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Emerging Member
Posts: 68
Registered: ‎06-30-2014
Kudos: 4
Solutions: 1
Accepted Solution

mFi Light Switch Install Help

Hopefully someone is still out here using this mFi stuff,

 

do we have to use the red wire (load). 

 

My old switch only had two wires coming from it. and thats how power got to my pole lights. 

I currently am using the white and black, and ground cables but it doesnt work and I really dont want to just jump and try using the red and black and kill something. 


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Emerging Member
Posts: 53
Registered: ‎03-04-2015
Kudos: 25
Solutions: 3

Re: mFi Light Switch Install Help

Hi @jayppatel1115,

 

It sounds like there may be some confusion about how to properly wire up a smart switch like the mFi.

 

Traditional 2-way dumb switches only require two wires -- the line wire that connects to your houses hot feed, and the load wire that connects to the light fixture. The light fixture will also have a common wire connected to it that generally also feeds back through the switch box (although not connected to the switch) to connects to the house's common feed. The common wires are normally white and the hot wires are normally black.

 

Thus, your switch box would generally have at least four wires in it (ignoring uninsulated ground wires):

 

+ The hot (black) feed wire from the house electrical grid

+ The common (white) feed wire from the house electrical grid

+ The hot (black) load wire that connects to the light fixture

+ The common (white) load wire that connects to the light fixture

 

If you removed the switch and connect the black load wire to the black line wire and the white load wire to the white line wire, you'd wind up with an always-on light.

 

In order to insert the mFi switch into this setup, you need to do things a bit differently. Since the mFi switch itself requires power (and is not just dumb), it must be connected to both the house's hot (black) and common (white) feed wires. In addition, it also needs to be connected to the light fixture's black load wire using the red load wire on the mFi. The light fixture's white common wire will also need connected to the houses common wire, which is normally done at the wirenut where the mFi switch also connects it's white wire to the houses common wire.

 

There's a diagram at https://dl.ubnt.com/guides/mfi/mFi-LD_Switch_QSG.pdf.

 

Please note, however, that miswiring such a switch can be a fire hazard and/or destroy the mFi device. Working on such systems can also pose a risk of electrocution if not properly shut off at your breaker box before use. Thus, if you're not comfortable working on such a system, it may be best to contact a qualified electrician to install the switch instead. 

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Highlighted
Emerging Member
Posts: 53
Registered: ‎03-04-2015
Kudos: 25
Solutions: 3

Re: mFi Light Switch Install Help

Hi @jayppatel1115,

 

It sounds like there may be some confusion about how to properly wire up a smart switch like the mFi.

 

Traditional 2-way dumb switches only require two wires -- the line wire that connects to your houses hot feed, and the load wire that connects to the light fixture. The light fixture will also have a common wire connected to it that generally also feeds back through the switch box (although not connected to the switch) to connects to the house's common feed. The common wires are normally white and the hot wires are normally black.

 

Thus, your switch box would generally have at least four wires in it (ignoring uninsulated ground wires):

 

+ The hot (black) feed wire from the house electrical grid

+ The common (white) feed wire from the house electrical grid

+ The hot (black) load wire that connects to the light fixture

+ The common (white) load wire that connects to the light fixture

 

If you removed the switch and connect the black load wire to the black line wire and the white load wire to the white line wire, you'd wind up with an always-on light.

 

In order to insert the mFi switch into this setup, you need to do things a bit differently. Since the mFi switch itself requires power (and is not just dumb), it must be connected to both the house's hot (black) and common (white) feed wires. In addition, it also needs to be connected to the light fixture's black load wire using the red load wire on the mFi. The light fixture's white common wire will also need connected to the houses common wire, which is normally done at the wirenut where the mFi switch also connects it's white wire to the houses common wire.

 

There's a diagram at https://dl.ubnt.com/guides/mfi/mFi-LD_Switch_QSG.pdf.

 

Please note, however, that miswiring such a switch can be a fire hazard and/or destroy the mFi device. Working on such systems can also pose a risk of electrocution if not properly shut off at your breaker box before use. Thus, if you're not comfortable working on such a system, it may be best to contact a qualified electrician to install the switch instead. 

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