Boost a fan wiring

[clarky456]

Hey guys and gals. Trying to do something that I'm not sure is possible; let me lay it out.

Several rooms, all with ventilation fans in the ceiling, think bathroom fans. Fans are tied into a single plenum of duct work and terminated outside of the building. All fans have individual switches, allowing plenum to build pressure and potentially discharge into other rooms versus at the termination point. The thought is to put a higher flow booster fan next to the termination point. Booster fan would need to come on only when a ventilation fan switch is active. 1 or more switches may be turned on at the same time. My mind is saying diodes, and relay. Total circuit would be less than 150 watts with 5 fans all running at once. Any thoughts?

Joe

 

[MikeF2316]

I'd bet those are AC fans, not DC. Diodes will only work as you envision on DC.

I'm no house electrician, maybe something's available.

But from what I know you need either double pole switches or relays for each point. Then you'd have to run wiring to each switch or fan depending on what you choose.

P.S. I believe house electricians call relays contactors.

 

[clarky456]

The fans in question are variable torque DC, though I dont care to mess with the guts and prefer to feed them unadulterated 120vac.

Original thought was wire from fan to relay/contactor, contactor switches on the booster. Im not familiar with the terminology, maybe a 4 pole single throw with 110 coil. Pricey.

Ive also spent some time digging into current sensing relays with no luck. Amperage needed to trigger the relay is substantially greater than my fans will draw.

Joe

 

[Fixin'Stuff]

There is a non-electrical solution, if you have access to the ducts. Install one of these in each line: http://www.batticdoor.com/bathfandraftblocker.html There may be better prices out there, I just picked that site at random.

 

[clarky456]

I have that as my second best option. A spring loaded damper is to be in place after the booster fan to prevent wind loading. Corn fields and a wide ranch house facing west does us no good. Accesability to vent termination is no big deal, but crawling through an attic pumped full of blown fiberglass to replace a failed damper is not my idea of fun.

Joe

 

[Fixin'Stuff]

I have that as my second best option. A spring loaded damper is to be in place after the booster fan to prevent wind loading. Corn fields and a wide ranch house facing west does us no good. Accesability to vent termination is no big deal, but crawling through an attic pumped full of blown fiberglass to replace a failed damper is not my idea of fun.

Joe

Scroll down that page and watch the video. No springs, no damper plate. It's some type of fabric sleeve that opens fully to let air flow out, then collapses when the air stops flowing.

 

[dogdog]

Not sure how much access you have to your wirings.... instead of a diode... why can't you use relays as isolation ?

means....

go buy 5x 120V coil relay... I think they exist... hook the coil side to your bathroom fan (so fan1 on, relay coil 1 energizes, and switch on the booster fan...etc etc.)... when the fan1 is on, relay activates... on the switch side, just parallel all 5 of those relays. so if any one of the relay activates it will run your booster fan without triggering your other fans. booster fan will be off only if all of the fans are off... It's a OR logic. Simple , but not fool proof... there are some down sides, such as if any of the relay is bad... or if any of the relay are stuck... or Don't mix in different legs of the AC source on the booster fan side.. and don't use SSR... they require heat sinks dependents on your load of cause. 2 extra wiring needed from each switch.etc etc

The major catch is that the booster fan must be on the same leg for all relay outputs.... otherwise you'll have a good spark.

I don't know if this is UL or NEC certified... but it works.


I know these relay exist in vacuum cleaners, I have two salvaged.... pretty sure ebay/amazon have them.. don't have to be high amp, just needed to be 120V coil in your case...

Sorry can't draw, maybe some one can draw for you maybe I can botch up some pen/paper thing....

 

[dogdog]

something like these 5x...
this is just a quick google... not exactly would or would not fit your case. you are at site so you'll know better.


https://www.ebay.com/itm/Zettler-Mi...A-AZ2280-1A-120AF-New-Pack-of-2-/232389191126

 

[Dingleburry]

Air flow switch/sensor at each fan to control the larger fan on/off?
Would this work? The 5 switches are flow switches.
When i try to close 2 switches it gives circuit error? But i think its fine...
Or something like this. On the main power feed for the 5 fans, if they all on same circuit.
You should be at 25a per fan. 1.25 for all

current sense relay
Item
Adjustable Current Sensing Relay
Contact Amps15.00A
Core TypeInternal
Contact Form SPDT
Input Voltage24 to 240VAC
MountingDIN Rail
Trip Delay0.10 to 10 sec.
Trip PointAdjustable 0.20 to 2.00A
Sensing Amp Range0.20 to 2.00A
Electrical ConnectionTerminal Strip

 

[Jackpod]

Browse some of the home automation sites, there are current sensing devices that when triggered will trigger an additional device, in your case the booster fan

 

[PhysicsDude]

I think your 2 best options are using 5 relays as mentioned above, or installing 2 pole switches for the individual fans.

1 pole controls the fan, and the other pole turns on the booster fan.

https://www.homedepot.com/p/Leviton...e-Toggle-Switch-White-R52-0CSB2-2WS/202027029