What is Zone-Doubling on a Honeywell VISTA System?

Zone-Doubling, available on the Vista-20P and Vista-21iP panels, is a method of using different resistor values to allow zones 2-8 to each be treated as two separate zones. When zone 2 is doubled, it becomes both zone 2 and 10. Zone 2 uses a 3K resistor, and zone 10 uses a 6.2K resistor.

The Vista-20P and Vista-21iP panels each have 8 hardwired zones built into the panel. Traditionally, additional hardwired zones were added to the panel using a Honeywell 4219 8-zone expansion board. But, in some cases, the user may only need to add one or two additional zones. In these situations, adding a 4219 is somewhat wasteful. Zone-Doubling is perfect for these circumstances.

Only zones 2 through 8 can be doubled, which adds up to seven additional hardwired zones. When zone 2 is doubled, it becomes both 2 and 10, when zone 3 is doubled, it becomes both 3 and 11, and so on. Zone 1 can not be doubled, as it is electrically isolated from all other zones on the panel, and it has a lower resistance tolerance than any other zone (100 ohms tolerance, vs. 300 ohms). This is because it serves as the panel's 2-wire smoke zone.

The following rules apply to doubled zones:

1. Response Time. The response time programmed for the lower zone number will also apply to the higher zone number. If zone 3 is programmed with a 700 millisecond response time, zone 11 will also have a 700 millisecond response time.
2. Normally Closed Only. Only Normally Closed devices can be doubled. A short across either resistor of a doubled zone will cause a tamper response (Day/Night) on both doubled zones. When the system is armed, this will report as an E135 and is treated as an alarm. When disarmed, it reports as an E383 and displays as a trouble.
3. Double similar zone types together. Earlier panel versions had issues when unalike zones were doubled together, such as when an Entry/Exit zone was doubled with a motion zone. In that particular case, the motion zone will most likely be bypassed in Stay mode, while the Entry/Exit zone will be active. As a result, walking around and faulting the motion zone while in armed stay mode could sometimes cause a false alarm on the Entry/Exit zone. For this reason, it was recommended to only double similar zone types. This was corrected in later versions, but it's not a bad idea to adhere to this logic, even now.
   
   The video below will show you how to wire the 3K resistor to the lower number zone in a zone doubled pair:
   
   
   Honeywell VISTA 21IP: Zone Doubling, Installing Orange, 3K Resisters
   
   
   The videos below will show you how to wire the 6.2K resistor to the higher number zone in a zone doubled pair:
   
   
   Honeywell VISTA 21iP: Zone Doubling, Installing 6.2K Resistors
   
   
   
   
   Honeywell VISTA 21iP: Zone Doubling, 6.2K Resistor Installation (Continued)