# Wiring inline bath fan for multiple bathrooms



## AllanJ (Nov 24, 2007)

You can have separate ordinary countdown timers, one in each bathroom. You would need to run 3 wire cable for electronic timers requiring house current power; two wire cable will suffice for spring wound timers and battery operated timers.

At the fan connect the fan's (black; hot) power lead to both blacks going down to the timers. Connect the power feed up at the fan box to both reds (whites if two wire Romex) going down to the timers.

For the 3 wire cable connect neutral to both whites going to the respective timers.

This way, turning either timer will turn on the fan. The fan shuts off when both timers are off. This is not a 3-way and does not need to be.

One disadvantage of a shared fan is that inside heated air or air-conditioned air is being sucked from both bathrooms whenever either bathroom is in use.


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## secutanudu (Mar 15, 2009)

This will be an electronic timer (neutral required) so i'll need 3-wire cable.

So basically, I am running two switches in parallel? What happens when both switches are ON? It gets feeds from two "different" sources? (i know, essentially the same source). This doesn't cause a problem? I assume not or you wouldn't have suggested it.


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## nap (Dec 4, 2007)

and make sure the circuit used at each timer is the same circuit (as in fed from the exact same breaker in the panel)

I know, it seems like a no brainer but trust me, it needs to be said.


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## secutanudu (Mar 15, 2009)

nap said:


> and make sure the circuit used at each timer is the same circuit (as in fed from the exact same breaker in the panel)
> 
> I know, it seems like a no brainer but trust me, it needs to be said.


Of course...i guess then I'd be getting two sources and pushing 240v to the fan?

I never thought of running switch loops in parallel to the same load. That's what I'd be doing, right?


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## brric (Mar 5, 2010)

As long as the power is at the fan as Allan described there is no possibilty of having two sources. With both switches on there will still be only 120 volts.


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## nap (Dec 4, 2007)

secutanudu said:


> Of course...i guess then I'd be getting two sources and pushing 240v to the fan?
> 
> I never thought of running switch loops in parallel to the same load. That's what I'd be doing, right?


2 reasons you run the same circuit.

1. if you pulled circuits from opposing legs, you would trip breakers every time both timers were on

2. if the circuits were on the same leg of the service, you would not trip breakers but you would have to turn off 2 breakers to kill the power to the fan. You also would feed power back to the other timer if both breakers were not turned off. Either situation could cause an unsafe condition if you needed to work on anything involved in the circuitry.


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## nap (Dec 4, 2007)

brric said:


> As long as the power is at the fan as Allan described there is no possibilty of having two sources. With both switches on there will still be only 120 volts.


that's true but if there are already fans and switches installed, it would be a very easy mistake to make to simply continue the existing wiring to the fan.

we are dealing with DIY. I would much rather take the time to explain what and why than leave it unanswered. I have been around this stuff long enough to know what some folks will do if you do not explain to them what not to do as well as what to do.


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## secutanudu (Mar 15, 2009)

Thanks to everyone for the input.

Now that I think about it, the timer switches do not require a neutral. I may run a neutral to the switches anyway, in case a future timer does...but does this diagram look correct, aside from grounds?


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## joed (Mar 13, 2005)

Wire the switches in parallel. That way if either switch is on the fan will be on. Only if both swtiches are off will the fan go off. You don't want threeways. With threeways if someone goes into the room and the fan is on they could turn it off without knowing.

Diagram will work. However to meet code the power to the switch should be the white and the switched power to the fan should be the black. That way you don't have two whites connecting at the fan.


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## secutanudu (Mar 15, 2009)

I always get that backwards. Thanks Joed.


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## secutanudu (Mar 15, 2009)

AllanJ said:


> One disadvantage of a shared fan is that inside heated air or air-conditioned air is being sucked from both bathrooms whenever either bathroom is in use.


Do they make a fan grill that you can close? Only one bathroom gets a lot of use, the other one is rarely used, so it'd make sense to just close the unused one.

I can post this question in the HVAC forum, just figured it was worth a quick mention here.


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## nap (Dec 4, 2007)

Now you are getting complicated.


yes, there is such thing as a powered louver or more appropriately, a powered damper. The problem now comes where you can power that damper only when the timer in the involved bathroom is on and not open the damper for the other bathroom at the same time.


now you are going to have to incorporate a couple relays to isolate the two switching systems. I will have to draw something out. The old picture is worth a thousand words and all and hopefully somebody else comes back with a drawing before I do.


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## secutanudu (Mar 15, 2009)

It could also be a manually closed vent grille....but a powered one would be cool 

Probably too expensive though.

I'd be interested to see yours (or someone's) drawing.


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## AllanJ (Nov 24, 2007)

Yes, you would get a small louver commonly used for hot air heating registers. With the shared fan and ducts leading to each bathroom, you probably have a custom made box where the duct reaches the wall (or ceiling) and you would choose a shape and size of louver to go on the surface. For a manually operated louver you just have to remember to open and close it at the appropriate times.


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## nap (Dec 4, 2007)

AllanJ said:


> For a manually operated louver you just have to remember to open and close it at the appropriate times.


and that is why a manual one should not really be considered.


since you are using a timer, you would have to go back in after the timer shut off the fan and close the louver. Whomever uses the bathroom would have to remember to open the louver when turning on the fan.

trust me, that is asking too much of those that will be using the bathrooms.


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## secutanudu (Mar 15, 2009)

It wouldn't be that bad. Currently, my parents are the only ones living in the house. When I (or my brothers) go stay with them for a weekend here and there, we'd open the louvers on the second bathroom. It's not a routine thing anymore.

Even so, I'd like to make it automatic.


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## Thurman (Feb 9, 2009)

Personally, I prefer this timer for bath areas. Much like the normal "paddle" switch.
Just me, David


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## jdanw (May 10, 2011)

*Drawing!?*

:help:BUMP! NAP! Sorry for resurrecting an old thread (not that old, huh), But what happened to the drawing. I am reading this thread, thinking "Thank goodness. The exact thing I am trying to accomplish and a drawing to boot!" then I click to the next page and no drawing! How much would I have to pay to get that drawing posted?:thumbup:


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## nap (Dec 4, 2007)

that is just too funny. As I was reading this I realized I never made a drawing and here at the end, somebody asks about it.


what do you need a drawing for? If it is exactly what the OP wanted, that's fine but I if there is anything different, let me know.


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## jdanw (May 10, 2011)

*Bad ettiquite*

I guess I committed a faux pas. It would have been proper to start a new thread with the specifics of what I wanted, but I figured posting after the drawing was mentioned, would be better than trying to start from scratch. But since I was not the OP...

Even though he didn't pursue it, at the bottom of his last post, OP did say he wanted it to be automatic, so I assumed that was asking for the drawing. Regardless, I just want to know how to wire it...

(All in good fun and respect, hope you meant too funny as in hah, hah, not WTF)


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## nap (Dec 4, 2007)

jdanw said:


> I guess I committed a faux pas. It would have been proper to start a new thread with the specifics of what I wanted, but I figured posting after the drawing was mentioned, would be better than trying to start from scratch. But since I was not the OP...
> 
> Even though he didn't pursue it, at the bottom of his last post, OP did say he wanted it to be automatic, so I assumed that was asking for the drawing. Regardless, I just want to know how to wire it...
> 
> (All in good fun and respect, hope you meant too funny as in hah, hah, not WTF)


yes, funny ha ha. not funny: weird or funny being used sarcastically. 

so, same thing?. I may not come up with it right away. I'm going to have to look it over and see what's happening and then, since my pen for my Vistablet crapped out, I have to do it in Paint so it takes longer.

I'll see what I can do though.


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## jdanw (May 10, 2011)

:clap:SUPER...attached is a PDF of what I am doing, splitting at the bathroom doesn't matter, just 1 fan, two bathrooms and two dampers. i thought the PDF might help get you started. I even added the breaker box and switches...Thanks a bunch for this really:notworthy:. I have to get this done so I can re-insulate my attic for the summer...


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## nap (Dec 4, 2007)

very nice. 

are the dampers going to be closer to the switches or the fan? 

how far apart are the dampers located from each other?

how far from the dampers to the fan?

will the 2 bathrooms be on different circuits? It can be done with it either way. If they are likely to be on different circuits, it just changes a few things in the circuiting.



it can be circuited multiple ways. Depending on the physical placement of the devices, it can determine the simplest installation.


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## jdanw (May 10, 2011)

NAP, I can do anything right now, nothing is even bought yet. I was going to order a simple system soon, but with this possibility, I might have to upgrade and spend a weekend getting it done. I was thinking of mounting the dampers right off the y from the fan and mounting the y right to the fan, so I would only be doing the "mounting" in one area, the just suspending ducts to the rooms. Again, I can do it the easiest/cheapest way. I have fans in each room right now, so I imagine I would be able to steal on of those leads for power, or even run another home run if I had to. I am not sure exactly how the power is split in the bathrooms, as there is a light and fan right there together. If I need to definitively answer the power question, let me know and I can do some investigating, but as far as the ducts, dampers and fan placement, whatever works...


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## jdanw (May 10, 2011)

*Answer*

Well, I had to resort to bothering an electrician acquaintance. I had something worked up, but it wasn't working, it energized both dampers. Here is what we came up with. It requires relays, but I got a couple at Grainger Supply. They have various models, as cheap as $10 each. The ones my outlet had in stock were about $14 each.

I have to run this by him one last time to make sure our figuring and this implementation work. I will edit the post if something is wrong. I guessed at the placement of boxes containing the connections and missed the ones around the timers. Where your components are might determine some fo the routing, but hopefully, this will be around for some time to come, so others can get an answer.:thumbsup:


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## dobbsj (Jul 5, 2008)

*What brand of timer switch*



jdanw said:


> Well, I had to resort to bothering an electrician acquaintance. I had something worked up, but it wasn't working, it energized both dampers. Here is what we came up with. It requires relays, but I got a couple at Grainger Supply. They have various models, as cheap as $10 each. The ones my outlet had in stock were about $14 each.
> 
> I have to run this by him one last time to make sure our figuring and this implementation work. I will edit the post if something is wrong. I guessed at the placement of boxes containing the connections and missed the ones around the timers. Where your components are might determine some fo the routing, but hopefully, this will be around for some time to come, so others can get an answer.:thumbsup:



Earlier someone said use Lutron MA-T51 countdown timers. Neither this switch nor the companion switch MA-T51MN (which requires a neutral but works on much lower wattage) will work according to Lutron. They use Triacs and mafunction if current is backfed into the switch. I guess that is the reason. I would like to use two switches in parallel also for on bath fan. What type of timer switch did you use? I want a Decora type if possible. 

Thanks


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## jdanw (May 10, 2011)

*finally DOING THIS THING*

I wonder if anyone will still lend me a hand on this installation. I am perfectly fine with starting another thread as mine is different than the OP's. And I think I am further along than in this last post, so I might as well start a new thread. I look to the community for guidance as to how to proceed...should reference this one?


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