def _clean(sensor, fetch_resp):
    """
    Clean data by deleting streams with zero values.

    Parameters
    ----------
    sensor : sensor name type to evaluate e.g. Zone_Air_Temperature

    fetch_resp : Mortar FetchResponse object

    Returns
    -------
    sensor_df : dataframe of nonzero sensor measurements

    setpoint_df : dataframe of setpoint values

    equipment : equipment related to the sensor measurement

    """
    # get all the equipment we will run the analysis for. Equipment relates sensors and setpoints
    equipment = [r[0] for r in fetch_resp.query("select distinct equip from {}_sensors".format(sensor))]

    # find sensor measurements that aren't just all zeros
    valid_sensor_cols   = (fetch_resp['sensors'] > 0).any().where(lambda x: x).dropna().index
    sensor_df           = fetch_resp['sensors'][valid_sensor_cols]
    setpoint_df         = fetch_resp['setpoints']

    return sensor_df, setpoint_df, equipment