I have 1 exhaust fan exhausting 3 rooms that need to be controlled separately . I know how to do this with motion sensors but is it against code to install with 1 pole toggle switches on a 120 volt system with out any relays? This would cause a backfeed on the switchlegs of 2 of the switches after 1 switch was turned on.
Exhaust fan switching
- Thread starter bbuckway
- Start date
- Status
roger3829
Senior Member
- Location
- Torrington, CT
Why not a set of 3-ways with a 4-way?
Because someone in room 1 can turn the fan on, someone else will enter room 2 and try to turn the fan 'on' and end up turning it off instead.
Or, the fan will be turned on in room 1, a person will enter room 2 and do nothing, then the person in room 1 will leave and turn the fan off.
If these are bathrooms, it could be a problem. But I'd like to know what these 3 rooms are before responding.
- Location
- Massachusetts
DARUSA
Senior Member
- Location
- New York City
Why back feed?
What is the idea?
Use a occupancy sensor for turn on the fan and istall one single pole switch with a means to lock in the fan for service!!!!!
What is the idea?
Use a occupancy sensor for turn on the fan and istall one single pole switch with a means to lock in the fan for service!!!!!
A possible design vs. what the code allows.
I'd have each room with a momentary contact switch. Any switch pushed starts a retriggerable fan timer and runs the fan for a default period, let's say 20 minutes.
In the unlikely event that all three switches are pushed in sequence each 19 minutes, you could have up to 57 minutes of the fan running.
If the fan noise is not audible you could have a "fan on" indicating light on each switch.
Use the motion detectors so either one turns it on and put an override switch where it would not be readily accessible so anyone can turn it off, to take care of the means of disconnect
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I see a problem with sp switches without a relay as the circuit will have parallel runs on the return legs at times. I see it all the time but it is not legal. The problem is when 2 switches are on.
fishin' electrician
Senior Member
- Location
- Connecticut
They may be paralleled runs but I don't think they are paralleled conductors (electrically joined at both ends to form a single conductor). What code article is it in violation of?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
They are joined back at the panel and at the fan- that is a parallel conductor.
Those, not that.
310.4 Conductors in Parallel.
310.4(A) General. Aluminum, copper-clad aluminum, or copper
conductors of size 1/0 AWG and larger, comprising each
phase, polarity, neutral, or grounded circuit conductor shall
be permitted to be connected in parallel (electrically joined
at both ends).
Exception No. 1: Conductors in sizes smaller than 1/0
AWG shall be permitted to be run in parallel to supply
control power to indicating instruments, contactors, relays,
solenoids, and similar control devices, or for frequencies of
360 Hz and higher, provided all of the following apply:
(a) They are contained within the same raceway or
cable.
(b) The ampacity of each individual conductor is sufficient
to carry the entire load current shared by the parallel
conductors.
(c) The overcurrent protection is such that the ampacity
of each individual conductor will not be exceeded if one
or more of the parallel conductors become inadvertently
disconnected.
Pipe from the panel, to switch box 1, to switch box 2, to switch box 3, then to a relay. Use #12 on a 20a breaker.... done deal.
Last edited:
fishin' electrician
Senior Member
- Location
- Connecticut
I don't see where any of the conductors are electrically joined at both ends.
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
Fantech makes a master/slave timer switch for multiple room controls of a single fan. I have installed them for residential applications.
The Master is a VT20M and the Slaves are VT20A.
www.residential.fantech.net/residential-products/bath/controls-accessories/
The Master is a VT20M and the Slaves are VT20A.
www.residential.fantech.net/residential-products/bath/controls-accessories/
- Location
- Massachusetts
Code wise for the installation you describe I believe it will be a violation of 310.4 any time more than one switch is closed.
However if you where to have your three switches control a relay or contactor you could apply exception 1
- Status