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Fox ESS · Problems & faults

Fox ESS problems & faults

Independent guides to Fox ESS faults. Pick the topic that matches what you're seeing for its step-by-step guide, or book a free remote diagnostic and we'll tell you what the fix is. WiFi isn't remote work: if the dongle won't reconnect after the Fox Cloud offline guide, we can set it up on site, from £195.
  • Free remote diagnostic
  • No fix, no fee
  • All Fox ESS models

Ron dealt with a battery issue within an hour on a weekend remotely. Very clear instructions to fix the issue worked first time. Excellent service.

Si Whaley · Aug 2026 Google

My 90-year-old father-in-law had a solar system installed nearly three years ago that never worked properly and kept tripping out. Neither the original installer nor GivEnergy could resolve the issues, and we were even pushed towards replacing the system entirely when GivEnergy went bust. I contacted Ron at Solar Tech Support via WhatsApp, and within a few hours he had diagnosed multiple faults — including incorrect wiring that posed a potential fire risk. He carried out a home visit in Nottingham for £295 (including parts), fixed everything, completed firmware updates, and ensured the system was fully operational. Since then, it has worked perfectly. Ron was knowledgeable, responsive, and took the time to explain everything clearly. Highly recommended — excellent value and complete peace of mind.

Julian Federici · Jun 2026 Google

Ron is one of those rare finds - an engineer's engineer. He insightfully and accurately diagnosed the problems with our GivEnergy system, very quickly, which helped get us back on track. We will be using him again!

Geoff Palmer · Sep 2026 Google

Sts does a extremely great job. Thank you.

Roy Morgan · Jul 2026 Google

Ron was brilliant. He really tried to help. He spent hours trying to fix our GivEnergy AIO and ultimately it became apparent that it needed parts to fix the BMS management system. As there appears to be no replacement parts available on the market, he gave excellent advice on what options are now available to move forward. He is incredibly helpful and knowledgeable.

Mark Mayson · Jun 2026 Google

Ron was really helpful. He remotely adjusted my battery settings on the same day I contacted him, and at a reasonable price. Great service.

Jackie Palman · Jun 2026 Google

Last updated

What actually goes wrong on Fox ESS systems

A Fox ESS fault isn't always broken hardware. It can be configuration. In Feed-in Priority, set in Fox Cloud, solar feeds the house first and then the grid, and the battery charges from solar only if the export limit is exceeded, so the battery can sit at low charge. A schedule in Mode Scheduler or a maximum charge level can stop the battery charging (Fox's inverter manual calls timed charging "Force time use"; the app has no mode of that name). A minimum charge setting stops it discharging.

Communication is another theme. A BMS Lost alarm (code 14) means the inverter has lost contact with the battery BMS. Fox's own action for it is to check the BMS cable between the inverter and the battery, and that check is an installer's job. And the 2.4GHz WiFi dongle can drop off Fox Cloud after a new router or a changed WiFi password, and then needs re-pairing; if it won't reconnect, we can set it up on site, from £195. Add grid protection alarms (Grid Volt Fault 26, Grid Freq Fault 27 and 10min Volt Fault 28) when the inverter sees voltage or frequency outside UK limits, Ground Fault and Iso Fault alarms, meter and CT faults, and EPS backup that never worked because the port was never wired.

We start with the Fox Cloud alarm history and the settings, work out whether the problem is configuration, BMS comms, grid or wiring, and tell you straight what the fix is. The remote diagnostic is free, and the remote fix is £125 only if we fix it remotely.

Got an alarm name or number? Look it up in the Fox ESS fault code index, and find datasheets and manuals on the Fox ESS documents page. For who to contact: start with your installer for wiring, commissioning and warranty, reach Fox ESS UK through our Fox ESS warranty guide, or ask us for an independent diagnosis; for a warranty claim, if your Fox ESS installer has gone bust, we can be the Local Installer you appoint to make the claim.

Problems & faults

Fox ESS problems and faults we cover

Each topic links through to a step-by-step guide.

Battery not charging or discharging: checks

Fox ESS battery not charging from solar or the grid, or not discharging? Check the work mode, Mode Scheduler and reserve settings in the Fox…

See battery not charging or discharging

Battery offline or BMS Lost: comms fault

Fox ESS battery offline or BMS Lost (code 14)? What the battery alarms mean, what you can check in the Fox Cloud app, and when to call your…

See Fox ESS battery offline or BMS Lost

EPS not working in a power cut: backup checks

Fox ESS gave no backup in a power cut? Check whether EPS was wired and switched on, the reserve settings and the load, and which jobs need an…

See EPS not working in a power cut

Grid voltage, frequency or grid lost fault

Fox ESS showing Grid Volt (26), Grid Freq (27), 10min Volt (28) or Grid Lost (1)? What each alarm means, what you can check and when to tell…

See details

Ground fault & Iso Fault — earth diagnosis

Fox ESS Ground Fault and Iso Fault are two different alarms: a failed ground connection, and low insulation on the PV side.

See Fox ESS ground fault & Iso Fault

Meter Lost Fault or code 240, causes and fix

Fox ESS Meter Lost Fault (242) or CT code 240? What each one means and what you can check in the Fox app without opening anything.

See details

Offline in FoxCloud 2.0 or the app: checks

Fox ESS offline in FoxCloud 2.0 or the app? See if it's the app, the dongle or the system, follow Fox's own checks, re-pair the dongle and…

See Offline in FoxCloud 2.0 or the app
FAQ

Fox ESS fault questions answered

Start in the FoxCloud 2.0 app with the work mode, any Mode Scheduler block and any battery alarm, because a battery communication (BMS) alarm stops charging until it clears. Forced charging from the grid has been set in Mode Scheduler since the app's V2.2.0 update in February 2026, when Fox removed the old grid-charge settings. In the cold, batteries with a heater, mainly the EP range in the UK, warm themselves first, depending on their settings and the batteries they're stacked with, while others, such as the ECS, have no heater and wait until they're above 0 °C. Our Fox ESS battery not charging guide takes each check in turn, including a battery that won't discharge.
Settings, yes: work mode, schedule and Min SOC changes in Fox Cloud, and grid settings if you request it, once we have access through an account transfer (£95) or your login, shared with your permission. Owners can't update the inverter's firmware from their own Fox Cloud login: it needs an installer-level account, or a request to Fox ESS UK service with the inverter's serial number. WiFi isn't remote work: if the dongle won't reconnect after our Fox Cloud offline guide, we can set it up on site, from £195. Physical work can't be done remotely: EPS wiring and BMS cable or DIP switch checks are for your installer or an engineer, and a failed battery goes through your installer to Fox ESS as a warranty claim, but if your Fox ESS installer has gone bust, we can be the Local Installer you appoint to make the claim.
The diagnostic is free. We read your Fox Cloud alarm history, settings and voltage data, then tell you what is wrong and what the fix is. If it is something we can fix remotely, such as a work mode, schedule or Min SOC change, the remote fix is £125 and you only pay if we actually fix it. Anything that needs an electrician on site is quoted before anyone comes out.
A remote diagnostic session runs for 30 minutes. If the fault is a setting we can change remotely, we tell you the fix during the session. Anything we can't do remotely goes to your installer or an engineer, and on-site work is quoted in writing before it starts.
Go by what you're seeing. If the battery won't charge or discharge, start with battery not charging; for a BMS Lost alarm, see BMS communication fault; for a Grid Volt or Grid Freq alarm, see grid faults; for Ground Fault or Iso Fault, see ground fault; for Meter Lost Fault or code 240, see meter and CT faults; for no backup in a power cut, see EPS not working; and for no data in the app, see Fox Cloud offline. If you only have an alarm name or number, look it up in the fault code index first.
Free remote diagnostic

Need a Fox ESS engineer?

Tell us what's happening with your Fox ESS system. Free remote diagnostic; £125 only if we fix it remotely. We don't set up or diagnose WiFi remotely or over the phone: it's quicker and more reliable done on site.

  • No fix, no fee covers remote fixes. On-site work is quoted in writing before we start.
  • Emergency response within 4 hours during business hours
  • Written report regardless of outcome

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