Need elec translation

C=closed meaning current flows (ie ON)
NC=NotClosed meaning current does not flow (ie OFF)

'C' common aka the connection that gets switched

'NC' normally closed, this one is connected to common right now with no pressure on switch, it will open aka break connection, when pressure builds to the correct level

'NO' normally open, closes to common when when the switch is activated

Typically for a relay/pressure switch etc

NC-----Normally CLOSED

C......CLOSED ?
Usually it is NC or NO (normally closed or normally open)


The 5000 Series #776062 15 n/c is a 'Single Circuit' 2 Terminals pressure switch factory set at 15 psi Normally Closed

https://sensing.honeywell.com/honeywell-sensing-switch-5000-series-productsheet.pdf

As MrWizard says, C is "common" between NC and NO. NC is normally closed (i.e. the contacts are on when the switch is in its "resting" or normal state), and NO is normally open (the switch is off by default).

Since there are only the two terminals on this switch, they are basically interchangeable. The switch connects or disconnects between C and NC, turning whatever is attached on or off.

MrWizard wrote:
'C' common aka the connection that gets switched

'NC' normally closed, this one is connected to common right now with no pressure on switch, it will open aka break connection, when pressure builds to the correct level

'NO' normally open, closes to common when when the switch is activated

X2

Here's a diagram (automotive relay)



Think of Common as the "Supplied power"

NO "Connected only when the relay is CLOSED/powered up"
NC "DisConnected only when the relay is Closed/powered up"

Both NO and NC reverse

OP...thanks for responses. To simplify even more for elec challenge like me...
Wire that gets 12 volts when key is turned on is "c"
Then elec goes thru switch. If not enough pressure, contact is made and terminal "NC" let's elec light up led light on dash.

This is being used as low pressure light for fuel pressure.

Thanks

NC remains connected to the power terminal until the pressure builds up. The NC terminal is a great place to connect a 12 volt LED for diagnostics. Connect the 12 volt pilot light from NC to chassis negative.

Then connect a 2nd LED from NO to chassis negative.

Turn key on

First LED glows, YOU HAVE POWER

Pressure builds up

First LED goes out and 2nd LED lights up

THE PRESSURE SWITCH HAS CLICKED ON

Use blinking 12-volt LEDs available on eBay and power consumed by the LEDs is almost immeasurable. I love self diagnostic systems.

path1

yes, and in this case, the LED will most likely blink on for moment when the key is turned on because there is no fuel pressure, then go off as pump builds pressure, do understand the the sensitivity of the PS must be less than the pressure of the fuel pump,
a 10 lb switch will not come 'open' if you have a 4 lb fuel pump

I like proof that power is appearing at the load.