Vaillant Radio communication interrupted
A message from the wireless sensoCOMFORT VRC 720f, not from the heat pump. Vaillant’s first instruction is to make sure the power supply is on; the second concerns reception strength.
Take care
What this means
The VRC 720f is the battery-powered wireless version of Vaillant’s system control. Instead of a cable it talks over radio to a receiver unit, which is wired into the heat pump’s eBUS and takes its power from it, and to a wireless outdoor temperature sensor with a solar cell on the front. "Radio communication interrupted" is what the controller shows when it cannot reach that receiver.
Vaillant’s manual answers it in a single line: if the display is on and shows Radio communication interrupted, make sure that the power supply is switched on. That is the whole of the first check, and it is aimed at the receiver rather than the controller — the receiver is dead when the heat pump is dead, so a tripped breaker, a switched-off isolator or a power cut takes the radio link down with it while the controller, running on its own batteries, stays lit and complains. The second dimension is signal.
Vaillant grade reception on a scale where 4 is the minimum acceptable, below 4 is not stable and 10 is highly stable, and the installer reads the figure in the installer level as the system control reception strength. Obstacles weaken the link, which is why the manual allows the receiver to be wall-mounted away from the heat generator on an extension cable to improve reception. A controller that was carried to a different room, or a receiver left inside a metal casing in a cupboard that has since been filled with things, is the everyday way a marginal link becomes a broken one.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Heat pump or receiver without power | Vaillant’s published response. The radio receiver is powered from the heat pump’s eBUS, so anything that cuts power to the indoor unit silences the receiver. | Common |
| Reception strength below 4 | Vaillant’s threshold for a stable link. Walls, metal casings and distance all weaken it, and a link that was marginal at commissioning fails first. | Common |
| Controller moved from where it was set up | The VRC 720f is portable, and the reception strength was measured where it was commissioned. A new spot on the other side of the house may be out of range. | Occasional |
| Batteries in the controller flat | Produces its own battery warning first, but a controller on its last legs can drop the link intermittently before it shows anything else. | Occasional |
What to try yourself
Check the indoor unit is powered and its display is lit. Look for a tripped breaker or an isolator that has been switched off. This is Vaillant’s own first instruction.
Put the controller back where it lived when the system was commissioned, and see whether the message clears within a few minutes.
Replace the batteries if they are low, using the LR06 type Vaillant specify, and mind the polarity.
Vaillant warn that fitting the wrong type of battery carries a risk of explosion, and that leaking cells cause chemical burns. Use the specified type only, and take used batteries out promptly.If the message stays with the heat pump live and the controller in place, ask your installer to read the reception strength and, if it is under 4, to relocate the receiver on an extension cable.
Get an F-Gas certified heat pump engineer to look at your Vaillant heat pump
We do not pass enquiries to a repair firm, so there is no form here. When you book an F-Gas certified heat pump engineer, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£0–£180
Time on site
15 minutes
Nothing if the cause is power or position, which it usually is. An installer visit to measure reception and relocate the receiver is typically £90 to £180.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Vaillant fault codes
- F.511Get it checkedThe sensoCOMFORT controller has lost contact with the heat pump control module. Vaillant give two causes, a defective cable or a plug connection, and the house may stay warm while it shows.Related: controller and communication
- F.9998Get it checkedThe heat pump has lost its eBUS connection to the controllers and wiring centre. Vaillant name an unconnected or miswired eBUS cable and an outdoor unit without supply voltage as the causes.Related: controller and communication
- E5Usually simple to fixE5 is not a Vaillant heat pump code. Vaillant’s aroTHERM, uniTOWER and sensoCOMFORT fault tables run F.5xx to F.9998, so an E5 on your display belongs to something else in the system.Related: controller and communication
- F.22Get it checkedWater pressure too low. Vaillant publish exact thresholds and two instructions: the indoor unit manual says inform your competent person; Vaillant UK’s fault page lets a competent owner top up to 1 to 1.5 bar.Related: same brand
- Vapour from the outdoor unitUsually simple to fixA cloud rising off the outdoor unit is the defrost cycle. Vaillant’s own wording is that you do not have to do anything.Related: same brand
- Running all the timeUsually simple to fixA heat pump is meant to run long and low. The alarm signal is not the running time, it is the bill — and turning the thermostat up will not warm the house faster.Related: same brand
Own a Vaillant heat pump? Save it and its codes come first next time.
Related guides
Common questions
Is this the same thing as F.511?
No. F.511 is the controller unable to talk to the heat pump control module over the wired eBUS. Radio communication interrupted is the wireless controller unable to talk to its own radio receiver. They can share a cause — no power to the indoor unit produces both — but they are different links.
The outdoor temperature sensor shows a fault as well.
That is the third radio link, between the receiver and the sensor outside. Vaillant publish a separate reception strength for it and a maintenance note: clean the solar cell with a damp cloth and mild soap, and expect a delay before the message clears because the sensor’s battery has to recharge first.
Will the heating stop while this is showing?
Not immediately. The controller stores its programme and the heat pump keeps running on its last instructions, but it cannot receive changes and it loses the room temperature the controller measures. Left long enough, comfort control degrades even though nothing has failed.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.