Old wiring inside wall gets voltage when shared switch is used - safe and to code?


What it means: Your house's wiring has no way to safely conduct any stray current that escapes the confines of the wires.

Code violation? No; grandfathered in. (Today's code requires grounded circuits and receptacles.)

Danger level: Minimal, as long as you don't use an adapter to fit a three-prong plug into a two-prong receptacle. Doing so could destroy the device you're plugging in, and increase the chance of electrocution.

Solution: Replace two-prong receptacles with properly grounded three-prong ones, if wiring allows it (see . Also, test all existing three-prong receptacles with a GFCI circuit tester to make sure they're grounded. Rewire any that aren't.

10. Plug Falls Out of Receptacle
What it means: Worn contacts in receptacle no longer grip the prongs firmly.

Code violation? No.

Danger level: High. Loose contacts can cause arcing, which can ignite dry wood and dust.

Solution:Replace the old receptacles as soon as...

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A wall switch is a mechanical device with moving parts; it gets thousands of uses over the course of its lifespan. Switches eventually wear out and go bad, and the first sign of trouble is when it behaves in a fashion that is abnormal in any way. For example, if there's an audible crackle, snap, or popping sound when you flip the lever, then it's pretty clear that your switch is defective and it's time to replace it.

Some other warning signs are a little more subtle, and some are even more obvious. Here are some of the most common signs of trouble.

Temperamental Lights

You've likely had this experience: you flip a light switch on and it takes a moment for the light to go on. This usually indicates that the metal parts inside the switch are wearing out and that its contacts are failing to make the connections needed to complete the electrical path and allow the light to illiuminate. Sometimes (not always) this symptom occurs at the same time you notice that...

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A new technician has joined the IT team and is about to service a heavy printer. What advice would you give this technician to avoid any injury when transporting the heavy printer to the service area?

Bend your knees to use the strength in your legs to lift the printer. Avoid bending your knees when lifting the printer. Bend your back to pick the printer up. Use your arms and back to lift the printer.

How does an inline UPS protect computer equipment against electrical power brownouts and blackouts?

by grounding excess electrical voltage by using a...
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You're actually posting two questions.

Is it threadsafe?

Well, obviously it is not, another thread might change the value of X while the first thread is going into the switch. Since there's no lock and the variable is not volatile you'll switch based on the wrong value.

Would you ever hit the default state of the switch?

Theoretically you might, as updating a 64 bits is not an atomic operation and thus you could theoretically jump in the middle of the assignment and get a mingled result for x as you point out. This statistically won't happen often but it WILL happen eventually.

But the switch itself is threadsafe, what's not threadsafe is read and writes over 64 bit variables (in a 32 bit OS).

Imagine instead of switch(x) you have the following code:

long myLocal = x; switch(myLocal) { }

now the switch is made over a local variable, and thus, it's completely threadsafe. The problem, of course, is in the myLocal = x read and its...

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Wall-mounted toggle switches usually warn you before they fail completely. If there is a brief delay before the lamp lights, or if the lamp flickers a bit when it is turned on, the switch probably needs to be replaced. Buy the correct type of replacement switch and follow safe electrical practices. The job itself is easy.

Switches that are used the most usually fail first. When a frequently used switch shows signs of failing, other much used switches of the same age will probably also need replacement soon. It may save time and trouble to purchase and install several switches at once, rather than wait for the unexpected failure. Be aware though, that sometimes the fixture controlled by the switch is faulty, not the switch; a loose wire connection makes a good switch appear faulty.

When switches need to be replaced, be sure that the new switch is the same type as the old. If in doubt, the number, color and location of the terminals are good clues. The most common...

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Help! I'm trying to add a the monoprice dual relay module to two light switches in my house. Of course, my house was built in 1926, which means nothing here is ever easy.

Here's my problem: I opened up the outlets, and the wiring doesn't make much sense to me.

Outlet one (far right, first photo below) has three wires - a red and black at the bottom, and white at the top.This is a 3-way switch - there's another switch that controls these lights. From what I've read, these relay modules can be installed on some 3-way switches, so I wanted to try it here.

Outlet two (middle of three outlets in photos, second photo below) only has two wires: A black and a white. And the white is coming from outlet 1, not the wall, which really confuses me.

Right now, here's my best guess: Black wire is live, white wire the load (and these two switches share a load - not sure if that's actually possible), and red wire goes to the other switch for the 3-way. And these are just...

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Here are four must-have tools if you plan to wire many switches and outlets:

Voltage tester. You can pick one up for a few bucks and use it to test for hot wires or to find a neutral. Just touch the probes between a hot and a neutral, or between two hot wires. The tester will light up if the wires are “hot.” The tester shown also tests for 240 volts.

Combination sheath and wire stripper. In addition to slots for stripping insulation from 14- and 12-gauge wire, it has slots to strip the sheathing from 14- and 12-gauge nonmetallic cable.

Voltage “sniffer.” The beauty of this tool is that you don't have to touch bare wires to see if they're hot. Just hold it near any wire or cable to see if it's energized. Use a noncontact voltage tester like this to double-check that all wires in a box are “dead” after turning off the circuit breaker.

GFCI receptacle tester. Just plug it into any GFCI outlet and the lights will indicate whether the outlet is properly...

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You can but you take the chance that if someone else is around when you are doing the job, the switch could inadvertently get turned on. Shutting the breaker off at the distribution panel goes one step further in a safety aspect. If you have the ability to lock the door on the distribution panel and you keep the key in your pocket then this is the ultimate in electrical safety. On industrial and commercial sites it is mandatory that you never work on "hot" circuits and there is a special procedure of locking the circuit off. As a word of caution never ask someone if the circuit is turned off, check it out for yourself.

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ELECTRICAL SPLICES, HOW TO MAKE - CONTENTS: How to splice electrical wires - Electrical Wire Splicing Guide for Homeowners & DIY Repairs. How to make a Pigtail Splice in Electrical Wire. How to Twist Electrical Wires Together When Making a Splice. Use an approved connector to secure your electrical splice. Types of electrical wire splices, requirement for mechanical connectors such as twist on connectors, wire nuts, or MARR connectors or Wago Wall Nuts, AMP COPALUM crimp connectors, AlumiConn connectors. How to Make Tap Splices in Wires - Older Knob & Tube Wiring. When can you just "tape" electrical wires that have been spliced? How to wrap the tape around an electrical wire splice. Requirement for enclosure of electrical splices in junction boxes POST a QUESTION or READ FAQs about electrical wiring splices, connections, connectors REFERENCES

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Whether you’re a contractor or building manager, it is important to keep Class 2 compliance in mind when retrofitting or creating new construction with low voltage LED lights and systems. The National Electric Code (NEC) requires that low voltage power supplies and electrical wiring be Class 2 compliant. The code was created to prevent electrical fires and shock.

Inspections: Who needs them and how they work

If you are creating new construction or adding major modifications, you will most likely require an inspection. New construction requires a work permit that must be obtained from a local safety or electrical inspector. Some small jobs may not require a permit but it is in your best interest to get a safety inspection to avoid any unintended problems. For example, if you re-wire a kitchen or basement without having it inspected and then try to sell the house, an inspector may ask you to tear the walls down to check the wiring. Also, if faulty wiring that...

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Three Parts:Removing Old SwitchesInstalling a Double SwitchTroubleshootingCommunity Q&A

A double-switch allows you to operate two lights or appliances from the same location. Double switches, sometimes called "double pole," allow you to separately control the power being sent to multiple places from the same switch. For example, you might want to turn on a bathroom light separately from the ceiling fan. To wire a double switch, you'll need to cut the power, remove the old switch, then feed and connect the wires into the double switch fixture. Though it is not difficult to wire a double switch, careful attention to safety is crucial to prevent injury.

Note: This article only describes installing the switch itself, not rewiring two conjoined feeds that need to be separated. If you are trying to separate two lights that use the same wiring, as opposed to two already separate sources, you will likely need a trained...

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What are two factors that must be considered when choosing a computer case? (Choose two.)
the size of the monitor
the vendor that manufactured the motherboard
the number of external or internal drive locations
the size of the motherboard and the power supply
the number of LED indicators at the front of the case

What are the two connector types for the 1394a interface? (Choose two.)

What is a function of a KVM switch?
digitizes an image or document and sends the information to multiple computers
stores images from both digital still cameras and digital video cameras on magnetic media
provides capability to share a keyboard, a mouse, USB devices, and speakers with multiple computers
provides biometric identification to an individual user by the use of fingerprints, voice recognition,or a retinal scan

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Welcome. If you're new here, be sure to subscribe to Ghost Hunting Secrets for free ghost hunting tips, videos, haunted locations, and other goodies. Thanks for visiting!

Jamie wants to know whether strange electrical activity could be a sign of paranormal activity. She writes:

Hi Michelle! I have a spirit here in our apartment. I have heard him speak before; I have felt his presence, and even caught an EVP of him. The past couple days, I noticed something strange: the nightlight in our guest bathroom turned a VERY bright white and then burned out….and last night, the lights on our ficus tree did the same thing (the lights got so bright that it woke me up…was like a sunlight)..and then they burned out, too.

Is this a sign of paranormal activity? I never heard of anything like this, with the exception of lights flickering and going off and on..all of which we have had in the past month as well. Thanks so much.

- Jamie from Wisconsin

Hi Jamie. Yes,...

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