ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Do bathroom exhaust fans have to be switched with the lighting or can they be individually switched?

Unless some local ordinance requires it, I can't think of any requirement to have them come on at the same time.

As a HO as well, I'd say it's preferable to have the fan on a separate switch. Switch with a timer is best.

HCE:
Design issue. Most commercial have fan on with lighting, and some local Health Depts require it, but I have no substantiation for that.

Hotline,

Out here in CA all commercial and industrial occupancies require the fan to be switched with the lights.

Either that or the fan must run continuously, or be on a timer so that the fan is on during business hours.

Of course, I don't have a substantiation for it either

I was wondering if anyone has ever considered using a humidistat for the fan in place of switches or timers .

it makes it hands-free and 120v units are available, could even remote a sensor and drive the fan with a relay and xfmr

For residences, IRC 2006, M1507.3 requires a bathroom or toilet room to have "Mechanical exhaust capacity of 50cfm intermittent or 20cfm continuous." IRC sets no requirement for how this is implemented, only that the capacity must be there. Same switch, separate switch, humidistat, timer, etc- all OK by IRC.

Commercial is different. IMC 2006 400.3 requires commercial bathrooms in dorms, hotels, etc, to have 35cfm ventilation/person. (Continuous is implied.) As 0 people are in the bathroom when the lights are off and 0cfm required, the fan can be tied into the light switch. I'm not familiar enough with IMC to know any other subtleties of the code, or what specifically applies to restrooms in stores or offices.

I always seperate fan and light, unless HO wants both together. No violation of NEC in residential.
I used spring timers when my daughters (4) were still at home. Now, we just use regular swiches so we do not have to listen to the fan until it times out.

I was told in MA the building code states the fan has to come on with the light if there is no windows in the bathroom.
I seperate then unless the owner wants them on at the same time. In a half bath I like the fan on with the lights and using panasonic you can't hear them anyways

Electure:
Yes, I agree. Comm is on w/lights, or TC control for occupied hrs. I can't place a Article thou, and say it's a design thing.