Multiple Switches to Energize a Fan Motor

draw a picture with each component and I'll draw a diagram for you...explain what you want the switches to do and their location you might not need a relay, just switches, I assume you mean wall switches

The 4 way switching option won't work, there are 3 bathrooms, each with a separate circuit, I believe the only way is by utilizing relays.

Actually he is putting a wrong question due to either he knows nothing about electrical wiring or making fun of CR4.

Have anybody listened about even 2 SPST switches controlling a device unless from each position switch-on and switch-off from the same position.

Though the answer of #2 is the best for CONTRILLING FROM MULTIPLE POSITIONS WITH 2P2T SWITCHES; which is the correct way but not with SPST

unless using relays to get the function

A 4 way switch was my first thought too as that is the standard solution for a residential installation. Relays are never a good idea in residential applications, the average homeowner could get electrocuted trying to troubleshoot even a simple relay panel because no DIY guides will know what to instruct them in. Now you are adding conditional issues to your problem by insisting on this. This is sounding more like a homework problem that is REQUIRING you to solve it with relays, so you will only accept that solution. But you know that if you posed it as a homework solution, we would deride you for being lazy and not willing to think to learn, just willing to find someone else to solve your problems for you. That makes you a management student, not an electrical engineering student. We as a group tend to despise management types.

On the offhand chance I am completely wrong and owe you an apology, prove to us that this is not a homework assignment and describe EXACTLY how your 3 separate circuits for 3 separate bathrooms are wired, where the power comes from and where you would plan to locate a relay solution. There is a simple solution, but a lot will depend on the way you describe your existing inflexible conditions. Without that, we could assist you in causing a fire, and none of us will want that..

I'm leaning that way, too.

OP, three different switches? Does that mean three seperate bathrooms??? You don't say.

Existing construction or new?

<unsubscribe>

So a heat exchanger...

A person uses a toilet room, then leaves and turns off the unit. The unit is, by a person in another toilet room, still desired to be running. How is this addressed?

Or, are these switches actually thermostats (your comment about SPST makes me think mercury switches)? How is that going to work out?

Never mind, you said switched with the lights. I have no idea what you are up to. I have added a few questions to the game, I believe we are now at twenty questions.

[edit] Do you want the heat exchanger to run when ANY of the three lights are switched on, and not run if NO lights are switched on?

GA Lyn, actually, good solution recommendation.

Ace

You can run a separate line through all three bathrooms and then to the fan, then use the circuit Lyn suggested.

If you don't want to do that, then maybe you would save yourself any bother at all by putting the fan on a remote-controlled outlet, and control it with remotes. Buy some extra remotes and hang one in each bathroom. This one is good for a range of 100 feet.

http://www.amazon.com/SVAT-WRC101-Wireless-Control-Outdoor/dp/B000HAVVKG/ref=sr_1_6?ie=UTF8&qid=1356958709&sr=8-6&keywords=remote+control+outlet+with+wireless+remote

If this is new construction, then it's easy.

If it's existing, pulling extra wire may be a big deal.

Op did say.

Probably best/cheapest is three SPNO relays, each coil wired in parallel with an existing light, and all contacts wired in parallel to feed the exchanger.

Multi-input programmable relays are available, but I'm not sure if they take 120 vac inputs. One of them is probably more expensive than the three others, anyway.

Use three of these http://www.futurlec.com/Relays/GR110V10ABL.shtml wired as Tornado has suggested. $15 solution to your problem, but you have to remember that if you don't do this to the NEC regarding Wiring and Control Enclosures, your homeowners insurance won't pay off if something goes wrong. Good luck.

<resubscribe>

So,

If all three bathroom lights are on, we've got three separate 120v circuits all feeding power into relays, and we have three seperate relays, all feeding power into the same motor?

How does that work?

The relay coils are all isolated from each other so there is no danger of backfeed from the individual lighting circuits. All three NO contacts are wired in parallel and fed from a source separate from or ahead of the lighting circuits.

The parallel contacts form an OR circuit, the closure of any contact or combination thereof connects the source to the fan motor, as long as any one light is on the fan turns. Properly done it mimics the logic found in industrial automation control systems.

Let's hope so.

Although technically doable, the problem with the DPDT switch is that it is absolutely essential that all three bathrooms be fed from the same circuit breaker. If not then there is the chance that two opposite polarity hot-leads will appear across one of the switches due to the three hot wires at the fan.

If there are two or more breakers involved and they are both on the same hot-side then it will be necessary to open all of the breakers to kill the crcuits since there will be a potential backfeed, again through the three hot legs tied together at the fan, this is dangerous and a clear violation of the NEC.

If there are GFIs involved there could be other issues that may result in nuisance tripping.

Oops, I meant DPST, not DPDT.

On second thought, while my suggestion may work in theory, I don't know how the NEC would look at it. This is something that you need a licenced electrician to figure out.

This is my own home. The three bathrooms are fed by one GFI, and to further complicate the issue, I have to run the air-to-air heat exchanger for at least 8 hours a day. Presently the heat exchanger is controlled by a heavy-duty timer, which I will still require, sorry I didn't think to mention that earlier.

So what is the whole story here? What data are there for the fan? (Which probably needs a dedicated circuit anyway.)

The heat exchanger is on a separate 15 amp circuit

You say you have to run this for eight hours. You still haven't clarified what the eight states of the light switches should do to the blower or now this eight hour timer. Technically the timer doubles the number of states to consider what happens with this heat exchanger fan.

I don't care if this is your house, hire an electrician. The life you save may not be your own.

Who spends 8 hours in the bathroom?

Why not forget about turning on the lights to turn on the A to A heat X, and keep the timer in play only? You never really explained the driving reason behind any of this.

(Light source - > electric eye relay - > definite purpose contactor - >)x3 parallel to fan motor + timer parallel to fan motor...??? NEC compliant? I have my doubts.

If this heat exchanger needs to run 8 hours a day why pray tell do you need to be able to switch it off in every one of your bathrooms? I can't think of anything that takes 8 hours in a bathroom. Library?

The OP hasn't said if it needs to be switched OFF in each bathroom, or just ON. We are all wasting our time here.

This idea is good, but off hand I don't recall any DPST switches in typical residential format. Quite possible, though.

Wiring this may present some challenges. Romex is a real bitch compared to conduit-enclosed industrial wiring.

I forgot about that; I even have some in plant inventory, complete w/ OL heaters.

I think Keith has gone in search of better answers.

Or he blew the deadline on the homework?

Wait a minute here! You said, "there are 3 bathrooms, each with a separate circuit" in post ##3.

# Now, it's "The three bathrooms are fed by one GFI" in post #24.

Yah, OP information on this one is sort of fuzzy.

I'll leave it to you guys to get this working. I'm going home.

To all of CR4, from Doorman and Doorman's Chick, may you and yours all be blessed with good fortune and good health in the coming year.

Kieth,

Why don't you just leave well enough alone.

You've get a dedicated circuit and a timer already.

If you need to do something, buy a programmable timer and replace the original.

Program the timer to run during the busy times of the day, for the bathrooms, that is.

Then run it during low electrical demand times to get the 8 hours.

air-to-air heat exchanger or Ventilator?

Possibilities: Motion sensing (wireless even)? Current sensing (good idea)? Humidity removal (Humidistat?)?

Why 8 hours?

Ventilators might already have a 24 VAC circuit.

I'm just totally confused. Or is this just to make some noise to tell if someone left the light on in one of the bathrooms?

Are the switches or ceiling fixtures fed with power? You can do the wiring either way.

Would it be OK, to run them if say some current is exceeded in any one of the bathroom circuits? e.g. running a hair dryer with the light off because it's daytime and the window is open

KeepItComplicatedGenius

I favor USB's and Raef#31 solutions for a fundamental reason. The input signals causing the desired action are obviously and graphically isolated from the circuit where action is to be taken. In these setups it is obvious, that more than one circuit breaker might be considered.The timing requirement on the top of it is OP's problem.

You will need a 120v coil relay and 3 x 400v 1 amp diodes and the circuit below.

The diodes will prevent feed back to the other switches and will provide half wave rectified current to the relay which will work fine.

The series diodes will halve the 120 V AC to around 60 V DC.

No it won't, the 120v is the RMS value of one half of the sine wave.

That value won't alter with rectification other than for the normal 0.6 volts drop across the diode.

The output will be half wave DC at 60 pulses per second, but due to residual core magnetism, the relay won't chatter.

Try it if you don't believe.

Well.. Happy New Year one and all.... and just to start the NY off with a bit of nonsense, we have this post.

I have read the answers..many of which I would have given.. however as it has already been stated.. the OP has not disclosed every bit of info. Now that tells me several things.. first, he's not an engineer, second, he doesn't understand the info required to make an educated answer as we try to do here.. cos we like problems!!

So I think the only answer one can now give, as there is so much info required, and so much not given for whatever reason.. is no answer at all.

Keith.. do yourself a favour and call in either a heating engineer or an electrician.

Miracles we can do... the impossible we're getting round to it!!

Needs full details or a drawing as #1 asked for

I hope I understood the problem correctly, you want to turn on heat to any one of 3 bathrooms when one of three lights is switched on.

You did not mention it but I assume that it should run the heat if either one, two or even three bathrooms are occupied.

The following circuit I think will do just that for you, though its a bit primitive due to using MS Paint.

Changing the normal light switches out for one with an extra signal contact would make things simpler, but normal single pole light switches are far, far cheaper and probably already installed!!!

:-

I can send a better copy if you need one, just send me a private email address via the CR4 email system. If anything is not easy to read or understand, just ask....I don't believe that anyone has done it in exactly the same manner as I have done.

The difficult to read text is as follows:-

"I have left out the ground to simplify the drawing. Ground should be used where local code dictates.

L = Light Bulb."

exactly

I don't believe you people.

Here we have a guy who obviously can't tell the difference between a relay and a power supply and you simpletons are recommending things that he can't possibly even understand, and certainly never make work.

I expected much more from some of you. We all know how brilliant you are!!!! Proving this brilliance to someone who doesn't have a clue what you are even talking about is the height of arrogance!

Get over yourselves and tell the guy to hire an electrician!!!

OH, and did I mention? Hire a licensed electrician.

Finally the voice of reason.

I'm with you on this one, lyn. At #29 I told him to hire an electrician. We still have far too many unknowns to give good advice here. The timer function has never been explained to my satisfaction but as I predicted this new piece of information was added later to guarantee superiority. We also have no data on the motor for this blower to select a relay or contactor other than it being powered by a separate (dedicated?) 15A line.

This is an electricity fool willing to risk his family's life and anyone else to modify a working system to an unclear whim.

No offense to the OP, but sending schematics to someone who admits he knows nothing about electronics is just plain stupid.

As usual, I've PO'd a lot of people here, but I don't care.

What we have here, again is failure to communicate. Every post by OP yields another tidbit of information.

I give up.

Although I agree with you about the safety aspect completely and I admit I completely forgot to mention it, there is little here that needs electronics knowledge....I would go as far as saying none.....

A little electrical knowledge IS needed and I would hope that anyone doing this would have or hire the knowledge......common sense would dictate that, if the OP has some!!!

Get over yourselves and tell the guy to hire an electrician!!!

I did say that.. but someone did like me stating the obvious!! :(

Might try the old X-10 control system, parts are available from multiple sources and works well unless your neighbor uses the same unit codes or power is down. At my shack it controls heat, video, lights, reads tripped security sensors, wets down intruders and turns on high voltage at low current that is extremely uncomfortable at window frames and doors.

Replace each bathroom switch with a DPST (double pole-single throw) switch; will need another conductor from the switch to the heat exchanger. Wire one pole to the respective bathroom light and the other pole the the heat exchanger.

The two poles isolate the heat exchanger from the light when in the off position (lights do not come on in all three bathrooms).

No relay required

You left off the timer for the part where OP states, "the fan must run for eight hours a day."

Hire a bonded, licensed electrician, but please explain all the rules to the game to him/her before the job begins.

Here's a re-hash of my earlier circuit to include the timer if that is still needed.

No changes required to switches, no extra wiring from switches, all additions can be done in roof space.

Extra items required are 4 x 400v diodes and a 120v AC relay.

Make sure the relay is rated for AC.

With AC, how are the diodes going to prevent partial-voltage feedback between the lights?

I'm assuming here that you really want me to explain this.

Assume the first switch only is closed and the +ve half cycle:-

The first diode will conduct, the relay coil will be energised with half wave DC, and the first lamp will light with the first half of the AC cycle.

The other diodes will be reverse biased and will prevent the other lamps from being lit provided their associated switches are open.

Now the -ve half cycle:-

The first diode will be reverse biased which will prevent any current flow via the other lamps and diodes, the relay coil will be de-energised but will hold in during the brief (around 10 milli seconds for a 60Hz supply) loss of power until the next +ve half cycle provided you use an AC rated relay. The induced voltage of the collapsing field of the relay will further reverse bias all diodes (which is why they need to be rated at 400v). The lamp will remain lit on the second half of the AC cycle.

The above holds true for any combination of switches.

If you use a DC rated relay (one without pole shading), then the addition of a suitably sized parallel electrolytic capacitor would provide the hold in capability to prevent chatter. This capacitor may also be required if a heavy duty AC relay were to be employed (ie with multiple contacts, large air gap, or heavy return spring, all of which may reduce the release time of the armature).

Thanks. I've never seen it done that way, but I don't know if any NEC provisions would prohibit it. I believe the OP said these lights were all on the same GFCI.

Bear in mind that I am situated in Australia where we use 240v 50Hz, and our wiring rules are necessarily much stricter than yours, so I would expect that if it meets our requirements, it will likely meet yours.

The circuit requires that all lights are on the same final sub circuit to conform with the wiring rules and to prevent loop feeds and possible shorts if different phases were in play, however the relay contacts may be on a separate circuit.

I originally used a variation of this circuit (no relay required) for multiple lamp test facilities on mechanical services switchboards, but numerous variations are possible with one being to enable two lights or appliances to be controlled separately via two switches using only one switchwire where it is not possible to easily install the extra wire.

That's the basis of a cute electrical puzzle from Martin Gardner many years ago.

And the OP said he doesn't know a relay from a power supply.

Build it and demonstrate its working on YouTube......

Diodes only block or allow DC or half the AC.

Your circuit will not work as planned on AC due to the half cycle left unblocked.......

You are thinking DC not AC.

You're kidding me - right?

This is really, reeeeally basic electronics.

The circuit will work equally well on both AC and DC inputs except for the anti chatter requirements mentioned for AC which would not be used for DC, and the obvious need to get the correct polarization for a DC input (+ve to the switches) which would not be needed for AC.

Very easy to set it up on a test bench and try it for yourself, but please do it with an ELV source as I only have an inkling of your abilities.

If you use a DC relay, hang a 470µf cap across the relay to stop chatter.

I still do not believe it, sorry.

I am also not alone here with my thinking......

What's with all the off topic votes? They were all good answers, but you won't tell what is necessary to answer fully. Get over yourself or get lost.

I stiill maintain, as a simple matter of separating of input from effect, that a magnetic transformer separates the input breaker from the output effects breaker, effectively.

Call me purist, I do not care. But mixing different breakers in the same circuit is a bad idea. Never mind code.

did some one say, hire an electrician, keith are you and yours going to be around next year?

just use the timmer on the unit and of course use it when the shower is being used the most. simple

oh and didnt i hear an echo......electrician hire one....one one one.....

After 60-odd postings in response, that the original poster hasn't seen it fit to post the logic table that describes the relationship between all these switches, the lights and the timer is quite abstruse, and leaves respondents guessing. Had the original poster done so at the beginning, then 50-odd posts would be superfluous, as the wiring design would have dropped out within the first ten postings, saving an inordinate amount of time. Perhaps the original poster doesn't have to worry about such things......

Careful. You just might be punished with an OT for making such a negative comment. Do not question the troll under the bridge.

I'm gone, too many amateurs here, have a happy new year Guys....

Sounds to me like this is for a grow-op.