Ampster
Renewable Energy Hobbyist
Merry Christmat to you as well.
What I'm learning about DIY Enphase and Hoymiles Microinverters
- Thread starter ncsolarelectric
- Start date
fromport
Solar Addict
You mean:
Your Enphase IQ battery 3T generated the micro grid and your AC coupled DIY hoymiles inverters (powered by batteries) helped.
ncsolarelectric
Engineering Support CEO
Yes, and our fear was that the outage would last all night and my IQ Battery 3T would only last about 2-1/2 hours with the heater running. We only have electric heat here. The DIY battery setup allowed me to run the Enphase battery at only 200W so that it could last all night.
It's great that your ad-hoc AC battery worked but it really seems like a different solution without iQ battery would have been simpler/cheaper.
ncsolarelectric
Engineering Support CEO
Probably, but I fell for Enphase and already had it in place. However, there are not many choices for UL 1741 "SA" qualified off-grid inverters that can do Freq/Watt control of the output. The new EG4 Hybrid says it is, so I would like to try this with one of those, but I can't afford one right now. I don't have enough subscribers to source it yet.
Quattrohead
Solar Wizard
Which one do you want? Maybe signature solar will sponsor you by sending you one to test out because obviously if you can make it work they will make them sell.Probably, but I fell for Enphase and already had it in place. However, there are not many choices for UL 1741 "SA" qualified off-grid inverters that can do Freq/Watt control of the output. The new EG4 Hybrid says it is, so I would like to try this with one of those, but I can't afford one right now. I don't have enough subscribers to source it yet.
ncsolarelectric
Engineering Support CEO
The new Hybrid 8kW hybrid is the only one that might work because it is 1741 "SA" certified. The 6kW doesn't say one way or the other.
What is ‘SA’ and why might one want it?
These NEP Microinverters: https://northernep.com/downloads/technical-sheet/BDM-600-Microinverter.pdf
State: ‘Globally certified for UL1741, SAA, TUV, VDE-AR-N 4105, VDE 0126, G83/2, CEL 021, IEC61727, EN50438, ABNT NBR 6149/16150’
Is that the same thing?
ncsolarelectric
Engineering Support CEO
UL1741SA has the specifications included for Freq/Watt and Volt/Watt control, that 1741 didn't have.
So 1741SA is just basic throttling of output through frequency shift (or voltage shift)?
I thought for several years now all Microinverters approved for sale in California needed to support that.
The APS-DS3: https://northernep.com/downloads/technical-sheet/BDM-600-Microinverter.pdf
also says: ‘CA Rule 21 (UL 1741 SA)’
While the detailed table of the NEP BDM600 states:
‘UL 1741 CSA C22.2 No. 107.1 IEEE 154’
So don’t all of these Microinverters support frequency shift and is there any reason either of them would not work in your setup for backup power as well as your Enphase Microinverters?
ncsolarelectric
Engineering Support CEO
You're missing the point. Grid-tied inverters have UL1741SA. Off-grid inverters mostly don't have UL1741 at all, or only have UL1741 without the SA, because they are not grid-tied. The new EG4 8kW is the ONLY one I've seen that is both, outside of Tesla, Enphase, & Generac.
Ahhh, gotcha. I though you were referring to the Microinverters themselves, not the hybrid inverters that can control them for backup power when the grid is down.
That makes slot more sense and thanks for clarifying.
zanydroid
Solar Wizard
@ncsolarelectric I'm curious about a related, possibly "opposite" application of Hoymiles export management. IIRC, you use it here to force the microinverters to behave like AC coupled batteries in local consumption only mode.
AC coupled systems typically have a recommended ratio of (solar AC output / battery inverter output) and and (solar AC power / battery capacity) when running off-grid. Do you think the export management can be used to adjust the output of a Hoymiles string to conform with this ratio? One worry is the 15-30 second response time you list above in the export management. I'm not sure how much value it adds on top of the frequency shift.
AC coupled systems typically have a recommended ratio of (solar AC output / battery inverter output) and and (solar AC power / battery capacity) when running off-grid. Do you think the export management can be used to adjust the output of a Hoymiles string to conform with this ratio? One worry is the 15-30 second response time you list above in the export management. I'm not sure how much value it adds on top of the frequency shift.
ncsolarelectric
Engineering Support CEO
Hi Z,
All you can do is set the maximum export power limit, and determine where to put your meter CTs, per the diagram shown.
I've seen the inverters frequency shift the output current on their own to prevent over voltage on the microgrid, so that is apparently a hardware safety that adjusts the power factor much faster than 15-30 seconds. But true export control by reducing the output current is much slower as it depends on the RS485 and Wifi network to get the message from the Meter => DTU => Inverters. It takes time.
All you can do is set the maximum export power limit, and determine where to put your meter CTs, per the diagram shown.
I've seen the inverters frequency shift the output current on their own to prevent over voltage on the microgrid, so that is apparently a hardware safety that adjusts the power factor much faster than 15-30 seconds. But true export control by reducing the output current is much slower as it depends on the RS485 and Wifi network to get the message from the Meter => DTU => Inverters. It takes time.
zanydroid
Solar Wizard
Thanks for the UI pic, that is helpful. IIRC this can be set over their modbus API too.
Putting down a couple thoughts for anyone who might come across this thread in the future.
I think the export management can help in a few ways —
1) don’t have to frequency shift as much if the overproduction occurs over a slow timescale. This leaves more “precision” available to make small adjustments
2) another knob to tweak if AC coupling is not as stable as desired
3) provides redundancy on top of frequency shift in case one or the other mechanism gets confused
If this is just used to clip the mid day production bump, 15-30 seconds is probably fine since the change is pretty slow.
Can’t see how it would hurt other than clipping more than needed, compared to if the solar panels were DC coupled or using faster responding microinverters (maybe the PLC ones are quicker).
In the normal export control case, 15-30 seconds will not respond quickly enough to hide appliances turning off, so it depends on the POCO export agreement as to whether averaging it out over time is acceptable. If it’s not, then this is not the right system. I believe Hoymiles targets Australia and Germany and has examples in their application notes for configuring export limits appropriate to those markets.
15-30 seconds with 2.4G radio control is probably not good enough to qualify for reducing the size of circuit conductors, and I’m not sure this feature is listed for that anyway.
Putting down a couple thoughts for anyone who might come across this thread in the future.
I think the export management can help in a few ways —
1) don’t have to frequency shift as much if the overproduction occurs over a slow timescale. This leaves more “precision” available to make small adjustments
2) another knob to tweak if AC coupling is not as stable as desired
3) provides redundancy on top of frequency shift in case one or the other mechanism gets confused
If this is just used to clip the mid day production bump, 15-30 seconds is probably fine since the change is pretty slow.
Can’t see how it would hurt other than clipping more than needed, compared to if the solar panels were DC coupled or using faster responding microinverters (maybe the PLC ones are quicker).
In the normal export control case, 15-30 seconds will not respond quickly enough to hide appliances turning off, so it depends on the POCO export agreement as to whether averaging it out over time is acceptable. If it’s not, then this is not the right system. I believe Hoymiles targets Australia and Germany and has examples in their application notes for configuring export limits appropriate to those markets.
15-30 seconds with 2.4G radio control is probably not good enough to qualify for reducing the size of circuit conductors, and I’m not sure this feature is listed for that anyway.
ncsolarelectric
Engineering Support CEO
Tell them you are an installer.
One more subtle way for Enphase to sell more batteries.Yup. I received approval and final certification this morning. Yay!
I also learned that they use an inaccurate rule of thumb regarding NEC 2017, 710.15(A). They said regarding my SLD that the ESS must provide less than or equal to the largest circuit breaker in the backup sub-panel. That is not what the code says. The code says, that the capacity of the ESS "...shall be equal to or greater than the load posed by the largest single utilization equipment connected to the system." It is clear throughout the code book that "utilization equipment" is referring to the actual loads themselves and not the size of the circuit breakers in the panel. Clearly, such a restriction would be unreasonable considering Eaton, SQD, GE do not make AFCI breakers of values less than 15A, or breakers less than 10A in general. The wiring must be sized appropriately for the breaker, but the breaker value is not what NEC 710.15 is looking for. They almost had me convinced I was screwed using an IQ Battery 3T, because I can't get 6A breakers! Thankfully, I verified exactly what the code says and I'm good with my breaker ratings as long as my loads don't pull more than 5.33A continuous, or 6.33 surge at 240V.
You cought it, many will miss it and buy another 3T.
Cheers!
Is that smaller PCB on lower right your current controller?
Is the design finalized?
Has it gone on for UL certification?
Are there any specs you can share?
Interested in any update you can provide.
Interested to understand whether those December 2022 final production samples actually ended up being final as well as any schematic or drawing you might have that you can share of how your whole rig is wired up…I'll be din-rail mounting the current controllers next to those 10A DC breakers. There is a 15A battery charger sitting in the bottom, that has no mounting brackets or available screw holes to mount it.
