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Diagnostic guide · Fox ESS

Fox ESS Meter Lost Fault or CT not detected

A Fox ESS Meter Lost Fault, code 242 in Fox Cloud, means communication between the meter and the inverter is interrupted. Code 240 means the CT or meter isn't detected, and a firmware mismatch after a battery change can cause it too. You can do five checks in the Fox app without opening anything, and leave work on the CT, the meter or the cable to your installer or an engineer.
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We check Fox ESS meter and CT alarms

Send us the alarm's exact words and number, the date and time it first appeared, and anything that changed shortly before, such as a firmware update. With your permission we review your Fox Cloud alarm history, settings and firmware version.

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What the alarms mean
Start here

What Fox's meter and CT alarms mean

A CT clamp, or a Fox meter (a Chint DDSU666 or DTSU666), on your incoming grid supply tells the inverter what is going to and from the grid. Fox's H1-G2 and EVO10 come with a CT in the box, and the H3/AC3 with a meter. Everything on this page is done in the Fox app (FoxCloud 2.0), on foxesscloud.com or by reading the inverter's own screen. Nothing here asks you to open a cover, touch a switch or move a cable.

Fox Cloud code 242

Meter Lost Fault

Fox says communication between the meter and the inverter is interrupted. Owners report it as a communication fault between the inverter's manager and the meter. Fox's action is to check the cable between the meter and the inverter is correctly and securely connected. That cable runs to the inverter and the meter, so it's your installer's job.

Code 240

CT or meter not detected

Code 240 means the CT or meter isn't detected, and a firmware mismatch after a battery change can cause it too. Owners quote it as "fail to detect CT". It isn't in the Fox user manuals we've read, so we have no Fox action for it. Owners report checking the CT, its cable and the Meter/CT setting, all installer checks. See our field note on a Fox ESS code 240 case.

No CT fitted

A CT error on a system with no CT

Fox says a hybrid with no batteries and no CT must have its CT option switched off, or the inverter goes into an error state. The setting has to match what's fitted, and your installer checks it. See no CT fitted, or a setting that changed.

Not a meter alarm

BMS Lost is a different alarm

Fox uses BMS Lost for a lost link between the inverter and the battery's management system, not the meter. See our BMS communication fault page.

The numbers

About the numbers

Names and numbers

Fox Cloud prints numbers, and one owner reports that the app's alarm history shows them. Fox's user manuals for the H1-G2, H3, KH and EVO10 list their alarms by name instead, so a number on its own won't lead you to the manual. Write down the words as well as the number.

Code 1292

If you have seen 1292, "Meter's CT line fault", quoted online, it comes from the manual for Fox's H3-Plus/P3-Plus, 50 to 125 kW commercial inverters. There the action is to check the meter's CT cables, and Fox doesn't say it is the same alarm as 240.

In the app
Diagnosis

What you can check in the Fox app

Five checks, all on your phone or on foxesscloud.com. Note what you find, then send it to us or to your installer.

1
Open the alarm list

In FoxCloud 2.0, alarms sit under the bell icon at the top right, in Current and History lists. Older versions of Fox's app manual call the screen Faults, under Me. A moderator on Fox's Tech Hub forum said in late October 2026 that notifications aren't in the latest version of the app yet, so you have to look.

2
Write the alarm down exactly

Note its exact words, its number if the app shows one, the date and time it first appeared, and whether it is still under Current or only in History.

3
Check whether the system shows Faulty or Offline

The app's plant list sorts systems into Normal, Faulty and Offline. Offline means the datalogger has lost its internet link, and the system usually keeps running, so check the inverter's own screen. That's a different problem, covered on our Fox Cloud offline page.

4
Look at the solar figure

Fox Cloud shows your solar, house load, grid and battery figures. The energy-flow screen refreshes every 3 to 5 minutes on most systems, or every 5 seconds on some newer models with recent firmware, so give it a few minutes. Note whether solar generation has dropped to zero while the alarm is current.

5
Note what changed shortly before

A firmware update, a battery added, a new meter or any other work on the system. Owners report 240 appearing after firmware updates, and a firmware mismatch after a battery change can cause it too. The app's Version section shows the inverter's firmware.

Then stop there. Leave the Meter/CT setting and the export limit to your installer or to us, because the right setting depends on what's fitted and Fox UK keeps export limitation for installer-level accounts. Don't open the inverter, the meter or the consumer unit to look at the CT clamp or its cable.

Export limit

When the alarm can stop your solar

Some systems have an export limit. It's set on the inverter and caps how much power the inverter may send to the grid. On Fox's H1-G2 that limit works from the CT or meter. If the app shows the alarm and no solar generation, book help rather than wait for it to clear.

H1-G2 with a hard limit

Fox's H1-G2 manual says that with an export hard limit set, losing the CT or meter communication makes the inverter disconnect from the grid and shut down. So on that set-up, a lost meter or CT link can stop your solar generating.

Every other set-up

The same manual says a soft limit holds export below the set value within 15 seconds, but it doesn't say what happens if the link drops. None of the other Fox documents we read says what other set-ups do, so look at the solar figure in the app. On an owners' forum, one owner reported a 242 that stopped production for hours each afternoon, and the reply told them to call their installer.

The Meter/CT setting

No CT fitted, or a setting that changed

Which setting is right depends on what's fitted, so ask your installer, or us, to check it rather than change it yourself.

No CT fitted

Fox's single-phase CT guidance says a CT is compulsory on any installation with batteries. If a hybrid is installed with no batteries and no CT, its CT option has to be switched off, or the inverter goes into an error state. On the H1-G2 only one of the two is needed, a CT or a meter.

A setting that changed

Owners report the Meter/CT setting changing to disabled (in some reports after a firmware update) or to Meter on a system with a CT. In those reports, setting it back cleared the alarm. We found no Fox bulletin or official fix for a 240 after an update, and one owner's CT alarm stayed after Fox support restored the firmware.

Firmware after a battery change

A firmware mismatch after a battery change can cause a 240, as our Fox ESS code 240 field note shows. Tell us if a battery was added or swapped before the alarm first appeared.

Updating firmware

Fox's release notes say the H3 Smart's Manager firmware V1.24 (26 January 2026) improved meter and CT detection at low load. 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. Fox advises updating only when the system is stable, so an update isn't something to try while this alarm is showing.

Installer work

Jobs for your installer

Fox writes its meter and CT checks for installers and qualified electricians. These are the checks owners swap on forums, and on a Fox system each one is your installer's job, or an engineer's on a site visit. Don't open the inverter, the meter or the consumer unit to look at any of these.

The CT's direction

On single-phase systems the arrow on the CT points towards the grid. On the three-phase Chint DTSU666 meter, Fox says it faces the load. A CT fitted the wrong way round stops the H1-G2's export limit working.

The CT and its cable

Fox's guidance includes a resistance test on the CT, which your installer does. Fox supplies about 10 m of cable and allows up to 30 m. Beyond that it suggests a Modbus meter instead.

The meter cable

The meter talks to the inverter over an RS485 cable, and the pins it uses differ between models.

The meter's settings

Fox's smart meter uses address 1 and 9600 baud.

A wireless meter

Some single-phase Fox systems use Fox's wireless meter, and its install guide gives no guaranteed range. Fox says it isn't compliant with G100, the network operators' rules for export limitation schemes, so a wired CT or meter is used where an export limit has to meet G100.

The H1-G2's self-test

The H1-G2 has a CT and meter self-test, run on the inverter's own screen with the battery and grid both connected. Fox's manual says remote access to it hasn't been developed yet.

Fox ESS can help too. In the app, Me > Contact Us lets you choose your system and send Fox a request. STS is independent, not affiliated with or endorsed by Fox ESS.

How we help

How we help with a Fox meter or CT alarm

Remote diagnostic

We cover all Fox ESS models. With your permission, we use your login or an account transfer (£95) to review your Fox Cloud alarm history, settings and firmware version, and tell you whether we think it's a setting or the CT, the meter or the cable. The remote diagnostic is free.

Remote fix

If it's a setting we can change remotely, it's £125 only if we fix it remotely.

Site visit

If the CT, the meter or the cable needs work, that's a site visit, from £295.

FAQ

Questions about Fox ESS meter and CT alarms

The remote diagnostic is free. With your permission we review your Fox Cloud alarm history, settings and firmware version and tell you whether it looks like a setting or a part. If it's a setting we can change remotely, it's £125 only if we fix it remotely. If the CT, the meter or the cable between them needs work, that's a site visit, from £295.
Code 242 goes with Fox's Meter Lost Fault, which means communication between the meter and the inverter is interrupted. Code 240 means the CT or meter isn't detected, and a firmware mismatch after a battery change can cause it too. Owners report 240 with the words "fail to detect CT", and the Fox user manuals we've read list Meter Lost Fault by name, print neither number and have no alarm for 240. Give us or your installer the alarm's exact words as well as the number.
Not if it's an H1-G2 with an export hard limit set. Fox's H1-G2 manual says a lost CT or meter link then makes the inverter disconnect from the grid and shut down. None of the Fox documents we read says how other set-ups behave, so look at the solar figure in the app. If it has dropped to zero while the alarm is current, book help rather than wait for it to clear.
If your hybrid has no batteries and no CT, Fox says its CT option has to be switched off, or the inverter goes into an error state. Fox's single-phase CT guidance says a CT is compulsory on any installation with batteries, and the H1-G2 and EVO10 come with one in the box. The setting has to match what is fitted, so ask your installer or us to check which is right rather than guess.
Owners report 240 and other CT alarms after firmware updates, in some cases with the Meter/CT setting switched to disabled, where setting it back to CT cleared the alarm. A firmware mismatch after a battery change can cause 240 too. We found no Fox bulletin or official fix for a 240 after an update, and one owner's alarm stayed after Fox support restored the firmware. Tell us your firmware version, which the app shows in its Version section, and when the update or the battery change happened.
Owners report the alarm clearing once a changed Meter/CT setting was put back, a job for your installer or us that needs no site visit. A CT, meter or cable that needs work waits for a site visit from your installer or an engineer. After any change, give the app a few minutes before you judge it, because on most systems the energy-flow screen refreshes every 3 to 5 minutes.
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Get help if your Fox ESS meter or CT alarm is still showing

Send us the alarm's exact words and number, when it first appeared, your inverter model and anything that changed shortly before. We cover all Fox ESS models. With your permission we review your Fox Cloud alarm history, settings and firmware version. Independent, not affiliated with or endorsed by Fox ESS.

  • Not affiliated with or endorsed by Fox ESS
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