Re: [RE-wrenches] Utility transformer limitations

[Peter Giroux via RE-wrenches]

Hi again wrenches. Have a customer looking for a LG Resu 10 “B” battery in good 
working order. Wants to add it to his current Resu 10 for additional storage.

 

Thx

Peter Giroux

ASAE

 

From: RE-wrenches  On Behalf Of 
Peter Giroux via RE-wrenches
Sent: Monday, December 26, 2022 9:40 AM
To: cwar...@entech-engineering.com; 'RE-wrenches' 

Cc: pgir...@mindspring.com
Subject: Re: [RE-wrenches] Utility transformer limitations

 

Morning all. Just got a call from a customer with a radian and fortress battery 
that caught fire. Has anyone had any issues with either unit?? We have numerous 
systems with combos of both and no issues. System has been in place for well 
over a year, climate controlled garage and system has worked well. Did a BMS 
board replacement earlier this year.

 

  Any and all help appreciated.

 

Thank you

Peter Giroux

ASAE

 

From: RE-wrenches mailto:re-wrenches-boun...@lists.re-wrenches.org> > On Behalf Of Christopher 
Warfel via RE-wrenches
Sent: Monday, December 26, 2022 8:17 AM
To: re-wrenches@lists.re-wrenches.org 
 
Cc: Christopher Warfel mailto:cwar...@entech-engineering.com> >
Subject: Re: [RE-wrenches] Utility transformer limitations

 

Wouldn't the microinverters shut down if the voltage rose?  They wouldn't be 
able to raise voltage about PUC/DPU limits I would think. They would shut down 
on high voltage. I am saying this because of an experience this fall where our 
infamous Block Island Power Company raised the taps on a local xfmr due to 
their "secret heat pump program" that was dragging down local voltage. They 
claimed solar was a burden, but were quiet on the load building program they 
embarked upon without any disclosure.   When the cooling loads disappeared, the 
voltage went above our grid tied systems set points and they shut down.  We 
told the utility they had a high voltage problem and they adjusted the taps.  
Of course they did not acknowledge or thank us.  It seems our little coop which 
is now head from a guy from the Vermont Electric Coop is taking an old utility 
approach instead of cooperation, integration and maximization of performance 
and economics. 

I'd think you be able to ask how the supply can raise the voltage when there is 
so much diversified load on the same device.   Electricians have to do a 
diversity calculation, and I know a utility has to conduct them as part of 
these studies. Worse case of no load and all generation is such a low 
probability that to design for it, when/if it occurred, is not a danger and of 
no material consequence makes little sense. But, we've been dealing with that 
ever since this person arrived in our neck of the woods.

 

Chris Warfel 

 

 

On 12/25/2022 5:21 PM, Garrison via RE-wrenches wrote:

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 Riegel

Celestar Solar

 

On 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 
mailto: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 

Re: [RE-wrenches] Utility transformer limitations

[Jay via RE-wrenches]

Yes often the study says, yes it’s ok to do the original design and you still have to pay. Remember it’s pay in advance of getting the report. If no then usually they give a cost estimate to upgrade what ever needs to be replaced or a downgraded solar  design that will work with existing equipment. JayOn Dec 26, 2022, at 10:12 AM, Christopher Warfel via RE-wrenches  wrote:
  

  
  
What happens if the study shows yes, that their no
was wrong. Or does that never happen?
On 12/26/2022 12:48 PM, Jay via
  RE-wrenches wrote:


  
  If the utility is PG in my experience here is
what happens 
  
  
  They say yes or no to the interconnection. 
  If no you have the option to request an engineering
study to determine how much solar. That study is at your
expense, paid in advance and the exact cost isn’t known until
the study is done. Could be $500 to $15,000 or more. 
  
  
  I’ll be curious to know what happens 
  
  
  Jay
  
  
  
  
  
  
  
  
  
On Dec 26, 2022, at 9:07 AM, Drake
  Chamberlin via RE-wrenches
   wrote:
  

  
  

  
  
  
  William, 
  I ran into this once on an
  old transformer, which fortunately they changed at no
  cost. It was a 10 kW transformer on a 200 A (48 kW)
  service. They had some dimming of lights on heavy loads,
  and the transformer was changed out on that basis, at no
  charge. 
  My questions for the utility
  would be?
  
Are there any other PV
systems feeding the transformer?
  
If so, what is their
maximum production.
  

What size is the
transformer?
What percentage of
transformer capacity is allowed to be back-fed.
  
  If the math comes out in
  your favor, you will have a good case to escalate to the
  next level. 
  
  
  Good Luck,
  Drake
  
  
  Drake Chamberlin
  Athens Electric LLC
  Ohio Electrical Contractor’s License 44810
  CO Master Electrician’s License 4526
  NABCEP Certified PV Installation Professional
  ---
  On 2022-12-25 13:58, 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 Solar
  17395 Oak
  Road, Atascadero, CA 93422
  805-438-5600
  www.millersolar.com
  CA Lic. 773985
   
   

  


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Re: [RE-wrenches] Utility transformer limitations

[Christopher Warfel via RE-wrenches]

What happens if the study shows yes, that their no was wrong. Or does 
that never happen?


On 12/26/2022 12:48 PM, Jay via RE-wrenches wrote:

If the utility is PG in my experience here is what happens

They say yes or no to the interconnection.
If no you have the option to request an engineering study to determine 
how much solar. That study is at your expense, paid in advance and the 
exact cost isn’t known until the study is done. Could be $500 to 
$15,000 or more.


I’ll be curious to know what happens

Jay





On Dec 26, 2022, at 9:07 AM, Drake Chamberlin via RE-wrenches 
 wrote:





William,

I ran into this once on an old transformer, which fortunately they 
changed at no cost. It was a 10 kW transformer on a 200 A (48 kW) 
service. They had some dimming of lights on heavy loads, and the 
transformer was changed out on that basis, at no charge.


My questions for the utility would be?

  * Are there any other PV systems feeding the transformer?
  o If so, what is their maximum production.
  * What size is the transformer?
  * What percentage of transformer capacity is allowed to be back-fed.

If the math comes out in your favor, you will have a good case to 
escalate to the next level.



Good Luck,

Drake


Drake Chamberlin

Athens Electric LLC

Ohio Electrical Contractor’s License 44810

CO Master Electrician’s License 4526

NABCEP Certified PV Installation Professional

---

On 2022-12-25 13:58, 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 Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com 

CA Lic. 773985


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PO Box 871, Block Island, RI 02807
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Re: [RE-wrenches] Utility transformer limitations

[Jay via RE-wrenches]

If the utility is PG in my experience here is what happens They say yes or no to the interconnection. If no you have the option to request an engineering study to determine how much solar. That study is at your expense, paid in advance and the exact cost isn’t known until the study is done. Could be $500 to $15,000 or more. I’ll be curious to know what happens JayOn Dec 26, 2022, at 9:07 AM, Drake Chamberlin via RE-wrenches  wrote:

William, 
I ran into this once on an old transformer, which fortunately they changed at no cost. It was a 10 kW transformer on a 200 A (48 kW) service. They had some dimming of lights on heavy loads, and the transformer was changed out on that basis, at no charge. 
My questions for the utility would be?

Are there any other PV systems feeding the transformer?

If so, what is their maximum production.


What size is the transformer?
What percentage of transformer capacity is allowed to be back-fed.

If the math comes out in your favor, you will have a good case to escalate to the next level. 

Good Luck,
Drake

Drake Chamberlin
Athens Electric LLC
Ohio Electrical Contractor’s License 44810
CO Master Electrician’s License 4526
NABCEP Certified PV Installation Professional
---
On 2022-12-25 13:58, 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 Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com
CA Lic. 773985
 
 




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Re: [RE-wrenches] Utility transformer limitations

[Drake Chamberlin via RE-wrenches]

William, 


I ran into this once on an old transformer, which fortunately they
changed at no cost. It was a 10 kW transformer on a 200 A (48 kW)
service. They had some dimming of lights on heavy loads, and the
transformer was changed out on that basis, at no charge. 

My questions for the utility would be? 

	* Are there any other PV systems feeding the transformer? 


* If so, what is their maximum production.

* What size is the transformer?
* What percentage of transformer capacity is allowed to be back-fed.

If the math comes out in your favor, you will have a good case to
escalate to the next level. 

Good Luck, 

Drake 

Drake Chamberlin 

Athens Electric LLC 

Ohio Electrical Contractor's License 44810 

CO Master Electrician's License 4526 

NABCEP Certified PV Installation Professional 


---


On 2022-12-25 13:58, 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 Solar 

17395 Oak Road, Atascadero, CA 93422 

805-438-5600 

www.millersolar.com [1] 

CA Lic. 773985 


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Links:
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[1] http://www.millersolar.com/___
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Re: [RE-wrenches] Utility transformer limitations

[Darryl Thayer via RE-wrenches]

Hello, my first thought is the BMS board, on the battery reaching near full
charge the BMS does a top balance where the board diverts the current
around fully charged cells and continues to charge cells not fully
charged.  this diversion current generates heat.  that the board must
dissipate.   When all cells are charged the heat depends upon charging
voltage.  Is the radian set at too high a charging voltage?  Also, if a
cell fails that cell will overheat and the board will overheat.  .

On Mon, Dec 26, 2022 at 8:40 AM Peter Giroux via RE-wrenches <
re-wrenches@lists.re-wrenches.org> wrote:

> Morning all. Just got a call from a customer with a radian and fortress
> battery that caught fire. Has anyone had any issues with either unit?? We
> have numerous systems with combos of both and no issues. System has been in
> place for well over a year, climate controlled garage and system has worked
> well. Did a BMS board replacement earlier this year.
>
>
>
>   Any and all help appreciated.
>
>
>
> Thank you
>
> Peter Giroux
>
> ASAE
>
>
>
> *From:* RE-wrenches  *On
> Behalf Of *Christopher Warfel via RE-wrenches
> *Sent:* Monday, December 26, 2022 8:17 AM
> *To:* re-wrenches@lists.re-wrenches.org
> *Cc:* Christopher Warfel 
> *Subject:* Re: [RE-wrenches] Utility transformer limitations
>
>
>
> Wouldn't the microinverters shut down if the voltage rose?  They wouldn't
> be able to raise voltage about PUC/DPU limits I would think. They would
> shut down on high voltage. I am saying this because of an experience this
> fall where our infamous Block Island Power Company raised the taps on a
> local xfmr due to their "secret heat pump program" that was dragging down
> local voltage. They claimed solar was a burden, but were quiet on the load
> building program they embarked upon without any disclosure.   When the
> cooling loads disappeared, the voltage went above our grid tied systems set
> points and they shut down.  We told the utility they had a high voltage
> problem and they adjusted the taps.  Of course they did not acknowledge or
> thank us.  It seems our little coop which is now head from a guy from the
> Vermont Electric Coop is taking an old utility approach instead of
> cooperation, integration and maximization of performance and economics.
>
> I'd think you be able to ask how the supply can raise the voltage when
> there is so much diversified load on the same device.   Electricians have
> to do a diversity calculation, and I know a utility has to conduct them as
> part of these studies. Worse case of no load and all generation is such a
> low probability that to design for it, when/if it occurred, is not a danger
> and of no material consequence makes little sense. But, we've been dealing
> with that ever since this person arrived in our neck of the woods.
>
>
>
> Chris Warfel
>
>
>
>
>
> On 12/25/2022 5:21 PM, Garrison via RE-wrenches wrote:
>
> 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 Riegel
>
> Celestar Solar
>
>
>
> On 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 <
> re-wrenches@lists.re-wrenches.org> wrote:
>
> Wrenched:
>
>
>
> Merry Christmas to those of you that observe such 

Re: [RE-wrenches] Utility transformer limitations

[Peter Giroux via RE-wrenches]

Morning all. Just got a call from a customer with a radian and fortress battery 
that caught fire. Has anyone had any issues with either unit?? We have numerous 
systems with combos of both and no issues. System has been in place for well 
over a year, climate controlled garage and system has worked well. Did a BMS 
board replacement earlier this year.

 

  Any and all help appreciated.

 

Thank you

Peter Giroux

ASAE

 

From: RE-wrenches  On Behalf Of 
Christopher Warfel via RE-wrenches
Sent: Monday, December 26, 2022 8:17 AM
To: re-wrenches@lists.re-wrenches.org
Cc: Christopher Warfel 
Subject: Re: [RE-wrenches] Utility transformer limitations

 

Wouldn't the microinverters shut down if the voltage rose?  They wouldn't be 
able to raise voltage about PUC/DPU limits I would think. They would shut down 
on high voltage. I am saying this because of an experience this fall where our 
infamous Block Island Power Company raised the taps on a local xfmr due to 
their "secret heat pump program" that was dragging down local voltage. They 
claimed solar was a burden, but were quiet on the load building program they 
embarked upon without any disclosure.   When the cooling loads disappeared, the 
voltage went above our grid tied systems set points and they shut down.  We 
told the utility they had a high voltage problem and they adjusted the taps.  
Of course they did not acknowledge or thank us.  It seems our little coop which 
is now head from a guy from the Vermont Electric Coop is taking an old utility 
approach instead of cooperation, integration and maximization of performance 
and economics. 

I'd think you be able to ask how the supply can raise the voltage when there is 
so much diversified load on the same device.   Electricians have to do a 
diversity calculation, and I know a utility has to conduct them as part of 
these studies. Worse case of no load and all generation is such a low 
probability that to design for it, when/if it occurred, is not a danger and of 
no material consequence makes little sense. But, we've been dealing with that 
ever since this person arrived in our neck of the woods.

 

Chris Warfel 

 

 

On 12/25/2022 5:21 PM, Garrison via RE-wrenches wrote:

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 Riegel

Celestar Solar





On 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 
mailto: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 

Re: [RE-wrenches] Utility transformer limitations

[Christopher Warfel via RE-wrenches]

Wouldn't the microinverters shut down if the voltage rose?  They 
wouldn't be able to raise voltage about PUC/DPU limits I would think. 
They would shut down on high voltage. I am saying this because of an 
experience this fall where our infamous Block Island Power Company 
raised the taps on a local xfmr due to their "secret heat pump program" 
that was dragging down local voltage. They claimed solar was a burden, 
but were quiet on the load building program they embarked upon without 
any disclosure.   When the cooling loads disappeared, the voltage went 
above our grid tied systems set points and they shut down.  We told the 
utility they had a high voltage problem and they adjusted the taps.  Of 
course they did not acknowledge or thank us.  It seems our little coop 
which is now head from a guy from the Vermont Electric Coop is taking an 
old utility approach instead of cooperation, integration and 
maximization of performance and economics.


I'd think you be able to ask how the supply can raise the voltage when 
there is so much diversified load on the same device.   Electricians 
have to do a diversity calculation, and I know a utility has to conduct 
them as part of these studies. Worse case of no load and all generation 
is such a low probability that to design for it, when/if it occurred, is 
not a danger and of no material consequence makes little sense. But, 
we've been dealing with that ever since this person arrived in our neck 
of the woods.



Chris Warfel



On 12/25/2022 5:21 PM, Garrison via RE-wrenches wrote:

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 Riegel
Celestar Solar

On 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 Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com 

CA Lic. 773985

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