Residential lighting relays

Discussion in 'General Electronics Chat' started by WMichaelis, Mar 10, 2008.

  1. WMichaelis

    Thread Starter New Member

    Mar 10, 2008
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    This may not be the venue for this question, if not please forgive me. My house was built in the middle '50s and has low voltage (24V) lighting relays in the ceiling fixture boxes. These relays are starting to fail. The relays are GE cat No. 3563, 1/3 HP 125V 15A latching. Pass & Seymour make a similar relay (1070-B), but they cost about $100 each! Is there another relay that will accomplish this purpose for less? I've extensively searched the I'net and found nothing so far.
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Check out Ebay! You can get some excellent deals if you keep an eye out for them :)

    Steve
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Potter & Brumfield make some latching relays, but only for 120 VAC or 12 VDC.
     
  4. WMichaelis

    Thread Starter New Member

    Mar 10, 2008
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    Thank you both for your responses, I'll keep looking. I may need to re-wire my house, which isn't a bad idea, because some of the methods used by the original electrician were not the best.
     
  5. Marko

    Member

    Feb 10, 2008
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    Allied Electronics (alliedelec.com) carries inexpensive board-mount latching relays for AC line voltages rated at 16 amps. They require soldering, and care must be taken not to overheat them while soldering. I acquired an inexpensive temperature controlled Hakko soldering station for this very purpose (model 936).

    Mark
     
  6. WMichaelis

    Thread Starter New Member

    Mar 10, 2008
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    Thanks, Mark, but the relays I need to replace mount through a hole in the lighting fixture box and have two pigtails that connect to line and load; low voltage wiring then runs down to wall-mounted rocker switches that control the relay. Apparently this is a seldom-used system.

    Wade
     
  7. Marko

    Member

    Feb 10, 2008
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    These days, the GE model is R-77. You can try names like “GE RR-7” in a google search. I've seen them on ebay for $25 - $30 without shipping.

    If that is still too much, you should be able to test the relays you have, if you haven't done so already. The 24 volt transformer has a diode hooked up to it. With so many relays going “bad”, it might be the diode, or even the transformer (though the transformer is most likely O.K.). Do you have aluminum wiring in your house? The problem could be bad or corroded connections. Another possibility is the wall switches themselves. They would get a lot of use and would tend to go bad sooner. Or loose connections to the switches.

    Assuming you haven't tested the relays yet, here is a general procedural outline. I don't know your electrical/electronics acumen, but you can remove the relay and hook it up to a known working test light bulb. If you are unsure of line voltage connections, you can use a low voltage bulb and batteries from a flashlight for the circuit to be controllED. Otherwise, judicious use of an extension cord plugged into an outlet, and using appropriate safety measures with it will work. For the low voltage controllING circuit, you can run test wire like bell or thermostat wire directly from the transformer output screws to the low voltage side of the relay. BUT, bypass the old diode and use a new diode in series with one of the wires, doesn't matter which as long as you know which wire will end up being positive and which is negative. Diodes are cheap, but make sure the diode is sized to adequately handle the 24 volt AC transformer. Then it is a matter of connecting the the correct wire (negative?) to the common lead or screw. Now you can touch the other wire to one of the other leads or screws. Doing so will turn the bulb on or off. For example, if it turns the bulb on, then touch the other lead or screw to see if it turns off. Hope this makes sense.

    Mark
     
  8. WMichaelis

    Thread Starter New Member

    Mar 10, 2008
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    Boy, do I feel foolish, Mark. After you mentioned "diode", I realized that I didn't remember seeing anything resembling a diode so I rechecked the stamping on the relay, and the coil is 24V. 60CY. So, that rules out the diode. But your suggestion and instructions about testing the switches is well taken, because one of the new Pass & Seymour relays that I installed a couple of years ago worked OK for a year or so then you had to start pushing the switch several times to finally get the light to come on or go off. Also, about the time the relays started failing, we had a nearby (very nearby, I believe it came down the outside TV antenna pole about three feet from the house) lightning strike, and it was shortly after that, as I remember, that the relays began to fail.

    By the way, my educational background is in electrical engineering but I didn't work in the field for very long so my experience is limited. Education is good but experience may be the best teacher.

    When we started having trouble with the lights, I checked the output voltage on the transformer and it was OK. I also have checked the continuity through the switches and they seemed to be OK. I'll try your suggested testing setup when I get a chance.

    These relays have three wires coming out of the low voltage coil. I probably knew at one time, but, how do you reverse the relay action with an AC coil? Thanks for your response and your suggestions.

    Wade
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Three wires from the low voltage coil, hmm?
    Sounds like a dual-action solenoid inside the relay - the winding has a center tap common. Energize one side of the solenoid winding, and the core is pulled one way, etc. You could confirm that by measuring the resistance between the relay's low voltage coil wires. If the relay's coil was rated at 240mA for 24v, you would measure 100 Ohms between two combinations of wires, and 200 Ohms between the third combination. Applying 24v across the third combination would cause the solenoid core to assume a position midway between the ends, and it would be difficult to predict if the contacts would be open or closed.

    It would be interesting to dissect one of those relays to see how they work, and determine the cause of failure.
     
  10. Marko

    Member

    Feb 10, 2008
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    Wade,

    actually, I have worked with these relays. Even though the stamping on the relays may state “24V. 60CY”, they still require a diode. Strange, but true. In reality, the single diode makes it output half-wave, bumpy DC, and roughly half of 24 volts. By experimentation, I've discovered that if I use a significantly lesser output voltage transformer but use a full wave bridge rectifier, the relays will work.

    Unfortunately, the trick is to FIND the diode in your house. In most installations, it is typically near the transformer, if not on it; but not always. The diode would be small. You may have a real witch hunt on your hands. If you can't find it, it may be best to just run new wire with a new diode. But first, test the relays like I previously mentioned - bypass everything and test the relays with a transformer (same transformer is fine), test wiring, and a test diode.

    The relay is referred to as a dual coil latching relay, and yes there is a common, but I don't know the actual internal config. Could very well be a single coil with a center tap. Each coil, or coil half requires DC, bumpy or not. Whatever polarity the common requires (I said “negative?” before, because it has been a while since I last worked on them), connect the appropriate polarity wire to the common lead. Momentarily touching the other polarity wire to one of the non-common leads should energize it's corresponding coil, or coil half, causing the relay switch to latch for that side (if it wasn't latched before). Obviously, momentarily touching the same other polarity wire to the remaining non-common lead does the same for its coil or half coil. And having previously rigged up an active circuit with a lamp for the relay to control will provide the feedback to you for the test.

    I suppose it is possible to install a diode for each relay, so as to reduce the cycling on a single diode, but I've never seen this. If this was done, each diode should be near each relay.

    Mark
     
  11. Marko

    Member

    Feb 10, 2008
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    Lightning strike, eh? Scary. Then I would indeed suspect that the failure lies with the diode, and hope like the dickens that the relays are unscathed. Do you have a whole house surge suppressor? In a house that old, I'd get one if I were you, and check that the house ground conductors and earth rod(s) haven't corroded away. Plus, make sure you have enough ground rods to meet current codes.

    A lightning strike near reaching distance is an unnerving thing to behold. I hope never to see one again. And I especially hope NEVER to see ball lightning. I've heard horror stories from witnesses.

    Mark
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    In a parallel vein;
    With the lightning strike, there may be the possibility that the solenoids inside the relays have become magnetized.

    To get rid of the magnetism, the solenoids would have to be degaussed.

    A bit of background in a similar vein;
    Lightning strikes wreak havok upon signal splitters in cable TV systems, because the toroidal cores used as signal-splitting bifilar transformers become permanently saturated. Until the signal splitters are degaussed, they are practically non-functional.

    If the (solenoid in) your relays took a lightning hit, the solenoid core may have become permanently magnetized. This would cause it to function abnormally. It would quite readily latch in one direction, but barely function (if at all) in the other direction.

    You may be able to degauss them in place using a relatively high frequency, high voltage signal that gradually decreases in voltage across the ends of the coil, as in a "ping." However, with devices that old it would be better to remove them from the circuit prior to degaussing via external means.
     
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