Dedicated 20 amp lines/should i use a sub panel

Thank you, Larry (lak). Jim (Jea48) is the expert when it comes to electrician-type matters, and hopefully he’ll chime in. But FWIW I agree with all of the comments by Dill. I doubt that adding a sub-panel would provide any benefit, and as Dill indicated inserting additional contacts into the path won’t be helpful.

Unless, that is, the sub-panel is something like those made by Equi=Tech which incorporate a high quality transformer and would provide balanced power to the system. However their models cost in the vicinity of $10K or more, and weigh upwards of 300 pounds.

Good luck. Regards,
-- Al

I agree with dill as well, no need for a sub panel, jmho.

noromance
899 posts                                                                       01-03-2018 10:23pm

I ran 2 x 20amp runs on 10 gauge from 2 side by side breakers for monoblocs. I ended up not using one of them because of a hum loop. Let us know how you get on.

@noromance,

By side by side, do you mean the breakers are installed directly across from one another? Connected to the same main bus breaker tie. (Both are fed from the same leg, Line.)
Or, do you mean one is installed above the other, side by side? One fed from leg, Line 1 and the other fed from Leg, Line 2?

Did you use Romex?
Did you try to keep the 2 cables separated from one another at least 6" after getting them out of the electrical panel, as soon as practical? Especially a long parallel run?
Is it possible one of the 2 is running parallel next to some other branch circuit?

Jim

Jim, Some replies below.

By side by side, do you mean the breakers are installed directly across from one another? Connected to the same main bus breaker tie. (Both are fed from the same leg, Line.) Or, do you mean one is installed above the other, side by side? One fed from leg, Line 1 and the other fed from Leg, Line 2?
>>> Same leg/busbar. One 20A breaker above other.

Did you use Romex?
>>> Yes. 8/2 NM-B (not 10 as I said before) cable from Lowes.

Did you try to keep the 2 cables separated from one another at least 6" after getting them out of the electrical panel, as soon as practical? Especially a long parallel run?
>>>Yes. 12 feet apart.

Is it possible one of the 2 is running parallel next to some other branch circuit?
>>>It’s possible but not obvious.

>>>I also tried tying the ground wires to the same terminal, removing the ground (to test only) and moving other equipment to different runs to no avail. I’ll be honest, I abandoned messing around with it after an hour and removed one leg and used the cable for another project. The one 8/2 run on a 20A breaker into a 20A L5-20/L5-20P receptacle/plug sounds great.

noromance
901 posts                                                                     01-04-2018 12:07pm

Jim, Some replies below.

By side by side, do you mean the breakers are installed directly across from one another? Connected to the same main bus breaker tie. (Both are fed from the same leg, Line.) Or, do you mean one is installed above the other, side by side? One fed from leg, Line 1 and the other fed from Leg, Line 2?
>>> Same leg/busbar. One 20A breaker above other.

>>>

Same leg/busbar. One 20A breaker above other.

If the breakers are directly above one another, there in on the same side of the electrical panel, they are not fed from the same leg/bus bar. (For standard size single pole breakers.) One is fed from one leg, Line, and the other is fed from the other Leg, Line.

You can easily verify this with a multimeter.
Insert one test probe in the Hot contact of an outlet fed from one dedicated circuit and the other test probe in the Hot contact of the other dedicated circuit outlet.
~ If both are fed from the same leg, Line, bus bar, the meter will measure zero volts.
~ If the meter reads 240V, nominal, then one circuit is fed from one leg, Line, and the other circuit is fed from the other leg, Line.

Did you use Romex?
>>> Yes. 8/2 NM-B (not 10 as I said before) cable from Lowes.

8-2 with ground? Not 8-3 with ground?

Jim

Besides having built-in noise cancelling features, and surge protection, another advantage to the sub-panel is that you end up with a star grounding scheme that is short, and therefore much less likely to cause differences in ground potential.

The biggest source of noise in my mind is usually other household appliances, and dimmer switches. If you get separate runs, without any noise cancelling, you are literally just making it easier to pick up noise from anywhere in the house. Having a 30 to 60 Amp subpannel that has its own noise and surge protection is the key.

Best,

E