[en] The feasibility of operating a Mound twin resistance bridge calorimeter outside a temperature-controlled water bath was demonstrated. An existing calorimeter was retrofit with two additional jackets through which water was transferred from an external reservoir. Comparison of test results collected before and after the retrofit indicated that the calorimeter performance was not degraded by this modification. Similarly designed calorimeters have potential applications in laboratories where equipment space is limited for inspectors who are required to transport their assay instrumentation