2 Systems tying to one main panel: eg4 18k pv + IQ7+

[zanydroid]

this is true. but I'd rather have a 8% return on $30k than a 16% return on $5k.

This is confusing. I would say the following are slam dunks over 8% on $30K (unless that's blended and factoring in the 16% on $5K):

16% return on $5K and then diversify $25K elsewhere.

16% on $5K, and then $25K on 8% returning solar equipment.

 

[Danke]

New build totally off grid. Workshop/garage that is a separate building will have PV on the roof. Location does not require permits or inspection. What are the pros and cons of adding RSD units at the panel level?

 

[zanydroid]

New build totally off grid. Workshop/garage that is a separate building will have PV on the roof. Location does not require permits or inspection. What are the pros and cons of adding RSD units at the panel level?

Pros:
Save money. Fewer points of failuire.

Cons:
VS crime scene investigation / firefighters getting upset at you b/c they wasted time looking for a shutdown, or you didn't have a system map placard in standard format.

 

[Danke]

Pros:
Save money. Fewer points of failuire.

Cons:
VS crime scene investigation / firefighters getting upset at you b/c they wasted time looking for a shutdown, or you didn't have a system map placard in standard format.

If there’s a fire, place would be so far gone by the time the fire department got there, I don’t think they’d be crawling on the roof.

Is there a greater fire hazard at the panel level if I don’t have an RSD device?

 

[zanydroid]

Is there a greater fire hazard at the panel level if I don’t have an RSD device?

RSD is not for preventing fires. It’s for protecting firefighters from HVDC when they start swinging axes.

MPPT Arc fault detection/interruption does prevent fires and that is not available in a fair chunk of off grid equipment.

EDIT: it is required for installation on most structures, but not for basic UL1741. For instance I don’t believe those EG4/Deye hybrid heat pumps have it. I was considering it for an ADU but this was a dealbreaker.

 

[Hedges]

I think if AFCI triggers RSD, that is more likely to prevent a fire than AFCI alone.

Twice as many connections that could cause a fire, and if they are interspecies then much more likely.

 

[zanydroid]

I think if AFCI triggers RSD, that is more likely to prevent a fire than AFCI alone.

Twice as many connections that could cause a fire, and if they are interspecies then much more likely.

I am not sure how to tie the two together. Haven’t seen it in a manual. I assume AFCI will stop MPPT. Might need an integrated RSD transmitter to configure also triggering a RSD.

Stopping MPPT I think would be good for series arc. RSD would help for both.

 

[Hedges]

Yes, AFCI stops current draw of MPPT. Where AFCI and RSD are both integrated into inverter, it might also turn off keep-alive, but only if the design spec or firmware coders happened to address that. Probably not an NEC requirement, so I'm not confident. Maybe this can be tested.

I picked up a couple Sensata AFCI modules, also Tigo keep-alive transmitter. If I do move my legacy system to roof I want to try using those together, and could have the AFCI signal cut AC to inverter, also cut keep-alive.

AFCI came before RSD, more likely to be in an older inverter. I think that is the case with SolArk as well. If an inverter had an error status output for AFCI, that could disable RSD.

 

[zanydroid]

I picked up a couple Sensata AFCI modules

How do these work? I assume they’re some kind of standalone AFCI.

AFCI came before RSD

(I assume you know this, just repeating it for others on the thread)

What I was getting at was that AFCI is often dropped (just as RSD is) esp for equipment designed for overseas, and this is a problem for inspections even if one chooses a UL1741 off grid inverter (just because it has the listing, does not guarantee it has the necessary features to pass in all possible installation scenarios).

 

[the.shining]

This is confusing. I would say the following are slam dunks over 8% on $30K (unless that's blended and factoring in the 16% on $5K):

16% return on $5K and then diversify $25K elsewhere.

16% on $5K, and then $25K on 8% returning solar equipment.

Yes, its blended. I'm factoring in the high initial roi (16%) prior to battery. Once battery gets involves, roi suffers, but emergency off grid backup power is a nice tradeoff for the lower roi.

Can't get better than an 8% return though for the manageable risk. T bills at 5.5%, but doubt that will last. Stock mkts only avg 7% over time, so 8% is as good as it gets.

 

[Hedges]

How do these work? I assume they’re some kind of standalone AFCI.

Stand alone, I don't think on the market anymore, now that inverters integrate that.

Haven't tried them yet, but PV wires pass through inductive pickup. 24VDC is fed to the module. It has a relay output. So I would use it to trip a power relay and cut AC to inverter. Also to keep-alive.

(I assume you know this, just repeating it for others on the thread)

What I was getting at was that AFCI is often dropped (just as RSD is) esp for equipment designed for overseas, and this is a problem for inspections even if one chooses a UL1741 off grid inverter (just because it has the listing, does not guarantee it has the necessary features to pass in all possible installation scenarios).

UL1741 was good enough years ago.
SMA SWR 2500U was UL1741 (anti-islanding) and has a 1A fuse for ground fault detection.
The 5000US I'm now using I think are the same, except maybe ground fault doesn't use fuse.
10000TL-US-12 I used for a while has AFCI.
TriPower 30000TL-US does not have RSD keep-alive, but it does have capacitor discharge.
SB 7.0 -41, which I picked up and will install later, has keep-alive for RSD, also capacitor discharge.