Abstract: The purpose of this research is to increase economic efficiency by adapting a selector valve to a switchboard to protect two switchboards with one cylinder. As a result of the detection tube’s operating temperature test, it was confirmed that the thermo-sensitive tube operates within ±5%. In the dispersion performance test, the switchboard fire protection system using selector valve detected fire within 5 sec on average and dispersed fire-extinguishing agent immediately. The fire-extinguishing agent’s dispersion time was about 47 sec and was suitable for the dispersion performance test’s acceptance criteria of the dispersion within 60 sec. Through this experiment, it was found that the thermo-sensitive tube used in the experiment was suitable for the acceptance criteria. It was also found that it was effective to protect two switchboards with one cylinder unlike the conventional case.