- Heat pumps
- Air-to-water heat pump
F1117
Vaillant F.1117 on an aroTHERM plus heat pump: compressor phase failure
Risk level
High
Professional inspection is recommended.
Urgency
Medium
Quick answer
On the aroTHERM plus, F.1117 means the compressor supply is missing. Check your consumer unit for a tripped heat pump switch and switch it back on once; if that fails, call a competent person and an electrician.
Safety first
Stop and check this first
- Vaillant warns of electric shock: before any work, disconnect all poles, secure against switching on and wait at least 3 minutes for the capacitors to discharge. If a switch trips again, do not force it.
Safe checks you can perform
- Heat pump disconnectors in the consumer unit
- Time the code appears
- Voltage and connections at the heat pump
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measure the supply before touching the compressor
- Do not attempt this professional task: Check the power company lockout setting
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.
Measure the supply before touching the compressor
What they doThe technician measures the voltage at the heat pump connection and checks fuses and terminals on the compressor and low tariff circuits.
They must show youthe voltage measured on each phase and the fuse checked.
In writingwhat was wrong with the supply and what they corrected.
Check the power company lockout setting
What they doWith a lockout tariff, the technician checks the lockout duration and how it is wired to the unit.
They must show youthe configured or contracted lockout duration.
In writingthe setting applied and the later test with no code.
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.
Heat pump disconnectors in the consumer unit
- Who:
- you.
- How:
- open the consumer unit and look for a heat pump switch that is off. Vaillant says to switch on all disconnectors of the product if it does not start.
- Result that matters:
- whether one was off and whether it trips again when switched on.
- If it was off and stays on:
- it was a supply cut; note the date and watch for repeats.
- If it trips again:
- do not reset it again; there is an electrical fault for an electrician.
- Evidence to keep:
- a photo of the consumer unit and a note of which switch was off.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
Time the code appears
- Who:
- you.
- How:
- note the time F.1117 appears over several days and check whether your contract has a power company lockout.
- Result that matters:
- whether it matches a lockout window longer than three hours.
- If it matches:
- the power company lockout is the suspect; Vaillant asks to keep it under three hours.
- If it does not match:
- the lockout is ruled out; the electrical installation remains.
- Evidence to keep:
- a list of dates and times of the code.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
Voltage and connections at the heat pump
- Who:
- an electrician or a competent person.
- How:
- they measure the voltage at the heat pump electrical connection, check the fuses and check and tighten the connections.
- Result that matters:
- the measured voltage against the rating plate and the state of each fuse.
- If a phase is missing or a fuse is blown:
- a supply fault is confirmed.
- If voltage and fuses are fine:
- the supply is ruled out and the technician checks the rest.
- Evidence to keep:
- a report with the voltage measured on each phase.
Mains voltage: isolate all poles and wait at least 3 minutes for the capacitors to discharge. Electrician or competent person only.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
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
- Vaillant
- Product type
- Air-to-water heat pump
Known code variants
- aroTHERM F.1117
- aroTHERM plus F1117
- Vaillant F1117
What it means
Vaillant defines F.1117 as a compressor phase failure. The causes it lists are a defective fuse, incorrect electrical connections, mains voltage too low, compressor or low tariff supply not connected, and a power company lockout longer than three hours. The code points at the supply, not at the compressor: it does not prove the compressor is faulty.
Warnings and stop conditions
- Highsource verified
Vaillant warns of electric shock: before any work, disconnect all poles, secure against switching on and wait at least 3 minutes for the capacitors to discharge. If a switch trips again, do not force it.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01
Symptoms and causes
Probable causes · in order
- Switch or fuse on the compressor circuitCommon
A blown fuse or a disconnector switched off cuts the compressor phase. It stands out because the rest of the unit can still be powered.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
- Power company lockoutPossible
On a tariff with lockout, Vaillant shows F.1117 if the cut lasts more than three hours. It fits when the code always appears in the same time window.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
- Low voltage or poor connectionPossible
Mains voltage too low or a loose terminal. Only a voltage measurement at the heat pump connection separates it.
Evidence: Vaillant VWZ AI heat pump appliance interface, operating and installation instructions 0020291573_01 · Vaillant aroTHERM plus VWL 35/6 to 75/6 A S2, operating, installation and maintenance instructions 0020330791_03
Virtual technician
Does F1117 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
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