How to run attic fan from solar, but also automatically from grid

**kimo** · 06-13-2012, 10:20 PM

Ya , I know this is an old thread.......but a damn good idea. If they don't already make a solar attic fan....then they should. I would buy two of them.

**kimo** · 06-13-2012, 10:23 PM

WOW ! I just googled them..$400-600 for a solar fan. UHG !

**russ** · 06-14-2012, 12:51 AM

Then look at the specs on the fan - the amount of air flow will be quite low as to be next to useless.

**wedgeantilles** · 07-31-2012, 12:51 PM

Originally posted by toddmanqa

I'd like to install a powered vent in my attic to blow out the hot air during the summer months.

I'd also like to get it to run on solar power, and there are commercially available solar powered fans.

However, I've read that the drawback to using solar is that a cloud can block the sun, and the fan shuts down, and that when the sun sets, the attic can still be hot and the fan should still be on.

My question is this:

How can I combine a solar panel and the current from my household supply so that the household current will kick in/take over automatically when the solar panel is not supplying enough power?

Also, I'd like the option of adding more and more solar panels down the road and using the excess power to replace some of the power currently being pulled from the grid.

Any advice would be appreciated on the necessary equipment.

Thanks,
Todd

Dear Todd,

I don't know how your fan is, but one idea is to use a device to measure the energy from your solar panels, and when there is not enough switch to the household supply. Maybe you will have to include a delay to avoid that the system begins to switch between solar panels / household supply.

Best regards,

Mod note - forget the links

**ppreceipt** · 08-01-2012, 02:04 PM

Originally posted by kimo

WOW ! I just googled them..$400-600 for a solar fan. UHG !

go to your local home depot and you can pick them up for around half that price.
make sure you have good venting. if your insulation is blocking your bottom eve's getting a fan is pointless. It doesn't take much to add some metal can vents on the bottom of the roof line.

**inetdog** · 08-01-2012, 04:33 PM

Originally posted by ppreceipt

go to your local home depot and you can pick them up for around half that price.
make sure you have good venting. if your insulation is blocking your bottom eve's getting a fan is pointless. It doesn't take much to add some metal can vents on the bottom of the roof line.

Be sure to read the reviews of the box store products and compare them with other choices. The life expectancy of the inexpensive units (and even some of the more expensive ones) is not good, especially considering that they don't move much air.

**ppreceipt** · 08-01-2012, 06:57 PM

click on the black triangle with White exclamation point to report

click on the black triangle with White exclamation point to report the post. Hopefully the moderators fix the issue.

**Sunking** · 08-01-2012, 07:01 PM

You guys really need to get a Sense of Humor. You hate ironic humor. Why is that? Because the irony has an element of truth to it and Honest Commentary which is allowed and encouraged?

**inetdog** · 08-01-2012, 07:29 PM

Originally posted by Sunking

You guys really need to get a Sense of Humor. You hate ironic humor. Why is that? Because the irony has an element of truth to it and Honest Commentary which is allowed and encouraged?

I think that use of the sarcasm font (TM) should also be applicable for irony. In this case the nature and intent of your comment was pretty clear, but for written communications any additional cues you can add are helpful and might help to defuse a tense atmosphere.

Sometimes it is hard to tell whether ridicule is good natured or demeaning. (note font)

I also get the impression that you are anxious to be moving on with your escape to a more congenial environment and are frustrated with the delays.

**SolarWatt** · 11-16-2012, 06:42 PM

Solar panel is expensive for this purpose
Just connect to the grid and blow out the hot air....

**John J.** · 02-21-2013, 02:44 PM

Unless the op is dead set on a solar vent fan I'm going to suggest 1 or 2 passive turbine style vents.

**inetdog** · 02-21-2013, 06:14 PM

Originally posted by John J.

I'm going to suggest 1 or 2 passive turbine style vents.

You will find a healthy discussion on whether the turbine style vents are actually any better than a similar size direct vent or one with a swivel so that it follows the wind.
I do not have any particular wisdom of my own on the subject.

They are entertaining to watch though.

**Mustang65** · 08-08-2013, 11:25 PM

I have have had a solar attic fan for a year now. Here are my findings:
- prior to installing the attic fan, the attic temperature reached 138 degrees in the Florida sun each afternoon.
- after installing a solar fan rated for a larger size attic than i have, the attic temperature still reaches 138 degrees each afternoon runninng on solar
The problem is that the panel does not track the sun, so it only produces a small portion of the motors needs.
I wii be connecting the solar fan to my larger solar panel system and will be adding a second fan..providing this new setup drops the attic temperature, else we go to a120vac setup.
Don