I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.
CT clamp installed wrong
- Affects all solar brands
- Diagnosable from monitoring data
- Often missed at installation
CT clamp errors are often misdiagnosed as battery faults or portal bugs. A remote diagnostic session can confirm the cause and walk you through the fix.
Book your free remote diagnosticWhat's includedA really big thank you to Ron and his team, he has vast amounts of knowledge and got my system back up and running, also good to get on with. I was absolutely lost as to know what to do, no help from installer and somehow came across Ron and am I glad I did. I would definitely definitely recommend him to anyone who has faults with there solar system, any make I would say. Thanks again Ron a pleasure meeting you.
Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.
Ron diagnosed the problem remotely - efficiently and order the part identified as the fault - this part came directly from to me and Ron visited within a few days and within the hour corrected the problem and since everything has been excellent -highly recommended - very pleasant manner and lovely to work with . Ivor Morris.
We reached out to Solar Technical Support after our solar energy system stopped working. As GivEnergy 'solar orphans,' we have been extremely pleased with the service from STS - our system was back up and working within a day of us contacting them. We found other solar engineers reluctant or unable to help us, so it has been great to find this organisation. We would definitely use them again and would recommend them to anyone, especially GivEnergy orphans!
Contacted Solar Tech about my Givenergy battery storage system that wasn't working. Battery status was "idle". Given the company Givenergy had gone bust, I need independent quality technical help. Very patient and clearly very knowledgeable about battery systems Ron diagnosed possible issues and suggested several possible remedies. Worked our way through them and fortunately it began to work. The fault was very specific and only an experienced engineer would have thought to check. Suffice to say I'll be back if I need independent support again. Lastly you only pay if there is a solution. Outstanding.
What does a CT clamp actually do?
A CT (current transformer) clamp measures the current flowing through a cable by clamping around the outside of it — no electrical contact required. In a solar battery system, the CT is almost always installed on the main grid feed cable at the point where the house connects to the grid.
This reading is the inverter's primary source of information about what the house is doing. It uses the CT data to decide: should the battery charge or discharge? Is the house importing or exporting? Should the export limit be applied?
If the CT clamp is giving wrong data — because it is backwards, on the wrong cable, or has a loose connection — the inverter makes the wrong decisions. The battery appears not to work. The portal shows nonsense figures. And none of it is the battery's fault.
Symptoms of a CT clamp fault
Any one of these should prompt a CT clamp check.
Timed charge is set correctly but the battery stays flat through the cheap-rate window. The inverted CT reading is suppressing the charge command.
Your portal shows grid export figures late at night when no solar is generating and no battery is discharging. The clamp is reading import as export.
Battery discharges when it shouldn't — for example, draining overnight when demand is low. The reversed reading is triggering unnecessary discharge.
The animated power flow in your monitoring portal shows energy moving in implausible directions — house consuming solar while simultaneously exporting more than the panels produce.
Your DNO has an export limit but you are breaching it, or solar generation is being curtailed to zero even when export headroom is available.
On installations where the CT monitors the solar circuit, a backwards clamp shows negative generation or figures that don't peak at midday on clear days.
How to diagnose it from your monitoring data
Work through these checks in order. You don't need to open any enclosures.
Open your monitoring portal late at night when the battery is idle and no solar is generating. Your house is drawing power from the grid, so the portal should show a grid import figure. If it shows export, the CT clamp is backwards. Portals differ on which sign means import, so don't rely on the sign alone. Note the grid figure, switch on a kettle, and it must move further in the import direction. If it moves the other way, the CT clamp is reversed.
If you have timed charge enabled, open the portal during the charge window. Grid import should rise noticeably as the battery charges. If it stays flat or shows export, the inverted CT reading is blocking the charge command.
Turn on a large known load — a kettle draws about 2,000–3,000W. Watch the grid reading in your portal in real time. It should rise by roughly the wattage of what you turned on. If the grid reading falls, stays flat, or moves by an unrelated amount, the CT clamp is backwards or on the wrong cable.
If the CT monitors the solar circuit rather than the grid feed, look at your historical generation data. It should peak at midday on clear days and drop to zero at night. If it shows the opposite pattern — high at night, flat during the day — the clamp is backwards on the solar feed.
Plug a smart plug or energy monitor into a known appliance and compare its reading to what the portal shows. If the portal's house consumption figure doesn't move when you turn appliances on and off, the CT clamp is either on the wrong cable, has a bad connection, or has failed entirely.
What the fix looks like
The CT clamp needs to be removed and refitted so its direction arrow points the correct way. State the reference point or the instruction is meaningless: the arrow follows the direction of IMPORT — from the grid, towards the consumer unit and the load. Fit it on the insulated part of the tails on the supply side of the meter. In many installations the clamp is accessible at the inverter end without opening the consumer unit.
The CT cable itself carries no mains voltage — only a millivolt signal. The work is low-risk if the clamp location is accessible. There is no software shortcut for a grid or meter CT — no GivEnergy or Growatt portal setting reverses it, so a backwards grid clamp has to be physically turned round. On Fox ESS the arrow rule is different and this is an engineer's job: see the brand notes below.
If the clamp is on a sub-circuit rather than the main grid incomer, it needs to be physically relocated. This may require accessing the consumer unit — notifiable work that must be carried out by a qualified electrician.
In some properties, the main incomer cable is in a separate meter box or at a different location from the inverter. This can make correct CT placement genuinely difficult, and is something we regularly correct during system recovery visits.
Brand-specific notes
GivEnergy portals display grid power flow clearly, making a reversed CT immediately visible. There is no portal setting that reverses a grid or meter CT — a backwards grid clamp has to be physically turned round. See the GivEnergy CT clamp guide for full steps.
Growatt systems use a separate meter device (ShineWiFi or ShineLan) which includes a CT clamp. The clamp arrow follows the same convention as the fix above — pointing the way import flows, from the grid towards the consumer unit. There is no portal setting that reverses a grid or meter CT: if it is fitted backwards it has to be physically turned round.
Sunsynk uses CT1 and CT2 clamps — CT1 is typically the grid clamp, CT2 is the load or solar clamp. Each has its own polarity setting in the inverter menu. Backwards CT on Sunsynk is a common cause of "battery not charging on cheap rate" complaints.
On single-phase Fox ESS systems (H1, AC1, KH and KA), Fox says the CT arrow points towards the grid, the opposite of the rule above. The three-phase H3 and AC3 come with a direct-connected meter. Where a CT meter has been fitted, Fox's guide for the three-phase DTSU666 has the arrow facing the load. Fox gives CT fitting to qualified electricians, so this is a job for your installer or an engineer. See our Fox ESS meter and CT guide.
Related faults and guides
Frequently asked questions
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