- Heat pumps
- Air-to-water heat pump
E16
Viessmann E16 on a Vitocal heat pump: low refrigerant pressure
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On the Viessmann Vitocal 100-AW, E16 is the low pressure protection of the outdoor unit refrigerant circuit. Your part is to read the message, keep the outdoor unit clear of leaves and snow and watch whether it stays iced up. Everything else is work for an F-gas certified technician.
Safety first
Stop and check this first
- The outdoor unit contains flammable R32. If you suspect a leak, keep flames, hot surfaces and battery devices away, ventilate and leave the circuit alone; Viessmann reserves that work for professionals.
- Viessmann warns that some board components stay live after power is switched off and asks for at least 4 minutes before covers come off; that wait applies to the technician, so do not open the unit.
Safe checks you can perform
- Read and acknowledge the controller message
- Clear the area around the outdoor unit
- Watch whether the coil stays covered in ice
Leave these tasks to a qualified professional
- Do not attempt this professional task: Check defrost, low pressure switch and expansion valve
- Do not attempt this professional task: Gauge pressures and leak test with R32 rated tools
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Check defrost, low pressure switch and expansion valve
What they doWith no leak found, the technician checks the low pressure switch and its connection, the defrost operation and settings, fin cleanliness and the electronic expansion valve and coil.
They must show youwhich step of the Viessmann diagnosis revealed the fault.
In writingthe part adjusted or replaced and any defrost settings changed.
Gauge pressures and leak test with R32 rated tools
What they doAn F-gas certified technician connects gauges, reads the standstill pressure and searches for leaks with a detector suitable for flammable refrigerants. If there is a leak, they repair it, pressure test, evacuate and charge to the nameplate amount.
They must show youthe pressures read on the gauges and the leak test result.
In writingwhere the leak was, how much refrigerant was charged and the tightness test.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Read and acknowledge the controller message
- Who:
- you.
- How:
- when the display shows Warning or Fault, read the type of notification and confirm it, as the manual's troubleshooting guide says. Also note whether the indoor unit shows the text HP Low Pressure, which Viessmann describes as outdoor unit low refrigerant pressure.
- Result that matters:
- knowing exactly which message is shown and how often it comes back.
- If the message returns after you confirm it:
- stop retrying and contact an authorised service centre.
- If the code stays away for several days:
- keep your note in case it reappears.
- Evidence to keep:
- photo of the display, the date and the rough outdoor temperature.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Clear the area around the outdoor unit
- Who:
- you, from outside and without opening any panel.
- How:
- look for leaves, drifted snow, plastic sheeting or objects in front of the air inlet or outlet. Remove loose items by hand. Viessmann wants the evaporator kept free of leaves and snow. Do not push brushes or water between the fins.
- Result that matters:
- an outdoor unit with free airflow at the front and back.
- If leaves or snow were blocking the air:
- after clearing them, watch whether E16 stops appearing.
- If it was already clear:
- the cause is likely inside the circuit and needs a technician.
- Evidence to keep:
- photo of the outdoor unit before and after clearing.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Watch whether the coil stays covered in ice
- Who:
- you, looking only.
- How:
- on cold days, notice whether the outdoor unit fins remain under a thick layer of ice after the unit has gone through its defrost cycles. Do not chip the ice or pour hot water on it.
- Result that matters:
- knowing whether defrosting is failing, one of the causes Viessmann gives.
- If the ice never clears:
- take photos and pass them to the technician, as it points at defrosting.
- If no ice builds up:
- that cause is unlikely, so leave the rest to the professional.
- Evidence to keep:
- dated photos of the outdoor coil.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Viessmann
- Product type
- Air-to-water heat pump
Known code variants
- aerotermia Viessmann E16
- Balay dishwasher E16
- Balay E16
- Balay E16 error washer
- Balay E16 lavadora
- Balay washer E16 door
- Balay washing machine E16
- Bosch dishwasher E16
- Bosch E16
- Bosch E16 error
- Bosch E16 lavavajillas
- Bosch Geschirrspüler Fehler E16
- code erreur E16 lave-vaisselle Bosch
- code erreur E16 lave-vaisselle Siemens
- codice E16 Bosch
- codice E16 Siemens
- código E16 Bosch
- código E16 Siemens
- E16
- E16 Bosch dishwasher
- E16 lavavajillas Balay
- E16 Siemens dishwasher
- E:16
- erreur E16 Bosch
- erreur E16 Siemens
- Error E16 Balay
- error E16 lavadora Balay
- error E16 lavavajillas Bosch
- error E16 lavavajillas Siemens
- errore E16 lavastoviglie Bosch
- errore E16 lavastoviglie Siemens
- F16
- F:16
- Fehlercode E16 Bosch
- Fehlercode E16 Siemens
- lavadora Balay E16 puerta
- Siemens dishwasher E16
- Siemens E16
- Siemens Geschirrspüler Fehler E16
- Viessmann air to water E16
- Viessmann bomba de calor E16
- Viessmann E16
- Viessmann heat pump E16
- Viessmann Vitocal 100-AW E16
- Vitocal 100-AW AM2V E16
- Vitocal baja presión E16
- Vitocal E16
- Vitocal E16 low pressure
- Vitocal low pressure protection
What it means
The outdoor unit fault table in the Vitocal 100-AW AM2V manual (Viessmann, 02/2026, North American edition) defines E16 as Low pressure protection. Viessmann lists six causes: refrigerant leakage, a badly connected or damaged low pressure switch, poor defrosting, dirty fins or poor ventilation, abnormal throttling and a blockage in the system. Do not apply this to other Vitocal models. The code does not prove the unit is short of refrigerant; diagnosis needs gauges and a leak detector suitable for R32.
Warnings and stop conditions
- Highsource verified
The outdoor unit contains flammable R32. If you suspect a leak, keep flames, hot surfaces and battery devices away, ventilate and leave the circuit alone; Viessmann reserves that work for professionals.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
- Mediumsource verified
Viessmann warns that some board components stay live after power is switched off and asks for at least 4 minutes before covers come off; that wait applies to the technician, so do not open the unit.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Symptoms and causes
Probable causes · in order
- Refrigerant leakCommon
This is the first cause in the table: the technician reads the standstill pressure, and a zero reading means the refrigerant has escaped and the leak must be found.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
- Defrosting that leaves the coil icedPossible
Viessmann names poor defrosting: when the fins stay heavily frosted the suction pressure drops; the manual suggests a manual defrost and adjusting the defrost settings.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
- Dirty fins or restricted airflowPossible
Fins clogged with dirt or poor ventilation cut the heat exchange of the outdoor unit and push it into low pressure protection.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
- Low pressure switch or expansion valvePossible
A loose or damaged low pressure switch, or a stuck electronic expansion valve, are also on the list of causes Viessmann asks the technician to rule out.
Evidence: Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Virtual technician
Does E16 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Viessmann Vitocal 100-AW AM2V installation, service and operating instructions 6221389-11
Viessmann · 2026 · manual
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