The Carter 3 way wiring system beware of this dangerous wiring when doing electrical work in old homes with Knob & Tube wiring

Got a call the other day from Maintenance Director at one of the Group Homes I take care of for a Institutional customer.Seems they can not get a 3 way dimmer to work in the hall way at the home so they can dim light at night while kids are sleeping.
They installed 2 both worked then stopped and 2nd one sparked and blew up. 

First thing is I check is it the correct dimmer for the correct light.. Yes it is it is rated for both LED and Fluorescent  fixtures. OK has he  wired it correctly common wire to common wire travelers to travelers. yes he has.

So whats going on ?

Well after looking at age of the home early 1900's  and the old knob and tube wiring

https://en.wikipedia.org/wiki/Knob-and-tube_wiring

  

 I suspect a carter wiring 3 way set up.

Unlike a conventional 3 way set up in picture below where all switching is done with just the hot conductor .

https://en.wikipedia.org/wiki/Multiway_switching

The carter system allows the switching of both the hot and neutral conductors 

Because the hot and neutral switch back and forth a 3 way dimmer can not be used  The Carter Circuit was banned in 1923 but I have found them in homes wired all the way up into the 50's and using romex wiring. Because  handymen and totally ignorant so called expert electricians refused to stop using it.

What makes this circuit deadly is the fact you can hook in a new switch improperly on a carter circuit and cause an dead short which is what happened at the group home.

How can you tell if you have a carter circuit in a home it takes a professional electrician familiar with old homes  to be able to determine this  by means of using a meter or induction probe and flipping of the switch and measuring to determine .

Are carter circuits safe to use in a home. Yes they are as long as they are not disturbed and if switches are replaced they are done so properly and due care must be taken to make sure wires are on proper terminal or you will have a short circuit .

 Due care must be taken when changing light bulbs
on a carter circuit as the shell of the light fixture socket can be hot with power even thou switch is off.

If a bulb breaks off  in socket and its an older home only safe way to replace it is to completely turn off power to the circuit.  or entire house if needed.
 and then removing the broken bulb or you risk getting shocked.

Itsy bitzy Spider was a real pain in the ass when they decided to make a home in a smoke detector

It started with a false fire alarm which took several days to track down and find  seems the fire alarm at a institutional customers group home was just going off randomly to make matters worse it was a conventional system which meant looking for the activated device or red LED lighted solid on the smoke detector None of which could be determined.

 The system had some older ESL smokes on it which I immediately replaced  as they are known trouble makers and have been known to go into alarm with out there LED locking in and the system settled down for the night till next morning more false alarms  thats when I found corrosion in the bathroom heat detectors and replaced them and again system seemed to settle . It was fine for 12 hours then another false  I suspected the pull station on the zone  which had been bumped numerous times and I have seen them cause random false alarms as no LED was lighted on any of the I3 System Sensor smokes  or older System sensor smokes which very rarely ever cause a problem. But thats when it really get weird. I take off the pull station and loop still shows it is being supervised despite fact the resistor is missing  as its attached to the pull station .This meant there was a 2nd resistor which was screwing with system that was improperly added to loop.  So I start looking for it and start taking every device apart thats when I find the trouble maker.

One of the smokes in bedroom 2 # has a spider web in it partially blocking the sensor and causing the false. But why was the LED not locking in? to make matters even stranger once I pulled the smoke out of the loop it was now showing a supervision problem no resistor? Hey wait a minute the I3 where never built with an in line resistor yet this unit appears to have one put it back in line its supervised.
Very strange apparently the spider managed to short out something in the smoke causing this issue.
I have contacted System Sensor and sending them the unit to inspect as they are just as curious as I am as to how this spider caused the problem when there are screens etc to prevent this kind of issue.
But thankfully the problem has been found and if it ever happens again I will know to better check all smokes on line when a false occurs and no LED is locked in .

Least Cost Routing LCR the Deadly Game Telephone Carriers Play with your phone calls which could prevent a signal from you Fire or Burglar alarm from being answered.

A burglar is breaking into your home or you are having a medical emergency and you push your emergency alert button .

No worry's the central station is being contacted and help is on the way.  But is help coming?

The answer could well be no because of a deadly game phone company's like Verizon , Comcast  etc play with how your phone call is transmitted from your home to the central station Via toll free numbers .  Which recently happened when a customers sprinkler system activated due to frozen pipes and a signal was not sent by the Silent Knight 5104 B dialer.

I check the dialer all was OK properly programmed phone line working but when it called central station the central station was getting an error message unknown account number#  So what is going on .

Lets say your home or business is in Pittsburgh Pa. and the central station you use is in Erie Pa. 

When the alarm dials the 800 number you would expect it stays with in the borders of Pa. on phone lines which run Between Pittsburgh and Erie  Wrong.

When the number is dialed the phone company central office switch gear looks at where the number is going and then determines the cheapest path to get it there which could be thru Ohio then thru NY and then finally into Pa. and Erie County . In some cases phone numbers being dialed in Pa are being routed as far away as Texas and every time it keeps switching the potential for line noise  and interference which can keep call from completing . All in a way to save phone company's money.  Once I reprogrammed the dialer to a different 800 number so it took a different path  it was operating fine .
But the problem is only getting worse and even if you use a central station with in the county you live with this new least cost routing and new VoIP internet phone switching phone company's are doing there is no guarantee you will not have a problem. Even if you have a traditional land line known as POTS or plain old telephone service.

https://en.wikipedia.org/wiki/Softswitch

While new fire panels are required to test both phone Numbers every 6 hours to the central station older panels only dial every 24 hours and test  and some burglar alarm systems only test every 30 days or not at all
and with many burglar alarms being serviced at central stations many states away   which is typical with big  national alarm company like ADT you can see the potential mess we have on our hands and why it is essential to check and find out why a panel has not sent in a test signal.

On many of my accounts I am now backing them up with cell phone and internet connections  via Honeywell Alarmnet  or thru Uplink   which provides triple redundancy of the signal getting out but even this is no guarantee.
As phone company's keep playing games to lower costs and refuse to properly maintain infrastructure it is only going to get worse.