Ok as I suspected you are not getting 240v off of those tandems, unless you use the right side of one with the left side of the other, or something like that
multi-wire branch circuits and AFCI breakers
- Thread starter RustyShackleford
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Whitenuckler
Feeling the Heat
I'm not sure what you mean...the surge protector is what you would call a tandem, and it is feeding 240V. It hooks onto two stabs. One stab comes from the bottom bus bar, and the other from the top bus bar.
No the surge protector is on a 2-pole breaker. The mini half sized breakers on the right are tandems.
I see a handle tie (screw?) on one of them, which made me suspicious as to how it is being used. If it's feeding a MWBC, that's not allowed.
Whitenuckler
Feeling the Heat
Oh OK ya. They are what I call mini. You can get 240 buy using two next to each other which
is what I do for the heaters.
(sorry Rusty for derailing your thread)
So if I understand this right, you're using both tandems to create two 240v circuits, and the "handle tie" on the left makes sure they both shut half way off, and there's no common trip on either of them.
If you needed 2 heater circuits you'd have been better off using a regular 2-pole and piggybacking the other heater on the surge protector circuit.
So if I understand this right, you're using both tandems to create two 240v circuits, and the "handle tie" on the left makes sure they both shut half way off, and there's no common trip on either of them.
If you needed 2 heater circuits you'd have been better off using a regular 2-pole and piggybacking the other heater on the surge protector circuit.
Whitenuckler
Feeling the Heat
Starting from the bottom right are 4 mini's. The first is a 120V plug. The second is a 120V plug. Both of those are wired with 14/2.
The next two mini's feed a 14/3 cable which goes to my porch were it goes to a 2 pole 240V switch. Then it goes to a receptacle. I have the link removed so the top is 120V and the bottom is 120V each fed by different breakers. I actually added thermostats as well. One for each.
The handle tie I added (sorry didn't have the listed one) is so that if one trips, I must shut off both to service the fault.
Ok that's even worse. The two circuits going out to your porch heaters are on the SAME leg, which means you are sending 30A back on the neutral wire.
Whitenuckler
Feeling the Heat
That sounds really bad. Each time you connect a mini breaker to a panel stab, the one next mini to it is the other phase. Remember that the min breaker attaches to a separate bus stab, they do not connect to the same stab. Each stab as you go along changes phase.
I'm going to shut those breakers off and get the panel cover off to check this out. I will check it for sure. I should not assume it's right.
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Yes the spaces alternate A,B,A,B as you go down. Each tandem breaker occupies a single space, connects to a single stab but gives you two circuits that are on the same leg. So if you had all tandems, the circuits would alternate A,A,B,B,A,A,B,B.
Check the voltage at your heater receptacle. Especially the voltage between the two hots. If you have 240v there, I'll eat my words.
By the way if I'm right and they are on the same leg, the fix is super easy just swap the black wire from your heater circuit with the one from your 2nd receptacle circuit, and move the handle tie over. So it's using the "middle 2" of the 4 mini breakers so to say. Then you'll have a proper MWBC.
Whitenuckler
Feeling the Heat
I think your right. Thanks for pointing out my error. I will open the panel and use breaker 2 and 3 for the heater. I will inspect the neutral. For some reason I thought the stabs were from different phases but they must be doubles of the same phase. Again, Thanks
Well, glad I generated some useful discussion anyhow.
All I wanted to know, is it ok to use two single-pole AFCI breakers with a handle tie on a shared-neutral MWBC ? The answer is "yes", if they're the AFCI breakers that let the circuit's neutral go straight to the neutral busbar.
Siemens makes such breakers (QA115AFCN and QA120AFCN), but it's interesting to note that the breaker does in fact have a neutral connection (using the "plug on"method) but only for the breaker's internal circuitry. Check the diagram here ...
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Whitenuckler
Feeling the Heat
Sorry for the hijack, however if it was not for your post, and the attention of gthomas, I wouldn't be opening up my panel today to wire my circuit properly, and see why I made my incorrect choice. I noted that it appears they use 4 breakers to create the 200A breaker, so I think they have 2 A bars and 2 B bars. re the AFCI -I do remember seeing a coil of wire next to a new breaker. Like you say, there is a DC power supply inside for the electronics. Some video's spend time explaining why they might trip due to noise ect.
Yeah, if it's "just" an AFCI then it does not monitor the neutral. A lot of AFCI breakers are the combination type that include some level of GFP in order to pass the UL testing since,as I suggested earlier, AFCI on its own is pretty worthless. GFP monitors the sum of hot and neutral current while AFCI only monitors the hot current. A few manufacturers have managed to get their straight AFCIs to pass testing without GFP so you can use those on a MWBC.
The way they make those breakers is just two 100A breakers in parallel. It is truly parallel so each leg still lands on 1 bus bar.
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