Control of Small Exhaust Fan

[charlie b]

An exhaust fan (1/2 HP, 120V, 1 ph.) will serve two restrooms, a janitor closet, and a small storage room in a small, remote building in a national park. The control systems in this building are rudimentary. There is no Building Management System (BMS) or similar mechanical control system. They don?t want the fan to only be running when a restroom is occupied. The concern is that odors might waft into other spaces after the fan turns off. It was suggested that the fan should be constantly running any time the building is occupied. I was asked to provide a ?simple 7-day timer switch? that the staff could use to schedule fan operation. I am not sure how to make that work, or what kinds of controllers are available to achieve this function.

Any suggestions?

 

[texie]

An exhaust fan (1/2 HP, 120V, 1 ph.) will serve two restrooms, a janitor closet, and a small storage room in a small, remote building in a national park. The control systems in this building are rudimentary. There is no Building Management System (BMS) or similar mechanical control system. They don?t want the fan to only be running when a restroom is occupied. The concern is that odors might waft into other spaces after the fan turns off. It was suggested that the fan should be constantly running any time the building is occupied. I was asked to provide a ?simple 7-day timer switch? that the staff could use to schedule fan operation. I am not sure how to make that work, or what kinds of controllers are available to achieve this function.

Any suggestions?

Off the top of my head I would just put a seperate relay for each room and energize the coil from the respective light switch. Then put all the NO contacts in parallel with the fan circuit. Cheap and easy to set up in a NEMA1 box in the ceiling or such.

 

[Strathead]

An exhaust fan (1/2 HP, 120V, 1 ph.) will serve two restrooms, a janitor closet, and a small storage room in a small, remote building in a national park. The control systems in this building are rudimentary. There is no Building Management System (BMS) or similar mechanical control system. They don?t want the fan to only be running when a restroom is occupied. The concern is that odors might waft into other spaces after the fan turns off. It was suggested that the fan should be constantly running any time the building is occupied. I was asked to provide a ?simple 7-day timer switch? that the staff could use to schedule fan operation. I am not sure how to make that work, or what kinds of controllers are available to achieve this function.

Any suggestions?

a few ways come to mind but 7 day timer switch is confusing. I would suggest an ET9000 series intermatic 365 day time clock if they actually want to "schedule" the on and off function. If they want manually turn the fan on, I would go to a digital time switch like a Leviton VPT24 which is a 24 hour switch that can be programmed to come on for however many hours they want the fan on for when it is switched on and then will go off.


I am picturing an entry room and all of the other rooms are off of it (as opposed to outside door access to the individual rooms) If so, I would suggest an occupancy sensor that triggers a timer that times out when someone triggers the sensor. Go one step further, and this is the one I would suggest. put OCC's in each room. trigger the lights with the OCC, and also send a signal to a TDR (time delay relay) that activates the fans set to the time you want. Here is a wiring diagram I did for one like it that has 277. Given the PE after your name and the intelligence of your posts I am pretty sure you can extrapolate:bye: I hope it attached let me know if it didn't

 

[Jraef]

It's unlikely that fart smells will last beyond even one air exchange in a room, certainly not 2 or three. The point is, all day whenever occupied seems a bit excessive and can lead to issues with the HVAC load being increase, plus the fan will wear out faster. The problem with time clocks and such on something accessible to the general public is that people mess with them, then can't figure out what's wrong or how to go back to what worked, so they end up bypassed. I would use Strahead's suggestion, and if they or you don't want anything as extravagant as an occupation sensor, then use relays or little current sensors on the existing wires going to the lights for each room so that if anyone turns on a light, it closes a contact, starts the Off-Delay timer and that then has the fan run for 30 minutes after the switch is turned off. Nothing the public can see or mess with.

By the way, I freaking HATE occupancy sensors in toilets. I find myself having to wave my hands when reading the newspaper...

 

[Dennis Alwon]

Feed the timer and then take a switch leg to the first fan, then to the second fan. Not sure what the problem is on this as the hookup is simple-- programming may be more the issue

 

[Strathead]

It's unlikely that fart smells will last beyond even one air exchange in a room, certainly not 2 or three. The point is, all day whenever occupied seems a bit excessive and can lead to issues with the HVAC load being increase, plus the fan will wear out faster. The problem with time clocks and such on something accessible to the general public is that people mess with them, then can't figure out what's wrong or how to go back to what worked, so they end up bypassed. I would use Strahead's suggestion, and if they or you don't want anything as extravagant as an occupation sensor, then use relays or little current sensors on the existing wires going to the lights for each room so that if anyone turns on a light, it closes a contact, starts the Off-Delay timer and that then has the fan run for 30 minutes after the switch is turned off. Nothing the public can see or mess with.

By the way, I freaking HATE occupancy sensors in toilets. I find myself having to wave my hands when reading the newspaper...

Use an Ultrasonic sensor and you shouldn't have that problem.

 

[dpeter]

What determines "occupied"? Is there an alarm system that can be used to operate some relay or how about the light switch that some one turns on when they walk in that also turns fan on.

 

[GoldDigger]

There are timers that will turn the fan on with a light and then keep it on for an adjustable time delay after the light is turned off.

 

[Strathead]

There are timers that will turn the fan on with a light and then keep it on for an adjustable time delay after the light is turned off.

That is what the components and circuit I provided do. I have a local engineer that is fond of just writing notes on a plan, so I had to design the circuit myself.