[RE-wrenches] Electrolytic Caps vs. Thin Film Caps

Thu Jan 19 07:06:28 PST 2012

Drake,

-20 to -28F is my best estimate. I do not have minimum registering
temperature gauges at inverter locations. The coldest areas in Vermont get
down to 40 below every few years. I don't have inverters in the coldest
locations. I've seen -15F out my front door a few times already this year.
If I walk 300 feet away from the house and take a reading in a field 40 feet
in elevation below the house, the temperature is 6 to 8 degrees lower there.

Dave

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, January 19, 2012 9:14 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Electrolytic Caps vs. Thin Film Caps

Dave,

That is really good news. I went through this with Steve Jefferson and SMA
recently.  They said that -13F was the limit.  Steve has posted to this
effect on the list, but I couldn't find it in the archives.  The
recommendation was that I get a Canadian model, but was not able to.  Where
we are, it seldom gets below zero, but has historically gotten to -26
officially, and according to many it has gotten below - 30.  The customer
has agreed to shut down the outdoor unit if it gets below -10F.  It would be
good to know that SMA's recommendations are over cautious.  What is the
coldest you have seen your inverters operate at?

Thanks,

Drake 

Drake,

Before installing Sunny Boys outside I did some checking several years ago.
I spoke with some installers in cold locations in the USA and also spoke
with contacts at SMA. The word back then was although the manual states
-13F, they felt the SB's would be OK outdoors here in Vermont. I also go the
go ahead from Solectria and Fronius.  James Worden, top boss at Solectria
said -40F. The Fronius engineer told me that the electronics in their
inverters were basically the same components that they use in their welders,
and that the welders sit outside in Siberia, in the winter. 

We try and install inverters in the basement, or garage, whenever possible
but have many outdoors with no problems so far. 

All Earth Renewables have been installing hundreds of trackers here in
Vermont and they all have Sunny Boys mounted on the pole.

Best,
Dave

From: re-wrenches-bounces at lists.re-wrenches.org [
mailto:re-wrenches-bounces at lists.re-wrenches.org
<mailto:re-wrenches-bounces at lists.re-wrenches.org> ] On Behalf Of Drake
Sent: Wednesday, January 18, 2012 6:47 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Electrolytic Caps vs. Thin Film Caps

The SMA inverters will suffer capacitor damage if operated below -10F, from
what I've been told.  Do you have different information?  

At 09:19 AM 1/15/2012, you wrote:

Hello David,

The minimum temperature rating for grid-tied inverters
is dependent on the manufacturer's specifications.  It's
a choice they make as a part of the product design
and certification.

The manufacturer must specify the coldest temperature
as a part of their UL1741 certification effort, and
that's the coldest to which it will be tested and
verified as operational by the UL certification
laboratory (NRTL).  Will it operate below the min
temperature spec?  It might.  But then again, it's
not verified to do so.  Some bad things can happen
if the components don't handle cold very well, and
power is applied (such as actual failure of parts.)

Quality electrolytic capacitors are generally rated
to -40C (which also happens to be -40F).  Film caps
are often rated for temperatures below -40C, but at
-40C, other components such as microprocessor clock
crystals and many integrated circuits will fail to
operate, so the point of film caps being rated for
colder temperatures than electrolytic caps is moot.

Note this is "fail to operate", not "fail".

Cold-temperature components rated to -55C *could* be
used in inverter construction, but parts of this type
add cost (sometimes considerably) to the finished
product price.

By the way .. to your point of cold temperature specs
not appearing in writing ...

Our PVAC Modules *are* rated to operate at -40C, and
have been tested to that temperature by the UL test
lab.  This rating is stated in writing in our brochures
as well as the PVAC Module Installation Manual/User's
Guide.

Dan

--- On Sun, 1/15/12, Dave Palumbo <dave at independentpowerllc.com> wrote:

> From: Dave Palumbo <dave at independentpowerllc.com>
> Subject: Re: [RE-wrenches] Electrolytic Caps vs. Thin Film Caps
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
> Date: Sunday, January 15, 2012, 7:32 AM
> Dan,
> 
> Any worries with inverters located out in 30 below zero
> temps with either Electrolytic Caps or Film Capacitors?
> It's very cold here this AM (minus twenty something F)
> and it makes me wonder about all the inverters, both
> micro's and string, outside in cold weather areas. We've
> been told in the past by SMA, Fronius and Solectria that
> we should be good down to 40 below, although this is
> typically not found in their technical documents in
> print.
> 
> David Palumbo
> Independent Power LLC 
> 462 Solar Way Drive
> Hyde Park, VT 05655
> www.independentpowerllc.com <http://www.independentpowerllc.com/>  
> NABCEP Certified PV Installer
> Vermont Solar Partner
> 24 Years Experience, (802) 888-7194 

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Drake Chamberlin         
ATHENS ELECTRIC LLC
OH License 44810        
CO license 3773
NABCEP Certified PV

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