PICS! ->Low Voltage? Limited Voltage? I have no-idea!


Old 08-29-06, 06:59 PM
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Angry PICS! ->Low Voltage? Limited Voltage? I have no-idea!


My wife and I recently purchased a rancher built in 1952.
The electricity is pretty screwy and though I have some understanding of electricty, the switches in the house make no sense. The electrician described it as "low voltage" and said that many homes in my area for some reason are wired this way.

Anyhow, take a look at the pics below. The wires hanging out of the wall do not appear to work. Or carry any voltage when I try and test it with a neon pen. The wires are white w/black stripe, white w/ red stripe and all white.

Also, if I try to hook up any other type of switch besides these, they will not work. Any suggestions for where to buy similar switches?

Basically I am completely stumped with this wireing and any advice you could give me would be appreciated.

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Old 08-29-06, 07:45 PM
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Some where in your house is a master control panel. It contains a bunch of relays that turn the lights on and off. The relays actually switch the 120 volt power to the lights.

This panel, when you find it, may be the source of much of your problems. It could be hidden in many places including in the attic or a closet.
Old 08-29-06, 08:15 PM
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You can probably find these switches at local electrical supply houses. They are low voltage. And when you go to diagnose and think through all this, forget all you ever knew about alternating current, because they don't act the same way. As Joed said, all the switches do is signal a relay (located somewhere you wouldn't expect). After the signal is received by the relay, it switches the AC current to the proper light fixture.
Old 08-30-06, 06:52 AM
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Here is a picture of our panel and what I assume is the main relay.

Can you recommend any books or websites where I may research how this low voltage sytem works? I noticed in the wall, tucked behind one of the receptacles a little brown box about the size of a matchbook. Is this one of the relays? Does each switch have it's own relay?

Old 08-30-06, 09:41 AM
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I have also seen the relays installed into the knock outs on the octogon boxes for the ceiling fixtures. The relays were physically outside the box with only the nipple and wires inside. We worked on a house that was full of them. The problem could be either with the switches or in the relays. Replacement parts for this type of system can be hard to come by. Your best bet is to find a local electrician who does alot of work in the houses in the neighborhood (others with low voltage control). They should know all of the tricks and suppliers for the systems, because they are all probably installed similarly.

P.S. The picture of the "relay" is actually the low voltage transformer. My recollection is that the relays are roundish and a couple of inches long. The ones I saw had a box fitting on the wiring end to mount to a box knock out.

Last edited by scott e.; 08-30-06 at 09:44 AM. Reason: added P.S.
Old 08-30-06, 11:35 AM
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Dale Electric supply carries parts that are not exact replacements, but are compatible with your system.

The most common failure points are the relays which are, as Scott said, probably mounted on the junction boxes of the fixtures they control. In their day, these systems were state-of-the-art. Today they're just art.

Each switch will have 1 power wire (24 volts - although your transformer shows it supplies 30 which is probably within the tolerance of the relays) 1 "on" wire and 1 "off" wire. The relays will also have 3 low voltage connections - "on", "off", and negative power from the transformer, and 2 line voltage connections - 1 for 120v hot, and one that connects to the hot wire of the controlled light. Some of the switches and relays may have additional wires for pilot lights if pilot lights exist on the switches.

In the more complex systems, all the 120V and low voltage wiring was run to a central panel that contained the relays. Switches to control any light could be run from the central panel to any location via the equivalent of a thermostat wire. Really fun systems to de-bug when you have no idea what's supposed to control what.

And today we have X10 or INSTEON to do all of this.

Doug M.
Old 08-30-06, 11:38 AM
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Originally Posted by ewheatley

Can you recommend any books or websites where I may research how this low voltage sytem works?
I have Richter & Schwan's _Wiring Simplified_ 38th ed.

Chapter 13 has a few pages on low voltage control systems including a couple of line drawings and diagrams. This book is fairly cheap and often available at the big boxes. Check your library too. Check the index for "Low voltage wiring" before you buy it.

Also Ray Mullin's _Electrical Wiring Residential_ 13th Ed., Unit 27, has some good diagrams and text on pages 470-478. It's a more expensive book but better than Richter and may be in your library. They credit "GE Total Lighting Control" for photos of switches similar to your photos.

For troubleshooting you will need a volt-ohmmeter available at Sears, big boxes, and many other places. Spend $10-30 for a basic digital meter. I would also recommend a probe such as the Fluke 1AC for 90+ VAC or the 1LAC for 20 to 90 VAC. Check your control voltage first to see what you need or see if somebody makes one unit that covers a wider range.

The switches you mentioned, I would have to guess, are SPDT NO that send the center-terminal control voltage one way or the other to latch the relay ON or OFF. You'll have to check your relays to see if they are working properly.

If these are common in your area, I would think hardware stores or even big boxes might carry them. If that does not pan out and you are anywhere near a wholesaler such as Graybar, take your bad parts in to the city desk and see if they stock or can order replacements. Graybar will not sell retail but they will sell to non-account holders on cash terms, so the difference is more or less semantics.
Old 08-30-06, 01:01 PM
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low voltage control system

This system sounds like the one provided by GE, i.e., if the relays are inserted into the various lamp junction boxes. Then what is necessary is a 24v control xfmr, and off/on SPDT (rocker) switches (2 wires + the common) with matching cover plates. Switches with pilot lamps are available, having an added connection for same. The relays are latching types which are --pulsed-- on/off and require no steady-state current to maintain the position. They work on AC current, no rectifier is required.

Some installations use a control panel with an added rotary selector that singles out a location controlled by a common, single rocker switch. The basic hookup:

24v. sw 24v relay coils
---120v in----XFMR---24v out---o/ o---2wires--ooo-----/o*
*The relay contacts inside the part pressed into the box pass/block the 120vac out to the lamp, etc., isolating the 24v from the 120v.
Old 08-30-06, 03:45 PM
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Assuming reasonable access such as an attic above the ceiling boxes I wonder if the OP might be better off just replacing them with regular 120 volt switch loops and standard switches? Certainly probably less costly and easier to repair if there are future problems.

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