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Mike, Master Electrician
Category: Electrical
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Experience:  Licensed Master Electrician - OnQ Certified Data Voice Audio Video Installer
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I have a GE low voltage lighting system in my house installed

Customer Question

I have a GE low voltage lighting system in my house installed 1973. The panel is RRF-78 and has 12 circuits/relays, all of which suddenly stopped working at one time. I have 2 transformers mounted to the panel: one 24VAC and one 12VAC output (slightly smaller). Both os thes seem to be working OK. What would have caused the whole panel to quit working on all 12 circuits?
Submitted: 3 years ago.
Category: Electrical
Expert:  AssuredElectrical replied 3 years ago.

Welcome to Just Answer, my name is XXXXX XXXXX would be glad to assist.


First, look in the panel for a Master Relay, as many of the low voltage panels had a Master that would disable power to each of the relay circuits.


Follow the wires from the transformers and find the first location that the wire is connected .


Is the transformer labeled? Wanting to be sure the 12 volt is supposed to be 12 and not 24 volts as well.


What relays are in the panel? RR-8,RR-9,RR-7?

Post what information you find.



Customer: replied 3 years ago.

There is no Master Relay that I could see.

Transformers are correct with proper voltage outputs (one 24VAC; one 12VAC). One leg of the 24VAC transformer foes to a rectifier; the other into the main panel where it connects to 4 or 5 other wires. The transformers have some writing on them which is hard to read without removing - don't want to do that, especially since there's nothing wrong with them. My neighbor has the identical system so I can compare - mine looks the same and has same voltage readings - 24 and 12 VAC.


Cannot tell what Model the relays are - impossible to read them the way they're installed in the panel. I don't want to remove them - relays were all working one minute, then all 12 stopped working all at once.


Cannot fathom what went wrong.


Pls help.

Expert:  AssuredElectrical replied 3 years ago.
Ok, thanks.

When you measured the transformer outputs, did you have one lead on each wire from the transformer?

The negative 24 volts will connect to every relay in the panel.
Need to follow the negative side and check every splice or connection for any loose ones.
Only takes a loose connection under a wire nut to kill the entire system

Not sure why they go to a rectifier on the other leg of the 24 volts, but the 24v should come off the rectifier and connect to every switch for the relays.

Positive goes out to the switches, then ON or OFF will activate the coils on the relay and make or break contact as needed for the lights.

The negative 24v is constantly applied to each relay.

So, find the first location from the rectifier that the 24v goes to, and use one lead at that point.
Then one lead at the first point where the negative 24v connects to the relays.

If you can take a picture of the transformer, rectifier etc, it may prove useful.

Pictures can easily be uploaded to and then post the link here or use the paper clip icon on the chat tool bar to post it here directly.

Post the findings on the voltage test.