Two wire return

[patricknola]

This week I was asked to wire a flow switch and the emergency bell to a power source as part of a fire sprinkler riser, my foreman told me to wire it like a light with a switch and a two wire return. Can someone please explain to me what a two wire return is . Thanks in advance.

 

[Strathead]

This week I was asked to wire a flow switch and the emergency bell to a power source as part of a fire sprinkler riser, my foreman told me to wire it like a light with a switch and a two wire return. Can someone please explain to me what a two wire return is . Thanks in advance.

I don't know for sure, but I am guessing your foreman is the confused one. Fire alarm circuits have to be supervised. (more on that later). But a flow switch emergency bell is not a supervised circuit. A flow switch has two sets of contacts. You wire either low voltage or 120 volts though one set of normally open to ring the bell upon activation and you wire the other set (which is supervised) through the other set either open or closed depending on the preference and design.

Supervised, means that all devices are wired in tandem. This is the correct term that many electricians like to call series, but isn't. Tandem means that the devices are parallel to each other, but the wire always go from one device to the next device until they get to the end, as in there is no point where either wire is tapped off to two locations at once. At the end of the line a resistor of the size required by the manufacturer is placed. When the proper resistance is not detected the panel knows there is something wrong (hence supervised). What the panel does with various information, short, open, wrong resistance, is deeper and for another day.

Anyway, the only thing I can guess is your foreman was basically telling you you need to bring each leg back from the bell, to either another location, or to a place where and end of the line resistor was going to be placed, but that is not applicable.

 

[ActionDave]

This week I was asked to wire a flow switch and the emergency bell to a power source as part of a fire sprinkler riser, my foreman told me to wire it like a light with a switch and a two wire return. Can someone please explain to me what a two wire return is . Thanks in advance.

Your foreman is talking about what I would call a switch loop where power starts at the light, goes down to the switch on the white wire and back up to the light on the black so there are only two wires at the switch location. He wants you to use the same arrangement for the flow switch since there isn't much room in the flow switch.

 

[iwire]

Your foreman is talking about what I would call a switch loop where power starts at the light, goes down to the switch on the white wire and back up to the light on the black so there are only two wires at the switch location.

That is my best guess as well, here we call it a 'switch leg'.

He wants you to use the same arrangement for the flow switch since there isn't much room in the flow switch.

I agree, sometime there is little room.

 

[Strathead]

Your foreman is talking about what I would call a switch loop where power starts at the light, goes down to the switch on the white wire and back up to the light on the black so there are only two wires at the switch location. He wants you to use the same arrangement for the flow switch since there isn't much room in the flow switch.

What terrible wording if that is what he meant.

 

[JFletcher]

See this page:

https://electrician101.wordpress.com/2013/09/20/single-pole-switch/

If you use a single 14/2 to feed a switch, the white wire must be marked/re-identified and used as the feed, and the black is the return.

When wiring anything this way, the white wire of the switch leg will be connected to the hot/feed, the black wire of the device will be connected to the black wire of the switch leg, and the white wire of the device will be connected to the neutral of the same circuit as the hot/feed.