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g/fire_alarm • Posted by u/fire_code_fred •

EST3 panel programming — Zone Input module wired Class A vs B, what's your default?

Programming an EST3 for a 200,000 sq ft warehouse. The spec calls for Class B signaling but the owner's risk consultant is pushing for Class A on all initiating device circuits (IDC) after a recent loss at another facility.

Class A vs B on the EST3 Z-modules: Class A is a 4-wire loop that supervises both directions — you detect the fault AND can continue to receive alarm signals past a single open or ground fault. Class B is 2-wire, single path, fault kills the entire zone.

For a warehouse with long cable runs and fork trucks, Class A initiating circuits are genuinely worth the extra wire. My concern is the programming and supervision verification time doubles on Class A.

Anyone have a standard EST3 template for Class A IDC that handles the end-of-line supervision differently than Class B?

💬 3 replies

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u/suppression_sue •

If the spec calls for Class B and the owner wants Class A, get that change documented in writing through the AHJ before you wire and program it. The AHJ needs to know the classification change because it affects their inspection protocol for the system. Don't just swap to Class A and call it "better" without updating the permit drawings.

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u/smoke_detector_steve •

Class A on all initiating circuits in a warehouse is the right call — the owner's consultant is not wrong. Fork truck damage to a single cable run shouldn't take out an entire zone. The EST3 handles Class A IDC well once you understand the Z-module addressing. Are you using the SLC-based Z-modules or the older hardwired modules? The programming differs significantly.

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u/panel_programming_paul •

I have an EST3 template for Class A IDC that I've used on several warehouse installs. It handles the end-of-line supervision via the class A trouble relay correctly. DM me and I'll share the programming notes — easier than typing it all out here.

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