Installing Autotransformers (aka variacs)

[lunatic]

Okay... we tried the cheap dimmers from Home Cheapo. DON'T DO IT! Alright, now that's outta the way we can move on

I have a couple Staco variacs arriving today and I get how to wire them but my question is this, How do you incorporate an variac into a 3-way switching system?

The live room is switched form two locations using a 3 way switch. I know I could put the variac *before* the switches but this would mean the variac is receiving voltage 100% of the time. Is this a bad thing?

The only other option I see is a switch before the variac and then then the 3 way switches after the variac.

Also, any tips on installing variacs? My thought was a metal box, grounded of course, just above the box with the 3 way switches. Another tidbit of information that may help is that all my outlet and switcfh boxes are metal and all of them are surface mounted.

Thanks!
-Brad

[Aaronw]

Hello Brad,

I seem to remember this exact question a few years ago, before I moderated this thread.

If I remember correctly, there is not a way to use a typical variac in a 3 way switch configuration, without going to a controlled lighting type of system (switches run on low voltage, going back to a central unit which controls the high voltage).

Steve might know what it is or where the link is.

I'm still kind of in a brain fart right now with loosing my dad 2 weeks ago.

You might do a search on 3 way lighting. I'm sure it'll pop up. It'll be an older thread.

[lunatic]

Aaron,

Thanks for the response. I'll search around. Sorry to hear about your Dad. Our thoughts go out to you and yours...

Peace,
Brad

[lunatic]

Okay, there *is* a way to use a variac is a 3-way system. If you have this setup:

AC --> 3-way switch --> 3-way switch --> light fixture

You can put the variac like this:

AC --> 3-way switch --> 3-way switch --> variac --> light fixture

In my setup, however, this places the variac on the other side of the room which isn't the 'natural' entrace to the live room. For it to make sense in our live room I would have to do this:

AC --> variac --> 3-way switch --> 3-way switch --> light fixture

This means that the variac will have voltage supplied to it all the time. Is this bad?

-Brad

[Aaronw]

This means that the variac will have voltage supplied to it all the time. Is this bad?

No. That's how mine are wired. In my setup, there is a home run from the panel, to the variac, to the light. No switches.

[lunatic]

Excellent! Imma go war dis thang up!

WOO-HOO!

::darts off::

[lunatic]

Just wanted to update everyone... we wired up a 5amp Staco 501c for the live room (8, 65 wtt light bulbs = 520 watts) and then put a Staco 171 (1.75amp) on each booth. You can get literature here, http://www.stacoenergy.com/variable_tra ... el%20Mount , for the Staco line of panel mount 'variacs.'

The 501c is BIG. It required a 6x6x4 metal pullbox which we found at Home Cheapo. The 171 can mount in a 4 square DEEP box but we had to be very careful where we put our connectors.

You see, the 171 will fit in a 4 square box. However, if you position the 171 right in the middle of a 4 square blank plate with the connection terminals 'up' then you have the potential to have those terminals hitting the connector that takes wire into or out of your box. If you had a connector in the back of your box then you could forget putting a 171 into a 4 square deep box!

Aaron, what would the next size box be after a 4 square deep... a masonry box? Can't you get those pretty deep in size?

-Brad

[Aaronw]

Here's an example of what I used. It's a 6x6x4 box.

[lunatic]

Yes that is exactly we used for our 501c. For the 171 that box would be WAY too big. There has to be something the next size up from a 4 square deep that isn't a 6x6x4.

-Brad

[Aaronw]

What size are you looking for? or need?

[lunatic]

My 171s are already installed in the 4 square deeps but it was a little close. There is room in there but it just seems that they would make a box between a 4x4 and a 6x6x4. That's all.

So, I guess I don't *need* anything I'm just having a conversation for conversation's sake (and for future people looking to install these).

-Brad

[Aaronw]

Is it the width and height that's too tight, or is depth an issue?

They might make a 5", but it's probably an uncommon size if they do.

[lunatic]

The height and width are alright as long as you plan out your connectors and do NOT mount the 171 dead center on the blank panel. You need to mount it lower than center if you want the termials up. You can mount it with the terminals down but you have to pay attention to how you want your lights to dim.

With the termials up the voltage increase is clockwise from lower left to lower right. Because we installed our 171s dead center on the plate and had connectors in the center KO at the top of the box, we have to mount our 171 with the termials DOWN. This made the voltage increase still be clockwise but from upper right, about 2 o'clock, to upper left, about 10 o'clock.

Not a huge issue really since the dial clearly labels where you are 'at' in voltage strength. It is a little annoying I guess because the numbers are upside down

I guess I could buy 2 new blank plates and remount them lower on the plate. Nah... it's probably fine like it is and I am being waaaaaay too picky

-Brad

[Aaronw]

Is the shaft for the knob notched, or is it completely round? If it's round, and the knob has a set screw, you can put it wherever you want.

[lunatic]

The shaft is completely round and has threads at the bottom (that go around the shaft and do not imprde the shaft movement). This model is small enough that you simply mount it to the panel via the threads at the bottom of the shaft. They supply the lockwasher and nut for you.

I'll live with it for now. If it gets to me I can remount in new panels pretty easily.

Here is a link to the PDF for the 171, http://www.stacoenergy.com/PDF_Files/Dr ... DF/171.pdf