Multiple switches on a single fan

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steve holt

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Are there any code guidelines regarding having multiple switches on a single load? I have a single exhaust fan controlled by more than one single pole switch. The owner does not want to use 3-way switches because they will end up being in the up/on position even when they are off, and you may not be able to tell if the fan is running. If we go with single pole switches, then the return on both switches will be live when either of them are on.
 
Nothing that forbids this, we use this setup when we install Fantech systems for multiple bathrooms. Obviously all the switching needs to be done in the same circuit.
 
May I suggest using an indicating switch. An inexpensive possibility is the combination threeway switch / pilot light, where the pilot light requires a neutral and can be separated electrically from the switch. Consider:
b65d40e9-1eb3-482b-9124-4ae776caea1c_1000.jpg


Which can be seen by clicking here. With the switched leg to the fan run to each pilot, they will indicate that the fan is energized.
 
480sparky said:
What Code prohibits that?
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Some argue that such a setup constitutes parallel wiring. For the specific use of that term in the Code, I disagree and see no prohibition.
Only a design issue.
Unlike DC where steering diodes can be used, for AC it is hard to have two switches control overlapping groups of loads. That would require multipole contactors or relays.
 
GoldDigger said:
Some argue that such a setup constitutes parallel wiring. For the specific use of that term in the Code, I disagree and see no prohibition.
Only a design issue.
Unlike DC where steering diodes can be used, for AC it is hard to have two switches control overlapping groups of loads. That would require multipole contactors or relays.
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Considering the exceptions in the NEC for parallel wiring in sizes smaller than 1/0 there is no doubt in my mind the CMP views the OPs wiring as parallel.
 
Problem with using single pole switches (other then the possible paralleling of conductors debate - already fought that battle with no success) is unlike three ways, you can turn the fan on from either switch location, but must turn both switches off. In fact you can use an unlimited number of switches - only one needs to be on to turn the load on, but all must be off to turn the load off.

If you want similar function to three ways, as in going to any switch location and turn it on or off regardless of the conditions at other switch locations, but don't want actual three way switches (maybe this is one of those ultra quiet or remotely located exhaust fans that you can barely hear so you can't tell if it is on or off very easily) another option is the typical control scheme that utilizes a contactor/relay with a holding circuit and start stop buttons at every control location.

My preference if it is ultra quiet exhaust fan is to tie it to a particular light in the room, whenever the light is on the fan is on. Nobody forgets to turn it on unless they don't want a light. Nobody forgets to turn it off either unless they forget to turn the light off.
 
kwired said:
Problem with using single pole switches (other then the possible paralleling of conductors debate - already fought that battle with no success) is unlike three ways, you can turn the fan on from either switch location, but must turn both switches off. In fact you can use an unlimited number of switches - only one needs to be on to turn the load on, but all must be off to turn the load off.

If you want similar function to three ways, as in going to any switch location and turn it on or off regardless of the conditions at other switch locations, but don't want actual three way switches (maybe this is one of those ultra quiet or remotely located exhaust fans that you can barely hear so you can't tell if it is on or off very easily) another option is the typical control scheme that utilizes a contactor/relay with a holding circuit and start stop buttons at every control location.

My preference if it is ultra quiet exhaust fan is to tie it to a particular light in the room, whenever the light is on the fan is on. Nobody forgets to turn it on unless they don't want a light. Nobody forgets to turn it off either unless they forget to turn the light off.
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The problem with using 3-ways arises when you have the switches in different rooms but they control the same lights. A common situation would be Mens' & Womens' restrooms in a commercial setting.

Let's say the lights are off in both, and a person enters one of the restrooms. A minute later, someone enters the other restroom and ignores the switch because the lights are already on. When the first person leaves, they turn off the lights, leaving the person in the other bathroom in the dark.
 
480sparky said:
The problem with using 3-ways arises when you have the switches in different rooms but they control the same lights. A common situation would be Mens' & Womens' restrooms in a commercial setting.

Let's say the lights are off in both, and a person enters one of the restrooms. A minute later, someone enters the other restroom and ignores the switch because the lights are already on. When the first person leaves, they turn off the lights, leaving the person in the other bathroom in the dark.
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Many ways to skin that one.

Last smaller church fellowship hall I did, we had a common exhaust fan ducted to both restrooms. From previous similar applications problems with people leaving restroom lights on - and in a small rural church where it may be left on for up to a week because nobody was there to notice it was on, we put both restroom lights and fan on one switch outside the restrooms, also had the hallway light outside the restrooms on it. This way nobody forgets to turn the fan on or off, as well as nobody leaves the lights on when leaving the building - unless they don't notice the hallway light is on. Board members liked the idea and AFAIK is working out for them.

Cost is a lot less then occupancy sensor, and nearly eliminates service calls altogether, compared to service calls when the occupancy sensor is not working right, those eat up more then what the occupancy sensor saves really fast.
 
kwired said:
Many ways to skin that one.

Last smaller church fellowship hall I did, we had a common exhaust fan ducted to both restrooms. From previous similar applications problems with people leaving restroom lights on - and in a small rural church where it may be left on for up to a week because nobody was there to notice it was on, we put both restroom lights and fan on one switch outside the restrooms, also had the hallway light outside the restrooms on it. This way nobody forgets to turn the fan on or off, as well as nobody leaves the lights on when leaving the building - unless they don't notice the hallway light is on. Board members liked the idea and AFAIK is working out for them.

Cost is a lot less then occupancy sensor, and nearly eliminates service calls altogether, compared to service calls when the occupancy sensor is not working right, those eat up more then what the occupancy sensor saves really fast.
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Until some smart-alek kid turns the switch off to annoy anyone using the facilities. :p

My usual solution:

bathfans.jpg
 
I would only consider multiple switches in parallel if all of them were either timers or occupancy sensors (unless they were all visible from one point in the room.)
 
iwire said:
I don't have a clue how you drew that line but I don't see it in the NEC.
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You won't find it in the NEC because it is a design decision. :)
The idea is that you do not have to go on an extended search to find out how to turn off the (whatever) if the switch you change does not do the job.

Of course it seems obvious that all of the switches should be mounted the same way in terms of which direction is on, since otherwise you have no clue as to whether you are turning a particular switch on and off.
If timers, for example, just turn off the one you are closest too and if lights do not go off you can just assume that they will turn off eventually.
 
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