3 phase and Grid tie... what will happend?

[ZoNiE]

Well, I have 3ph in my 2000 sq ft McMansion in the USA. In my neighborhood, in the 1950s, any AC installation 3-ton or bigger got 3ph. Many people have heard of 3ph

Same here in Arizona. Older neigborhoods had 3ph power for the larger AC units, until they figured that they could put two AC units on a house... My house just missed having 3ph power by a couple of years. (Bummer)

They also only usually meter TWO legs, and some people have been known to rewire their panels so all the 110V loads run on the unmetered leg only. Not sure how widespread that was or if new meters still only read two legs.

Also, people confuse the "Phase" as the wire (like saying two-phase), not the potential between the wires. Hence why two hots (240V) is still called single phase.

Houses in the EU sometimes have all three legs of 380/240. Not sure why, it just is.

I had a 480/277 service on an industrial bldg I once rented. It was nice, but I did have two large transformers for my 240/120 loads. Lighting was all 277, and every motor containing piece of equipment I bought was 480V, even had a single phase 480V fan motor in a chiller. That was weird. The idea was to avoid getting another transformer.

Not sure how any of this useless info applies to the OP's question, but hope it helps. The use of one leg for each floor is strange, and there must not be any line to line loads in that house, unless the OP has 380V 3 PH shop tools as indicated, but with 240 to neutral, makes sense. I'd get a 3phase inverter and tie it in to the panel as usual, but that is just me. Our single phase systems cannot be perfectly balanced either. Depends on how the family uses what plugged into where...


My 2 cents.

[russ]

Ya you got me, I was thinking single phase and knocking it down for 50Hz. Strange seeing 115/199v LOL

I still can't believe you have 430v in your house be careful that will cook you fast!

Is it a Y or Delta Hi-Leg system?

No idea about the connection type - I am the user. In Europe 3 phase systems and higher voltage in not uncommon.

[Colt45]

Actually, that would be 115/199, not 115/230.
In the US the standard nomenclature would be 120/208 (written as 208Y/120) for three phase compared to 120/240 for single phase.

Ya you got me, I was thinking single phase and knocking it down for 50Hz. Strange seeing 115/199v LOL

I still can't believe you have 430v in your house be careful that will cook you fast!

Is it a Y or Delta Hi-Leg system?

[russ]

Wow, in a residence... Why? What do you power at that voltage?
Also PF is a problem in all 3 phase systems, non linear loads cause bad thing to happen. Try loading a generator with 100% reactive loads some time if you want a demo.

That is what comes off the utility transformer to our meter and incomer panel. The only item on 3 phase in the house is the heat pump. On a separate side the well and pressure pumps are on 3 phase.

All 230 volt loads are split between the three phases.

[inetdog]

Why not just install a three phase inverter or three single phase units?
You say you have only one phase per floor but that would only have a 115V panel? Most of the time you will have a single phase panel feed with two of the three phase legs to give you 115/230v.

Actually, that would be 115/199, not 115/230.
In the US the standard nomenclature would be 120/208 (written as 208Y/120) for three phase compared to 120/240 for single phase.

[Colt45]

Why not just install a three phase inverter or three single phase units?
You say you have only one phase per floor but that would only have a 115V panel? Most of the time you will have a single phase panel feed with two of the three phase legs to give you 115/230v.

Is there a main 3 phase disconnect for the entire service or did each unit get it's own disconnect? You should have all 4 wires in one place at the service entrance location, put the inverters in that spot. (or run from it)

[Colt45]

Here everything is 3 phase power - my home main panel has a 430 volt (or there abouts) 3 phase feed - power factor is of no consideration for residential.

Wow, in a residence... Why? What do you power at that voltage?
Also PF is a problem in all 3 phase systems, non linear loads cause bad thing to happen. Try loading a generator with 100% reactive loads some time if you want a demo.

[Mike90250]

I have a question, I know the utility company don't charge residential customer the bad power factors. but how about off grid system? does the bad power factor equipment affect the amount current draw from the battery bank?

Thank you.

The watts drawn from the battery = watts consumed (+ overhead) BUT, the inverter has to be able to support the poor power factor. So if you have a 1Kw load, with a .6PF, your inverter is required to do the work of 1.6Kw and consumes 1Kw from the battery. When the I & E vectors get out of phase from poor power factor, the inverter has to be the device that keeps it all working.

[russ]

Here everything is 3 phase power - my home main panel has a 430 volt (or there abouts) 3 phase feed - power factor is of no consideration for residential.

[paulcheung]

It is a little technical to go into, but yes motors, inductive, capacitive, and non linear loads use more current than they measure. The extra power is unused and reflected back at the source and burned off as heat on the wiring. In AC volts x amps = VA or Volt amps, not watts as most think. There is a power factor involved and all that means is the voltage and current are not in phase with each other. In inductive circuitcs (motors) voltage leads the current, and in capacitive circuits current leads voltage. The difference in the phase angle is expressed as the Power Factor which is a number of 1 or less where 1 = 0 degree phase shift or a purely resistive circuit.

So watts in an AC circuit = volts x amps x PF, and Apparent power = Volt Amps. So for example lets say you have a refrigerator that you measure using 120 volts x 10 amps at a PF of .8. The VA = 120 volts x 10 amps = 1200 VAR's, and the power = 120 volts x 10 amps x .8 = 960 watts. So in order to run that fridge your generator must produce 1200 VAR's

OK as for residential, utilities do not charge customers for VAR's, only true power used. For commercial and industrial customers they do charge them for VAR's, they charge them a lot of money for it.

I have a question, I know the utility company don't charge residential customer the bad power factors. but how about off grid system? does the bad power factor equipment affect the amount current draw from the battery bank?

Thank you.

[onkelrolle]

Residential 3-phase power

I think the question is what are you talking about?

I am very familiar with European electrical architecturre as I have designed many systems for clients there. Eurpoean electrical systems are no different than what we use in the USA other than the standard residential service is 220-240 single phase service operating at 50 Hz, compared to the USA 240/120 volt single phase service.

That is how every electrical distribution service in the world is constructed. However what you just described for residential service IS NOT 3-PHASE, It is Single Phase just like it is done on every where in the world. The distribution is 3 phase, but for your residential electrical service you are only connected to 1 of the 3 phases via a transformer to step the voltage down from say 13.2 Kv to 220 volts.

So go ahead and take that picture and I will show you what is really happening.

My apologies for perhaps a slightly off-topic interjection. I live in Finland and here, like in some other european countries, the last stage of the distribution network is fed to the consumer as a 3-phase utility. Residential voltage is 230 volts between any phase and the neutral wire and 400 volts between any two phases. Obviously some power companies over here still have a product called 1-phase power but it is rarely used not being that much cheaper. Even then the feeder cable to the building is 3P+N but only one phase is metered.

Best regards, Rolf Möller, authorized electrician

[Sunking]

so do the motors and appliances use more electricity?

It is a little technical to go into, but yes motors, inductive, capacitive, and non linear loads use more current than they measure. The extra power is unused and reflected back at the source and burned off as heat on the wiring. In AC volts x amps = VA or Volt amps, not watts as most think. There is a power factor involved and all that means is the voltage and current are not in phase with each other. In inductive circuitcs (motors) voltage leads the current, and in capacitive circuits current leads voltage. The difference in the phase angle is expressed as the Power Factor which is a number of 1 or less where 1 = 0 degree phase shift or a purely resistive circuit.

So watts in an AC circuit = volts x amps x PF, and Apparent power = Volt Amps. So for example lets say you have a refrigerator that you measure using 120 volts x 10 amps at a PF of .8. The VA = 120 volts x 10 amps = 1200 VAR's, and the power = 120 volts x 10 amps x .8 = 960 watts. So in order to run that fridge your generator must produce 1200 VAR's

OK as for residential, utilities do not charge customers for VAR's, only true power used. For commercial and industrial customers they do charge them for VAR's, they charge them a lot of money for it.

[russ]

Your bill will not change whether you have a power factor correction device in use or not.

The utility would have to generate a small amount less - that is true but you are not billed for it.

References

http://www.nist.gov/pml/quantum/power_121509.cfm

1) http://www.splatco.com/tips/pwrfact/pfarticl.htm

Following the general theme of the thread (or at least part of it) my home has 3 phase power to the main panel inside the house. The heat pump has a 3 phase motor while the other loads are split between the phases. Well pump and system pressure pumps are 3 phase.

[Ernesto1]

utilities dont charge for VARs ?

so do the motors and appliances use more electricity? if you dont have a Correction device ? do they last less?
Thanks for the info!!

Unbalanced does not affect the bill, but you might have overlooked something.

As I said earlier 3-phase is typically used for industrial and commercial users. With those customers they typically have very large motor and non linear loads which results in low power factor. Here in the USA utilities do not charge residential customers for reactive power, only resistive or the real power because in a home you just do not have large reactive loads that a electric utility is concerned about.

However utilities do charge commercial and industrial users for reactive power. The lower the power factor (more reactive), the more the utility charges. The higher the power factor (less reactive), the less they charge. This is why large industrial users have capacitor banks to correct the power factor, it saves them large amounts of cash, and save the utility a lot of generating capacity. In other words the utilities penalize the users for low power factors. Both benefit when the power factor is closer to 1.

To take it one step further, the power factor correction devices you see marketed to residential customers is fraud because the utilities do not charge residential customers for VAR's.

[miket]

Back to the original topic there alre lots of places in europe with 3 phase residential. germany Norway etc. And yes they are adding them into new homes and they sell 3 phase appliances.