Controlling exhaust fan via brewery control panel

[emjay]

I have a ventilation hood with exhaust fan in pretty much an identical configuration to Kal's electric brewery. It'll be fed by a circuit in the wall and controlled by a fan dimmer.

The walls are still open and while they are, I'm looking for a (non-dangerous) way to wire things to electively pass control of the exhaust fan over to my control panel (and hence to my computer by way of the BCS module) at will. The ceiling is also still open, but when it's closed up, the fan itself will be hidden above it.

So what I'm thinking so far is to add a second switch (on-off-on) to the wall beside the fan speed controller that's already there. "Off" is self-explanatory, and one of the "on" positions should be as well. The other "on" will redirect the circuit through a relay that is controlled by my control panel.

So it seems easy enough in theory, but I need a bit of help figuring out how to do this in practice. For instance, how the control panel will interface with the wall to get the signal and return wires to the aforementioned really. I'm also unsure of what kind of relays are okay to use in walls (eg I don't want a fire risk!), how exactly I would mount it in the wall, etc.

Aside from the added bling factor (and I expect it to be bling as possible considering the expense of this whole ebrewery-in-progress), I'd also like the ability to start heating the strike water remotely (which the BCS already easily makes possible) so that it's hit temp by the time I'm home. But to do so without simultaneously running the exhaust fan will end up putting a LOT of water into my basement... which is obviously less than desirable. Though if I'm being honest, the cool factor is reason enough for the geek that I am.

So... anybody here done something like this before (ie controlled a built-in exhaust fan with a BCS), or can otherwise at least help me with the specifics of it all?

 

[BadNewsBrewery]

I can't say I've ever done it before, but it sounds doable. You'd basically want ON - OFF - AUTO in which case auto is your BCS. You can find control modules and relays of all sorts that are rated to handle 120v loads. I wouldn't expect a whole lot of on/off cycling during use, so you wouldn't have to go with a SSR, just a standard relay. What I would likely end up doing is placing a junction box in the wall with the relay of your choice, set for 120v load and whatever signaling voltage your BCS provides to power the coil. You could then panel mount a banana plug or an XLR or any other type of receptacle into the junction box cover plate. Then just run a cable from your panel to that receptacle and flip the switch to "AUTO".

Of course, I can't say if any of the above is actually code compliant, but there are plenty of 120v relays that will mount in a junction box just fine, and as long as the amperage rating matches your load and you have your voltages right, I wouldn't be concerned about fire risk. The only thing I could see as being a problem code-wise / safety wise is if you use banana plugs / XLR / any type of plug that's not NORMALLY associated with power. Put a nice label on the junction box (FAN CONTROL - 5.5vdc Power Input Only [or whatever voltage the BCS runs at]) and you should be safe enough. Plus, putting it all in a junction box allows you to easily demo it out when its time to move and the new tennant doesn't want any of your stuff in the wall.

 

[Taz420NJ]

It's won't have the 'off' position, but the easiest/cheapest (and technically code-compliant) way is to use a standard three-way switch (the kind you put at the top and bottom of a stairwell). The line that goes out to the fan goes to the black screw, the line in from the BCS (auto) goes to one of the brass screws, and you run constant 120v to the other brass screw. That will give you an "on-auto" selection. When it's in "auto", use the BCS to turn it off.

Otherwise you'd simply use two switches.. One power on/off, and the other on/auto.

 

[emjay]

I'd definitely want a switch that has 3 positions for on-off-auto control.

Does anybody know of such a wall switch I could use for this? Also, does anyone have a specific recommendation for a relay that would be appropriate to use here?

Basically, I understand the theory here... I guess I just need guidance as to which actual parts I ought to order.

 

[BadNewsBrewery]

The critical information we don't have - what is the operating voltage and amperage of the signaling side of the BCS? If it's putting out 120VAC, then what Taz suggested may work. If the BCS only has the ability to send out low amperage low voltage DC signals, then what Taz suggested could blow up your BCS.

 

[emjay]

The critical information we don't have - what is the operating voltage and amperage of the signaling side of the BCS? If it's putting out 120VAC, then what Taz suggested may work. If the BCS only has the ability to send out low amperage low voltage DC signals, then what Taz suggested could blow up your BCS.

It signals with 5VDC, I know I'd have to use a relay of some sort.

 

[jeffmeh]

Here's a wall switch that should work, although you would still need to step one of the 120v legs down to 5v DC. Not cheap, and there may be othe options, but it is the first one that came up in a quick google search. http://www.grainger.com/Grainger/HUBBELL-WIRING-DEVICEKELLEMS-Wall-Switch-2LBU7#

 

[Taz420NJ]

Ok..

When I said 'the output of the BCS' gets connected to one leg of a switch, I did mean a line voltage output. So now that I know you're tapping off a 5VDC trigger, it would need to be the output of a relay. I was under the impression that this controller had a dedicated line-voltage fan output, but I guess I'm wrong? And FYI technically if it had been hooked up correctly, the 3-way switch method would not have blown the controller up, it just would not have worked.

For safety and code-compliance reasons you can not have high and low voltage (ie: 120VAC and 5VDC) in the same box unless certain precautions are taken. I know what you want, just give me a bit to draw it up.

Just to be sure, this is a permanently installed, hardwired 120v fan, correct?

How big of a stickler are you for staying code-compliant?

 

[emjay]

Ok..

When I said 'the output of the BCS' gets connected to one leg of a switch, I did mean a line voltage output. So now that I know you're tapping off a 5VDC trigger, it would need to be the output of a relay. I was under the impression that this controller had a dedicated line-voltage fan output, but I guess I'm wrong? And FYI technically if it had been hooked up correctly, the 3-way switch method would not have blown the controller up, it just would not have worked.

For safety and code-compliance reasons you can not have high and low voltage (ie: 120VAC and 5VDC) in the same box unless certain precautions are taken. I know what you want, just give me a bit to draw it up.

Just to be sure, this is a permanently installed, hardwired 120v fan, correct?

How big of a stickler are you for staying code-compliant?

It's an 8-inch Vortex inline duct fan (Kal uses the 6-inch model of the same fan). It'll be permanently installed - hidden above a drywall ceiling - but right now it still has the plug it came with. I'm not sure if I'll be cutting it off and hardwiring yet.

And I'm only a stickler for code insofar as it prevents real danger.

 

[orangehero]

Wrong thread.

 

[jeffmeh]

Ok..

When I said 'the output of the BCS' gets connected to one leg of a switch, I did mean a line voltage output. So now that I know you're tapping off a 5VDC trigger, it would need to be the output of a relay. I was under the impression that this controller had a dedicated line-voltage fan output, but I guess I'm wrong? And FYI technically if it had been hooked up correctly, the 3-way switch method would not have blown the controller up, it just would not have worked.

For safety and code-compliance reasons you can not have high and low voltage (ie: 120VAC and 5VDC) in the same box unless certain precautions are taken. I know what you want, just give me a bit to draw it up.

Just to be sure, this is a permanently installed, hardwired 120v fan, correct?

How big of a stickler are you for staying code-compliant?

One could always run the 120v leg to the control panel, and convert it to 5v DC in the control panel.

 

[Taz420NJ]

One could always run the 120v leg to the control panel, and convert it to 5v DC in the control panel.

No, that's backwards.


So emjay, when you say 'fan dimmer', you mean something like one of these, right?

Now as far as this thing being behind drywall, that has two implications.. First, you can't have 'cord' running through or behind a wall, or use an extension cord in any application that is considered 'permanent'. So you will have to change it to romex.

Second, you can not hide a junction box behind a wall or ceiling. Those kind of fans were designed to be installed in an accessible attic or basement. When you change the cord to Romex, it must be done in a junction box, and that box must remain accessible.

If the fan is in a place that will remain accessible (ie: an accessible part of an attic), you can install an outlet (which the fan will plug into) and connect it via Romex to the fan speed control and a device called a power inlet plate (pic below). That is how you will legally and safely feed power from the controller to the fan.

We use these to feed power from surge protectors/battery backups to wall mounted TVs (because you can't run the cord down inside the wall).

The relay and switch will be mounted in a 4x4" metal box near the controller. For code's sake, that should not be permanently installed and should remain as a separate surface-mount, 'plug together' module.

 

[kal]

It's an 8-inch Vortex inline duct fan (Kal uses the 6-inch model of the same fan). It'll be permanently installed - hidden above a drywall ceiling

I would not recommend installing it permanently where you can never replace it if required. Put in an access door, just in case. (That's what I did).

I have an outlet installed above my hood fan that is accessible by two trap doors. See the two doors above the hood in this picture:

Like Taz420NJ mentioned, you can't hid a cord behind drywall.

Kal