Douglas Krantz - Technical Writer - Describing How It Works
Get the book Make It Work - Conventional Fire Alarms

How do I Connect a Tamper Switch?

Inside the tamper switch assembly is a switch that is bought by the tamper valve / switch assembly manufacturer. That means the labels on the switch itself are often wrong. Use an Ohmmeter to figure out how to connect the switch to the fire alarm system.

The labels on the switch can mean that NO means Normally Open or Normally Closed. It depends on how the valve-to-tamper-switch mechanical connections were made by the valve manufacturer.

Greetings Douglas,

I tried to connect the tamper switch to the module, but I get a supervisory even though the valve is open. How am I supposed to wire it?

Thank you, R

The problem you are experiencing is the same problem that many fire alarm system installers experience. It's trying to connect systems so that, even though they were made by different manufacturers, the systems will work together.

When connecting sprinkler tamper switches, I have found that the best way to make sure the system is going to work correctly is to:
  1. Follow the fire alarm manufacturer's installation sheet exactly. These sheets show the correct wiring.
  2. DO NOT USE the labels on the switch inside the tamer switch assembly. Half of the time those labels are wrong. Those labels are for any system, sort of, and not just for fire alarm systems. Instead, use the Ohmmeter to figure out which screw terminals to use.

Ohmmeter

When the valve itself is open, the tamper on the valve should not be sending a supervisory signal, the contacts should be open, NOT SHORTED together. When the valve is open, disconnect the tamper switch and check the connections on the tamper switch. Use the Ohmmeter to find the contacts that are open.

WARNING: NEVER OPEN A VALVE THAT SOMEONE ELSE HAS SHUT. WATER COULD JUST FLOW OUT OF AN OPENING WHERE SOMEONE IS WORKING - PROPERTY DAMAGE AND POSSIBLE INJURY CAN RESULT.

When the valve is shut, the valve should be sending a supervisory signal, the contacts should be SHORTED together. Disconnect the tamper switch and check the connections on the tamper switch. Use the Ohmmeter to find the contacts that are shorted together.

Gatevalve

You have to think in terms of "Gatevalve Tamper System", not in terms of "Labels on Switch Parts".

As if the switch wasn't in the tamper assembly, but in the palm of your hand, the Switch Parts show N O and N C - The letters N O and N C only show what the contacts are doing on the switch when the switch is turned off.

The Switch Parts are really just part of a Gatevalve Tamper System - In the Gatevalve Tamper System, the switch could be turned on, or turned off, when the gatevalve is open to allow water to flow. You have to figure out which way it is.

It's the gatevalve, what is stopping water from flowing to the building sprinklers, that you are "Tampering". If someone turns off the water, the fire panel shows a supervisory and is supposed to say "Someone has Tampered with the Sprinkler System". When the valve is open, so water can flow to the building sprinklers, the fire alarm panel does not say anything.

Measure When the Gatevalve is Open or When the Gatevalve is Closed



The fire alarm panel is showing that the gatevalve is open to allow water to flow (normal), or that the gatevalve is closed, stopping water from flowing (tampered with). The supervisory signal on the panel shows that the gatevalve has been tampered with (closed to prevent water from flowing).

What the panel is looking for is what you are looking for with the ohmmeter. Disconnect all the wires from the switch before trying to use your ohmmeter.

Open the Gatevalve and Leave It Open While Taking the Ohmmeter Readings

WARNING: NEVER OPEN A VALVE THAT SOMEONE ELSE HAS SHUT. WATER COULD JUST FLOW OUT OF AN OPENING WHERE SOMEONE IS WORKING - PROPERTY DAMAGE AND POSSIBLE INJURY CAN RESULT.

Normal Condition of the Gatevalve - The gatevalve is open, allowing water to flow - the contacts on the switch are open - either the COMM / N O contacts on the switch are open, or the COMM / N C contacts on the switch are open.

Without trying to open or close the gatevalve, measure the contacts on the switch to find out which switch contacts are open.

Close the Gatevalve and Leave It Closed While Taking the Ohmmeter Readings

Tampered Condition of the Gatevalve (Supervisory) - Someone has Tampered with the gatevalve so it is now closed, stopping water from flowing - the contacts on the switch are shorted - either the COMM / N O contacts on the switch are shorted, or the COMM / N C contacts on the switch are shorted.

Without trying to open or close the gatevalve, measure the contacts on the switch to find out which switch contacts are shorted.

Write Down Which Contacts to Use

Write down on a piece of paper which switch contacts are open when the gatevalve is left open, and which switch contacts are shorted when the gatevalve is left closed so no water will flow. That will be the switch contacts to use for the fire alarm system.

Wire According to How the Installation Sheet Shows

Remember, always, the installation sheet that came with the box with the fire alarm device has itself been tested by a third party like UL, CE, ULC, FM, etc. This shows the exact wiring that will work.

Douglas Krantz
Having serviced fire alarm systems for nearly 20, Douglas Krantz has compiled his knowledge of the causes of Ground Faults and how to reliably detect them into the book Make It Work - Hunting Ground Faults. The book shows the three types of ground fault, what equipment should be used with each type of ground fault, and how to locate those hard-to-find ground faults.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

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