Attic Fan Install - Pilot Switch Override

Attic Fan Install and Pilot Switch Override


Let me start by saying that installing the gable end attic fan is part of a process that has been going on for years.  We replaced our 25 year old central air unit last year after some of the internal valves broke and it was blowing out luke warm air all summer.  That helped but it was still hot in the upstairs of our house.  Typically in the summer the basement is around 65 degrees, the first floor is around 74 and the upstairs is over 80.

One day i had to look up in the attic for something and was amazed at how hot it was up there.  There was no air flow and i started sweating immediately.  After checking with a non-contact thermometer i found out that it was between 135 and 145 degrees fahrenheit!
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That's when i knew that the upstairs was so hot because there was this pocket of 140 degree air up in the attic.  And if i could cool down the attic, the whole house would be cooler as well.

My original plan was to buy a whole house fan.  At night when it dropped below 70 degrees outside i would open up  a window, turn on the fan and the entire house would fill with the 70 degree air.  The problem was that whole house fans cost $250 minimum, on Craigslist they are usually old ones torn out of houses and people still want $100.  Here's a small one at Menards that was $220.
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They also had gable end mounted fans for $72.  They would be mounted at the end of the attic and help circulate air sitting in the attic, hopefully bringing in cold air from outside.
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So i thought that i could make one.  I went through all my electric motors till i found one that would work, i had fan blades that i made years ago, and i drew up plans to build a frame and mount the motor to the joists.  This was an old motor that revved at a super high RPM.
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Years ago i made fan blades out of a PVC pipe.  Here's me testing out the blades on the motor.
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I even went so far as to draw the homemade attic fan up on AutoCAD to get dimensions for the frame i planned on making.  I was also planning on making my own baffles and foam box that would close when the fan turned off.
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These were 2 other electric motors i was trying out.
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And here's a 4th motor i was considering.  This one came off our old central air unit.  It was 220 volt but still ran at 110 volt.  It also still had fan blades on it that i was thinking of using.
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I was a little bit scared to cut a 3 foot hole in my ceiling, but i was ready to go, and then i walked through Lowe's one day and saw that gable end attic fans were 60% off.  Normally costing $70 or $80, they were marked down to $33.  
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I figured at that low of a price i should give it a try.  Worst case scenario it doesn't help at all and i can still make the attic fan.  They also had the thermostat for the fan for just $10.
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This would be a quick and cheap test to cool the house down, and didn't involve me cutting a whole in the ceiling.

One big difference to know is that attic fans and whole house fans work in completely different ways.  Whole house fans are turned on in the evening when the air outside is cooler than the air in the house.  The whole house fan then suckes in that cool air and blows it up into the attic and out the gable end vents.  Attic fans have a thermostat mounted to them and only turn on at the hottest times of the day when the air in the attic goes over the set temperature on the thermostat (typically between 100 and 120 degrees).

My plan was to install the attic fan but to also install a switch where i could turn the fan on manually.  Also i was a little worried that the fan might be running constantly and the only way to turn it off would be to get out the ladder and climb up there and adjust the thermostat.  So i wanted to also install a power on/off switch.

So i unboxed the fan and started looking at the thermostat.
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Luckily it wasn't that complicated.  They had the white wire running through the thermostat, which would press 2 metal tabs together to complete the circuit, when a certain temperature was reached.

I realized that i could bypass the thermostat fairly easily.  But it's a good thing i tested it in the basement because it took a couple of tries to get the wiring right.
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Here's my sketch at the top of how i bypassed the thermostat.
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You can see the switch on the right.  I finally got it wired up correctly that the fan would turn on by flipping the switch and it didn't matter if the thermostat was giving it power.
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But eventually i got it to where the fan would turn on when the thermostat activated or if i flipped the pilot switch.  Here's the whole test setup.
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And here's another close up of the wiring.
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Then one day when i had a few hours i put all the tools i thought i would need into a milk crate, grabbed the ladder and headed up to the attic.  Most of the tools and materials were electrical stuff, twist ends, wire strippers, etc.  
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Also some boards i cut to frame the opening for the fan.
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I wasn't sure what wires i would be tapping into, and didn't want to have to constantly climb up and down from the attic, so i just turned all the power to the house off at the circuit breaker.

You have to be a bit of a contortionist to get through the access hole in my attic, and the first thing i learned is that the milk crate didn't fit, so i had to change to a couple grocery bags.  The second thing i learned is that i could only work for a max of 10 minutes up there in the 140 degree heat.  Of course you're never doing this when it's cold outside, that day it was 90 degrees.  Here's what i looked like after less than 10 minutes.
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The third thing i learned is that at some point bats lived up in my attic.  I saw a couple of dead ones.
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So i took some insulation and stuffed it in to any cracks i could find leading outside.  Hopefully blocking any more bats from getting in there.

I wanted to start by getting the fan up, which meant framing up the gable end opening with the scraps of wood.  Then i screwed the fan into that wood frame.  But before i attached the fan, i stapled up some chicken wire to hopefully keep any more bats from coming in.  Here's what the final result of attaching just the fan looked like.  It's pretty bad but i didn't care, at this point i got out of the attic and drank some water.  
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After about an hour i went back up and started working on the wiring.  I attached the thermostat on the right side of the fan and started running 1 wire to power and the other wire to where i wanted to mount the pilot override switch.  Also you can see that i stapled up some thick felt insulation to help force airflow through the vent.
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Let me tell you, you might have the best of intentions, but when you are hunched over in your attic, straddling a dead bat, in 140 degree heat, your standards of how well you want to install something drop dramatically.  I know it isn't pretty, but at the time it looked just fine to me.
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I got out of the attic, drank some water, and took another break.  Then it was back up to run power to the fan.  This part i totally screwed up, and i bet it's a common problem.  I saw power running to a box and thought, "oh that will work perfectly."  The problem was that the box was the ceiling light in our bedroom.  So i ran the wire from the box to the fan, climbed down, switched on power to the circuit breaker and went back upstairs to see if it worked.  It didn't.  Then i switched the light to the bedroom on and wouldn't you know it, i could hear the fan turn on too.  That's when i realized the mistake i made.  The box i tapped into wasn't a constant source of power, only when the light was switched on.  So back to the basement to turn off the breaker, then back up to the attic to find a new source of power.  I found one, it was an outlet in the ceiling of my closet that powered 2 little lights.

When i rewired the power to that it worked fine.  I set the temperature on the thermostat to 105 and that has seemed to work well.  Not constantly running but on a hot day the fan is on for a few hours.  I didn't wire up the pilot switch or the power switch that day.  I was pretty tired from being in the attic.

But a week later i started working on the 2 switches.  I thought a lot about where i wanted the switches to go.  Some place out of the way, but still near the fan.  I figured that in the closet ceiling next to the other outlet would work and be easy to install.  I wouldn't have fish any wires down through the wall.  Here's the existing outlet (blue) in the ceiling and the new double switch outlet (gray) that i installed next to it.
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So back up to the attic, take off the old switch that i temporarily taped to a truss, and run a wire to the new box.  I traced where the double outlet box would go and cut a hole with a drywall saw.  Then nailed the box to the 2x4 and inserted the wire.  Then i cut the power wire i ran the week before and inserted that into the box as well.  The power was pretty straight forward to install.  Connect the black wires then connect the white wires to the switch.  Here's that same picture from before, but at the bottom you can see the way i wired the pilot switch.
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For the pilot switch i spent some time looking online before i finally found how to wire it.  There's lots of diagrams on the "proper" way to wire it, but there's also an "alternative" way of wiring it up.  Officially they want you to run a separate wire from the fan to the switch called the Load.  That will tell the light on the switch that the fan is running.  The alternative way is much simpler and only takes the 1 wire that i ran from the fan originally.  I did the easier alternate way, it took 2 tries to get it correct but works fine now.

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Here's the jumper wire that it shows in the diagram.
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Again this actually took me a couple tries to get right.  I had to switch the black and white wires from the diagram because apparently my black wire was connected to neutral.  Here's the existing outlet and the new power switch and pilot switch override.  
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But eventually it worked perfectly.  I was able to override the thermostat with the pilot switch and the little red light turned on to let me know that i was manually turning the fan on.  Now i would be able to run the fan before going to be, when it's cooler outside, and try to get that colder air in the attic, so that our AC doesn't have to work to cool the upstairs.

It's been a few weeks and i've noticed a small improvement.  Again it's not like a whole house fan where you turn the thing on and cool your house in minutes.  But hopefully it will reduce the AC from turning on a couple times a day and lower the electricity bill during the summer.  I still want to install a whole house fan at some point.  But it's going to take a year or so before i forget how hot it is up in the attic in July.

1 comment:

JL said...

I installed an attic fan in a past house, and it made an amazing difference. I am doing so again right now and am lucky to have found your post. It came at just the right time to assure my confidence. I am very grateful for your wiring diagrams! Great share!