Cleaned & checked 3 gas furnaces and 1 Cleaned and checked gas boiler. Inspected heat exchanger & flue venting. cleaned burners, pilot & flame sensors. Checked voltage & amp draw of motors. Test capacitors. Replaced air filters. Boiler: supply: 107. Return: 93. Tested pressure relief. Checked vent. Main: Inducer: 1.75A. Blower: 6.8A. Checked temperature rise. 66. East: blower: 2.0A. Inducer: 0.9A. Checked temperature rise. 52. Rear: Inducer: 1.33A. Blower: 3.5A. Return: 69. Checked heat tape. Checked drain.