# Split Phase vs Single Phase confusion

Registered Users Posts: 164 ✭✭
edited June 2019 #1
ok, this has been bugging me for a bit and I'm sure it can be easily explained or at least I hope so. I have a XW6848, and I have contacted my electric company to verify that I have a single phase coming into my home, this has been confirmed, thought they didn't say the voltage however I assume single phase 240 or maybe 250? I'm going to guess 240 based on this I see in my combox...

But also further down in my combox settings I see where the min/max voltage is set at the 120v arena, shown below...

I'm sure this can be explained really simple by someone who knows the system better than I. I read that the inverter would need some specific changes to make it a "Single Phase" system and also a firmware modification. As I would prefer not to make these changes myself or if not necessary due to a really good explanation of why this is, I'm hoping someone can educate me really quick
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For North American residential power, we typically have 120/240 VAC split phase power...

https://en.wikipedia.org/wiki/Split-phase_electric_power

It is created by two transformers connected in series (or one "center tapped" transformer). The center tap (in North America) is usually grounded at the pole and in the home panel to "earth" (cold water pipe, ground rod, etc.) and is at "zero volts".

The two other leads (typically Black and Red) are "hot" with respect to ground (nominally ~120 VAC).

When you measure voltage between the black and red "phase", you get 240 VAC.

You can measure 120 VAC between L1 and neutral, and L2 and neutral and "know all is OK". You do not need to do another voltage measurement between L1 and L2, because (assuming everything is wired correctly), L1 and L2 is simply the sum L1+neutral with L2+neutral measurements.

Split Phase power, technically is to phases 180 degrees apart, and you cannot create a "rotating field" for motors without using motor start/motor run capacitors, or other techniques.

With Poly Phase Power (3 phase being the most common), when you connect the three phases to three field coils, they create a rotating field, which can start a 3 phase motor (cause it to rotate with high torque) with the use of motor start capacitors.

https://en.wikipedia.org/wiki/Three-phase_electric_power

AC power is a very complex subject (vs DC power)... And why Tesla (a math genius) was the eventual winner over Edison (practical lab/experimental engineer) in the "war of the currents":

https://en.wikipedia.org/wiki/War_of_the_currents

Regarding your "single phase" conversion question... I am going to give a very rough explination of what you may be talking about and why--I believe older XW inverter systems had this reconfiguration capability (a bit of internal rewiring and new firmware)... I have no idea if yours is capable or not.

With Split Phase power systems, you have a neutral (common) bus (the white wire), and you have the option of pulling 120 VAC between L1 and neutral or L2 and neutral, or 240 VAC from L1 to L2.

For utility power, 120/240 VAC gensets, and XW inverters, there are two transformers (or winding sets in a genset). Say each is rated at 30 amps and 120 VAC. You can put the two transformers (windings) in series, for 120/240 VAC @ 30 amps split power, or you could put the two transformers in parallel for 120 VAC @ 60 Amps of "single phase" power.

Most of the time, we don't really care--A single phase 120 VAC genset or AC inverter--That is what you get.

If you have a 120/240 VAC power source (the two transformers put in series for L1/L2/Neutral wiring), you spread your 120 VAC loads between the L1/Neutral and L2/Neutral (i.e., put 10 amps on L1/Neutral and 10 amps on L2/Neutral) for 120 VAC power. And if you have a 240 VAC well pump, you put it between L1/L2 for 240 VAC and 20 Amps loads... And all is OK.

However, say you have a 120 VAC @ 40 amp load (120 VAC well pump, etc.)... On a 120/240 VAC @ 30 amp split phase system, your maximum available current is 30 amps (at 120 or 240 VAC)....

If you rewire your XW (and firmware change) or your Genset (some can be rewired, others cannot) by putting the two transformers (genset windings) in parallel, you can make a 120 VAC @ 60 Amp power source--So if you have "heavy" 120 VAC only loads, rewiring allows you to have full rated 120 VAC @ 30 amp output (aka 3,600 Watts).

There are a lot more details, and rating "adjustments" on L1/N output current limitations on the XW... But to keep it simple, this is basically how it works.

Questions?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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edited June 2019 #3
The single phase 240V feed has a center tap in the transformer, this tap is the neutral which is grounded at the main distribution panel.
Each leg has a voltage of 120V between it and neutral ground, hence the split phase 240/120V designation. The feed from the panel to the inverter would use 240V via a 2 pole breaker with neutral.

The voltage settings, lower screen view,  are most likely the voltage set-point between each line to neutral, depending on which line has the highest loading the voltage could be different between Line 1 to neutral and Line 2 to neutral, added together would be L1 to L2 voltage.

Note, I am not familiar with the split phase inverter as mine is 230V single phase so only one line and neutral/ground, hence the word likely.

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• Registered Users Posts: 164 ✭✭
Ok, I think I understand. It’s just the numbers displayed from the inverter were throwing me off. I guess tomorrow I’ll take the panel off and take a look. I read in the manual how to change the wiring for single phase (not that I’m going to do it) more I just want to see if it has been done already. I’m wondering what if anything would act crazy if it were not setup properly.....
• Registered Users Posts: 164 ✭✭
I’m hoping master Dave can enlighten me tomorrow:)
One of the reasons that there are Lx to Neutral measurements is because there can be failed neutral connections (broken wire, corrosion, loose connection, etc.).

What can happen is you have very steady 240 VAC between L1 and L2... But with a "poor neutral" connection, you can see the L1/N and L2/N voltages vary... Start a heavy load on L1/N and the voltage falls to 80 VAC... And any loads on the L2/N connection can see 160 VAC.

A common symptom is the lights in your home, you will see some lights dim and others brighten when a large 120 VAC load is turned on (garbage disposal, electric heater, etc.) because of a poor neutral connection.

I have had this happen in two homes... Both because a small amount of rain water got in through the weather head (utility power connection) and dripped down into the meter/main breaker panel and caused the neutral hardware to corrode).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 164 ✭✭
I suspect such a situation would be relatively obvious to see in the wiring?
• Registered Users Posts: 4,496 ✭✭✭✭✭
Not necessarily obvious for a couple of reasons; not a lot of folks regularly look at the guts of their meter sockets and main panels, and the corrosion may only be a problem when the circuit is loaded (a multimeter continuity test may look fine).
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Elevated to master status now, what could be next? Maybe 2 tickets to paradise?
Why would you want to change an XW in NA to single phase?
The only reason you would do this is if you were going to wire 3 XW's for 3 phase power! Or, for some weird reason you wanted 120vac only.

You should also not be casual about opening up an XW. You need a wrist ground strap and know how to follow anti static procedures.
The parts of XW that are installer accessed are protected. Other parts of XW are not and Schneider can tell if you have been in there.
It is a good way to void a warranty.
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• Registered Users Posts: 164 ✭✭
I just wanted to see how they have it setup. Since I am seeing the voltages in one place in the 120v range but in another in the 240v range, and there is a question about how qualified the installers are/were. The electric cooperatives told me my house is single phase coming in, but I don’t know if that makes any difference in the a/c settings I showed up earlier.
• Registered Users Posts: 4,496 ✭✭✭✭✭
In my (limited) understanding of AC power, split phase 120/240v as is common in NA residential and small commercial/industrial is really single phase.  It's 240v single phase line to line, with each line conductor at 120v (RMS) with respect to a grounded neutral.

There are other (polyphase and/or higher voltage AC/DC) systems used for distribution and larger industrial applications and in non-NA parts of the world.  Interesting, but not necessary to know for a typical NA residential system.
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edited June 2019 #12
@Estragon

I beg to differ.......you are correct as to residence being split phase but small commercial is also split phase!!!
Split phase is single phase with a center tap to neutral.....

Estragon, what you describe as single phase with 240 volts line to line and 120 volts line to neutral...IS SPLIT PHASE.

Split it phase is 120/240
Single phase is 120  normally

There are a very few legacy POCO power feeds that are 240 volts only, no neutral.....very rare...mostly Ag water pumps existing since the 1930's,  I've only seen two single phase 240 volt services here in California, you cannot get a utility to provide that now , it is not allowed by the California Public Utility Commission.

There is also 240 volt delta three phase ungrounded and also 240 volt delta three phase corner grounded, B phase is grounded, also not allowed , but existing systems can remain but cannot be upgraded......again the PUC does not allow new installations of ungrounded or corner grounded three phase, again legacy systems from the 1930's, I've seen a few and upgraded some to 3 phase delta hi-leg

Three phase is not available in a residence in California and probably not in any state.  I have done many 3 phase rotary converters to provide three phase power from single phase, BUT.....it is NOT  3 phase 120/208 which is common in large apartment houses......it is 3 phase 120/240 delta hi leg , where C phase IS NOT 120 volts to neutral and neutral is 60 degrees OUT OF PHASE with C phase.......it is allowed to run a 3 phase commercial washing machine in a residence and some other limited applications..It is very rare.

Large apartment houses are 120/208 volt WYE three phase, A,B, and C phase is 120 to neutral
Commercial and Industrial is 120/240 volt DELTA HI-LEG three phase, A&B phase is 120 volts to neutral, C phase also known as the "stinger leg" is 180 to 208 volts to neutral!

There is no reason in a grid tied XW to reconnect the transformer to single phase, it would only be applicable in an off grid system with massive 120 volt only loads. AFAIK the XW only qualifies A phase,  but dave Angelini will correct me if I'm wrong on that.  The "AC1" and "AC2" referenced in the XW menu references  to input 1 , power co input  and input 2, generator input, NOT A phase and B phase!
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In one home, yes, could see the corrosion in the main panel (after removing the faceplate).

The other, was in a "sealed" by utility meter socket--And I had to cut the seal and pull the meter to see the corrosion and overheated wiring.

So, "obvious" issues may be hidden in various locations / behind sealed access. (cutting a seal and calling the utility to re-seal after inspection/repair, was not a problem for my utility PG&E).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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PG&E does allow contractors to cut their seals for that reason, it will not raise an issue with them, but do not cut the small seal on the meter itself, it raises a big flag and that meter will be impounded and sent back to the calibration lab for inspection and recalibration. I'm not talking about the seal on the band, the small seal on the back of the meter.
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• Registered Users Posts: 437 ✭✭✭✭
@BB, I can't count the times I've seen faulty neutral connections, it often will burn out all the appliances on the phase with voltage above 130-140 volts, electronics will let the magic smoke out!
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Yep, bad neutral connections are really hard on 120 VAC appliances/devices.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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edited June 2019 #17
If you need to get PG&E out there real fast, report a lost neutral at the weatherhead, they are liable for any damage resulting from that, one of my customers lost all her electronics due to that in Monterey, facing the Ocean! They paid for all the damages, TV, computers, it nailed everything with few exceptions, even the electric stove, all the controls were 120 volt!
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Can anyone link me to what a single phase and a split phase would look like behind the meter?
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DickyDck said:
I just wanted to see how they have it setup. Since I am seeing the voltages in one place in the 120v range but in another in the 240v range, and there is a question about how qualified the installers are/were. The electric cooperatives told me my house is single phase coming in, but I don’t know if that makes any difference in the a/c settings I showed up earlier.
They did not set-up anything except wire AC1, AC2, and Gen wiring. That compartment is protected. The section where Schneider would wire for 3 phase is to be opened and wired by Schneider or a qualified technician.

Saying this nicely, you are overthinking this!
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120 VAC service--You should only have two wires coming into the home from the utility.

120/240 VAC service, you should have 3 wires coming into the home.

Can you post a picture of your main panel (fuses or breakers)?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 437 ✭✭✭✭
edited June 2019 #21
@Dave Angelini

EXACTLY......There is a reason that most high tech manufacturers do seal their products, end users have no business in there and will only muck things up. We had that same problem at GE, going in there will void your warranty! Customers who had a service contract were billed at top shop rate for going in there, if they continued their service contract was redrawn at a not so favorable rate!  It's a tough job supporting equipment when the end user has mucked things up. No documentation on what was done!
2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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DickyDck said:
Can anyone link me to what a single phase and a split phase would look like behind the meter?
I will not.   It's dangerous.  I will not be responsible for your death.

You are messing with un-fused utility feeds and don't have a clue as to how dangerous that is.
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• Registered Users Posts: 164 ✭✭
mike95490 said:
DickyDck said:
Can anyone link me to what a single phase and a split phase would look like behind the meter?
I will not.   It's dangerous.  I will not be responsible for your death.

You are messing with un-fused utility feeds and don't have a clue as to how dangerous that is.
in all fairness I actually do know how dangerous it is, however I have had it off before and just didn't pay any attention to how it was wired up. My electric company is pretty cool, and they would have no problem coming out and doing it for me, but they have already said to me in an official email that I have single phase, but from what everyone here is saying this is rare in north america, so I'd like to find out. If indeed it is single phase, then I am guessing that my inverter is wired up incorrectly.
• Registered Users Posts: 164 ✭✭
BB. said:
120 VAC service--You should only have two wires coming into the home from the utility.

120/240 VAC service, you should have 3 wires coming into the home.

Can you post a picture of your main panel (fuses or breakers)?

-Bill
Sure can, but not tonight, I've been out in the sun all day pouring a concrete slab for my patio, and I'm dead beat. tomorrow morning I can take off the cover and take a picture. If I recall though there were only 2, I was in there earlier this year running a 240 circuit for my welder.
• Registered Users Posts: 4,496 ✭✭✭✭✭
Seems to me if you ran a 240v circuit for the welder, you almost certainly have typical N.A. 120/240 split phase service.  2 line wires (usually a red and a black), and a white neutral.
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sounds about right @Estragon , I remember 2 big ass wires at the top going down each side, but can't remember if the white was neutral use or going to ground block. I'll know for certain tomorrow and post up pics.

• Registered Users Posts: 4,496 ✭✭✭✭✭
The white neutral is often tied (bonded) to ground in the main panel.  Each of the red and black wires typically feeds one side of the panel.  You get 240v between each line, and 120v between either line and the grounded neutral.
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DickyDck said:
BB. said:
120 VAC service--You should only have two wires coming into the home from the utility.

120/240 VAC service, you should have 3 wires coming into the home.

Can you post a picture of your main panel (fuses or breakers)?

-Bill
Sure can, but not tonight, I've been out in the sun all day pouring a concrete slab for my patio, and I'm dead beat. tomorrow morning I can take off the cover and take a picture. If I recall though there were only 2, I was in there earlier this year running a 240 circuit for my welder.
You answered your own question, if you ran a 240V circuit and have other 120V loads the service is a single phase 240/120V split, which is typical for a north American domestic installation.
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• Registered Users Posts: 164 ✭✭
mcgivor said:
DickyDck said:
BB. said:
120 VAC service--You should only have two wires coming into the home from the utility.

120/240 VAC service, you should have 3 wires coming into the home.

Can you post a picture of your main panel (fuses or breakers)?

-Bill
Sure can, but not tonight, I've been out in the sun all day pouring a concrete slab for my patio, and I'm dead beat. tomorrow morning I can take off the cover and take a picture. If I recall though there were only 2, I was in there earlier this year running a 240 circuit for my welder.
You answered your own question, if you ran a 240V circuit and have other 120V loads the service is a single phase 240/120V split, which is typical for a north American domestic installation.
This makes logical sense, but back to the original confusion I'm having.... shouldn't the range in the screenshot I posted at the beginning... by a min/max in the 220-250 range?
• Registered Users Posts: 4,496 ✭✭✭✭✭
I don't know Schneider stuff, but my guess is the first screen shows the point-in-time actual line to line voltage (240v +/-), and the second shows a line to neutral range (120v +/-) over time.
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• Registered Users Posts: 164 ✭✭
That could be, I have a service ticket in with Schneider, but they work bankers hours and I suppose I'll get an answer tomorrow sometime.