Taking Input Signal from Class A Fire Alarm Control Panel

RamseyJ

Member
Hello all,

I'm currently working on creating a SCADA system for fire alarm in a company. I'm taking the input for SCADA's PLC by utilizing the existing Fire Alarm Control Panel (FACP) that has 10 zone detection which i need all this 10 zone input for my 24 VDC relay.

The problem is when I try to tap the input from the FACP terminal, it detects fault in the control panel and the voltage drop to 12 VCD. After some research i found out that this happen because I disrupt the Resistance in the zone's circuit as i connect my relay (with 700 Ohm coil resistance) in parallel with the zone circuit.

The circuit is Class B wiring, with 10k Ohm end of line resistance, 50 Ohm maximum Loop Resistance, and it says 1,35 mA maximum per zone circuit (excluding the end of line resistance current).

Any idea guys? I'm trying to isolate my work area only in the FACP. Maybe using any electronic device (transistor or etc) to take the input signal.

I also attach some ilustration on the class B wiring circuit

Sincerely thanks,
 

Attachments

GoldDigger

Moderator
Staff member
As you have seen, trying to tap the input signal of an FACP is not easy to do. I have my doubts as to whether is either safe or legal, no matter how well you isolate it.
I suppose that you could do a non-contact non-invasive, no harm-no foul sensing by putting a hall effect device around one of the wires to allow you to sense current in the loop. Then you just have to interpret that current to distinguish between a fault (open or short) and an alarm condition.
 

iwire

Moderator
Staff member
I will just point out that if the work is being done under the NEC you cannot modify the FACP circuits in any shape or form not authorized by the manufacturer.

If you are trying to remote monitor the zones there are plenty of ways that don't involve making your design and changes to monitored FACP circuits.
 

nhfire77

Senior Member
As iWire said it isn't complaint to pick up the zones individually and is impractical. If this panel has a zone putput for an remote annunciator, you could use at to trigger something- again it wouldn't be compliant with NEC UL. Does the panel have aux contacts not in use so you can at least monitor the general alarm or trouble conditions?


How is it currently monitored?
 

ryant35

Member
What is the make and model of the existing FACP? How many zones and what types of devices are in your work area?

If there are smoke detectors check to see if they have an auxiliary relay, or replace them with a model that does have an auxiliary relay. Some pull stations and waterflow switches have a second set of contacts that you can use, assuming the waterflow isn't activating a 120VAC bell.
 

gadfly56

Senior Member
Hello all,

I'm currently working on creating a SCADA system for fire alarm in a company. I'm taking the input for SCADA's PLC by utilizing the existing Fire Alarm Control Panel (FACP) that has 10 zone detection which i need all this 10 zone input for my 24 VDC relay.

The problem is when I try to tap the input from the FACP terminal, it detects fault in the control panel and the voltage drop to 12 VCD. After some research i found out that this happen because I disrupt the Resistance in the zone's circuit as i connect my relay (with 700 Ohm coil resistance) in parallel with the zone circuit.

The circuit is Class B wiring, with 10k Ohm end of line resistance, 50 Ohm maximum Loop Resistance, and it says 1,35 mA maximum per zone circuit (excluding the end of line resistance current).

Any idea guys? I'm trying to isolate my work area only in the FACP. Maybe using any electronic device (transistor or etc) to take the input signal.

I also attach some ilustration on the class B wiring circuit

Sincerely thanks,
Do you need to monitor each zone, or only determine if any zone on the panel is in alarm?

Or are you trying to send a signal from the PLC to the FACP?

Whichever you're trying to do, the interface between the two systems should involve dry contact inputs and outputs. There should be no significant voltage or current flowing from one to the other.

Most fire alarm panels, certainly 10-zone panels such as the FireLite MS-10UD-7 or the Silent Knight 5208 have optional modules that can drive an annunciator or relay output for each zone.
 

RamseyJ

Member
As you have seen, trying to tap the input signal of an FACP is not easy to do. I have my doubts as to whether is either safe or legal, no matter how well you isolate it.
I suppose that you could do a non-contact non-invasive, no harm-no foul sensing by putting a hall effect device around one of the wires to allow you to sense current in the loop. Then you just have to interpret that current to distinguish between a fault (open or short) and an alarm condition.
Oh ok, can you please give me some suggestion on the hall effect sensor that meets the criteria of the problem?

I will just point out that if the work is being done under the NEC you cannot modify the FACP circuits in any shape or form not authorized by the manufacturer.

If you are trying to remote monitor the zones there are plenty of ways that don't involve making your design and changes to monitored FACP circuits.
Hemm I guess that NEC code does not apply in Asia.

As iWire said it isn't complaint to pick up the zones individually and is impractical. If this panel has a zone putput for an remote annunciator, you could use at to trigger something- again it wouldn't be compliant with NEC UL. Does the panel have aux contacts not in use so you can at least monitor the general alarm or trouble conditions?


How is it currently monitored?
The existing fire alarm system was intalled in 1990s (estimation) covering large area (in the mean time I only need to monitor the office area) in which the data has vanished and I can't find any output contact in the office FACP. Therefore my best bet is only utilizing the line signal from the FACP

What is the make and model of the existing FACP? How many zones and what types of devices are in your work area?

If there are smoke detectors check to see if they have an auxiliary relay, or replace them with a model that does have an auxiliary relay. Some pull stations and waterflow switches have a second set of contacts that you can use, assuming the waterflow isn't activating a 120VAC bell.
The manufacturer is Nohmi Bosai Ltd and the model of FACP is 'FAP121N' but i can't find the correct model datasheet in the internet. It's not a recondition work but I only need to the signal for the 10 zone alarm for the SCADA.

Do you need to monitor each zone, or only determine if any zone on the panel is in alarm?

Or are you trying to send a signal from the PLC to the FACP?

Whichever you're trying to do, the interface between the two systems should involve dry contact inputs and outputs. There should be no significant voltage or current flowing from one to the other.

Most fire alarm panels, certainly 10-zone panels such as the FireLite MS-10UD-7 or the Silent Knight 5208 have optional modules that can drive an annunciator or relay output for each zone.
I need to differentiate each zone in an event of alarm. I know that I should not interfere significant voltage or current, therefore I created a circuit of transistor for amplifying the current to drive my 24 VDC relay and I calculate the Base-Emitter current is 2,4 mA (which i think is not significant)
 

gadfly56

Senior Member
Oh ok, can you please give me some suggestion on the hall effect sensor that meets the criteria of the problem?



Hemm I guess that NEC code does not apply in Asia.



The existing fire alarm system was intalled in 1990s (estimation) covering large area (in the mean time I only need to monitor the office area) in which the data has vanished and I can't find any output contact in the office FACP. Therefore my best bet is only utilizing the line signal from the FACP



The manufacturer is Nohmi Bosai Ltd and the model of FACP is 'FAP121N' but i can't find the correct model datasheet in the internet. It's not a recondition work but I only need to the signal for the 10 zone alarm for the SCADA.



I need to differentiate each zone in an event of alarm. I know that I should not interfere significant voltage or current, therefore I created a circuit of transistor for amplifying the current to drive my 24 VDC relay and I calculate the Base-Emitter current is 2,4 mA (which i think is not significant)
One of the problems you'll face, code issues aside, is that conventional zones report an alarm condition to the panel by creating a dead short across the zone. Is your circuit going to give you any useful information in that case? I would urge you in the strongest possible terms to contact the manufacturer directly to get the installation and operation manual(s) for this product before you go charging in.
 
Top