Odd wiring...? 240v with 120v mixed??

I came across a weird wiring setup. From a 20amp double pole....goes up in attic to a junction box. This y's off from there....one line goes to a 240v 20amp outlet. The other goes to the remaining 120v outlets in the room. The black wires, white wires, and ground wires are all nutted together in 3's while the red is only nutted to the 240v receptacle red wire. This doesn't seem right? I thought 240v circuits had to be on their own.

 

You are right that is not only incorrect..... it's dangerous.
What is the 240v receptacle used for ?

 

It's in a small room / utility closet by garage. Using the 240v for a table saw right now via extension cord when in use. The other outlets aren't in use except for a couple lithium battery chargers for weedeater and leaf blower. Mainly storage closet.

 

If you have a 20/2 breaker, you have a multi-wire branch circuit. There are advantages and disadvantages to these circuits. Devices must be installed using pig-tails so the neutral will not be opened if a device is removed because serious over voltages and undervoltages can result in damage to equipment that is plugged into the receptacles on that circuit where the neutral is shared. You are allowed to operate both 240v and 120v receptacles using a multi-wire branch circuit. The breaker must be a common trip that opens both lines when opened. As pointed by PJmax, these circuits can be a hazard. I would not advise their use in a dwelling.

 

As long as the circuit is able to carry the load that it is intended for, I see nothing wrong with the wiring. It is a multi-wire circuit, and cautions should be taken when dealing with these circuits as Bahtah pointed out, but they are allowed by the NEC. As long as the circuit is protected with the proper breaker, which it sounds like it is, I would continue to use this circuit.

 

You would not advise the use of MWBC in a dwelling? That's a pretty bold statement, please elaborate....

In my opinion, there is nothing wrong with a MWBC as long as its wired and fused correctly. It is a very common method of wiring, usually done to save material and you will likely find one in your own house on maybe the kitchen small appliance circuits, dishwasher/disposal or in a rec room.

 

The service on a typical house is a large MWBC.

If properly sized I don't see the issue.

 

bigboypete

I have no issue with a properly installed MWBC however in dwellings where they are installed for multiple receptacles I have seen many cases where the unknowing homeowner trying to do the work himself has not properly handled the neutral pig-tailing and ended up with the voltage problems that have been mentioned. From the description of the posters installation it would appear the receptacles do not share the neutral as only one receptacle is 240V. Not really an issue for a disposal/dishwasher as it is unlikely the single neutral termination would be a problem. Its the shared neutral being worked on by the unqualified homeowner that creates the problem the homeowner is unaware of.