Replace mechanical timer for attic fan


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Old 08-03-14, 09:03 PM
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Replace mechanical timer for attic fan

Just moved into a new home with a 2 attic fan setup. They're QuietCool brand models QC-4500 and QC-1500. There is a 3 switch module connected to a 60 minute timer (Intermatic 885l). I'd like to replace it with a timer with more than 60 minutes. The only thing my local Home Depot has that would fit in place is a Defiant 49817. Looking at the current wiring setup, I'm not sure how this one would go in or if it's compatible at all. I've attached a couple pictures. Can anyone give me any advice on what to do? Thanks


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Old 08-03-14, 09:09 PM
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The timer you linked to is for lights not motors.
 
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Old 08-03-14, 09:25 PM
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Depot has several different timers that will fit and work for you.

For my attic fan I'm using a 1,2,4,8 hour pushbutton timer from them.
 
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Old 08-04-14, 08:40 AM
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The packaging says it's also for exhaust fans. Are those not considered the same as attic fans?
 
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Old 08-04-14, 10:00 AM
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Exhaust fans usually draw for fewer amps when running then a whole house fan and have far smaller staring amps. The "switch" in the linked timer is electronic and may not be able to handle heavy starting currents. If it could there would probably be a maximum horsepower rating listed.

resistive loads only resist the current and are the simplest type of load. In inductive loads, such as an electric motor, the voltage wave is ahead of the current wave. The difference between the two waves creates a secondary voltage that moves in opposition to the voltage from your energy source, known as inductance. Because of this property, inductive loads tend to experience power surges when they are turned on and off, a phenomenon not seen with resistive loads.

Read more : http://www.ehow.com/info_12181159_di...ive-loads.html
 
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Old 08-04-14, 10:47 AM
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Yes, the switch lists 1/2 HP on the package. The documentation I have doesn't list anything about HP for the fan or amperage, but when I google around I found a reseller site lists the below details for the 4500. I have no speed controls on my panel so I'm guessing they're just running at high speed all the time. The 1500 appears to be rated at 1.3 amps. I guess the amp ratings are once the fan has started up so maybe it's more initially. Is there any way for me to confirm?

Motor Voltage 120 V. AC 60 Hz.
Motor Amperage 2.5 Amps Low Speed
5.0 Amps High Speed
Power
Consumption 300 Watts Low Speed
600 Watts High Speed
 
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Old 08-04-14, 11:12 AM
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Just contacted the fan manufacturer and they confirmed each fan motor is .25HP. The larger QC-4500 is a dual motor fan while the 1500 is a single fan. From what they told me you only count the highest rated HP on the circuit when choosing a timer, not add them all up. Can anyone confirm if this is the case? If so, I believe the Defiant switch I bought will work and just need to wire it up to where red is going to the load connection and black is going to the line connection from talking to product support earlier.
 
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Old 08-04-14, 09:59 PM
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It looks like the Defiant timer you chose should work ok for your application.
 
 

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