Were there “standards” back in the early 1950’s for the color of live wires in houses?
I ask because I’m replacing a simple fluorescent kitchen light in my uncle’s house, and I disconnected the old light before making note of the color of each wire and where it connected.
The house has no ground wires installed to the outlets, so there are only two wires at the outlet where the replacement light will go.
I don’t have a voltmeter, but if there’s no clear-cut answer to be had here, then I’ll get one- I was just hoping to be able to pop it in this afternoon.
I assume one wire is hot and the other is neutral. I also assume the hot is being fed from the wall switch.
Does the new fixture have a manual? Does it indicate where hot and neutral should be connected?
Theoretically it should not matter if the fixture does not contain an integral on/off switch. If it has an integral on/off switch then the hot should be connected to the switch.
Another thing to keep in mind: Some fluorescent fixtures require the metal reflector to be connected to earth ground. The reflector provides a capacitive path to start the bulb. Check the manual to see if this is the case.
You will not need an earth wire unless you can touch another piece of metal , sink,radiator etc. at the same time as touching the light fitting.
It may be earthed in any case if the wires have been run to the light-fitting inside metal conduit or trunking.
I was an apprentice electrician but I never quite finished my time but we did re-wire some really old houses and the live wire in flexes and such have always been red or brown but when it comes to the set-up you describe it does not matter what colour they are, you cannot go wrong so I say just go ahead and connect them up.
Unless of course there are two light switches controlling that one light fitting, in which case I would suggest using a meter.
White or light grey is always neutral. Any other color (except green or bare) is hot.
Are you sure there is no ground? If the junction box is metal it may be grounded thru metal conduit encasing the wires.
To test without a meter:
Set the wires from the ceiling such that they are hanging down not touching anything.
Temporarily attach the non-white one to one prong of the cord of a known working lamp. Attach the other prong of the lamp cord to the metal junction box.
Restore power to the circuit
Turn on the switch. If it works you have a ground.
Find out which, if any, wire on the fixture is bonded to the metal body of the fixture. Attach this one to the white wire from the ceiling. If none is, then you can attach either wire from the ceiling to either wire to the fixture.
If you are sure there is no ground and the fixture has a ground wire (green or bare), don’t attach it to anything.
There is only one light switch that controls the light, and no integral one.
The wires are indeed in metal conduit, so am I to understand that’s the way they grounded electrical fixtures back in the day?
Now, if I do have a light that’s metal reflector needs to be connected to ground, how do I go about grounding the reflector, since there is no ground wire.
In Chicago, to this day you need to encase all wiring in rigid metal conduit, not for grounding, but for protection. It has the added convenience of providing a ground. Under some conditions, in some jurisdictions, it will suffice as a ground. Other conditions require an additional ground.
In the '50s there was flexible conduit known as BX. It is no longer approved, and should not be depended upon to provide a ground.
Since your fixture is ungrounded, you have no problem. Ceiling fixtures are often not grounded, since they are normally out of reach of living things. The ground is only for your protection, and has no affect on the operation of the circuit, if properly connected or entirely missing.
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The wires are indeed in metal conduit, so am I to understand that’s the way they grounded electrical fixtures back in the day?
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Conduit is just one of many options and most industrial sites utilise this method and they also opt for SWA (steel wire armour) a lot, this is where the earth wire is wrapped around a plastic sheath that is wrapped around the insulated live wires, then the armour has a plastic covering as well. It is pretty tough stuff.
Honestly though, there are too many different set-ups too mention.
Oh yeah, but back in the day they had wires which were insulated then coated in lead, but it was an expensive method.
You may find that the cables in the house are paper or fabric soaked in oil wrapped around insulated wires so remember to keep them away from oily rags, oh wait…
If you suspect the box might be grounded, then verify it with a voltmeter. To do this:
Turn on the light switch
Verify there’s 120 VAC rms between the two wires
Turn off the breaker. (Keep the light switch on)
Verify there’s 0 V between the two wires
Put the meter on “ohms” or “continuity” function
Check for continuity between each wire and metal box.
(BTW: The reason I’m making you go through this is in case the wall switch is switching the neutral. It should be switching the hot, but you never know…)
If the metal box is grounded, then you should have continuity between one of the wires and the box. If the box is not grounded, then you will not have continuity with either wire.
If the box is not grounded, and if the metal reflector or chassis requires an earth ground for the bulb to start, then you have two choices:
Run a ground wire to the box
Use a fixture that doesn’t require an earth ground. You might be able to find a fluorescent fixture that doesn’t require an earth ground. If not, then just go with incandescent.
Sure, it will work but it will violate code, and be potentially dangerous. The reason you put the hot wire through the switch is that power is cut off to the fixture when the switch is turned off. If you route the neutral lead through the switch and connect the other side to the hot lead, your fixture will be hot all the time (even though it’s turned off, because no complete circuit).
I think Trigonal Planar was inquiring if polarity at the fixture was important.
My point was that, in theory, it is not important as long as the fixture doesn’t have an integral on/off switch.
But fluorescent fixtures are strange beasts. Many require the metal reflector and/or chassis to be connected to earth ground. This is not so much for safety as it is for performance. It’s notoriously difficult to get a fluorescent bulb to “start,” and manufacturers will often use current flow resulting from capacitance between the bulb and (grounded) metal reflector to start the bulb.
But you will not find out if the switch is on the hot or nuutral with the tests you have recommended.
Turn on the light switch
Verify there’s 120 VAC rms between the two wires Makes sure there is power to the circuit and the switch works
Turn off the breaker. (Keep the light switch on)
Verify there’s 0 V between the two wires All you have done here is to verify that the hot is no longer hot. You have not done anything to find out which side of the circuit the switch is on.
Put the meter on “ohms” or “continuity” function
Check for continuity between each wire and metal box. * tells you which wire is grounded, but still not which side is switched!*
Here is what I would suggest.
Switch on, breaker on
Check for voltage between the two wires, you should have line voltage.
Check for voltage from each wire to the box. You should read line voltage from one wire, and zero volts from the other. if you do then the box is grounded. If you read zero from both wires then the box is not grounded. if you are good to this point, then
Turn the switch off and re-check from each wire to the box Now you should read zero volts on both wires if the switch is on the hot lead, if it is on the neutral, you will still read hot on one wire.
Rick: If was not my intention to determine if the wall switch was switching the hot or the neutral. I consider that a separate issue. Smoke wanted to know of the box was grounded, and my procedure works fine for doing that. I simply designed the procedure to be safe in the event the switch was switching the neutral.
Assuming the house was wired to standard, the hot lead will always be connected to the brass screw in fixtures, and the neutral will be connected to the silver screw. This has been the standard for at least the past 100 years AFAIK. Well, that’s how it’s supposed to be. YMMV.
Sorry it took so long to respond. To test the wires at the box, do what crafter_man suggested in his post.
You may find that they are switching the nuetral, they did this in the old days.
Most likely they are switching the hot. The hot wire should be the darker of the two (usually black). The nuetral should be the white (or grayish, depending on the age of the wires).
If the box is grounded (testing from the hot to the box gives you 120v., or continuity between the nuetral and the box is 0 ohms) then the following should work for you…
The box itself should have a threaded hole in it for a #8 grounding screw. If it doesn`t and you still want to ground the fixture get a self tapping #8 screw and use a screw gun to drill it into the back of the box. Being careful not to drill into any wires or cables. Then take a length of solid bare wire and wrap it around the screw, then tighten the screw. Wire nut the other end of the wire to the copper lead from the fixture.
I believe all fixtures come with a ground wire these days… how would the manufacturer know where you are going to put the fixture?
Q.E.D. this is a flourescent fixture, so there will not be any screws. There will be wire leads of black and white however (and green or copper for ground).