A Viessmann Vitocal error code is a fault number shown on the programming unit, alongside the date, the time, a short description and a subscriber number that identifies the part reporting the fault. On newer models such as the Vitocal 250-A, codes look like F.686 or F.1007. Older and related Vitocal units use two-character codes such as D7 or 03.
Viessmann keeps its full fault descriptions in a separate online document referenced in the installer manual, rather than in a homeowner guide, so this page gathers the codes that are known from Viessmann's own manual, its community forum and an independent repair guide. Some come from different Vitocal models than yours, which we flag in the list below. Never open the unit or touch internal wiring, as the electronics carry mains voltage.
If a code returns or you cannot match it here, book a Viessmann heat pump repair and our engineer will read the full fault list on site. Our heat pump error codes hub covers other brands.
Is it safe to fix a Viessmann heat pump fault yourself?
Only basic outside checks are safe: reading the display, checking the breaker, clearing the outdoor unit and looking at system pressure. Viessmann's own manual treats fault diagnosis and clearing as technician work through the Service menu.
Do not open panels or touch electrics inside the unit. Several Vitocal codes point straight at the refrigerant circuit, and in the UK only an F-Gas certified engineer can legally work on it.
Warranty matters here as well. Manufacturer warranties generally expect qualified installation and servicing, so a DIY repair inside the casing can complicate a later claim.
Please read first: this guide is here to help you understand what your Viessmann heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and codes can differ between models and software versions, so always check the official Viessmann manual for changes before acting on anything here. Do not attempt anything that could be dangerous, and avoid any work that could void your warranty. If in doubt, call a qualified heat pump engineer.
If your Viessmann Vitocal heat pump is not showing a code, or you want to rule out the basics first, our guide to what to do when your heat pump is not working walks through the general checks and matches common faults to error codes across every major brand.
Which Viessmann error codes can you check yourself?
Only a few known Vitocal codes leave room for a homeowner check, and even then the check is limited. Write down the code and subscriber number before you do anything.
| Code | What it means | Safe homeowner check | Stop and call an engineer if |
|---|---|---|---|
| D7 | Flow controller fault, likely too little water flow | Check visible isolation valves are open and the pressure gauge, if fitted, is in range | Straight away if it persists. Do not keep restarting, as running on after a flow fault can damage the compressor |
| D6 | Flow controller fault with an interrupted defrost | Clear snow, ice and leaves from around and under the outdoor unit | It returns once the unit is clear |
| 21, 34 | Low evaporation pressure or temperature | Make sure the outdoor unit's airflow is not blocked by debris, ice or stored items | It shows again with clear airflow |
| F.686 | Lost communication inside the unit | After a power cut, check the breaker is on and note the subscriber number | It is still there once power is stable |
What are the most common Viessmann heat pump error codes?
The Vitocal codes owners ask about most are flow faults, low evaporation and high pressure faults, sensor faults and the newer F-codes for communication and critical faults. Causes from published sources come first below; anything marked general engineering knowledge is our own experience, not a Viessmann manual.
D7 and D6: flow controller faults
D7 most likely means too little water is flowing, according to an independent repair guide, with a clogged filter, a worn circulating pump or a faulty flow sensor as the usual causes. The same guide warns that running the unit on after resetting a flow fault can damage the compressor. D6 has been reported with an interrupted defrost cycle, and in one case a new flow controller and desludging did not cure it.
General engineering knowledge: closed isolation valves and low system pressure also cut flow. If your gauge keeps falling, read our guide to a heat pump losing pressure, then book an engineer rather than resetting again.
21 and 34: low evaporation pressure or temperature
Code 21 is low evaporation pressure and 34 means the minimum evaporation temperature was not reached, possibly from too little refrigerant. The published remedy is to adjust the heating circuit setpoints or check the refrigerant charge, which is F-Gas engineer work.
General engineering knowledge: an iced coil or blocked airflow at the outdoor unit gives the same symptoms in a cold snap. Our page on a frozen outside unit explains what you can safely clear.
22: high condensation pressure
The refrigerant is condensing at too high a pressure, and the source advises reviewing the heat pump's control settings. General engineering knowledge: poor flow on the heating side is the usual reason, caused by sludge, scale, air locks or closed valves. A heat pump powerflush is sometimes part of the fix.
31, 32, 33 and 35: temperature range faults
These mean the gap between evaporator and condenser temperatures is too large (31) or too small (32), or a minimum return or suction gas temperature was not reached (33, 35). The listed remedy is adjusting setpoints or checking the refrigerant charge. General engineering knowledge: scale, sludge or air locks that reduce heat transfer can trigger them too.
03, 06 and 0E: temperature sensor faults
These show a short circuit or break in the suction gas (03), liquid refrigerant (06) or hot gas (0E) sensor. A technician measures the sensor's resistance and replaces the sensor or its cable.
4B and 48: expansion valve and superheat
Code 4B points to a faulty expansion valve cable or stepper motor, fixed by replacing the cable or valve. Code 48, reported by Viessmann's community team on a different Vitocal model, means suction gas superheat is too low, which points to the refrigerant circuit. Both need an F-Gas engineer.
F.686: communication fault
The control electronics and the refrigerant circuit have stopped talking, as reported on the Vitocal 151-A. Likely causes are a board, the bus wiring, a cable or a software update issue. A technician needs to diagnose it.
F.1007: critical fault
This is a serious refrigerant circuit or compressor fault, reported on the Vitocal 151-A, and possible causes include overcurrent, overheating or a sensor fault. The unit locks out until a certified professional diagnoses it. It is not proof of compressor failure, but it does need prompt attention.
Which error code might you see in common situations?
The situation often tells you more than the code on a Vitocal, because so few codes are published. Use this table as a starting point, not a final diagnosis.
| Scenario | Vitocal codes you may see | First check |
|---|---|---|
| Cold snap and iced outdoor unit | D6, 21, 34 | Clear snow and ice from around the unit and let a defrost finish |
| Losing pressure or low pressure | D7 | Read the pressure gauge, if fitted, and look for drips |
| Radiators lukewarm | 22, 31, 32, 33, D7 | Check radiator and isolation valves are open |
| No hot water | No hot water code is published; D7 or F.1007 if the unit has stopped | Note the code and subscriber number |
| After a power cut | F.686 | Check the breaker, then note whether the code clears |
| Unit noisy or fan not spinning | F.1223 (reported on the Vitocal 060-A) | Look for anything blocking the fan from outside |
| After a service or filter clean | D7, 1F | Check valves were reopened; 1F after a parts or settings change needs the engineer back |
When the house is cold but no code shows, our guide to a heat pump not heating runs through the other causes.
How do you reset a Viessmann heat pump?
On a Vitocal, faults are cleared by a technician in the Service menu once the cause has been fixed. The Vitocal 250-A manual does not describe a homeowner reset step, so there is no published button sequence for you to follow.
Some faults, such as F.1223 on the Vitocal 060-A, have been reported to clear by themselves after the compressor stops. Others, like F.1007, lock the unit out until a certified professional has diagnosed them.
Repeatedly switching the power off and on to clear a code is a bad idea. With flow faults such as D7 in particular, running on without fixing the cause risks damaging the compressor, turning a valve or filter problem into a far bigger repair.
Viessmann error code list
These are the 18 Vitocal codes we could confirm from published sources. The two-character codes come from an independent guide covering several Vitocal models, and some F-codes were reported on other models, so check your manual or ask an engineer before relying on a meaning.
| Code | Meaning | Who should fix |
|---|---|---|
| 03, 06, 0E | Suction gas, liquid refrigerant or hot gas sensor fault (check your manual) | Engineer |
| 1F | Refrigerant circuit configuration does not match the unit (check your manual) | Engineer |
| 21 | Low evaporation pressure (check your manual) | Homeowner check, then F-Gas engineer |
| 22 | High condensation pressure (check your manual) | Engineer |
| 31, 32 | Evaporator to condenser temperature gap too large or too small (check your manual) | F-Gas engineer |
| 33 | Minimum return temperature not reached (check your manual) | Engineer |
| 34 | Minimum evaporation temperature not reached (check your manual) | Homeowner check, then F-Gas engineer |
| 35 | Minimum suction gas temperature not reached (check your manual) | F-Gas engineer |
| 4B | Expansion valve cable or motor fault (check your manual) | F-Gas engineer |
| 48 | Suction gas superheat too low (reported on another Vitocal model) | F-Gas engineer |
| D6 | Flow controller fault with interrupted defrost (check your manual) | Homeowner check, then engineer |
| D7 | Flow controller fault, likely low water flow (check your manual) | Homeowner check, then engineer |
| F.686 | Lost communication between controls and refrigerant circuit (reported on Vitocal 151-A) | Engineer |
| F.1007 | Critical refrigerant circuit or compressor fault (reported on Vitocal 151-A) | F-Gas engineer |
| F.1223 | Fan connection lost (reported on Vitocal 060-A) | Engineer |
Nothing specific to the Vitocal 100-A was found, and the 150-A is covered only through reports on the 151-A.
Where can you find the official Viessmann manual?
Viessmann's UK site links to ViBooks, its online manual database, where you can download the manual for your Vitocal by entering the article or serial number from the type plate or control unit. We could not find a Vitocal manual PDF hosted directly on a Viessmann site.
Need help with a Viessmann heat pump fault?
We repair Viessmann Vitocal heat pumps across the UK, including the 250-A, 150-A and 100-A ranges. Our engineers are F-Gas certified, we are MCS accredited, and every repair is backed by a 12-month guarantee.
Because so few Vitocal codes are published, proper diagnosis matters. Our engineers read the stored fault list and subscriber numbers through the Service menu, then test flow, sensors and the refrigerant circuit to pin down the cause. Same-day visits are available where possible, and our emergency heat pump repair service helps if you have no heating or hot water.
Flow and pressure faults like D7, 21 and 22 are much less common on a well-maintained system. Annual heat pump servicing keeps filters and airflow clear, and our heat pump cover plans combine servicing with repair cover. See our Viessmann heat pump page for more.
Call 0333 041 5130 or contact us online to book.
Frequently asked questions
What is the subscriber number shown next to a Vitocal fault?
It identifies the component that raised the fault. On the Vitocal 250-A, CAN bus 1 is the HPMU electronics module, 45 is the inverter, 54 is the refrigerant circuit controller and 59 is the programming unit. Give this number to your engineer along with the code.
Does a Vitocal keep a record of old faults?
Yes, the 250-A controller stores the 10 most recent faults, including ones that have already cleared. Installers view them in the Service menu under Message history and Fault list. That history helps an engineer spot a pattern, such as a flow fault that only appears in cold weather.
Why can't I find my Vitocal code online?
Viessmann keeps its detailed fault descriptions in an installer document rather than a public homeowner list, and code formats differ between models. Older units use two-character codes, newer ones use F-numbers. If your code is not on this page, note it with the subscriber number and we will look it up during diagnosis.
Does a Vitocal error code affect my warranty?
A code on its own does not, since it is the heat pump protecting itself. Problems come from leaving a fault unrepaired or from unqualified work inside the unit. Our Viessmann Vitocal review has more on owning one.
Can I see Vitocal faults remotely?
If your system has a Viessmann communication module fitted, faults may be visible through Viessmann's online services as well as on the programming unit. Not every installation has one, so ask your installer. Remote alerts are handy, but a repeat fault still needs a visit.
