Connecting Enphase IQ7 micros to 240v 3ph

Status
Not open for further replies.
J

JoeNorm

Senior Member
Location
WA
We have a job on a building that is supplied by 240v 3ph

I have never seen this before but that's not surprising because I haven't dealt much in 3ph.

Between the phases reads 240v
A to Neutral is 120v
B to neutral is 208v
C to neutral is 120V

My question is whether I can use a single phase Enphase inverter here. I think I can by just picking two phases to connect to, am I right?

Would it matter which two phases it is? Is it this simple?

thanks fo the help.
 
masterinbama

masterinbama

Senior Member
Location
Huntsville Alabama
JoeNorm said:
We have a job on a building that is supplied by 240v 3ph

I have never seen this before but that's not surprising because I haven't dealt much in 3ph.

Between the phases reads 240v
A to Neutral is 120v
B to neutral is 208v
C to neutral is 120V

My question is whether I can use a single phase Enphase inverter here. I think I can by just picking two phases to connect to, am I right?

Would it matter which two phases it is? Is it this simple?

thanks fo the help.
Click to expand...
You have a delta service.

Sent from my moto e using Tapatalk
 
J

JoeNorm

Senior Member
Location
WA
ptonsparky said:
Depends. Read the fine manual.

I Know some drives do not like the hi leg, so I wold use the two lower voltage, 120 volt to ground.
Click to expand...
How would the high leg be any different if the voltage across is the same? I'm not challenging you I am just curious because I don't know much about 3ph. Thanks
 
C

Carultch

Senior Member
Location
Massachusetts
JoeNorm said:
How would the high leg be any different if the voltage across is the same? I'm not challenging you I am just curious because I don't know much about 3ph. Thanks
Click to expand...

Voltage-to-ground is the issue. The issue in question is whether the inner-workings of the device are built with insulators that are rated for 120V nominal to from the housing to the power electronics. A product may only actively uses the 240V, but you have to verify that it is rated to withstand the the voltage to ground, if using it on anything other than a 120/240V split phase or 120/208V wye system. It's the same issue that doesn't allow slash-rated breakers to touch the high leg, because they require 120V to ground. You need straight-rated breakers for the breakers that touch the high leg, so make sure to specify it as such for any panelboards. Most (if not all) 3-pole breakers are straight rated, and by contrast most 1-pole breakers are slash rated. For 2-pole breakers, it could go either way, and you'll need to see the straight-rating documented to use it that way.

Enphase microinverters don't put any voltage on the neutral, or even get a neutral connection, so the device entirely works off the 208V or 240V line-to-line voltage. I concur with Syncro's source, that it establishes that Enphase can use the high leg delta systems, or even corner-grounded delta systems. As that manual indicates, it is the communication gateway that needs the 120V to neutral, which just means using the A/C/N phases to power it and measure the power-line-carrier signals.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Enphase has a technical brief on this somewhere. I'll see if I can find the link. You can connect IQ inverters to all three phases as far as Enphase cares. The question is, have you asked who else cares? The utility might object to either backfeeding the high leg or not backfeeding it, depending on details. You may need to just ask them.

Probably if the system can be backfed on the phase with the neutral (A-C) without upgrading the service panel you can just do that. And if that is not possible you should not build anything until you have the interconnection passed through the utility engineering review. But that's just a really general guess, don't make any assumptions.
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I do not see any mention of high leg delta in the linked pdf, certainly not on page 8.
It discusses 208Y/120 and corner grounded delta only.
For the latter, a transformer is required.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
GoldDigger said:
I do not see any mention of high leg delta in the linked pdf, certainly not on page 8.
It discusses 208Y/120 and corner grounded delta only.
For the latter, a transformer is required.
Click to expand...

Sorry, I got my links confused.

This link has the high-leg delta on page 8.


Perhaps I should also point out that it is three years older and not hosted on Enphase's site, so I don't know if Enphase is still supporting that application.
 
Status
Not open for further replies.
Top