul W. Abernathy]

Probably the reduction in the dimmer....depending on the setting. As Mark stated...Dimmers on receptacles is a no-no.....

[Gregory C. Scheer, Jr.]

Thanks Paul. I found this by checking with my plug. I noticed that the lights were on regarless of the push-to-turn-on switch position. The dimmer is located on the upper portion of the switch. The outlet plug has constant voltage. Thanks for all the info! I'm guessing who ever wired the switches probably mixed up the fan light switch with this one--in all three bedrooms.

[Mark Nahrgang]

Originally Posted by Marc D. Shunk

Switched receptacles are prohibited from being served by dimmers. That's your problem.

I didn't know that either... Thanks Marc!

Can you educate us some more as to the reasoning's behind that? Is it some sort of safety concern? Or what?

[Paul W. Abernathy]

Origionally I believe it was the problems it caused to the vacuum cleaner industry and their motors. But I am sure Marc will elaborate.

It is also a concern since most dimmers have a specific wattage rating it will allow....and without knowing what could be plugged into it.....you could exceed the rating of the dimmer which will heat up and potentially cause a fire among the largest concern.

[Mark Thorman]

Is it a code thing.

[Jim Port]

Yes, the Code has a prohibition against receptacles being controled by dimmers.

If you think about the reduced voltage on a receptacle it would be similar to starting a manual transmission car off in 3rd instead or 1st gear.

[Mark Nahrgang]

Originally Posted by mnahrgang

I didn't know that either... Thanks Marc!

Can you educate us some more as to the reasoning's behind that? Is it some sort of safety concern? Or what?

Siting code isn't particularly helpful in a home inspection situation. We are not code inspectors, and as soon as we site code on one defect, we are liable for all other code violations that we might not be aware of.

The reasoning behind why the outlet is unsafe with a dimmer is useful.

Can someone explain the why behind it?

Thanks

[Michael Larson]

Most household motors and appliances are designed to start and run at full voltage and either will not start or damage the power supply if full voltage is not available.

This is also true of fluorescent bulbs including CFLs

Resistive loads like tungsten bulbs would have no problem.

[Paul W. Abernathy]

hmmm...I did explain why....guess no one reads my posts anymore....lol....no problem...

[Michael Larson]

Originally Posted by pabernathy

hmmm...I did explain why....guess no one reads my posts anymore....lol....no problem...

Oops, must have missed.
Guess that means I did't read your8 post Paul.

[Paul W. Abernathy]

thats ok fella.....my posts are crap anyway....Ask Marc...lol

[Marc D. Shunk]

Not everything that a person might purposely or accidentally plug in to a switched receptacle will react well to a dimmer. The results can be undesirable, often ruining certain equipment. Motors, in particular, can overheat and fail when run through a dimmer. A television set might just "die". The dimmer itself can fail when serving certain loads. It doesn't really matter what a person promises they will do with that outlet. There's a host of good and required reasons to not serve a switched receptacle by a dimmer.