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Security & Fire Protection Systems/Napco Security Systems class 2 transformer TRF 8/T116


QUESTION: Hello, my plug-in transformer for my home security system feels very hot!  Should I be concerned?  Should I replace this, and can you tell me where I can purchase one in or around Sacramento, CA.?

NAPCO Security Systems, TRF 8/T116, Class 2 transformer, 120VAC, 60Hz, 20W, 16VAC, 900mA.  

this is for an older model home security system.

ANSWER: When was the battery in the system last replaced?  Transformers are often hot to the touch, but if you feel it's "excessively hot", try replacing the battery (if you can't recall when it was last done).

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QUESTION: Not sure what the battery has to do with the transformer!   The battery is in the main panel box inside a bedroom closet.  The transformer is a plug in type in the garage.  As far as I know the battery has never been replaced.  Could you explain why the battery would make the transformer hot please?  Thanks.

If the battery has never been replaced, then likely it's completely depleted (dried out), and the panel is putting excessive charging voltage to the unit to compensate (drawing more power from the transformer as a result).  If the transformer is unusually hot, I would suggest replacing the battery.  They do normally run warm if the transformer is a 20VA unit (small for this panel).  If you replace the battery and install the recommended 40VA unit (16 Volt output!) which you can easily source online, things will run a lot cooler.

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Frank Kurz


Questions relating to Burglar Alarm and Security Equipment, Fire Alarm and Extinguishment Systems, Access Control, CCTV Systems, Installation, Service, Testing, Verification


30 years installing, servicing, and testing security, access control, extinguishment, and fire alarm systems

Chair of ULC Working Groups for Fire Alarm Testing (CAN/ULC-S536) and Fire Alarm Verification (CAN/ULC-S537), Executive Director of the Fire Protection Technicians Network (

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