Re: [RE-wrenches] Imbalanced Legs in 3-Phase systems

2008-08-08 Thread jay peltz 

Hi Bill,

Can you explain why the 6kVA rule on split phase systems?

I mean why 6?

thanks,

jay

peltz power
On Aug 8, 2008, at 8:48 PM, Bill Brooks wrote:


Jeff and Ryan,

The 6kVA value comes from the California Rule 21 that I worked on.  
It only
applies to split-phase 240V systems (6kVA on 120V). There is no  
specific

limit for imbalance on a 3-phase service.

A basic rule for single phase generation on a 3=phase service is to  
rotate
among the phases in a balanced manner. This means the largest  
imbalance

possible right now is 7kVA because of the SMA SB7000US. There is a
single-phase SatCon that is 30kVA, but it would be silly to buy a
single-phase Satcon when the major on 3-phase units.

The best way to place the imbalanced single-phase generators on the  
service
is to test the current on all three phases and put the inverter(s)  
on the
most heavily loaded phase(s). This reduces the site imbalance by  
reducing

the imbalance on the serving transformer (lowering current on the most
heavily loaded phases). It is common for 3-phase services to have  
imbalances
of 10 kVA or more, so single-phase inverters can reduce the problem  
rather

than make it worse.

Make any sense?

Bill.




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Re: [RE-wrenches] Imbalanced Legs in 3-Phase systems

2008-08-08 Thread Bill Brooks 
Jeff and Ryan,

The 6kVA value comes from the California Rule 21 that I worked on. It only
applies to split-phase 240V systems (6kVA on 120V). There is no specific
limit for imbalance on a 3-phase service. 

A basic rule for single phase generation on a 3=phase service is to rotate
among the phases in a balanced manner. This means the largest imbalance
possible right now is 7kVA because of the SMA SB7000US. There is a
single-phase SatCon that is 30kVA, but it would be silly to buy a
single-phase Satcon when the major on 3-phase units. 

The best way to place the imbalanced single-phase generators on the service
is to test the current on all three phases and put the inverter(s) on the
most heavily loaded phase(s). This reduces the site imbalance by reducing
the imbalance on the serving transformer (lowering current on the most
heavily loaded phases). It is common for 3-phase services to have imbalances
of 10 kVA or more, so single-phase inverters can reduce the problem rather
than make it worse.

Make any sense?

Bill.



-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ryan
Mayfield
Sent: Friday, August 08, 2008 3:40 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Imbalanced Legs in 3-Phase systems

Jeff,

My memory also recalls something about a 6kW value. 

I've talked to one of our local utilities about this as well and they base
the accepted imbalance by the size of the transformer serving the building.
I have never read their white paper on the subject though. When I described
a similar situation for an install we were working on, the engineer
acknowledged that he would not have any concern with such an arrangement.
You may approach your utility and see if they have a standard protocol you
could follow for your system.

Ryan



-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Jeff
Clearwater, Village Power Design
Sent: Thursday, August 07, 2008 10:14 AM
To: RE-wrenches
Subject: [RE-wrenches] Imbalanced Legs in 3-Phase systems

Hi Wrenches,

How does one determine how much imbalance can be tolerated on a 3 phase
system?

I'd like to feed 2 SMA SB5000s at 277 VAC into a 480 VAC panel 
instead of 1 13 KW Solectria at 480VAC as the PV system is only 9500 
Watts STC.  The main on the backfed service panel is 600 A.  But I'm 
not that sure of the loads as it's new construction and hasn't been 
characterized.

What are the appropriate calcs to do here?

Thanks!

Jeff C.
-- 
~
Jeff Clearwater
Village Power Design
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
[EMAIL PROTECTED]
NABCEP (tm) Certified Solar PV Installer

Voice: 413-259-3776
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
~`~
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Re: [RE-wrenches] Tax Deductible RE Donations

2008-08-08 Thread Joel Davidson 
Yes. contributions to Redwood Alliance qualify for tax deductions. Also, 
giving equipment and services (education, training, consulting, etc.) to 
local churches, schools may qualify.


- Original Message - 
From: "Michael Welch" <[EMAIL PROTECTED]>

To: "RE-wrenches" 
Sent: Thursday, August 07, 2008 11:21 PM
Subject: Re: [RE-wrenches] Tax Deductible RE Donations


Well, I must toot my own horn a bit.

Redwood Alliance has been the recipient of a couple used RE equipment 
donations in the past. But we are pretty much lined out (except we need a 20 
watt system for a mesh network radio). What we do with other RE equipment 
donations now is to turn them into funds via eBay.


Joel  Davidson wrote at 06:54 PM 8/7/2008:

Most state solar incentive programs are limited to new equipment. I don't 
recall if used equipment qualifies for the federal tax credit. Perhaps 
someone on this list can advise.


Some good people who can use new and used equipment are the Rahus Institute 
http://www.rahus.org/ and Solar Energy International 
http://www.solarenergy.org/


Any others?

Joel Davidson
- Original Message - 
From: Allan Sindelar

To: 'RE-wrenches'
Sent: Wednesday, August 06, 2008 9:10 PM
Subject: Re: [RE-wrenches] Tax Deductible RE Donations (inspired by 
InverterforSwitch to GT)


We would never donate PV equipment to charity, Joel. I would guess that 
most organizations wouldn't know what to do with this stuff. Pretty soon 
somebody discovers it (at a church rummage sale?), buys it cheap and tries 
to put together a cheap and funky system with major safety issues. I 
wouldn't want to install a system with outdated hardware with an unknown 
history.


We keep a periodically-updated sale flyer with descriptions of used 
equipment. Typically I (as the old fart specializing in off-grid here) will 
suggest something we have in the shop to a prospective customer on a 
budget. Since they're looking for guidance as well as a good deal, I can 
generally make up a safe and complete system using a package of used stuff. 
Everyone benefits.


Sometimes I even install it. Just today I completed installation of a 
Code-compliant (for tax credit eligibility) system package that we first 
installed elsewhere six years ago. The former clients brought in grid (to 
run an electric kiln; she's a potter) and rewired the array to run a Sunny 
Boy when the batteries died. The new owners saved several thousand $$, as 
we resold the entire BOS at 55% of original price. New array, rack, and 
batteries; reused SW4024, T240, PSDC, SB50. TM2020, even cables, 
interconnects, and internal wiring. We charge regular rates for 
installation; the client saved on labor as we reconnected existing wires, 
previously carefully disassembled.


We will generally sell equipment we replace on consignment; very little 
goes unsold, given enough time. Our consignment schedule (worked out over 
many years) is part of our general Rates and Policies:



Resale and Recycling of Used Equipment

We often remove serviceable used equipment when upgrading a power system. 
We will resell this equipment for you if you request it, according to the 
following terms:


·No "blue book" exists for solar components. We will estimate a 
reasonable resale price based on our experience and intuitive fairness.


·We sell on consignment, and while we may predict an item's resale 
appeal, we won't guarantee when or if it will sell.


·We will resell for you only specific component hardware items. 
Wire, conduit and fittings, electrical equipment, etc. will be reused or 
recycled, but will not be sold on consignment for you, as the recordkeeping 
becomes too difficult.


·We will pay you when a resale is made according to the following 
schedule:


o   Our base commission is 35% of the sale price excluding tax.

o   If you have bought a full system from us, our commission is reduced 
by 10%. (This is quite common.)


o   If the buyer of the component has bought a full system from us, our 
commission is reduced by an additional 10%. (This is rare, but it happens.)




All materials that leave a jobsite in our truck will be sorted and reused 
or recycled to the greatest extent possible. We recycle all standard 
household recyclables as well as copper, brass, aluminum, steel, batteries, 
packing peanuts, cardboard, and anything else we can reasonably keep out of 
the landfill.




Joel, this has resulted in many happy customers over the years. The check 
that shows up in the mail from us is seldom expected. I hope this helps.


Allan


-Original Message-
From: Joel Davidson

Wrenches,
Following on comments about switching to grid-tie (or any other changes), 
what do you do with modules, mounts, inverters, etc. that no longer serve 
your clients' needs? Do you or your clients contribute the unneed

Re: [RE-wrenches] Imbalanced Legs in 3-Phase systems

2008-08-08 Thread Ryan Mayfield 
Jeff,

My memory also recalls something about a 6kW value. 

I've talked to one of our local utilities about this as well and they base
the accepted imbalance by the size of the transformer serving the building.
I have never read their white paper on the subject though. When I described
a similar situation for an install we were working on, the engineer
acknowledged that he would not have any concern with such an arrangement.
You may approach your utility and see if they have a standard protocol you
could follow for your system.

Ryan



-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Jeff
Clearwater, Village Power Design
Sent: Thursday, August 07, 2008 10:14 AM
To: RE-wrenches
Subject: [RE-wrenches] Imbalanced Legs in 3-Phase systems

Hi Wrenches,

How does one determine how much imbalance can be tolerated on a 3 phase
system?

I'd like to feed 2 SMA SB5000s at 277 VAC into a 480 VAC panel 
instead of 1 13 KW Solectria at 480VAC as the PV system is only 9500 
Watts STC.  The main on the backfed service panel is 600 A.  But I'm 
not that sure of the loads as it's new construction and hasn't been 
characterized.

What are the appropriate calcs to do here?

Thanks!

Jeff C.
-- 
~
Jeff Clearwater
Village Power Design
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
[EMAIL PROTECTED]
NABCEP (tm) Certified Solar PV Installer

Voice: 413-259-3776
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
~`~
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No virus found in this incoming message.
Checked by AVG - http://www.avg.com 
Version: 8.0.138 / Virus Database: 270.5.12/1597 - Release Date: 8/7/2008
5:54 AM

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[RE-wrenches] Xantrex GT250 issues, heads ups, performance?

2008-08-08 Thread Geoff Greenfield 
Greetings wrenches-

Looking for field experience on the GT250 (or GT100).  How long has your
install been running? Performance?

Any "gotcha" stories, "heads ups" or advice appreciated.  Thanks to all!

For a brighter energy future,

Geoff Greenfield
President
Third Sun Solar & Wind Power Ltd.
340 West State street, Unit 25
Athens, Ohio 45701
(740) 597-3111   fax: (740)597-1548
www.third-sun.com

Clean Energy - Expertly Installed


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Re: [RE-wrenches] Tax Deductible RE Donations

2008-08-08 Thread Michael Welch 
Well, I must toot my own horn a bit.

Redwood Alliance has been the recipient of a couple used RE equipment donations 
in the past. But we are pretty much lined out (except we need a 20 watt system 
for a mesh network radio). What we do with other RE equipment donations now is 
to turn them into funds via eBay.

Joel  Davidson wrote at 06:54 PM 8/7/2008:
 
>Most state solar incentive programs are limited to new equipment. I don't 
>recall if used equipment qualifies for the federal tax credit. Perhaps someone 
>on this list can advise.
> 
>Some good people who can use new and used equipment are the Rahus Institute 
>http://www.rahus.org/ and Solar Energy International 
>http://www.solarenergy.org/
> 
>Any others?
> 
>Joel Davidson
>- Original Message - 
>From: Allan Sindelar 
>To: 'RE-wrenches' 
>Sent: Wednesday, August 06, 2008 9:10 PM
>Subject: Re: [RE-wrenches] Tax Deductible RE Donations (inspired by 
>InverterforSwitch to GT)
>
>We would never donate PV equipment to charity, Joel. I would guess that most 
>organizations wouldn't know what to do with this stuff. Pretty soon somebody 
>discovers it (at a church rummage sale?), buys it cheap and tries to put 
>together a cheap and funky system with major safety issues. I wouldn't want to 
>install a system with outdated hardware with an unknown history.
> 
>We keep a periodically-updated sale flyer with descriptions of used equipment. 
>Typically I (as the old fart specializing in off-grid here) will suggest 
>something we have in the shop to a prospective customer on a budget. Since 
>they're looking for guidance as well as a good deal, I can generally make up a 
>safe and complete system using a package of used stuff. Everyone benefits.
> 
>Sometimes I even install it. Just today I completed installation of a 
>Code-compliant (for tax credit eligibility) system package that we first 
>installed elsewhere six years ago. The former clients brought in grid (to run 
>an electric kiln; she's a potter) and rewired the array to run a Sunny Boy 
>when the batteries died. The new owners saved several thousand $$, as we 
>resold the entire BOS at 55% of original price. New array, rack, and 
>batteries; reused SW4024, T240, PSDC, SB50. TM2020, even cables, 
>interconnects, and internal wiring. We charge regular rates for installation; 
>the client saved on labor as we reconnected existing wires, previously 
>carefully disassembled.
> 
>We will generally sell equipment we replace on consignment; very little goes 
>unsold, given enough time. Our consignment schedule (worked out over many 
>years) is part of our general Rates and Policies:
> 
>
>Resale and Recycling of Used Equipment
>
>We often remove serviceable used equipment when upgrading a power system. We 
>will resell this equipment for you if you request it, according to the 
>following terms:
>
>·No “blue book” exists for solar components. We will estimate a 
>reasonable resale price based on our experience and intuitive fairness.
>
>·We sell on consignment, and while we may predict an item’s resale 
>appeal, we won’t guarantee when or if it will sell.
>
>·We will resell for you only specific component hardware items. Wire, 
>conduit and fittings, electrical equipment, etc. will be reused or recycled, 
>but will not be sold on consignment for you, as the recordkeeping becomes too 
>difficult.
>
>·We will pay you when a resale is made according to the following 
>schedule:
>
>o   Our base commission is 35% of the sale price excluding tax.
>
>o   If you have bought a full system from us, our commission is reduced by 
>10%. (This is quite common.)
>
>o   If the buyer of the component has bought a full system from us, our 
>commission is reduced by an additional 10%. (This is rare, but it happens.)
>
> 
>
>All materials that leave a jobsite in our truck will be sorted and reused or 
>recycled to the greatest extent possible. We recycle all standard household 
>recyclables as well as copper, brass, aluminum, steel, batteries, packing 
>peanuts, cardboard, and anything else we can reasonably keep out of the 
>landfill.
>
> 
>
>Joel, this has resulted in many happy customers over the years. The check that 
>shows up in the mail from us is seldom expected. I hope this helps.
>
>Allan
>
> 
>-Original Message-
>From: Joel Davidson
>
>Wrenches,
>Following on comments about switching to grid-tie (or any other changes), what 
>do you do with modules, mounts, inverters, etc. that no longer serve your 
>clients' needs? Do you or your clients contribute the unneeded or unwanted 
>equipment to a charitable or non-profit organization that qualifies the 
>donation for a tax deduction? What are your favorite charities and non-profit 
>orgs (what churches, schools, etc.)?
>Joel Davidson
>
>
>--
>___