solar attic fan *troubleshoot*

jvmagicApril 18, 2009

hi,

I just noticed that I have a solar attic fan on my roof while inspecting my solar pool heater panels. It has been a bit over 80 degrees today here in San Jose, CA and I did not hear the fan spinning on this fan??????? I happened to see this same fan at costco (being displayed) and I saw that the fan was spinning etc....

Is my solar attic fan not working? what can I do to troubleshoot?

thanks in advance

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solargary

Hi,
There will be a PV panel on top the fan cover or attached to the fan by wires. If the PV panel is in the sun, the fan should be turning. The PV panel must be in the sun for the fan to run -- the air temperature is irrelevant.

If the fan does not run with the PV panel in the sun, I'd look for a loose connection, or something keeping the fan blades from moving. Does the fan turn freely if pushed with a finger?

If its nothing obvious, then disconnect the PV panel, and with it in the sun, check it with a volt meter to see if it is putting out voltage. If its a nominal 12 volt panel, it will have an open circuit voltage around 17 volts DC if its working OK.

If the PV panel appears OK, check and see what the motor voltage is on the nameplate. If its 12 volts DC, then you could hook it up to a car battery and see if it goes.

Gary

    Bookmark   April 18, 2009 at 10:44PM
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jvmagic

thanks for the response.

what is 'PV'

do I do the troubleshooting from the top (remove the top) or from the attic side?

    Bookmark   April 19, 2009 at 12:48AM
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solargary

Hi,
PV is photovoltaic -- its the panel that generates electricity when exposed to sunlight. It has to be in direct sun to generate electricity to run the fan.

Gary

    Bookmark   April 19, 2009 at 2:57PM
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jvmagic

Gary,
I removed the PV and the fan was spinning. I made the mistake of assuming it was not working before removing the panel. It just happens to be very quiet.
out of curiosity, being that I have had this solar attic fan since purchasing my phome, do they really make a difference?

thanks

    Bookmark   April 19, 2009 at 8:37PM
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solargary

Hi,
Quiet is good :)

The idea is that the fan reduces the attic temperature, and therefore reduces heat transfer into your home through the ceiling.

There is a bit of controversy over the rather powerful attic ventilators -- some studies have shown that they pull air from the living space through small unsealed areas of the ceiling (like plumbing and wiring penetrations). This air must be replaced by air from outside, and you have to then cool this incoming air. The ones that plug into an outlet also use electricity. Search www.Soutface.org for the study on this if you want to know more.

But, I think the solar power ones are good -- especially if the previous owner put it in for you :)
They move a moderate amount of air, and should not lower the pressure in the attic enough to cause airflow through the ceiling, and they don't use any electricity.

If it was not already there, and you wanted to spend some money to reduce heating/cooling bills, I would: 1) seal all the penetrations for the living space to attic (wiring, plumbing, light fixtures, ...) -- according to the EPA this is the major cause of infiltration losses on most homes, 2) add more insulation (e.g. blown in cellulose), and 3) insulate and seal (with duct mastic) any heating or cooling ducts that go through the attic. I think that all of these give more bang for the buck than an attic fan.

Gary

    Bookmark   April 19, 2009 at 11:24PM
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