Low Voltage Switching

When we first purchased our home, I was intrigued with the odd looking wall switches.  They were momentary rocker switches, so I surmised that they were operating relays via low voltage.  When an electrician was in to do some work, he volunteered some sketchy information about the odd switches, and something about how “that system”  represented guaranteed employment for his profession.   I sought further information and found this article in Better Homes & Gardens Decorating Book, 1961 edition, which explains how it looked forty years ago:

Low voltage switching adds convenience to your home.  An outstanding advance in electrical systems is low-voltage switching.  You may have heard of it as “remote control,” “l-v” (for low voltage), or “multi-control switching.” 

Some folks have added a little confusion by calling this system low-voltage “wiring” instead of switching.  True, it uses low-voltage “door bell” wire leading from switches.  But all the lights and outlets still feed from the usual 115-volt current. 

How does it work?  You can compare low-voltage switching with your automobile’s electrical system. When you press a car’s starter, you’re not working directly with the strong surge of electricity needed to operate the starter motor.  A spark of current travels from dashboard to a magnetic relay.  This commands the battery’s full punch to start the engine. 

In a house, you press a touch-plate switch and a small (24-volt) flash of current notifies a relay (grouped near service entrance, or, in some systems, right at the fixture).  A magnetic switch then opens, and the full 115-volt current is sent to do whatever task you have in mind. 

Simple as that!  But why is this better than the standard method of switching?  The one where a wall switch operates as a gate through which the actual current flows? 

With low-voltage switching, a dangerous shock at the switching point is no longer possible.  This means low-voltage switching is a natural for outdoor use, the laundry, kitchen, workshop, or other areas where the shock’s more of a potential hazard. 

The smaller current load allows much smaller wire than in a conventional system. This wire is easy to drag through a wall;  it requires no rigid conduit or bulky bindings and insulators.  

What’s the biggest feature?  The thing that makes this system so popular in today’s sprawled out “ranch style” houses is its remote and multi-control characteristics. To control one light from two points, conventionally, you have to double heavy, expensive 115-volt wire running between the switches.  To add a third control gets costly and complicated. Remote control over a great distance shoots cost up in a hurry when you’re stringing out doubled Number-12 wire, plus conduit. 

With low-voltage switching—where one magnetic relay works the light—it’s no trick to have a third or fourth control to every one of the lights.  And with the cost of low-voltage wire and switches less, there’s no reason why you can’t enjoy complete mastery of your home’s lighting.  This means an end to groping into a dark room looking for a switch. 

Costs of low-voltage or a conventional system are about the same in a small house—or in a house over 2,000 square feet (where long halls and large rooms necessitate multi-switching). Costs for low-voltage switching in a medium size house are slightly more than for conventional.

Well okay then.  Flip forward forty years.  Most of the frequently used switches in our house have been replaced over time—for good reason.  Those aforementioned inexpensive wall switches were not only inexpensive, they were cheap.  The style in this house have a switch button that tends to get hung up under the mounting plate, and sit so low relative to the cover plate that the button has to be pushed way below the surface of the cover plate. Aside from that, they have to be pressed down and held for a moment while the relay actuates.  And some are just plain temperamental and need to be pressed a few times to work, which I suppose is more a sign of a failing relay .  Speaking of which... in this house they are distributed, not nicely ganged at a central control panel.  In a distributed system, the relay is located in each individual electrical box, so often a little difficult to get to.  Replacement parts are available though may take extensive hunting around.

Things have changed.  GFI receptacles have solved the wet/exposed area safety issue, and in fact are now required by code.  Two- and three- way switches are commonplace.   Unlike many of the historical and occasionally quaint features of our vintage homes, L-V switching retains no charm.  No tough choices here when it comes to upgrading electrical devices.  Make mine Leviton Decora.     

A  One style of L-V wall switch. The control is a momentary rocker.  Press one side and the relay is activated to turn a light one; press the other side and the relay shuts the light off.   The cover plate is made of fragile styrene, with a gold –printed paper panel pressed in from the back side.   

B  The bare switch component on its mounting bracket, front and back C.  Note the small gauge doorbell wire. 

D  Another style wall switch that has a huge rocker switch for its entire face. These probably operated a lot better, and certainly looked neater.  Made of phenolic, so they are very stable and durable.  They even look something like today’s Decora style switches. 

E  The relay that actually does the switching.  Signal from the wall switch comes in on the small gauge wires; line voltage goes to the light on the large gauge wires.  

F  Typical assembly of a relay in an electrical box; in this case, a ceiling light fixture.  Here, replacing a failed relay would not be so difficult as it could be fished out through the device side of the box.

G  These are Touch-Plate 5000-series wall switches, currently available.  Yes, that's right-- its not too late to get an LV system for your home!  These are simple momentary switches (push on / push off) so may not be compatible with older systems that have rockers that must be pressed on the on side or the off side.

Looking for replacement parts?  Even the modern equivalents  seem to be sort of hard to find.  I point seekers to Dale Electric which has a large online catalog.  Go to: www.dale-electric.com  and search on "low voltage relay"  or "low voltage switch.  Try these links to get to the exact topics within the Dale catalog :      relays     switches

Do you have a home with L-V relays ganged at a central location?  I’d like to take a photo and add it to this page.