Originally Posted by Glimmie
This is WRONG
. And I doubt it's legal in an local codes. Look at it from an EE perspective. If I am pulling 35amps (assume 12ga wire) between those tow hots, the neutral will be overloaded. Sure it works most of the time because household loads are very light.
This is a hack. No true professional electrician would do this. And if a fire ever resulted, the electrician would be liable.
But your statement that many do this is true. My last house was wired this way, that is red and black to a tandem breaker. And it seems to have passed inspection too. I fixed it in short order!
Glimmie , I'm assuming you are refering to the action being wrong , not my comment about seeing this countless times . Correct me if I'm wrong in my assumption.My comment to Colm about being partially incorrect was limited to the part about "qualified electricians" not the technical aspects of his statement.
"Professional" electrician is subjective here . One who is responsible , thorough , and concerned about a quality , safe installation , no , they would not. Someone who is certified , licensed , or paid as an electrician , yes , plenty of them do. I just passed inspection on a house I took over after the licensed electrical contractor was fired , had several instances of what we're discussing , not to mention that he took out the AFCI breakers that are required by 2011 code
because he couldn't get them to work with 12/3 and 14/3 because of the shared neutral . He was nice to the homeowner about it , charged the price of the AFCI's (@50ea) , cut the pigtails off of the ones he left to render them useless , then installed $5 breakers , of the wrong type so they had to be replaced as well. This is mild compared to some of the hack jobs I get to correct these days , done by legitimate , licensed "professional" electricians. I carry the information on how to lodge a complaint against a contractor in my state with me to give to homeowners , I'm seriously thinking about having the info printed on my invoices. I work both for myself and union in California , and can say that many of the big contractors have the same poor ethic , as long as the work lasts 1 year and 1 day they don't care about anything else , thats all they are obligated to warranty most of the time.From Gregzoll : I do tend to be more on the technical side, due to growing up around electronics and what I did in the Navy, along with dealing with electrical circuits on a weekly basis, doing side work for people when they have a problem, or even with networking setups.There are two types of Tandem breakers. There is the Single slot and double slot form factor, depending on the manufacturer and panel. The Double slot can have a handle tie on it, to tie both handles together, same goes for the Quad pole breaker. You remove the handle tie, and you have a single unit with two separate poles that can allow you to control two individual circuits that are not Multi-wire branch., or you can use it to control a device that is 240vAC or MWBC, by keeping the handle tie in place.Technically
, I don't know of a manufacturer who refers to them as "tandem" , and for an example , Murray ( Crouse-Hinds) refers to theirs as duplex, triplex and quadplex , so there are 3 types from them.Quote : A single slot can only be used for MWBC or a 240vAC circuit, if you have two in two single slots, and tie the handles in a way, that the two middle handles are tied together. A Single slot Tandem is not the best way to create a MWBC circuit or sistering with another breaker next to it in another slot on the other leg, because they were not intended for that.
First off , the first statement , HUH? A single slot in no way or form can be used for anything except HALF of a MWBC. Secondly , are you saying that the outer , linked , common trip handles of a quadplex can not be classified as providing MWBC ? You also say "tie the handles in a way..." insinuating linking them yourself , then you say "sistering" is not the right way to do it , but if you tie handles together to achieve a MWBC the only way to do it would be to "sister" , otherwise , how would you achieve voltage between the load wires ? A single slot duplex can not
create a MWBC because it is drawing from a single stab , or slot on the buss. Just buy the right breaker for the job , If you need MWBC , then get a triplex or quadplex ( or whatever the manufacturer calls theirs). Working on obsolete panels , there is sometimes need to "sister" with the proper handle tie , either the bracket type or the pin type , but if breakers are still readily available , get the right tool for the job. I do agree that sistering is not preferred , but sometimes you have to set aside your preferences , but never safety, for the benefit of the client.
Saying "there is no such thing as a 240v breaker" is foolish when you yourself use nicknames for electrical equipment. walk into ANY Home Depot , Lowes , local hardware store , or electrical supply house and ask for a xx amp 240v breaker and guess what happens, they will put one in your hand. You might get a pompous ass who feels like correcting your terminology every once in a while , but you still get the same damn part that you asked for . I'm rusty on this point and don't feel like opening the book , but I believe that breakers are UL listed , and modifying a device negates it's UL listing , so a 2 pole common trip breaker installed in a split phase residential panel can only supply 240v , so it is in effect a 240v breaker. Remove the handle tie , you have a non-compliant device in the panel that you are liable for.