Stupid question

in parallel at the last sensor

ie... Class B fire.

NO means Normally Open. The answer is in parallel at the last sensor.

Jim Rojas

JohnO wrote:

In most cases the answer should be in parallel at the last sensor. However that assumes that you will generate a trouble on open and alarm on short. If you were trying to be too clever by half, you could program certain panels to have the alarm triggers reversed and wire it a number of funny ways. You would be shot on site by the next technician that serviced the account however. Some panels use zone doubling that can be equally as irritating to service if done incorrectly.

Sensors are wired in parallel and the EOL goes in parallel with last sensor.

If you were to put it at the panel end by mistake then cutting the wire has no effect.

This is how it works...

With sensors open the impedance = EOL ohms = normal status With sensors closed = 0 ohms = Alarm With wire cut = Open circuit/High ohms = Tamper With wire shorted = 0 ohms = Alarm (tamper)

or if using 4 cond you could put it on the return in the panel.

anyway you look at it though they are a PITA to troubleshoot.

I suppose it should be N.O., but I frequently see NO or NC.

Then I always have the question with things like relays, what is normal? Is it normal for the relay to be energized? Or not energized?

NOT energized, for a relay.

Unfortunately, the alarm industry confused things like this by not stadardizing on what is "normal" for a magnetic contact.

In relays you will have.

Single Pole Normally Open Single Pole Normally Closed Double Pole Normally Open Double Pole Normally Closed etc. etc.

When energized the relay contacts will change state to the opposite of what it was at rest.

In industrial wiring you have switches that are either of the following.

Normally Closed

Normally Open

Normally Open Held Closed

Normally Closed Held Open

In the alarm industry it is thought of as an OPEN Loop or a CLOSED Loop.

Wiring colors for an electrician is mostly Black is Hot, White is Neutral and Green is Ground. Any other color is considered to be Hot.

The phone guy uses Green for TIP and RED for Ring unless it is twisted pair then it is White w/ Blue strip as TIP and Blue w/ White strip as Ring for the first pair and then on Orange, Green, Brown, Slate to ID the other colors.

Alarm guys us RED as Positive and Black as Negative for power unless it is a current limiting circuit for a zone then it can be many other things. Generally is it Red/Black for first pair, Green/White for second pair, Blue/Brown for third pair, Yellow/Orange for the forth pair................................ then I start to lose my brain...............................

THEN you have the guy that thought he was a homebrew electrician that is now doing alarms and only buys telephone station wire for all his jobs because it is very cheap.

He ends up using Black for positive and Yellow for negative and the Red and Green for the motion zone loop.

If you have worked in multi-professions it can all be rather mind-bending. REALLY!!!!

They are coming to take me away Ha Ha Ha Hee Hee Hee............................................

Have a good day all.

Les

panel.

I have done that.

I do 2 wire smokes like that...4 cond home runs, eol in panel, less labor for me.