| 165 / | HD | HEAT EXCHANGE |
| DIG 1 | | WITH ALARM, INDICATOR, RECORDER, TEST, OR INSPECTION MEANS {7} |
| DIG 2 | DD | .~> Energy, efficiency, performance or malfunction |
| DIG 3 | DD | .~> Remote control inspection means |
| DIG 4 | DD | .~> Sight glass |
| DIG 5 | DD | .~> Fluid level or amount |
| DIG 6 | DD | .~> Temperature |
| DIG 7 | DD | .~> Flow or valve position |
| DIG 8 | DD | .~> Leakage |