110 volt from a 220 volt inverter?

the_uglydog

I have a project in The Philippines, the utility uses two 110 volt legs with a ground, no neutral 60hz. The system uses no 110, only 220 for all lights and appliances.  The original contractor here had no idea what he was doing, nothing on the system was correct or even close to it, and he installed inverters that are less than 1/4 of the size needed for our 220 usage, so I studied solar installation and did it over myself. Now I have some 220 volt inverters left over that tie in with two 110 lines both in and out, I want to use one to make 110 volts to run our US appliances.  Does anyone know if an inverter marked for 220 volts with two 110 lines can be just wired to a US type load center with each 110 line feeding each side and a separate ground just like in the US? Here they just tap into a 220 breaker and hack the 110 by grounding the other side, the inverters don't seem to like it, I know I could buy a 110 inverter, but I already have some of these, I want to do it right and feed each 110 to it's own side of the box. 
Thank you for your thoughts on this......        the dog

mike95490

I'd use a step-down transformer.   Anytime you do something a inverter does not like, it's going to die early.

BB.

Can you give us a link to a manual or the inverter you want to use?

In general, a 220 VAC output inverter is only 220 VAC.

You do get into a gray zone here... Most 220-230 VAC inverters are 50 Hz (European).

And most 60 Hz inverters are 240 VAC (north American). And it is possible that the inverter has a neutral available (aka a USA model 60 Hz transformer labeled for your 220/240 usage and "ignoring" the neutral... But that is a wild guess and really depends on what the inverter mfg. actually did (some inverters are 50/60 Hz switchable).

In North America (sounds like you know the power here well)... Our L1/L2/N (120/240 VAC split phase) is the result of a center tapped transformer (L1 and L2 are the two "end taps", and Neutral is the center tap--And the Neutral is usually tied to earth ground through cold water pipes and/or ground rod--Earth ground can be as much as 25 Ohms, so the ground rod is only for safety, such as lightning strikes, and not for any significant 120/240 VAC current "through the dirt").

A split phase PSW/TSW (pure/true sine wave inverter) for 120/240 has a center tapped transformer for L1/L2/N connections (L1/N and L2/N are 120 vac, and L1/L2 are 240 VAC).

A single voltage 120 or 240 VAC output MSW (modified square/sine wave) inverter--Only has 2 legs. Both legs are "hot" with respect to the battery bus--If you negative ground the battery bus and chassis ground the inverter, you will see voltage between L1 and ground, and L2 and ground (not sure if of exact voltage). But it is not usually done to use the battery negative bus like a Neutral (that I am aware of). And you cannot ground bond L1 or L2 from a MSW inverter as it creates a short circuit with the battery bus--Smoking the inverter. MSW inverters (generally) do not have a transformer isolated output (like most PSW/TSW inverters).

As Mike says--If you have an MSW inverter, and try to use the battery bus as a "return/neutral" connection... You are definitely operating outside the norm... Not sure what would happen.

And if you have an MSW inverter, transformers tend to get hot on MSW inverter output--So you would need a larger (VA or kVA rated) transformer for step down use (buck type transformer).

If you have a PSW/TSW inverter that is 220 VAC only, I don't know if anyway to connect a center tap when there is no transformer centert tap.

-Bill

mcgivor

The 220V 60Hz should be live with neutral, to verify test each leg to ground, the one with no, or very low, voltage would be the neutral. The neutral bonding is typically done near the transformer, however its not always done, from what I'm told by my electrican friends from the Philippines. They say it's a mixed bag of different systems delta 3 phase, wye 3 phase with split phase on U.S. military bases using plugs and recpticals designed for 110V with 220V. 

There a split phase inverters available which can provide 110/220V 60Hz on Aliexpress, but you would have to weigh the expense of either a transformer or inverter against the cost of replacing the appliances with 220V ones, when I came to Thailand from Canada I simply bought 220V tools and appliances locally. There is no hack that can convert the existing inverter to provide 110V that I'm aware of and probably not something I would  recommend experimenting with.

the_uglydog

Hi, Thanks for the input. The electric system here is a mess. Sometimes the voltage is 230 volts sometimes it gets as low as 180 volts. We have the Meralco system, it is two 110 lines 60hz, the ground is on the meter and no neutral. Or maybe the neutral is on the meter and there's no ground. The ground on the meter works much better than the grounds to earth, I have three 10 ft rods with the ground lines connecting to all of them together, this works almost as well as the ground on the meter. We have a number of "electricians" working for us here, they have all been told that any 110 installations must be connected through a 110 box and grounded correctly. I have noticed anyplace someone hacked the system and just grounded an outlet, the voltage is about 20 volts lower than the ones with the good ground and about 30 volts lower than the ones hooked to the meter. The units I have are Must 4K Hybrid Pure Sine Wave Inverters, the one that I have hooked up feeds a small 220 service. They have space to hook up 3 wires for the ac input as well as on the inverter output. The manual labels them as Ground-yellow green, line-brown or black, neutral-blue, the one we're using for 220 uses the line and neutral with the ground connected to my 3 rod ground. It is switchable 50-60 hz and it will maintain between 58 and 62 hz when operating. I am also operating Aimes Global LF Series 10 kw single phase inverters for 220, everything at this site is hooked up as per Aimes directions, maybe that will help you know what we have here. From what you describe, if I test both lines and they are 110 on each output leg is it possible that one of these Must inverters may work? Thanks for your assistance...... the dog

BB.

With a transformer (isolated output--I.e., a "real transformer" with two sets of windings and not an auto transformer with a single set of multi-tapped windings), you can always pick one output and "neutral to ground" bond it (whether a two tap L1/L2 transformer or a L1/Center tap/L2 transformer.

But if you have a 220 output PSW hybrid inverter, It just has two power outputs--L1 and L2, you can ground bond either and make it "the neutral" (in general--As always the manual and "real life" trump wondering posts)... But it does not make 110 VAC.

It sounds like the standard power there has L1/L2 output of a transformer--And on some utility transformers, they may have a grounded center tap, and other places the do not.

One of the ways we "trick ourselves" when measuring voltages is the use of a DMM (digital multimeter). They are such "good" volt meters, they have very high input resistance (something like 1,000,000 to 10,000,000 Ohms). It means that they can measure almost any circuit and get a (relatively stable) voltage--Whether or not there is a "solid copper" connection, or just a bit of capacitance, dirt on insulation, etc...

That is why some meters have a "low resistance" setting... Like this meter that has something like a 3,000 Ohm resistor to put a little load on the wiring:

https://www.amazon.com/gp/product/B019CY4FB4

And the old but reliable "wiggy" type solenoid voltage tester (the coil that moves the indicator provides significant load on the tested circuit):

https://www.amazon.com/Ideal-Industries-61-085-Vol-Test-Solenoid/dp/B000NBCD1K

-Bill

the_uglydog

I have 3 types of multimeter, when tested between my ground and each leg with air conditioners running on the circuit, I tested both the Ames inverter and the Must inverter: We use some cheap Harbor Freight meters, they give a stable voltage of about 100 on each leg, a Synergy SMT-750 which gives widely changing readings from 0 to about 750, and Ames AC 600v Cat III clamp meters which show one leg at about 100 and the other at about 93 using the probes not the clamp when the systems are running on the batteries. The Meralco lines test at 96 and 83 on both the Harbor Freight meters and the Ames. Could I tell by pulling the cover on 1 of the Must inverters which type transformer it has?
In the US, all the load centers I worked on had the neutrals and the grounds hooked to the same bus bar with both neutral and ground leading to earth outside the houses below the meter. I set up the 110 here the same way. Would I be better off moving the neutral line to the terminal on the meter? I'm not a professional electrician, but I have rewired a number of houses in the US, all passed inspection with no problems I understand most things, but sometimes I'm a bit slow...............Thanks     the dog

BB.

Another way to "load" your test connections... Just get a ~10-50 Watt 220 VAC filament lamp. And connect it across the wiring you want to check. If there is "high resistance" the lamp will short out the stray voltage. If there is good power, the lamp will draw enough current for an accurate meter reading, and possibly even light (depending on line voltage).

Looking at the transformer may tell you how the mfg. built the system... But it is not always obvious.

Getting wildly different voltage readings with your meters--Not a lot of confidence. I guess your inverters are PSW/TSW?

I would not even want to begin to guess at how to wire to a Philippines meter/drop to a home. It is just too dangerous for me to make such recommendations.

-Bill

the_uglydog

I can sure understand that!  The utility power ranges widely, if it's hot and a lot of people are using a/c it's really low, like 80 to 90 volts per line. There's so many different systems, ours is "supposed to be" the same as the old US military bases two 110 lines with a ground or neutral at the meter, no one uses it, It makes me crazy sometimes..  I have a couple of guys who do things right most of the time, especially when I'm watching, but even them..... When I'm gone they hack something.. I found a circuit yesterday that someone in one of the apartments tapped into one of our outlets along the perimeter fence and connected his service to it and disconnected his meter so he was running off our electric! I've had a few circuits that wouldn't work on the solar, so after what I found here, I checked them all the way and also found a few outlets that someone hacked to 110. Maybe I'll just buy a 110 inverter when I go back to the US and bring it over here.  Thanks for all the help. the dog 

LesGurley

I am wondering if I can use a center tap 1/1 wound transformer hooked to a pure sine inverter to supply 110 to both bus bars in a breaker panel and go between them as usual in order to get both 110 and 220 simultaneously as long as the total amperage drawn isn't enough to trip the main and the individual circuits aren't enough to trip those breakers. It seems that is the way the utilities work it with the modification to make it a drop down transformer instead of a 1/1 total winding with a center tap.

BB.

Welcome to the forum Les,

Yes you can... Here is an example from Outback's Autowound transformer (manual links too):

https://outbackpower.com/products/integration-products/miscellaneous/item/autotransformer

There are downsides too... Transformers can be significant loads themselves. They take energy to start (magnitization) and they also have losses of their own. And a good sized autotransformer is not cheap either.

-Bill