# Calculating the current of a household appliance

#### electrophile

Joined Aug 30, 2013
126
I'm trying to build a ceiling fan regulator which incorporates a triac. I was trying to figure out the current rating for this and I was hoping someone would let me know if this is the right way to do it. Here goes:

The ceiling fan is rated for 75W. For 220VAC and a power factor of about 0.85 (from my research on the web but feel free to correct me) would the current be:

75/(220 x 0.85) = 0.4 A?

If this is correct, can I use a 1A (constant on-state) rated triac?

#### Alec_t

Joined Sep 17, 2013
11,520
I'd use a higher current version. Not much difference in price, greater safety margin.

Joined Jul 18, 2013
21,222
I agree, with triac's there is not a lot of point sizing them tight.
Max.

#### be80be

Joined Jul 5, 2008
2,049
Ceiling fans dont last long if you wanting to use this for speed control too.
Plus it will start humming loud

#### be80be

Joined Jul 5, 2008
2,049
I replace about 50 to 75 fans a year that people put on a dimmer they use capacitors to change speed and don't like dimmers at all

Joined Jul 18, 2013
21,222
I have had mine for 25 yrs, buzzes a little at low rpm but not a problem.
Max.

#### be80be

Joined Jul 5, 2008
2,049
That's cool but most new ones are lucky to make it a year before you can't stand to be in the room with them and forget to turn it up to full speed to start the fan and your just cooking the wires in it. I'm a electrician 35 years I've seen most anything that can go bad happen there are dimmable fans but most are not made to use dimmer

#### electrophile

Joined Aug 30, 2013
126
@Alec_t and @MaxHeadRoom Thanks. I however, have a space constraint and the 1A ones fit in quite nicely. I saw a few 4A in DPAK cases which could also work.

Ceiling fans dont last long if you wanting to use this for speed control too.
Plus it will start humming loud
Thanks. What would you recommend for fan speed control?

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,155