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Question DetailsAsked on 5/4/2014

I had a hard-wired smoke alarm installed that would not stop beeping until the red wire was disconnected.

The installer capped the red wire and said it was okay. Will it still work properly without the red wire plugged in? I am a little concerned about it. Is it safe to use it like this?

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4 Answers

Voted Best Answer

The red wire is supposed to be connected to other smoke alrams in the house. If this is indeed your configuration, then another alarm was telling the alarm in question to sound off. If this is not your configuration, then I wonder what the red wire was connected to?

Answered 6 years ago by Kestrel Electric


If this was a single alarm just installed, with no interconnected alarms, then that is right - red is not used in that case - only black and white, and occasionally green ground connection also.


Otherwise, if you have interconnected alarms - following applies:

he violated the law - that red wire provides a link between two or more alarms so when any one sounds, all the others that are hooked together alarm also. If you have more than one alarm, then one of the other alarms in the circuit had either failed its self-test routine, or had a dead battery.

You need to track down which one is beeping and why, then get the red wire hooked back up.

With almost all alarms he is right that that particular alarm will still work all right - but by disabling the interlinked alarm capability he significantly reduced the safety of your home.

He should rewire it for you for free (unless you are electrical savvy and do it yourself) because what he did was illegal and lazy.


BTW - if you ever doubt if a smoke detector is working right, you can buy a spray can of test vapor for about $8 at ekectronics, box, hardware, and lumber yard sources, that you spray in front of the detector to simulate smoke. Does NOT work with carbon monoxide alarms - only smoke detectors. Can lasts for probably about 50-100 tests - I have one probably 5 years old that still works fine.

Answered 6 years ago by LCD


OK - these type alarms are designed to work alone, or in interconnect mode. So, if it has a fourth wire (black, white, green or bare ground as usual, plus a red or blue wire lead or pigtail, then it is designed to allow interconnect alarming. All are designed to work independently if they lose connection with the others opr another one goes bad, though they will beep to warn you inmost cases. If it came with only black, white and maybe green pigtails, it is a standalone system.

As to what is required in your code jurisdiction, check for a FAQ on residential fire alarms at your local building department website. Usually, current construction requires one fire alarm on each floor, within 10' of bedroom doors if any on that floor, interconnected on 120V plus battery backups in each alarm, plus a CO alarm in the hall outside bedrooms on each floor that has them.

Sounds like your issue was wiring them live - with either a live hardwire connection to one or more before all were hooked up, or battery already in while still doing wiring would sound beep, but once hooked up and good batteries in all, AFTER hitting reset/test button on each unit for some makes, the beeping should have stopped.

Another possibility is bad wiring - if you swap the red and black or white and red, it might fry it, or might beep at you. Swapping black and white can also cause it to beep, saying something is wrong, Mac. Also, with at least one manufacturer, if wired WITHOUT interconnect, then the red wire has to be plugged into a port on the alarm to fake it into thinking that it is connected to another live alarm via the red wire.

This is not rocket science - with the wiring diagram that came with them or downloadable from manufacturers website, it is pretty straight forward. I grant complications can arise when also hooking into a security system at times- usually when an electrician hooks the 120V lead from the alarm into a low voltage alarm system - Honeywell and Simens techs LOVE that when some contractor does that in a highrise apartment building messing with their alarms, because commercial alarm master control circuit boards can run thousands of $ to replace.

Answered 6 years ago by LCD


Here is what I discovered. My alarms are interconnected. The person who installed the replacement alarms threw away the instructions. So I downloaded them from the company site. Installer did not turn off the power to the alarms while doing the installation. I found the breaker that controls the power to the alarms. I am going to try and reinstall them myself tomorrow or the next day. I will turn off the power and remove the batteries before I do the wiring; then will reinstall the batteries, and turn the power back on. Hopefully the testing will go well and I will be in business.

BTW, the installer was a handyman who apparently wasn't very knowledgeable.

Thank you LCD for your help!!! Between you and the instructions that I downloaded, I think I can do this.

Answered 6 years ago by novice


Sounds good - just be sure, since he was not an electrician, assume he may not have connected correct wires in correct place in either or both alarms. Wire coming out of the alarm, o connection spots inside it if no pigtail leads, should be color coded. So, make sure the colors on the alarm match the colors on the power leads, and that the red wire (or whatever color leads to other alarms) connects to the interconnect wire. Remember - black is "live", white is neutral (also called return), green or totally bare is ground, red or bllue or bluish white (typically) is the interconnect wire to other device, though sometimes an electrician will run a separate piece of romex and use only the black in it for the interconnect. If that was done, SHOULD have been marked red at ends, but don't count on it. Just keep track of which incoming wires are currently connected - since it works as standalones, the black and white leading to them now are the live ones, and the single wire (coming out of a cable with how ever many leads in it) that he capped off is the interconnect wire to the other alarm. If you have a volt-ohm meter, that one will also be a dead wire when breaker is on, whereas other incoming leads will be live with breaker on. If you test this up front, BE SURE TO TURN BREAKER BACK OFF before starting, and test BOTH alarms with VOM or without battery in BEFORE working on to be sure power is off - because the two alarms should be on the same powwr circuit, butno guarantees of that,so one could be dead but other live when you turn "the breaker" off.

Get EVERYTHING wired before powering up and testing, as if you do one and try to power it up and wires are wired wrong at other alarm, will zap them with a short circuit. So do ALL wiring complete before turning power back on.

Good Luck - sounds like you are in business. This is another case where a Handyman exceeded his abilities - and probably the law as well, by doing electrical wiring. That is the problem with Handymen - unless doing it as a retirement job, generally they are the master of only one or even no trades, but commonly try to do anything that comes their way - so commonly get into trouble or leave a problem behind, or do poor quality work.

If I were you, I would be trying to get my money back from that guy, because he did little or no productive, correct work for you.

And time for a Review on AL maybe ?

Answered 6 years ago by LCD

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