This is the reference for heat meter faults seen in the field and the error codes on the meters Sycous supplies. For a step by step approach, use Quick Approach to Heat Meter Fault Finding. For how a heat meter works, read How Heat Meters Work.
Faults you will meet in the field
| Fault | What causes it | Typical sign |
|---|---|---|
| Air in the flow sensor | Air trapped after a refill or from a poor mounting position. An ultrasonic sensor cannot measure through a pocket of air. | Flow reads zero or erratic. The C5 shows 20 or 40 and the Sharky 775 shows E7. |
| Temperature sensor open circuit | A broken cable, a damaged connector or a sensor pulled out of its pocket. | Temperature reads very high, or an open circuit error. Energy stops. |
| Temperature sensor short circuit | Crushed cable, water in the cable or connector. | Temperature reads very low or below zero, or a short circuit error. Energy stops. |
| Flow and return sensors swapped | Sensors fitted on the wrong pipes. | Negative or tiny delta T, little or no energy counted. |
| Flow sensor fitted backwards | The arrow on the body does not match the flow direction. | Reverse flow indication, volume not counting or counting down. |
| Low delta T | Poorly controlled system, heat exchanger or HIU not cooling the return, or bypass flow. | Meter appears to measure little energy even though heat is being used. It may be reading correctly. |
| Flow too low to register | A meter that is oversized for the real flow. | Energy appears lower than expected. Check the minimum flow in the datasheet. |
| Transducer fault | Failure or a short in the ultrasonic transducer or its cable. | Hardware error in the ultrasonic measurement. Flow and power are withheld. The Sharky 775 shows E4 and the ZENNER C5 shows 8, 9 or 100. |
| Flat battery | Reached end of life, or the radio was left transmitting at a fast interval. | Blank display, no communication, or a battery code. The C5 shows 7 or 1000 and the Sharky 775 shows E9. |
| No communication | Wrong MBus address, duplicate address, baud rate mismatch, no bus voltage or a meter in sleep mode. See the C5 guides for changing the primary address and waking from sleep. | Meter reads on the display but cannot be read by the data logger. |
| Sludge or magnetite in the system | Dirty water fouling the sensor or its strainer. | Drifting or low flow, repeated flow errors. |
| Overheating of the calculator | Calculator fitted where it sits too hot or has been lagged over. | Short battery life, a faulty display or condensation. |
Good to know: A meter showing zero energy is not always faulty. Heat meters start to count only above a minimum flow and minimum temperature difference, so a very small draw, or a flow and return with almost no difference, can be correctly read as zero. Check the datasheet for the start up limits.
Reading the error codes
Error codes differ between makes, so always check the manual for the exact model. These two are the ones you will see most.
| Meter | Code | Meaning and action |
|---|---|---|
| ZENNER C5 IUF | 1 and 2 | Temperature out of measuring range. Check sensors. |
| ZENNER C5 IUF | 3 and 4 | Short circuit or interruption of the return sensor. Check sensors. |
| ZENNER C5 IUF | 5 and 6 | Short circuit or interruption of the supply sensor. Check sensors. |
| ZENNER C5 IUF | 7 | Battery voltage. Exchange the device. |
| ZENNER C5 IUF | 8, 9 and 100 | Hardware error. Exchange the device. |
| ZENNER C5 IUF | 10 | Error in the measuring system. Exchange the device. |
| ZENNER C5 IUF | 20 | No water in the measuring tube. Check the operating pressure. |
| ZENNER C5 IUF | 30 | Reverse water flow detected. Check the installation position. |
| ZENNER C5 IUF | 40 | Air inside the medium. Vent the system. |
| ZENNER C5 IUF | 50 | Measured value outside overload range. Check the dimensioning. |
| ZENNER C5 IUF | 800 | Wireless interface fault. Exchange the device. |
| ZENNER C5 IUF | 1000 | End of battery. Exchange the device battery. |
| ZENNER C5 IUF | 2000 | Initial verification expired. Exchange the device. |
| Sharky 775 | C1 | Basic parameters saved in flash or RAM have been lost. |
| Sharky 775 | E1 | Temperature outside the measuring range, for example a sensor short circuit or a broken sensor. |
| Sharky 775 | E3 | Flow and return sensors interchanged. |
| Sharky 775 | E4 | Hardware error in the ultrasonic measurement, for example a defective transducer or a short circuit. |
| Sharky 775 | E5 | Communication not possible because of too many frequent read outs. |
| Sharky 775 | E6 | Flow direction of the flow meter is incorrect. |
| Sharky 775 | E7 | No plausible ultrasound receiver signal, for example air in the measuring path. |
| Sharky 775 | E8 and E9 | E8 no primary power supply. E9 battery nearly discharged, end of life reached. |
| Sharky 775 | EA, Eb, EC and Ed | Leak detection: pipe break, energy meter leak and leak pulse inputs 1 and 2. |
The C5 shows the sum of the codes when more than one fault is present. For example 1005 means error 1000 and error 5 together. The Sharky 775 clears an error by itself once the cause is fixed, and its error memory keeps any fault that lasted longer than 6 minutes.
Caution: Where the manual says to exchange the device, do not open the flow sensor or cut and rejoin the factory cables. Many are sealed and covered by calibration approvals.
Frequently asked questions
Why does my heat meter show zero?
Common reasons are air in the flow sensor, a temperature sensor fault, very low flow or temperature difference, a flat battery, or a meter in a storage or sleep mode.
Can a heat meter be wrong and still show no error?
Yes. Meters flag faults they can detect. A swapped pair of sensors or a meter fitted on the wrong pipe can give a plausible but wrong reading, which is why commissioning checks matter.
What does error 40 mean on a ZENNER C5?
Air inside the medium. Vent the system and watch the display until the flow reading is steady.
What does error E4 mean on a Sharky 775?
A hardware error in the ultrasonic measurement, for example a defective transducer or a short circuit.
Need a hand on site? Contact Sycous at info@sycous.com and have the details from the checklist above ready.