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jetlag

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Thanks iwire

Thanks iwire

That is false, you can have DC multiwire circuits.

You are correct , I had a wrong mental picture of a DC MWBC . What is still weird is the code states we can not connect loads in series but on a MWBC if the loads are equal there are 2 loads in series with 240 v and the voltage drop across each is 120 v . The same as the old 2 bulb in series home made testers , burn normal 240v , burn dim 120 v (60v for each bulb). In other words if both loads are the same on a MWBC you can remove the neutral with no affect, leaving two loads in series with 240 V . :)
 

jetlag

Senior Member
It doesn't work that way. Find it. :)

oh yes it does , connect two rubber light sockets in series so they have a leg connected together , supply 120 volt to the other legs, the bulbs will burn dim because each receives 60 volt , connect the legs to 240 volts the bulbs burn normal (they dont Blow) because each receives 120 volt , keep the set up for a 120 - 240 volt tester. ;)
 

jetlag

Senior Member
No, I am saying you don't get to let others do your homework. Find it.

Why would the code let us connect lights in the manner of the tester I discribed , and yet you doubt it is against the code . I know it is in the code . You need to do the home work so you wont forget we dont connect loads in a series unless you want to divide the voltage between the loads
 

iwire

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Why would the code let us connect lights in the manner of the tester I discribed , and yet you doubt it is against the code . I know it is in the code . You need to do the home work so you wont forget we dont connect loads in a series unless you want to divide the voltage between the loads

Jet, that is not how it works here.

If you want to say something is against the code you need to provide the section number.

I can tell you there is no section that prohibits wiring in series.

Furthermore as long as the neutral is present the lamps in your example are not wired in series.
 

mcclary's electrical

Senior Member
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Why would the code let us connect lights in the manner of the tester I discribed , and yet you doubt it is against the code . I know it is in the code . You need to do the home work so you wont forget we dont connect loads in a series unless you want to divide the voltage between the loads




You would have to provide a code article first,,,,,before we can discuss the "why"
 

jetlag

Senior Member
Jet, that is not how it works here.

If you want to say something is against the code you need to provide the section number.

I can tell you there is no section that prohibits wiring in series.

Furthermore as long as the neutral is present the lamps in your example are not wired in series.

I have to disagree on thats not how it works , how do you think the bulb tester works ? I am still looking for the code. But I agree the neutral being present would make it not be a series circuit as the neutral carries the unbalanced load. I was just saying if the loads were exactly the same and the neutral current is zero , at that time the circuit is working the same as a series because you could disconnect the neutral , it is not being used .
 

iwire

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I was just saying if the loads were exactly the same and the neutral current is zero , at that time the circuit is working the same as a series because you could disconnect the neutral , it is not being used .

I agree, if you removed the neutral you would have a series circuit.

But something to consider is that the same thing happens if a panel feeder neutral opens, all the circuits would be in series.
 

hurk27

Senior Member
I have to disagree on thats not how it works , how do you think the bulb tester works ? I am still looking for the code. But I agree the neutral being present would make it not be a series circuit as the neutral carries the unbalanced load. I was just saying if the loads were exactly the same and the neutral current is zero , at that time the circuit is working the same as a series because you could disconnect the neutral , it is not being used .

I was going to ask if you ever used any rope lights, every five lamps are in series, same goes for Christmas lights. half the string is in series, H'mm code seems to allow them?
 

jetlag

Senior Member
I agree, if you removed the neutral you would have a series circuit.

But something to consider is that the same thing happens if a panel feeder neutral opens, all the circuits would be in series.

Thats good iwire , you are correct , the 240 volt loads wont mind a bit . The higher wattage loads will receive low voltage but the lower wattage loads will receive over 120 v and blow . Most circuits will open beause the series will be broken. Try the bulb tester on 120 volt with two different watt bulbs , the lower watt will burn a little brighter than the higher watt. Dont connect to 240 the lower watt bulb will blow. :)
 

jetlag

Senior Member
I was going to ask if you ever used any rope lights, every five lamps are in series, same goes for Christmas lights. half the string is in series, H'mm code seems to allow them?

That is a factory assembly that doesnt use 120 volt bulbs , the total bulbs in the series strand ad up to the equivalent of a single 120 v bulb . There are lots of factory assemble things that have series circuits inside. But the assembly has a total rating. We cant connect 120 v rated assemblys in series with other loads they all will receive very low voltage .
 

jetlag

Senior Member
Should I mention that I scanned through the entire 2008 PDF last night while I was watching TV and found nothing?

Naaaa... :D

Im still looking all I can find now is 210.6 b . It states where 120v is permitted to be connected. if two lights are in series the 120 v will not be connected to the lampholder terminals , a hot will connect to one terminal on one lamp , two lampholder terminals will connect together and only a neutral will connect to the other lapholder terminal. same for the cord and plug equipt . One equipt will receive a hot from the plug the other will receive a neutral. I remember there was a picture of some lights where I read it , exhibit 210.4 in the handbook shows the allowed connections for 210.6b, note there are no series shown as permited. It had to be an older nec handbook that had a note about series connections not allowed. I am still looking.
 

iwire

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Location
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Im still looking all I can find now is 210.6 b . It states where 120v is permitted to be connected. if two lights are in series the 120 v will not be connected to the lampholder terminals , a hot will connect to one terminal on one lamp , two lampholder terminals will connect together and only a neutral will connect to the other lapholder terminal. same for the cord and plug equipt . One equipt will receive a hot from the plug the other will receive a neutral. I remember there was a picture of some lights where I read it , exhibit 210.4 in the handbook shows the allowed connections for 210.6b, note there are no series shown as permited. It had to be an older nec handbook that had a note about series connections not allowed. I am still looking.

So just to be clear.

You are looking for a code rule that says 'we can't wire anything in series' to show that MWBCs are against the code if the neutral opens? :confused::confused::confused:

What exactly is the point you are going for?
 

jetlag

Senior Member
So just to be clear.

You are looking for a code rule that says 'we can't wire anything in series' to show that MWBCs are against the code if the neutral opens? :confused::confused::confused:

What exactly is the point you are going for?

NO I dont really know how we got off on the subject , I think it was when I said the multiwire circuit will be in series if the the loads are equal , but I just meant it would be working the same as a series , as long as the neutral is there it is not wired in series. The open neutral you mentioned is not wired in series either, if someone wired it originally with no neutral , that would be the violation I was talking about, it would be wired in series.
 
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