What Voltage/AMPS does power enter most US homes?

[Daddy Tanuki]

just curious, what makes you think it is 3 phase? US dryers use 240 split phase as has been explained above. while I am not an appliance guru I have never seen a 208 3 phase dryer offered for a house. I ahve seen them in gyms and in industrial settings but these are freaking huge honking speed queens that run about 12k USD each when I was looking at them for a contract I was bidding on... i just cannot see it in a house... this was for the outdoor rec center to mass dry rental ski wear/sleeping bags etc....

I am betting that you are confusing split phase with 3 phase... they both can put out 220-240 ish but it one is 120 degrees out of phase the other is 180 out of phase. totally different animals.

 

[Koyaanisqatsi]

Honestly I was not expecting to find this, and not so easily either: https://products.geappliances.com/appliance/gea-support-search-content?contentId=38410

I dealt with 208V/3ph at a past employer when I was building out our data center. As far as appliances go, the vast majority of appliances that are "240V" support anything from 200-250V AC, so it's not a huge concern in that regard.

But for inverters, you must be careful to configure them correctly, and be sure they can handle the configuration. The reason you get 120V from a 208V/3ph system is because the 120V legs are each 60 (oops! that should be 120) degrees out of phase with each other, whereas with 120/240V split-phase, the two 120V legs are in phase (some will say they are 180 degrees out of phase, but that is incorrect because they are actually the same phase, just split in half by the neutral wire). I have not seen (nor have looked for) any inverters that can be configured for 208V/3ph. Most are either 120V or 120/240V split-phase.

You could actually have 480V/3ph service in your house. I have a friend with that, and he about crapped his pants when PG&E wanted a $3000 deposit when he bought the house. It's very unlikely, but possible. Make sure you are certain whether you have 208V/3ph or 480V/3ph. Both will present certain challenges. But they require completely different approach to wiring your inverters, and how you would need to balance your loads across the three phases.

 

[hwy17]

You probably don't have all 3 phases but you have 2 phases of a wye, giving you 120/208 power and your lines are 120 degrees out of phase. It comes from a three phase transformer bank, but it mostly acts like regular split phase power.

This is very easy for a grid tied inverter like a Sunny Boy or Enphase to deal with and more complicated for a battery backup system to work with.

 

[timselectric]

I have not seen (nor have looked for) any inverters that can be configured for 208V/3ph.

Most can be configured for 3-phase, with multiple units.
Or , you can buy a dedicated 3-phase inverter.

 

[JohnnyDangerDude]

just curious, what makes you think it is 3 phase? US dryers use 240 split phase as has been explained above. while I am not an appliance guru I have never seen a 208 3 phase dryer offered for a house. I ahve seen them in gyms and in industrial settings but these are freaking huge honking speed queens that run about 12k USD each when I was looking at them for a contract I was bidding on... i just cannot see it in a house... this was for the outdoor rec center to mass dry rental ski wear/sleeping bags etc....

I am betting that you are confusing split phase with 3 phase... they both can put out 220-240 ish but it one is 120 degrees out of phase the other is 180 out of phase. totally different animals.

Oh, did I say I had a 3 phase dryer? If I did, I may have misspoken. No, I don't have a 3 phase dryer but I do have 3 phase AC unit, pool pump and various other large motors in my house. I know they are 3 phase because the metal plate on them say its 3-phase and my power company told me that my house is has 3 phase which is very rare for a house.

I have also had issues where the power company has dropped a phase and the lights, tv computers, etc.... have worked by the AC and other motors would not turn on.

 

[JohnnyDangerDude]

Honestly I was not expecting to find this, and not so easily either: https://products.geappliances.com/appliance/gea-support-search-content?contentId=38410

I dealt with 208V/3ph at a past employer when I was building out our data center. As far as appliances go, the vast majority of appliances that are "240V" support anything from 200-250V AC, so it's not a huge concern in that regard.

But for inverters, you must be careful to configure them correctly, and be sure they can handle the configuration. The reason you get 120V from a 208V/3ph system is because the 120V legs are each 60 (oops! that should be 120) degrees out of phase with each other, whereas with 120/240V split-phase, the two 120V legs are in phase (some will say they are 180 degrees out of phase, but that is incorrect because they are actually the same phase, just split in half by the neutral wire). I have not seen (nor have looked for) any inverters that can be configured for 208V/3ph. Most are either 120V or 120/240V split-phase.

You could actually have 480V/3ph service in your house. I have a friend with that, and he about crapped his pants when PG&E wanted a $3000 deposit when he bought the house. It's very unlikely, but possible. Make sure you are certain whether you have 208V/3ph or 480V/3ph. Both will present certain challenges. But they require completely different approach to wiring your inverters, and how you would need to balance your loads across the three phases.

So assuming I have for sake of argument 480V/3ph. What happens if all the power inverters are on a single same leg. The micro-inverters detect what the grid is providing and tries to match the same volts, frequency, phase, etc right? What if a single legs and phase gets all the solar power and its uneven. Do you still get the energy savings but the power company thinks it looks weird?

Do you have to put the power on the same phase that is supplying the rest of your house vs the 3rd phase lines?

Does the 480V input vs the smaller 240 or 120 volt produced by solar guarantee that no power will ever flow upstream to the grid itself doe to the volt difference?

Like having main water pipe with 80PSI and water being backfeed in at 20 PSI into a garden hose facet( not that anyone would ever do this).

100 PSI is going to overwhelm/overpower the 20 PSI?

 

[Bkord]

So assuming I have for sake of argument 480V/3ph. What happens if all the power inverters are on a single same leg. The micro-inverters detect what the grid is providing and tries to match the same volts, frequency, phase, etc right? What if a single legs and phase gets all the solar power and its uneven. Do you still get the energy savings but the power company thinks it looks weird?

Do you have to put the power on the same phase that is supplying the rest of your house vs the 3rd phase lines?

Does the 480V input vs the smaller 240 or 120 volt produced by solar guarantee that no power will ever flow upstream to the grid itself doe to the volt difference?

Like having main water pipe with 80PSI and water being backfeed in at 20 PSI into a garden hose facet( not that anyone would ever do this).

100 PSI is going to overwhelm/overpower the 20 PSI?

If you have 480, your inverter will probably be set up for 480/277. No house in the United states has 480, without a step down transformer to give you 120/240 or 208

 

[wpns]

I suspect you have 120/208 3-phase, what voltage do you read on a clothes dryer outlet?

If so you'll want to put your 120V micro-inverters (approximately) equally on all three phases. Which probably means having an electrician run wires to the attic for three separate 120V plugs on each of the three phases.

Then again, with the way Net Metering is going, I'd run high voltage DC strings from the roof to the basement in metal conduit with RSD on each panel, and do all the wiring and grid interface in the basement. I mean, I don't want to project on you, but in a few years you are going to want zero export and battery backup and enhanced self-consumption, and maybe even off-grid operation, and you are _not_ going to want to pull everything off the roof, swap the micro inverters for RSD boxes, and run metal conduit to the basement... Do the roof work, racking, modules, and wiring once.

 

[JohnnyDangerDude]

I suspect you have 120/208 3-phase, what voltage do you read on a clothes dryer outlet?

If so you'll want to put your 120V micro-inverters (approximately) equally on all three phases. Which probably means having an electrician run wires to the attic for three separate 120V plugs on each of the three phases.

Then again, with the way Net Metering is going, I'd run high voltage DC strings from the roof to the basement in metal conduit with RSD on each panel, and do all the wiring and grid interface in the basement. I mean, I don't want to project on you, but in a few years you are going to want zero export and battery backup and enhanced self-consumption, and maybe even off-grid operation, and you are _not_ going to want to pull everything off the roof, swap the micro inverters for RSD boxes, and run metal conduit to the basement... Do the roof work, racking, modules, and wiring once.

You are saying that micro inverter should be replaced with a RSD. RSD is a disconnection system right? My power goes into the garage not a basement. In Florida, basement flood during hurricanes.

I have a lot of commercial stuff in my house and I think my biggest power demand if from a 20-ton water chilled AC unit along with the circulating pump, fans, etc.

I looked at one of the Square D box connected to a circulating water pump and it said " 30 AMP, 240V AC"

STD 3, 240V A.C 3 phase max 7 1/3

So I at least have 240V, 3 phase and 30 AMP.

So 240V X 30A = 7,200W?
for 3 phase means you can do it twice so like 7,200W on each rail? 14,400W theoretical limit?

Also, why deal with batteries unless you are off grid cabin in the woods setup? That makes things more expensive. What do you mean by a few years wanting to zero export? Do you mean because power companies are cheating customers are buying back power at lower rates then they charge? So some people it might be cheaper for them to keep extra power on like a Tesla power wall or other battery backup system?

Thanks.

 

[JohnnyDangerDude]

If you have 480, your inverter will probably be set up for 480/277. No house in the United states has 480, without a step down transformer to give you 120/240 or 208

I think there is a step down Transfer before the meter by the street in front of my house . In one of those green boxes.

 

[Supervstech]

Ok, residential 3 phase is NOT the same as commercial.

Usually, they install a high leg 240V 3phase setup.

You really need to know what you have exactly before buying equipment to inject solar into it.

208/120V 3phase is common in apartments, and light commercial.
480/277 would never be in residential, but 480 high leg, 240/120 has been seen, along with 360 hogh leg, 240/120

Find out what you have first.

 

[Hedges]

Check with DMM, likely all lines are 120V L-N, and between any two lines 208V L-L.

A number of single phase inverters support 208V and 240V, maybe jumper configured or just by connecting L1, N, L2 it will auto-detect. Some also work at 277V, but you aren't going to have 277/480Y in the house. Possibly to a shop, with transformer to feed house 120/208Y.

Or high-leg as Supervstech says! 240V high-leg delta would make sense. I met PG&E's requirements to get it but connection cost was too high.

You can also get 3-phase inverters. Plenty of commercial solutions available.

You need to start with utility company rules on grid tie PV. Is net metering available, and on what terms? What features are required for inverters? Some locations (e.g. California) have done away with retail credit for backfeed, so PV only makes sense if you add a battery, or if it is worthwhile to offset loads at the moment sun is shining.

How much is your electric bill? How many kWh/month do you consume?

Why do you say "microinverters"? There are other architectures that are less expensive, more reliable, more efficient, more flexible in terms of battery backup capabilities. Microinverters are the preferred choice to simplify design effort, therefore the preferred choice to sell to consumers.

 

[wpns]

You are saying that micro inverter should be replaced with a RSD. RSD is a disconnection system right?

Correct. Any roof-mounted panels should have RSD. Code requires them in some circumstances, but I like them for safety in all circumstances. In fact, when my Round Tuit arrives I'm going to upgrade my ground mount to RSD.

My power goes into the garage not a basement. In Florida, basement flood during hurricanes.

Yes, but you live in the "USA" so please substitute "the place where all your power distribution happens".

I looked at one of the Square D box connected to a circulating water pump and it said " 30 AMP, 240V AC"
STD 3, 240V A.C 3 phase max 7 1/3

OK, so you have a box that'll work on 240V, but you still don't know if you have 240 or 208. You have a DVM, go measure it. You don't even have to open a box, just unplug your clothes dryer and stick your DVM leads in it. Most "240V" equipment will run on 208, so until you measure it, you won't know for sure. Also, as others have pointed out, there are a number of ways to get "120V and 240-ish-volt" power from 3-phase systems, and the details of what you have matter.

Also, why deal with batteries unless you are off grid cabin in the woods setup? That makes things more expensive. What do you mean by a few years wanting to zero export? Do you mean because power companies are cheating customers are buying back power at lower rates then they charge? So some people it might be cheaper for them to keep extra power on like a Tesla power wall or other battery backup system?

Well, in my experience (and that's all it is, my experience) the worst solar mistake I made was to go with grid-tie equipment that _didn't_ support batteries and then had to replace it all within 6 months with inverters that do support batteries. This forum is full of stories of folks who had Net Metering, and then had it changed, or had NEM{1,2} and are either stuck or have to re-engineer for NEM{2,3}, or had the PoCo call them for having the temerity to push entire watt-hours of power back into the grid without permission.

Plan for the future:

 

[JohnnyDangerDude]

Ok, residential 3 phase is NOT the same as commercial.

Usually, they install a high leg 240V 3phase setup.

You really need to know what you have exactly before buying equipment to inject solar into it.

208/120V 3phase is common in apartments, and light commercial.
480/277 would never be in residential, but 480 high leg, 240/120 has been seen, along with 360 hogh leg, 240/120

Find out what you have first.

I don't know why these guy don't print what type of hookup you have on the meter or some equipment.

I called my power company and asked them what type of setup I have and they had no clue. Every phone option is about different ways to pay your bill but the people answering the phones don't know anything about power or phases.

How am I suppose to tell my hookup type. The picture on the pump shutoff switch said 3 -phase, 240V 30amp, That is the only information I have been able to see so far.

 

[JohnnyDangerDude]

Check with DMM, likely all lines are 120V L-N, and between any two lines 208V L-L.

A number of single phase inverters support 208V and 240V, maybe jumper configured or just by connecting L1, N, L2 it will auto-detect. Some also work at 277V, but you aren't going to have 277/480Y in the house. Possibly to a shop, with transformer to feed house 120/208Y.

Or high-leg as Supervstech says! 240V high-leg delta would make sense. I met PG&E's requirements to get it but connection cost was too high.

You can also get 3-phase inverters. Plenty of commercial solutions available.

You need to start with utility company rules on grid tie PV. Is net metering available, and on what terms? What features are required for inverters? Some locations (e.g. California) have done away with retail credit for backfeed, so PV only makes sense if you add a battery, or if it is worthwhile to offset loads at the moment sun is shining.

How much is your electric bill? How many kWh/month do you consume?

Why do you say "microinverters"? There are other architectures that are less expensive, more reliable, more efficient, more flexible in terms of battery backup capabilities. Microinverters are the preferred choice to simplify design effort, therefore the preferred choice to sell to consumers.

I think FPL for the south Florida area is they charge you like 12.5 cents per kwh but if you provide them power, they only pay like 2-3 cents per KWH. So, your cost is 12.5+ cents but if you sell to them, its only 2-3 cents. Does not seem like a good deal to ever produce more than you use if those are the rates.

If you have any excess net metering credits at the time of your true-up, FPL will pay you out at the “average annual cost of generation” per kWh. The annual cost of generation is substantially lower than the retail rate of electricity, usually between $0.02 and $0.03 per kWh for FPL. Then your net metering credit bank will be reset to zero.
Also, I am using almost 13,000 kwh at any given time. So there is no way I am ever going to produce more then that. Plus my micro inverters have a mode where they will only produce power for my house but "zero export" to the real grid. Even looking at a hour by hour of my power usage on the lowest billing months, it was never less then 8,000 kwh.

I don't necessarily have to use my solar panels to do 3-phase power since even my non-3 phase power usage is greater then I could ever produce with solar. Also, the battery backup option will probably eat away at any savings with constantly having to replace those batteries. I was told that its best just to use what you produce in real time rather then trying to deal with batteries(Unless you are in a cabin in the woods off-grid situation)

What is the other architectures that are less expensive, more reliable and more efficient then micro inverters? Can you give me a name or link to a product that I can checkout? All the youtube people are talking up microinverters. I thought that was the current technology.

Please tell me the other options?

Thanks.

 

[wpns]

How am I suppose to tell my hookup type.

Read back in this thread and take the requested measurements.

 

[wpns]

Also, I am using almost 13,000 kwh at any given time.

That makes no sense at all. I can’t tell if you have solar panels and (120V?) micro inverters or you are planning on installing them without permits.

You need to help us to help you.

 

[JohnnyDangerDude]

That makes no sense at all. I can’t tell if you have solar panels and (120V?) micro inverters or you are planning on installing them without permits.

You need to help us to help you.

What does not make sense? I am in the process of trying to buy and set this system up It's a work in process.
We use 120V in the US except for bigger stuff like motors use 240.

I hope to be able to take the edge off my power bill. I have no plans to export anything to the utility. The inverter has a special mode which is will not export to the utility, just your house.

Thanks.

 

[JohnnyDangerDude]

Correct. Any roof-mounted panels should have RSD. Code requires them in some circumstances, but I like them for safety in all circumstances. In fact, when my Round Tuit arrives I'm going to upgrade my ground mount to RSD.

Yes, but you live in the "USA" so please substitute "the place where all your power distribution happens".

OK, so you have a box that'll work on 240V, but you still don't know if you have 240 or 208. You have a DVM, go measure it. You don't even have to open a box, just unplug your clothes dryer and stick your DVM leads in it. Most "240V" equipment will run on 208, so until you measure it, you won't know for sure. Also, as others have pointed out, there are a number of ways to get "120V and 240-ish-volt" power from 3-phase systems, and the details of what you have matter.

Well, in my experience (and that's all it is, my experience) the worst solar mistake I made was to go with grid-tie equipment that _didn't_ support batteries and then had to replace it all within 6 months with inverters that do support batteries. This forum is full of stories of folks who had Net Metering, and then had it changed, or had NEM{1,2} and are either stuck or have to re-engineer for NEM{2,3}, or had the PoCo call them for having the temerity to push entire watt-hours of power back into the grid without permission.

Plan for the future:
View attachment 250702

I will never produce more power than I use. I have a small flat area that I can have solar panels and use nearly 13,000 watts at any given time.

I'm not going to ever produce anywhere near that amount.

I checked one of my motors and it said " Volts 230/460" and its running 24/7

It does not say 208. I am not in a apartment building.

So. 230V must be what I have.

That is a funny scene by star wars by the way.

 

[HarryN]

A lot of people wish that they had 3 phase / 208 at their homes - wish I did.

The motor might say a variety of things, what matters if it says 3 phase or not.

Of course, it slightly complicates using residential solar equipment vs you will want to look at 3 phase micro inverters to do it " conventionally".

It is tempting to consider instead to try to just power a couple of critical loads that are always using some power and do it as a DC based system instead of micro inverters. For example maybe things in the garage such as a second refrigerator, etc.

If you have a pool pump or similar, see what it would take to move that off grid. Mostly solar and then backed up with the grid using a charger.

Your 20 ton air conditioner is a big consumer, but it might be tough to try to run that from solar. Smaller loads are easier for solar to deal with. Let the utility deal with the harder to run loads - take on the 1 - 4 kW stuff.

 

[HarryN]

Here is a little bit about 3 phase in case it is helpful.

Three-phase electric power - Wikipedia

en.wikipedia.org

 

[Supervstech]

I don't know why these guy don't print what type of hookup you have on the meter or some equipment.

I called my power company and asked them what type of setup I have and they had no clue. Every phone option is about different ways to pay your bill but the people answering the phones don't know anything about power or phases.

How am I suppose to tell my hookup type. The picture on the pump shutoff switch said 3 -phase, 240V 30amp, That is the only information I have been able to see so far.

That is good info, pull your breaker panel cover and look at the wiring color codes.

 

[Supervstech]

So, take your volt meter, measure phase to neutral on each lug, and record the voltages.
Two will show 120, one will show 208.

 

[timselectric]

Just take a Picture of your service panel, with the cover removed (please be careful). And we can tell you what you have.

Actually, there should be a label on the panel (probably on the inside of the door) that should tell you what it is.

 

[wpns]

I will never produce more power than I use. I have a small flat area that I can have solar panels and use nearly 13,000 watts at any given time.

Your base load is 13KW? Your monthly electric bill is around $1000?

I checked one of my motors and it said " Volts 230/460" and its running 24/7

Again, many "230-volt" motors will run just fine on 208, 220, 230, 240, whatever you feed them. The nameplate on the motor doesn't tell you how your house is wired.

Either measure it or send pictures of the inside of your panel, and we'll all know for sure. Note: Please DO NOT pull the cover off your main service panel if you don't know what you are doing, and are comfortable with and experienced at that task. Find or hire someone who is.

Or, you know, measure your dryer plug, as above. I can't believe we're a week and 50 responses into this, and you're still not taking the simple steps to determine what you have, so people here can help you with your original query.