I was reading in my installation manual last night about using EOL resistors. Basically it shows how to put them into the loop, but does not explain why you need them? What is the purpose of using the resistors in the loop? How do you know when to use 2 in the loop, one, or none? Does it have something to do with the length of the run, or with the number of modules on that run?

My other question is about smoke alarms. I would like to purchase smoke alarms to use with this system. I have read about 4 wire, and 2 wire alarms. Which ones should I be looking at to purchase?

Are there certain advantages to using one over the other????

Any help you can offer would be much appreciated.

 

EOL's help the system monitor the line as well as the device. With two properly configured eol's in a circuit, the system will be able to alert you to any open circuits, shorts or grounds.

 

Which to use depends largely on the capabilities of the alarm system you are attaching them to. The 2 wire design is much simpler to install and maintain, but not all panels support them, and those that do usually have just one or two zone inputs that support 2 wire protocal.

The 4 wire smokes have the advantage of being able to be connected to any zone input, but you have to deal with the power supply wiring as well as the alarm connections; and to do it correctly, you need a end of line relay to make sure that the power to the smokes can't be interrupted without you knowing it.

As far as the end of line resistor, in general. Properly installed, it allows you to do things like mix Normal Open and Normal Closed contacts and devices in the same alarm loop, and gives the loop supervision. Whether you need this depends on your actual security needs.

I think that the loops should have the supervision resistor, but in a simple, residential installation, not having a supervised alarm loop doesn't really make a major difference. In a house that was prewired during construction, often, you simply can't get to the device connection to put the resistor on.

 

I think the terminology "supervision" has me thrown.. If I don't use a resistor in the loop with an NC contact, and the contact is opened that WILL set the alarm off correct? Where does the "supervised" part come in? Is this for reporting certain codes/zone to the monitoring company? I would think any modules if properly connected to the panel would be "supervised" as they retain the ability to set off the alarm.. Again-I'm confused on this.

 

A supervised circuit is one designed to expect to see a certain resistance value across the circuit (within a specific range of tolerance, usually +/- 5--10%). A low value like a short (closed switch) or high value like an open switch triggers the loop.

If you don't put the resistor somewhere in the loop for a system that requires it, your zone will never close (you won't get a "ready" light).

There are systems that use specific values of resistors to effectively double the zones available. Zones programmed as fire zones often use a different resistor value, and all fire zones on modern systems require a supervision resistor, even on systems that have an option to turn off the resistor requirement.

Some systems, most notably DSC models, have the option of turning off the resistor requirement, but this means that all of the non-fire zones are strictly NC loops.

 

EOL resistors are typically used with N/O contacts. It lets the system know that the wiring is still intact. With the resistor, there is always voltage present through the circuit, if the voltage is lost, the line has been broken somewhere.

N/O contacts are paralleled so that if any one contact closes, it completes the circuit (actually is lowers the resistance in the line. the resistor actually is completing the circuit in normally operating conditions.)

I has to be placed after the last n/o contact for it to allow the system to monitor the entire circuit wiring. It would still work if you put it at the control panel but that would not allow any circuit wiring to me monitored (supervised).

Only one resistor per run/zone is needed

Now n/c contacts are run series circuitry so that if any one contact opens, the circuit is broken.

The benefit of using n/o contacts with an EOL resistor is that an alarm panel can tell the difference between a broken wire and a closed contact and will go into "trouble" rather than "alarm" if it sees a lost circuit. A full voltage signal (from a clsosing contact) will be read as an alarm.

If a n/c circuit is opened, it cannot tell if the wiring has a problem or there really is cause for alarm so by default, it will go into alarm.

Now the problem comes with trying to run n/c and n/o contacts int the same run. It just shouldn't be done. While the system will still basically work, it removes the benefit of a supervised system because in this method, an opening n/c contact will be seen the same as a broken wire. Therefore, there can be no "trouble" registered, merely an alarm condition.



Mrronfl: you have me puzzled here:

.

If you can turn off the requirement for an EOL resisitor, a n/o contact should be able to be used as well. if the contact closed, the panel sees voltage and therefore, alarm.

Is there something elso going on that would require a closed loop?

 

[QUOTE=napMrronfl: you have me puzzled here:

.

If you can turn off the requirement for an EOL resisitor, a n/o contact should be able to be used as well. if the contact closed, the panel sees voltage and therefore, alarm.

Is there something elso going on that would require a closed loop?[/QUOTE]

Yes, the design of the alarm system. Systems that allow the software disabling of the EOL resistor only support NC loops in that configuration. If you try to use NO loops on such a system, your zone will never close, and you will never get a ready light.

While I don't recommend mixing NC and NO devices on a loop, there are systems where you do have to. Some hardware only comes with NO or NC contacts but must be on the same zone with the opposite number. Again, not generally a DIY situation, but it does come up. In an ideal system, every device would have it's own zone.

 

Thanks MrRonFl.