Need help—shunt masterbox

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Paulbalentine
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Wed Oct 30, 2019 1:25 pm

I need help with a shunt type masterbox. I want to wire an initiating device (pulls and/or heats) directly to the shunt loop. The problem is that many of the devices are NO and close on alarm, the shunt loop for the gamewell box is Normally closed and opening the loop causes the box to trip. Are there any normally closed FA devices? Or could I use a relay? Anybody have experience doing this?
Can anybody supply part numbers or recommend products do do this?
This is for a display, it is not a life safety system.
I do run a LARGE 100 mil system on my property with 3 circuits covering my one acre of land with 8 fire alarm systems, each with its own gamewell masterbox. The systems are spread between my house and two sheds. Image
Paul Balentine
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Sun Nov 03, 2019 2:03 pm

Anybody have any ideas?
Paul Balentine
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Tue Nov 19, 2019 3:13 pm

Pull stations that use switches could be arranged to be NC instead of NO by simply disassembling the pull station (carefully) and flipping the switch around, so that instead of closing when the handle pushes on it, it opens.
Pull stations that use buttons you would need to find the size spec of the button, and purchase an equivalent one that is NC instead of NO, and replace the entire button.
As for heat detectors, my recommendation would be to connect the contacts of the detector to a relay and a power supply, and connect your shunt connections to the NC and Common contacts on the relay, so that when the detector energizes the relay, the relay can open the shunt circuit.
This goes without saying, but doing any disassembly/modifications will wreck the UL rating of the device and so it could not be used for a life safety system, but you've already stated that this is not the case.

My only other remark would be to make sure that the contacts of the switch are capable of handling whatever current is going through the shunt circuit. Most modern pull stations have switches designed for 24VDC circuits and typically only support 1 or 2 amps of current.
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Tue Nov 19, 2019 7:05 pm

I found some devices you can use for your display.

Simplex 2099-9102 lists a N/C annunciator contact that can be used to shunt your master box.

Fire detection Devices still makes mechanical heat detectors that are available with N/C contacts. I would recommend the CR series with the highest temperature rating. These are combination fixed temperature and rate of rise units. Having the highest available temperature unit reduces the chance of melting the fixed temperature element during a demo. Once that is tripped the heat detector would have to be replaced.
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