Why 20 amp circuits?

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peter d said:
I would go to the other way - drop bedrooms and other living spaces down to 1.5 Va per square foot assuming central heating and cooling.
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But what if the furnace breaks? Or you have another Aquidneck?


Before AFCIs most electricians wired to about 5-8va per foot and it was ideal IMO.
 
mbrooke said:
But what if the furnace breaks? Or you have another Aquidneck?


Before AFCIs most electricians wired to about 5-8va per foot and it was ideal IMO.
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Good point. :ashamed1: Truthfully I really hate the 20 amp requirement in formal dining rooms, if just that alone went away I'd be happy. :lol:
 
peter d said:
Good point. :ashamed1: Truthfully I really hate the 20 amp requirement in formal dining rooms, if just that alone went away I'd be happy. :lol:
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Around here you have homes with 15amps to the dinning room, but also some dedicated 20amps in newer homes.
 
mbrooke said:
I say we mandate 5va per foot and drop all the 20amp requirements.
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:happyno:

That be one 15A circuit for every 360 SF.

Maybe too little for a kitchen and pushing overkill for bedrooms.

Current 3 VA to determine how many circuits (minimum) is needed is fine and even overkill in some instances, but applies to entire dwelling load. One room may have heavier load in some cases and nothing wrong with letting installer/designer allow for that by their own methods.
 
kwired said:
:happyno:

That be one 15A circuit for every 360 SF.

Maybe too little for a kitchen and pushing overkill for bedrooms.

Current 3 VA to determine how many circuits (minimum) is needed is fine and even overkill in some instances, but applies to entire dwelling load. One room may have heavier load in some cases and nothing wrong with letting installer/designer allow for that by their own methods.
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Before AFCIs you had more circuits, sometimes even double- at least homes did where I live. Less so in apartments, but still if you had 4 bedrooms most got their own circuit now two will share on circuit. Granted back then you often had the baths on those circuits, but overall the VA per foot was higher.
 
mbrooke said:
Before AFCIs you had more circuits, sometimes even double- at least homes did where I live. Less so in apartments, but still if you had 4 bedrooms most got their own circuit now two will share on circuit. Granted back then you often had the baths on those circuits, but overall the VA per foot was higher.
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AFCI's didn't really make me run circuits any differently. But I generally have done and still put all receptacles on 20 amp circuits and all the lighting on 15 amp circuits. I will put receptacles of 3 or 4 bedrooms on one 20 amp circuit and all the lights on one end of typical house on one 15 amp circuit. Amounted to two maybe 2.5 circuits for 4 bedrooms on average. Many guys were running 4 circuits to 4 bedrooms (all 15 amp) before AFCI, and now are running about 2 circuits to 4 bedrooms like you said. 12 AWG not that much more expensive, and less home runs can offset cost some as well. Lights don't dim when you turn on that vacuum cleaner or some other heavy load especially when not on same 15 amp circuit.

Works for me.

Add: this be for new construction/new additions with central cooling/heating that will sufficiently condition the space. If existing home being re-wired considerations for window AC's or possible need for portable heaters is taken into consideration and more circuits may be run.
 
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My rule of thumb is 2 rooms per circuit with living and bedroom areas, code required for everything else. It works fine without issue. I think dedicated circuits for bedrooms is stupid.
 
kwired said:
AFCI's didn't really make me run circuits any differently. But I generally have done and still put all receptacles on 20 amp circuits and all the lighting on 15 amp circuits. I will put receptacles of 3 or 4 bedrooms on one 20 amp circuit and all the lights on one end of typical house on one 15 amp circuit. Amounted to two maybe 2.5 circuits for 4 bedrooms on average. Many guys were running 4 circuits to 4 bedrooms (all 15 amp) before AFCI, and now are running about 2 circuits to 4 bedrooms like you said. 12 AWG not that much more expensive, and less home runs can offset cost some as well. Lights don't dim when you turn on that vacuum cleaner or some other heavy load especially when not on same 15 amp circuit.

Works for me.

Add: this be for new construction/new additions with central cooling/heating that will sufficiently condition the space. If existing home being re-wired considerations for window AC's or possible need for portable heaters is taken into consideration and more circuits may be run.
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I agree with what you are saying, but if those bedrooms are big enough and up north, expect space heaters. It was one of the drivers behind having more circuits in terms of the contractor's reasoning- when AFCIs came out at $45 per breaker and no 14/3 it made wiring to code minimum essential.

My point is that if the NEC changed 3va to 5va it would have effected few before AFCIs.
 
If you go back 60 years, what was in our house as it is today?
A big difference in the area where the actual living is going on. And there is where the 3 watts per square foot is.
Now, I have more lighting, nine computers in the house, TV, Phones being charges, etc., and I do not trip any 15 amp breakers. The 3 watts per square foot was overkill from the start.

Who knows what the number should be, but it stands to reason that you can only put so much crap in a house given the square foot... The 3va has proved it works and we have accepted it.

No way we are ever going to reduce the 20 amp circuits in the code. That is a dream that will never happen. I would think it will go in the other direction if any...
 
Gary11734 said:
If you go back 60 years, what was in our house as it is today?
A big difference in the area where the actual living is going on. And there is where the 3 watts per square foot is.
Now, I have more lighting, nine computers in the house, TV, Phones being charges, etc., and I do not trip any 15 amp breakers. The 3 watts per square foot was overkill from the start.

Who knows what the number should be, but it stands to reason that you can only put so much crap in a house given the square foot... The 3va has proved it works and we have accepted it.

No way we are ever going to reduce the 20 amp circuits in the code. That is a dream that will never happen. I would think it will go in the other direction if any...
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More lighting, but modern lighting is more efficient. Some appliances are more efficient. It still takes a certain watts to boil a set amount of water in a specific amount of time or similar, though a microwave may do it more efficiently than a hot plate will.

The computers, phones, TV's aren't really all that significant of a load, though we did have a lot of these things even 20-25 years ago and many of them today are also more efficient then what we were using then. My notebook likely uses less energy than my first desktop, and has more abilities than that first desktop had as well. My wife seldom uses a computer, does most all "computer stuff" on her phone, which has to be even more efficient energy wise.
 
kwired said:
More lighting, but modern lighting is more efficient. Some appliances are more efficient. It still takes a certain watts to boil a set amount of water in a specific amount of time or similar, though a microwave may do it more efficiently than a hot plate will.

The computers, phones, TV's aren't really all that significant of a load, though we did have a lot of these things even 20-25 years ago and many of them today are also more efficient then what we were using then. My notebook likely uses less energy than my first desktop, and has more abilities than that first desktop had as well. My wife seldom uses a computer, does most all "computer stuff" on her phone, which has to be even more efficient energy wise.
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When did the first 3va per square hit the code? I bet we had 100 amp services to the house or less... They had to make a calculation way back then. How did they figure that first calculation with what they knew was in houses at the time... No way could they have anticipated loads of today from back then. The incandescent lighting alone jumped considerably

I would assume they took the approach of you can only cram so much crap in a house per square, and took a wild ass guess...
 
Gary11734 said:
When did the first 3va per square hit the code? I bet we had 100 amp services to the house or less... They had to make a calculation way back then. How did they figure that first calculation with what they knew was in houses at the time... No way could they have anticipated loads of today from back then. The incandescent lighting alone jumped considerably

I would assume they took the approach of you can only cram so much crap in a house per square, and took a wild ass guess...
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Well many old houses out there only had 30 amp services originally, then maybe when electric ranges came around got 60 amp services, and many of those 60 amp fuse panels were still in operation into the 90's, although there were often 30 amp fuses on 14 AWG branch wiring - but the 60 amp mains still held if they hadn't added too much as in water heater, dryer, air conditioner. Remember that 3 VA is mostly for the service/feeder calculation and not for branch circuit calculations. We still have to account for individual branch circuit loads, 1500 VA for the laundry, 1500 VA for each SABC...

You may have more gadgets in your house today but what is the real load compared to years ago? You might have many kitchen appliances (talking countertop type appliances), but how many do you use at one time? And even if using several of those at one time, you likely have something else in the house that you aren't using - you are in the kitchen cooking and not in the bathroom drying your hair.
 
Gary11734 said:
When did the first 3va per square hit the code? I bet we had 100 amp services to the house or less...

I would assume they took the approach of you can only cram so much crap in a house per square, and took a wild ass guess...
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That 3 VA pr sq ft is just for the general lighting load and doesn't add up very fast. When doing a load calculation you normally only use the first 10 KVA at 100% and the remainder at 40%.

Where the load started to add up was when people go central A/C units ( many of the older units were not that efficient ) . Then there were the heat pumps with back up heat strips. Then there were the hot tubs. The tankless water heaters. The EV chargers.

100 amp service is still good for many homes with gas heat, gas water heater, gas range, gas dryer. Depending on the A/C units you may be able to use electric water heater (tank type) or even some electric cooking ( counter top).

Most of the bigger services on homes are just to be prepared for what may get installed. Cheaper to install a larger service and have it in place than to come back and redo the service.
 
growler said:
That 3 VA pr sq ft is just for the general lighting load and doesn't add up very fast. When doing a load calculation you normally only use the first 10 KVA at 100% and the remainder at 40%.

Where the load started to add up was when people go central A/C units ( many of the older units were not that efficient ) . Then there were the heat pumps with back up heat strips. Then there were the hot tubs. The tankless water heaters. The EV chargers.

100 amp service is still good for many homes with gas heat, gas water heater, gas range, gas dryer. Depending on the A/C units you may be able to use electric water heater (tank type) or even some electric cooking ( counter top).
Most of the bigger services on homes are just to be prepared for what may get installed. Cheaper to install a larger service and have it in place than to come back and redo the service.
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The 3va was overkill. IMHO... Just as the 20 amp circuits are now...
 
Gary11734 said:
The 3va was overkill. IMHO... Just as the 20 amp circuits are now...
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Only 20 amp circuits required are SABC's, laundry, bathroom and more recently garage. Though I have no issue with running 15 amp circuits to those area's either from a code perspective, from a design perspective I'd run 20 amp circuits to them (and more) anyway. This kind of pushes things as far as code not being a design manual IMO especially when it comes to a general purpose recetpacle outlet that doesn't have any designated load to be connected to it.

Running an individual 15 amp circuit to every kitchen receptacle - in most instances gives you more total VA ability in that kitchen than splitting them up over the minimum required two 20 amp circuits, and no reason this shouldn't be able to be a design choice, but this is not any new rule by any means either, think it goes back at least 50-60 years if not more.
 
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