Re: Replacing Radionics with Vista 20P

[Frank Kurz <tech@xxxxxxxxxxxxx>]

On 21/01/2011 5:45 PM, JoeRaisin wrote:
> On 1/21/2011 12:26 PM, RockyTSquirrel wrote:
>> Jim wouldn't the 4 conductor return as Joe was saying be the same as a
>> class A so long as the resistor was in the cabinet of the control?
>> (just asking)
>>
>> RTS
>>
>
> Not really. With one break in the line, a class A circuit would still be
> able to get an alarm signal from any detector on circuit. The EOL in the
> can will still result in losing any devices past the break.
>
> It's just that we used to prewire complete circuits with four conductor
> just in case something happened to our wire.
>
>
>
>

That's correct.  Having the end of line in the can is not a class "A"
circuit.  It's still class "B".  A class "A" circuit will recognize
alarms and supervisories from any device on either side of a single
"break" in the circuit and doesn't use end of lines.  An end of line in
the can using normally closed contacts won't provide the necessary
supervision on the circuit (you'll still be able to jumper out a surface
mounted contact with no one being the wiser).  On commercial installs
you should be using contacts with built-in EOL's or ones that use NO/NC
contacts as Jim has mentioned if you have more than one contact on a
zone.  On high security residential jobs, it may also be wise to go this
route.  GRI custom manufactures contacts with a variety of EOLR values
(don't know about Amseco and don't even mention Tane).

--
Frank Kurz
www.firetechs.net