Re: [RE-wrenches] Utility transformer limitations

[Garrison via RE-wrenches]

Hi William,One possible path forward would be to ask the utility co what AC inverter capacity would be allowed. Maybe the solution would be to unplug a micro or two if you are just over the limit. Even better, maybe they would allow you set an export limit on the micros you have installed.I had a recent situation where a 40kW DC system had exceeded a utility transformer by only 2kW AC, so a simple redesign avoided an $8k invoice from the utility. The utility was not transparent about this option at first and only made it clear after some persistence.Good luck,Garrison RiegelCelestar SolarOn Dec 25, 2022, at 3:14 PM, Darryl Thayer via RE-wrenches  wrote:It is common practice for the utility to overload the transformer a lot for the potential load.  They expect no one will use their service at maximum, furthermore, they expect non coincidence of loads.  Look at the transformer most have a label as to the kW or the unit, and the utility should give you that number along with the impedance.  Note I have had area engineers not understand that solar reduces the load on the transformer.  They have two concerns, you will overload and you will raise the voltage to other customers.  Overload is ridiculous; the transformer must be at least 20 kW if a 15 kW concern is valid.  However, raising the voltage is not.  If all the customers shut off their power, the voltage would rise to the inverter limit,and/or feed current back on the distribution line raising up/downstream customers voltage.  I have had this problem, on three occasions discussions with the utility upper engineering, not local engineer, i prevailed, one case I did not.   In one cast utility allowed connection and put a voltage monitor on secondary voltage, then later allowed permanent connection..   Good luck   On Sun, Dec 25, 2022 at 1:16 PM William Miller via RE-wrenches  wrote:Wrenched: Merry Christmas to those of you that observe such traditions, or substitute the winter festivity of your choice. I helped a previous employee install an Enphase IQ8 system on his home.  He applied for the utility approval concurrently with his building permit  The day he got his final inspection the utility contacted him and claimed "The aggregate generation exceeds the identified transformer rating" and refused him a Permission to Operate letter. Adding up the service ratings of the homes on his secondary we get about 336 kW of potential consumption.  Adding the grid-tied systems on his secondary we get about 16.5 kW.  How is it that the back-feed exceeds the transformer rating? I would appreciate any insight on how to consider this situation and how to fight it. Sincerely, William Miller Miller Solar17395 Oak Road, Atascadero, CA 93422805-438-5600www.millersolar.comCA Lic. 773985  
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Re: [RE-wrenches] Utility transformer limitations

[Scot Arey via RE-wrenches]

I have found many of the utilities,  especially the cooperatives will undersize transformers relative to main service capacity.Wel always try to check and very infrequently is the transformer smaller than proposed system design.We have had to upgrade some transformers.  Tough pill but hard to argue with logic if one is pushing back more power to transformer than it is sized at.Howard "Scot" AreyOwner, Solar CenTex254-300-1228
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Re: [RE-wrenches] Utility transformer limitations

[Darryl Thayer via RE-wrenches]

It is common practice for the utility to overload the transformer a lot for
the potential load.  They expect no one will use their service at maximum,
furthermore, they expect non coincidence of loads.  Look at the transformer
most have a label as to the kW or the unit, and the utility should give you
that number along with the impedance.  Note I have had area engineers not
understand that solar reduces the load on the transformer.  They have two
concerns, you will overload and you will raise the voltage
to other customers.  Overload is ridiculous; the transformer must be at
least 20 kW if a 15 kW concern is valid.  However, raising the voltage is
not.  If all the customers shut off their power, the voltage would rise to
the inverter limit,and/or feed current back on the distribution line
raising up/downstream customers voltage.  I have had this problem, on three
occasions discussions with the utility upper engineering, not local
engineer, i prevailed, one case I did not.   In one cast utility allowed
connection and put a voltage monitor on secondary voltage, then later
allowed permanent connection..   Good luck

On Sun, Dec 25, 2022 at 1:16 PM William Miller via RE-wrenches <
re-wrenches@lists.re-wrenches.org> wrote:

> Wrenched:
>
>
>
> Merry Christmas to those of you that observe such traditions, or
> substitute the winter festivity of your choice.
>
>
>
> I helped a previous employee install an Enphase IQ8 system on his home.
> He applied for the utility approval concurrently with his building permit
> The day he got his final inspection the utility contacted him and claimed
> "The aggregate generation exceeds the identified transformer rating" and
> refused him a Permission to Operate letter.
>
>
>
> Adding up the service ratings of the homes on his secondary we get about
> 336 kW of potential consumption.  Adding the grid-tied systems on his
> secondary we get about 16.5 kW.  How is it that the back-feed exceeds the
> transformer rating?
>
>
>
> I would appreciate any insight on how to consider this situation and how
> to fight it.
>
>
>
> Sincerely,
>
>
>
> William Miller
>
>
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com
>
> CA Lic. 773985
>
>
>
>
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Re: [RE-wrenches] XW Grid Support or?

[Darryl Thayer via RE-wrenches]

Assuming this is a zero instantaneous no export, not on the daily or
monthly.   I have installed a few XW, and XW PRO inverters, however, I have
never done an instantaneous no export project on the entire service.  The
problem is the load.  Ideally you want to monitor the service entrance and
control off the service current.  This would mean the total current would
have to pass through the XW.  However, this would be a very limited
electrical use household, like an off-grid house.  For the No Export to
work on a more normal load, you want maximum current possible to pass
through the XW (where the control is) to the priority circuit panel, (you
will want to measure these loads allowing for non-coincidence).  You will
want to charge the batteries from solar only and deplete the battery to
about 15% SOC.  What you want to do is sell all the solar that comes in, do
not charge from the grid, to reduce the electric bill the maximum amount.
 I use an Egauge for measuring these loads.  (PS) the XW has no monitoring
of the LiFe battery so use the charge controller Voltage to maintain SOC.
(PS) you may have to use the generator support mode input.  I do not
remember.

Sorry about my poor writing ability, hope this helps.

On Fri, Dec 23, 2022 at 3:45 PM Dave Angelini Offgrid Solar via RE-wrenches
 wrote:

> It can be done but it is not an easy job. You are 2 generations of XW back.
>
> XW+ was good at this and XW pro was designed for this
> along with being able to charge based on Soc (from the BMS) as well as 
> voltage.
>
> Is this an insured home?  You might need a permit as this has to be legal for 
> your area.  Out west of you is what we do.   Good Luck !
>
> The main impact of Rule 21 for solar installers is that *any of your 
> installations in the state of California must now use Rule-compliant 
> inverters*.
>  In effect, these are smart inverters that have been certified as UL 1741-SA 
> or that are listed on the California Energy Commission's compliant inverter
>  database.
>
>
>
>
> *Dave Angelini Offgrid Solar
> "we go where powerlines don't"
> http://members.sti.net/offgridsolar/ 
> e-mail  offgridso...@sti.net 
> text 209 813 0060*
>
>
> On 2022-12-21 5:23 am, Jeremy Rodriguez via RE-wrenches wrote:
>
>
> I’ve inherited a XW. 6048 system that we just installed a LiFePO4 battery
> bank with.
> Has anyone successfully used Grid Support with Sell disabled?
> This system never had an Interconnection Agreement with the utility co so
> it cannot sell.
> Currently we have :
> AC charger on , Multi Stage
> PV input
> Sell disabled
> Grid Support disabled
> There is no TOU metering.
>
>
> Regards,
>
> Jeremy Rodriguez
> Solar Installation / Design
> All Solar, Inc.
> 1453 M St.
> Penrose Colorado 81240
>
> Sent by Jeremy's iPhone. Sorry for typos and shorthand.
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[RE-wrenches] Utility transformer limitations

[William Miller via RE-wrenches]

Wrenched:



Merry Christmas to those of you that observe such traditions, or substitute
the winter festivity of your choice.



I helped a previous employee install an Enphase IQ8 system on his home.  He
applied for the utility approval concurrently with his building permit  The
day he got his final inspection the utility contacted him and claimed "The
aggregate generation exceeds the identified transformer rating" and refused
him a Permission to Operate letter.



Adding up the service ratings of the homes on his secondary we get about
336 kW of potential consumption.  Adding the grid-tied systems on his
secondary we get about 16.5 kW.  How is it that the back-feed exceeds the
transformer rating?



I would appreciate any insight on how to consider this situation and how to
fight it.



Sincerely,



William Miller



Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985
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