I’m a relatively new Fox customer based in the U.K. I currently have a fully working 3-Phase ‘hybrid’ setup composed of 5 x Foxx EP11 batteries, a H3 Pro 15 inverter, and 31 Aiko 450w solar panels each with its own associated Enphase micro inverter.
I would like my setup to be able to switchover and continue to operate fully (‘whole house’ mode) using solar generation and stored battery power, in the event of a full grid outage. I’m aware that you can have a single plug socket or a single mains circuit become live in the event of a full grid outage fairly easily, but I’m seeking auto-cutover for the whole house.
My installer told me at the point of installation that my system could not do this, but that new products were coming out from fox ‘soon’ that could enable this. I spoke with Fox technical support recently who told me that a new product was indeed coming out later this year that will meet my needs, specifically for 3-phase systems. The new product is a ‘EPS BOX PRO-HC’ I’m told.
Is anyone else aware of, or tracking, this upcoming new EPS product?
Have a read here about the single phase product, there is a delay in switching gear that you might not like
viewtopic.php?p=15407#p15407
viewtopic.php?p=15407#p15407
Thanks for the link. That is indeed not what Fox infer on their website. I can see (and agree with) your frustration here.
I did spot that a 2-3 second cutover delay would occur even with the new EPS product, which seems unavoidable. I currently have a small UPS that protects my NAS, NUC and Unifi kit which gives me about 10 mins of cover in a power failure (its been tested a few times). The battery in the UPS is quite old now so I could probably move that up to 20 mins with a new battery and/or a larger UPS to protect this most critical equipment. Even with the current UPS in place, I'll be able to accommodate a sub 10s cutover period without issue I think. None of that will protect things like fridges or freezers that are currently wired into the mains, which I've seen first-hand blow during a power cut and restoration. Hopefully the Fox equipment will at least smooth some of that out spikiness out in the power supply.... (he hopes).
I did spot that a 2-3 second cutover delay would occur even with the new EPS product, which seems unavoidable. I currently have a small UPS that protects my NAS, NUC and Unifi kit which gives me about 10 mins of cover in a power failure (its been tested a few times). The battery in the UPS is quite old now so I could probably move that up to 20 mins with a new battery and/or a larger UPS to protect this most critical equipment. Even with the current UPS in place, I'll be able to accommodate a sub 10s cutover period without issue I think. None of that will protect things like fridges or freezers that are currently wired into the mains, which I've seen first-hand blow during a power cut and restoration. Hopefully the Fox equipment will at least smooth some of that out spikiness out in the power supply.... (he hopes).
for info, here is the data sheet for the upcoming 3-phase EPS that Fox told me about:
https://www.fox-ess.com/Public/Uploads/ ... 250905.pdf
https://www.fox-ess.com/Public/Uploads/ ... 250905.pdf
You can run all your back up on auto contactors. You need to spread the load out over the 3 phases as you only have 5kW/phase with a 15kW inverter.wilks wrote: ↑Sat Apr 18, 2026 8:59 pm 3-Phase ‘hybrid’ setup composed of 5 x Foxx EP11 batteries, a H3 Pro 15 inverter, and 31 Aiko 450w solar panels each with its own associated Enphase micro inverter.
I would like my setup to be able to switchover and continue to operate fully (‘whole house’ mode) using solar generation and stored battery power, in the event of a full grid outage.
My installer told me at the point of installation that my system could not do this,
You could do your system with a 4pole 2NO 2NC (below) and a 2pole 1NO 1NC contactors. To cover all 3 phases.
You can run 4 circuits on a 4 pole and 2 on a 2 pole.
On a 4 pole R2 & 2 (combined) go to 2 circuits as do R4 & 4 (combined).
R1 & R3 go to 2 separate EPS ports and 1 & 3 go to the grid.
A1 to Grid L and A2 to Grid N.
Normally power runs from grid 1 and 3 to CBs connected to R2&2 & R4&4.
In a blackout the power it cut to the coil A1 & A2 the contactor will automatically switch to R1 & R3 and thus runs off the EPS. When the power is restored the contactor coil it automatically switches back to the grid.
Please do NOT consider the solution suggested above for several reasons - use a proper auto transfer switch (ATS) system.
Just five reasons not to consider netsheriff's' suggestion:
Just five reasons not to consider netsheriff's' suggestion:
- Single phase failure may not be detected, likely resulting in the inverter tripping out or possible back-feed to grid (safety issue)
- Short duration breaks will result in rapid change-over from mains to inverter supplying the load and back likely causing damage to the contactors
- No true detection of out of tolerance of mains voltage, although the contractor coil is nominally rated at 230v its pull-in and drop-out voltages are likely outside the normal tolerance for mains voltages
- Using two contractors in the manner suggested can result in the change-over of all phases not being simultaneous, increasing the likelihood of equipment damage
- An ATS will provide a means to perform a manual change-over if necessary
H1-3.7-E-G2, 2xEP11-H and 6Kw solar
Manager(ARM):1.76
Master:1.57
BMS:1.012
Manager(ARM):1.76
Master:1.57
BMS:1.012
Well you had better relay (pardon the pun) your concerns to Aussie installers as this is what is done there or a manual change over switch as there are no ATS boxes (compatible with Fox in Au atm).
If a single phase fails (very highly unlikely), if it is the phase your coil is on then that will trigger your backup working if not and one phase is down (turn off the main dirsto board - best) or you can manually/remotely (however you have the coil MCB wired) switch it off to trigger the backup. EPS is protected with an MCB.
If you think you are going to get lots of short duration breaks and rapid change over of the coil (unlikely and you probably have bigger problems at foot) then install a time delay relay on the coil. That is what is in an ATS box (along with auto contactors). The EPS is also protected with a MCB.
Coil voltage are not outside the normal ranges.
Coils within spec will not result in non-simultaneous change over.
As mentioned above, you should have a protecting MCB on the coil and this can be used as a manual change over switch
If a single phase fails (very highly unlikely), if it is the phase your coil is on then that will trigger your backup working if not and one phase is down (turn off the main dirsto board - best) or you can manually/remotely (however you have the coil MCB wired) switch it off to trigger the backup. EPS is protected with an MCB.
If you think you are going to get lots of short duration breaks and rapid change over of the coil (unlikely and you probably have bigger problems at foot) then install a time delay relay on the coil. That is what is in an ATS box (along with auto contactors). The EPS is also protected with a MCB.
Coil voltage are not outside the normal ranges.
Coils within spec will not result in non-simultaneous change over.
As mentioned above, you should have a protecting MCB on the coil and this can be used as a manual change over switch
Last edited by netsheriff on Sun Jul 05, 2026 8:24 am, edited 1 time in total.
What the Aussies do is their business, but there certainly are 3-phase ATS boxes available out there.
Back to the OP's question, I've not yet seen any information other than the data sheet you link to.
With the solar panels being AC coupled this will likely add complications which could be difficult or impossible to overcome unless the new EPS box offers a way around this.
If the solar panels were DC coupled to the inverter then it's relatively simple.
Back to the OP's question, I've not yet seen any information other than the data sheet you link to.
With the solar panels being AC coupled this will likely add complications which could be difficult or impossible to overcome unless the new EPS box offers a way around this.
If the solar panels were DC coupled to the inverter then it's relatively simple.
H1-3.7-E-G2, 2xEP11-H and 6Kw solar
Manager(ARM):1.76
Master:1.57
BMS:1.012
Manager(ARM):1.76
Master:1.57
BMS:1.012
Dunno about UK but an auto contactor is fine and compliant with regs in Au anyway.
Here is an article about using a contactor.
https://www.solarquotes.com.au/blog/bac ... contactor/
All systems in Vic Au must pass a safety audit b4 they can be turned on.
A Certificate of Electrical Safety which must be issued by a licensed electrical inspector before your system can be connected to the energy network.
https://www.solar.vic.gov.au/safety-aud ... lar-system
https://www.energysafe.vic.gov.au/certi ... -consumers
And here is an image of a grid compliant 3 phase back up which has been passed by a licensed electrical inspector.
Note the auto contactors, MCBs for EPS and coil also LEDs for the gird. It would be relatively straight forward to add a time delay relay if you wanted it.
Here is an article about using a contactor.
https://www.solarquotes.com.au/blog/bac ... contactor/
All systems in Vic Au must pass a safety audit b4 they can be turned on.
A Certificate of Electrical Safety which must be issued by a licensed electrical inspector before your system can be connected to the energy network.
https://www.solar.vic.gov.au/safety-aud ... lar-system
https://www.energysafe.vic.gov.au/certi ... -consumers
And here is an image of a grid compliant 3 phase back up which has been passed by a licensed electrical inspector.
Note the auto contactors, MCBs for EPS and coil also LEDs for the gird. It would be relatively straight forward to add a time delay relay if you wanted it.