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Measurements for a dedicated line

The question of whether a homeowner should get a dedicated line is often like "should I get bangs." It’s a little complicated. Here are a couple of reasons to consider not:

I. My experience is that you won’t eliminate all the other noise coming from your home even if you do run a dedicated line. I still hear motors switching on and off despite being on completely different circuits.

II. A little resistance and a little inductance may actually be a good thing in keeping noise out of your line, so overkill on the wire gauge may not help this.

Why you definitely should get a dedicated line, with thicker wiring:

 

Less voltage sag.

 

Voltage sag means that under load the resistance in the line will cause the AC cabling int he wall itself to consume some of the AC voltage, giving your gear less volts to work with. This sag is proportional to current, so the more amps your gear is drawing the more sag.

This sag is something you can measure. There are two things you need to look: The hot to neutral voltage and the neutral to ground.

With nothing on the circuit your N-E (neutral to earth or ground) should be 2V or less. If it’s significantly higher than that stop and call an electrician. That’s true for any circuit in your home. High N-E values are indicators of a problem which may be in the circuit or in the service wiring from outside to the panel.

What happens when you turn your equipment on and play music is that the line will sag. The H-N (hot to neutral) voltage will drop, and the N-E will go up. Some sag as you turn on big amps is normal. So long as you are not tripping breakers you are fine. What you want to measure is the sag after your system has stabilized and while it’s playing music.

Keep an eye on the N-E value, as this will be a good indicator of the sag independent of the incoming line voltage. It may also point out where you may have issues. That is, if you measure an extra 2V of N-E, your sag is probably around 4V, so you went from 120V to 116V and you can be relatively comfortable it isn’t outside influences.

Of course, any good multimeter will work for this but I like plug in meters with built in N-E measurements. This one is cheap, and the N-E may not be hyper accurate, but it is the only device I’ve found on Amazon that will show you both the H-N and N-E voltages at the same time.

The nice thing about any plug-in type voltage meter is you can watch it over  a couple of days without hand holding probes in the socket.

If you find another which does both please post.

 

 

erik_squires
dpop
293 posts
 

@erik_squires Good point Erik. I have a Panini maker which is rather light in weight, and easier to relocate vs. my pizza oven or microwave. It consumes 11.8 amps (the pizza oven consumes 11.5 amps). I plugged it into my 10 AWG main audio feed AC outlet. Volts available at the outlet at that moment was 121.8. Volts available with the Panini maker on was 119.0 (a voltage drop of -2.8 volts). N-E volts was 00.

I knew the 10 AWG feed was about 15 feet in length from the circuit breaker box to the measuring point. My other AC circuit feeds for my microwave and pizza oven I discovered are on the same 20 amp circuit as each other (good thing I never have a reason to run the pizza oven and microwave at the same time). The pizza oven and microwave are on a completely different circuit than my 10 AWG AC feed. My house was built in 1942, and the pizza oven wiring has never been updated, except with a new outlet at some point. The microwave outlet was installed at a later date, with copper wiring. The previous owners of the house had that installed. It was tied into the same circuit as the pizza oven outlet. Within the past 10 years I updated that microwave/pizza oven circuit breaker to the recent AFCI type. I’m guessing the wire run to the pizza oven outlet is around 20 feet, and the microwave outlet is 30 feet. Suffice to say there was more voltage drop at the pizza oven outlet (consuming roughly the same amount of amps as the panini maker), at -3.7 volts, than there was at my dedicated 10 AWG feed (-2.8 volts), consuming roughly the same amount of current.

Some of this was eye-opening, as I didn’t anticipate I would see that amount of voltage drop with high current demand at my 10 AWG feed, only 15 feet away from the circuit breaker box. One thing is for sure, I would not want to have any audio components on a microwave or pizza oven circuit when they would be in use.

erik_squires OP
16,406 posts
 

My house was built in 1942, and the pizza oven wiring has never been updated, except with a new outlet at some point.

@dpop

Ahhh! Yeah, you can’t do that today. The microwave gets it’s own circuit, which as of 2023 has to be CAFCI and GFCI protected.

Within the past 10 years I updated that microwave/pizza oven circuit breaker to the recent AFCI type.

Nice! Please make sure that all your kitchen counter top circuits are GFCI protected as well. Not sure if an outlet or updated breaker will be the most convenient for you in this case. Leave the fridge alone though, those trip GFCIs all the time. GFCI for kitchen counter top outlets has been code for decades but the latest 2023 NEC code expands GFCI to the dishwasher, microwave, and washer/dryer combos. I’m not sure you need to go that crazy, but I do think it’s worth the GFCI outlets on the counter tops for sure, and any outlets under a kitchen counter as well.

If you buy more GFCI outlets, any major brand but Leviton seem to have high trust factors with online electricians.

 

dpop
293 posts
 

I have a dual gang countertop outlet that has a GFCI outlet in it. It is then connected to, and protects the outlet right next to it. The microwave is across the room, and isn’t within 6 feet of the kitchen sink. When I first moved in in 2001, I inspected and replaced all of the outlets in the house. When I changed out the pizza oven outlet, the insulation on the wires was cracking, and I told myself I hope I don’t have to replace this outlet for a long time after that - so I won’t be switching that outlet to a GFCI. Since we’re discussing this, I’ll probably change out the current AFCI circuit breaker for the microwave/pizza oven circuit with the combo CAFCI/GFCI type (I have a Siemens load center). Having been an apartment maintenance guy for over 10 years, we too never installed GFCI’s for refrigerators. 

erik_squires OP
16,406 posts
 

@dpop Sounds good!!

GFCI outlets are cheaper ($20), but if it's not in a convenient location to reset when it trips then a new combination breaker is the way to go.

I also have Siemens.  My panel used 100% Siemens breakers, that were 15 years old when I moved in.  My neighbor had a weird assortment of breaker brands in hers.  I've replaced 100% of the single pole breakers and added a whole-house surge suppressor.  It makes me feel better, but I still lost a laptop in a storm that had no other surge protector on it.

dpop
293 posts
 

I too have whole house surge suppression (never lost anything from storm damage the entire time I lived at this location - going on 23 years now), but since I have so much money wrapped up in audio, video and AC isolation and filtering gear, I sometimes contemplate spending the money on a higher quality surge protector. 

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