You could do this..
SELECT ReadingDate, AvgCondensateTempF, AvgFeedWaterTempF FROM BoilersTestDataSupplyWaterAveragesPerDay WHERE (SystemID = 33) AND (ISNULL(AvgCondensateTempF, 0) <> @CT) AND (ISNULL(AvgFeedWaterTempF, 0) <> @FW1)
ONLY one parameter can be 0 at a time. You can use 0 or any number the column is not equal too like 999999999 or -1.
the column with...



