Cooling 8 Sunny Boys [RE-wrenches]

Wed Apr 7 10:46:35 PDT 2004

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Jeff C./Wrenches:

For multiple units the centralized PS and multiple fans is probably a
great idea to reduce costs.
We suggest a 12 Vdc fans running at 9 Vdc to make them last longer,
reduce power requirements, and keep things quiet.  Below 9 Vdc they may
have trouble starting - depends on the fan.
A 6V (18 Cell) PV module seems to work pretty well since the voltage is
close to 9 when direct driving the fans and the Voc is high enought to
get them started.
If you are goign to use a larger PS running from the grid you might
want to use a small plug in timer instead of / in addition to the temp
switch.  On at 10:00 off at 17:00 should be more than adequate for most
sites.
Play with the start time and stop time since your results may vary due
to local conditions.

Best Regards,

John Berdner.

>>> clrwater at earthlink.net 4/6/2004 11:35:41 PM >>>

Hi All,

Anyone out there have

Before the sunny breeze was introduced, I installed 4 sunny boys with 
a cooling fan set up consisting of a tranformer-based 4 A, 12V power 
supply powering four 12 V, .6 amp ball bearing fans controlled by 
running the AC input to the power supply through a standard line 
voltage make-on-rise thermostat mounted above one of the sunny boy 
heatsinks. It also powers a fifth fan for the power shed. It's 
worked perfectly for almost 2 years.

Now I'm adding 4 more sunny boys to the shed and coincidently while I 
was pondering how best to expand the system the power supply failed. 
It may have failed because the on-time is high since it senses 
ambient temp - not heat sink temp.

So my options as I see it:

1) Tear that all out and buy 8 sunny breezes - $700 and live with 3 
wall warts with questionable life
2) Buy four more fans, a 50 watt solar panel and run them direct. 
$400. Concern: Fans will have short life if run during all 
sunlight hours without heat sink thermostat control.
3) Buy a high quality solid state 8 amp power supply (like a 
MeanWell) and four more fans and either move the thermostat closer to 
the heat sink or get a heat sink thermostat rated to the AC input 
amperage and control the power supply.

SO QUESTIONS:

1) Does anyone know of a reliable off-the-shelf heat sink mountable 
thermostat that can handle the amperage of the input of the power 
supply (perhaps .1 amp at 240VAC or 2 amps at 120) (I've used 
standard electric water heater thermostats in the past for custom 
solar hot water systems - their double pole double throw so you can 
use one side for make on rise - Thier temp range is about right and 
surely can handle the amperage - but are really bulky and 
unprofessional looking! (and no way to cover exposed wires)

2) Does anyone have experience with high reliability fans and/or 
power supplies and/or heat sink thermostats?

3) Generally what do we think the life of a sunny breeze is? Is it 
the fan or the wall wart that'll fail first? How long?

Any help before I go out and spend money would be most appreciated 
from such esteemed colleagues as you.

Best,

Jeff C.
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
http://www.villagepower.com 
jeffc at villagepower.com 
Sustainable Energy & Water Solutions for Home & Village

NABCEP Certified PV Installer

Office: (413) 256-6777, Cell: (720)480-8455
Fax: (413) 825-0372
61 Baker Road
Shutesbury, MA 01072;
PO Box 115
Boonville, CA 95415
(877) 765-2784

Council Member - Ecovillage Network of the Americas -
http://www.ecovillage.org 
Advisory Board - Living Routes - Ecovillage Education - 
http://www.livingroutes.org 
Founder: Ecovillage Research, Development, and Demonstration Program:
http://www.home.earthlink.net/~clrwater/RDD/rdd.html 
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