Using furnace fan on/off input as electronic timer


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Old 09-13-09, 09:47 AM
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Question Using furnace fan on/off input as electronic timer

I have installed one 120vac 18 watt UV-C anti-germicidal light in the return duct and one after the A-coil of my natural gas furnace. (These lights supoosedly kill viruses, germs, mold, etc.)

I would like to connect the lights to the furnace fan on/off switch so that they would be on only when the fan is on. I would like to tap onto the 120vac electricity going to fan to power a separate residential socket receptacle into which the lights would be plugged.

Is this possible and safe? Is there a better way of doing this?

Thanks.
 
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Old 09-13-09, 02:58 PM
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You need to get a flow switch... and a auxiliary low voltage relay with 120 volt contacts that is connected to the 'R'(hot)of your furnace.
 
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Old 09-13-09, 03:14 PM
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Wink

Thanks for the info! I'm a novice at this. Any more details you could provide would be very helpful. Thanks again.
 
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Old 09-13-09, 09:38 PM
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I have mine plugged right into the outlet, and never shuts off, unless I don't have my fan on for a long time.

My fan is on most of the time, and the UV light keeps the A-Coil "clean" all times.

And I don't think I've ever seen UV light cycle on and off with the equpment.
 
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Old 09-14-09, 12:25 AM
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If your furnace control board has terminals on it for an electronic air filter you could probably connect the lamps to those terminals. You need to be mindful of how much power the lamps draw and the rating of the electronic air cleaner terminals.
 
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Old 09-14-09, 05:53 AM
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The UV will not be affective on mold or viruses in the air stream. You have to much CFM of air. You would need closer to 6 to 8 feet in an average residential HVAC system to give the UV enough contact time to kill. Average light only has enough intensity about 14 inches from light source. Better install choice would be under and above the coil to keep mold from growing on the coil.
 
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Old 09-14-09, 07:01 AM
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Wink The UV will not be affective on mold or viruses in the air stream.

What you say makes sense. I was also wondering about the effectiveness of the UV-C lights considering the massive amount of air flowing by. But Honeywell and other manufacturers make UV-C light units they claim kill bacteria, viruses, etc., when the lights are placed in the return duct. They also claim to keep the coil clean when placed near it.

You have to believe Honeywell don't you?

Honeywell has basically 3 types of modules:
1. Just a light that stays on constantly.
2. A "Smartbulb" that cycles 3 hours ON & 3 hours OFF, 24 hours/day. Extends bulb life & saves on electricity.
3. A light that has a flow sensor that turns the light on/off when the fan is on.

Obviously, Type #3 is the way to go if possible, but they are way too expensive for me. I am hoping to be able to somehow rig up my lights (type #1s) to get the same #3 effect for a lot less money.

See my problem?

Any help or advice is greatly appreciated.
 
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Old 09-14-09, 07:04 AM
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Wink If your furnace control board has terminals on it for an electronic air filter.

I don't think mine has that, but I'll double check. Thanks for the idea.
 
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Old 09-15-09, 02:35 PM
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Help!

Originally Posted by Gabby1234 View Post
There are basically 3 types of modules on the market:
1. Just a light that stays on constantly.
2. A "Smartbulb" that cycles 3 hours ON & 3 hours OFF, 24 hours/day. Extends bulb life & saves on electricity.
3. A light that has a flow sensor that turns the light on/off when the fan is on/off.

Obviously, Type #3 is the way to go if possible, but they are way too expensive for me.

I am hoping to be able to somehow rig up my lights (type #1s) to get the same #3 effect for a lot less money..
Can anyone help me figure out how to do this? It doesn't seem that hard, but I'm no technician.

Thanks for any help.
 
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Old 09-15-09, 07:53 PM
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If you are going to go with #3, then you are going to need a switch that is line voltage to kill the power.

I would wire it up on the board that has the EAC (Electronic Air Cleaner) hook up.
 
 

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