oh dear, oh dear.....
An unexpected power cut tested out the new installation today...and I am not happy
The whole point of using this expensive system was to prevent interruption of the supply to the house
The website https://fox-ess.uk/eps-box-sp-backup-gateway/#eps-more makes a point of, and clearly states that it provides uninterrupted power, changes over instantly, seamlessly and without interruption
I quote:
Whole home backup for residential storage installations
The Fox ESS EPS-BOX-SP is a single-phase whole home backup gateway that provides uninterrupted power during grid outages. Designed for single-phase installations, it automatically switches between on-grid and off-grid modes to keep your essential (or all) household circuits running without interruption.
How it works
The EPS-BOX-SP sits between your Fox ESS inverter, utility supply, and household circuits.
Normal Operation – When the grid is active, power flows normally from your solar and grid supply.
Power Outage – The EPS-BOX-SP instantly disconnects from the grid and switches to your battery and solar supply, maintaining power to your home.
Grid Restoration – When the grid returns, it seamlessly reconnects and resumes standard operation.
...except that it doesnt....when the power cut happened the whole house went off, then a few seconds later (!!!!) the supply to the house resumed from the battery......when the power came back again the same thing happened
I later ran the test again this time using the supply isolator switch to give a clean break and exactly the same happened.....router died, NAS offline, CCTV offline, PC shutdown potentially with open files then went offline etc. etc
Even this says the switchover time is only 20mS
https://www.google.com/search?q=fox+kh7 ... fId=ChxjMe
This is exactly the scenario I was hoping to avoid!
Completely unrelated but it is now pitch dark but the panels are showing 240V albeit at zero current...
You are obviously upset, but what Inverter do you have, and what errors are showing on the screen?
If you have a small 3.68kW Inverter and 5kW load, it won't handle it.
If your battery SoC is not enough, it won't work either.
Then theres the chance they wired things up wrong.
If you can provide more details, then some help can be given hopefully.
If you have a small 3.68kW Inverter and 5kW load, it won't handle it.
If your battery SoC is not enough, it won't work either.
Then theres the chance they wired things up wrong.
If you can provide more details, then some help can be given hopefully.
Hi, indeed I am not happy.....
system comprises:
14 x Aiko Neostar 2p plus 475W panels (6.6 kWP)
Fox EP12 10.4kW usable battery (>40% SOC)
FOX KH7 7kw hybrid inverter
EN-EPS-BOX-SP gateway
Pretty much all perfectly matched as far as I can tell...
system comprises:
14 x Aiko Neostar 2p plus 475W panels (6.6 kWP)
Fox EP12 10.4kW usable battery (>40% SOC)
FOX KH7 7kw hybrid inverter
EN-EPS-BOX-SP gateway
Pretty much all perfectly matched as far as I can tell...
Last edited by davidwf15 on Tue Mar 31, 2026 9:02 pm, edited 1 time in total.
Same inverter as mine, should be able to handle 7kW EPS load... unless you was using more than that at the time.
Do you have fault codes on Inverter screen?
I would expect grid loss and Voltage warnings to be stored (and usually in the FoxCloud2.0 App you can view once running) on the Inverter screen/history.
Do you have fault codes on Inverter screen?
I would expect grid loss and Voltage warnings to be stored (and usually in the FoxCloud2.0 App you can view once running) on the Inverter screen/history.