Fluorescent Relay Switches/ Which one?


Do I need a 5 amp or 15 amp switch? Now I know this is decieded by my devices and their loads but I am curious as to how the ratings work. Do so many watts = one amp? If this is the case, how do you rate fluoecent bulbs? Would you take their wattage equilent and add that up?

What about small bathroom exhust fans?

I would like to use all 5 amps switch just for the cost savings, but do not want to under power the circuit or create a hazard.

Power (in Watts) equalls Voltage (in Volts) Times Current (in Amps).

So Curent = Watts/Volts.

Your voltage should be around 120 (in the states).

So, lets say you have a total of 10 watts of fluorescent lighting.

That would draw 10/120 or 0.8 amps.

Note this is for a typical resistance load so to be totally safe I would give myself a 20 percent cushion factor and get a switch rated for:

20% of 0.8 amps = .16 add this to 0.8 for a total switch rating needed = 0.96.

Hope this helps. If you would like, post your wattage ratings.
BraveSirRobbin said:
So, lets say you have a total of 10 watts of fluorescent lighting.

That would draw 10/120 or 0.8 amps.
add a 20% safety factor and you have 0.096 amps.
BraveSirRobin has the theory right, but the math slipped a digit. Probably a typo.

10/120 = 0.08 (not 0.8)

10 Watts of flourescent lighting is pretty small though.

A 5 amp switch, minus 20% safety rating, would still give you 4 amps capacity. 4 amps X (times) 120 volts = 480 Watts maximum. If you trust the manufacturer and don't need a safety factor, then 5 amps X 120 volts = 600 watts.

A 15 amp switch X 120 volts would control 1800 watts with no extra safety margin, 1440 watts with a 20% margin.

For flourescent lighting you use the REAL wattage of the lamp, not the "equivalent" wattage. The equivalent wattage is really just a fudge factor so people have some idea how bright a bulb they are buying. Most 100 Watt incadencent (old fashioned regular) bulbs burn with "about" the same brightness, regardless of brand, so they use that reather than trying to confuse you with the real output (expressed in lumens).

Now some of the compact flourescent are known to actually use about twice what the bulb is rated for. For example, a 14 watt fl bulb (with an 80 watt equivalent rating) may actually draw 28 watts or so, including the ballast (transformer). So you would use that 28 watt number, if you knew that you had one of those. Check your packaging carefully for more details.
Thanks you two for the quick replies. I knew math would be involed, I just wasn't sure what formula was used.

On one switch I have [5] 18w compact flourescent and a small string of low-voltare lights, so I should be ok with the smaller cheaper switch. switch.

The other circuit has an small exhaust fan and a 100 watt. Can't find a rating on the fan, I guess I will go to Home Depot and get a rating off of a similar fan.

Thanks again
You might be able to find usefull data at homedepot.com or someplace like broan.com or whatever brand you have. A typical bath fan is under 1 amp, 120 watts. So, the fan plus a 100 watt lamp would be about 220 watts, under 2 amps.

Yes, 5 x 18 watts = 90 watts. A typcal low voltage (Christmas?) string would another 20-30 watts or so. So well under 5 amps.
Ahhhh, sorry about that error. I was in a big hurry when I typed that reply.

Seems like I'm just good for the theory! :eek:

Anyway, thanks Wayne.
Anyone wanna throw me a gimme?

Model #, Part #, etc....

I'm in the market for something similiar.... (Must.... Cut... Up... Credit.... card).

...so, in the interest of becoming future proof.....?
Martin is correct in that I am talking about the Switchlinc's.

...so, in the interest of becoming future proof.....?

Personaly [but remember I am a newbie] I would consider nothing but 2-way switches. Two-way switches may come at an additional expense of adding equipment to deal with the higher signal absorbation rate, but for a reialable system it is worth the extra expensive to me anyway. I think 2-way switches are espically important if you are considering using a smart keypad controler like the Keypadlinc.

(Must.... Cut... Up... Credit.... card).

I hear you there. This HA stuff is just plain additive. My credit card co. will probrable cut me off or my wife will kill me before I get a chance to cut up my card. :D