Too many disconnect options -- help choosing please!

[TheHappyNomads]

I'm hoping to make the final couple of purchases of equipment to get my system installed. I'm down to fuses, cables\wiring, and disconnects. I have been reading through different build threads and there seem to be a ton of OV disconnect options and I really would love some advice on which one(s) make the most sense.

4s2p 415w roof top panels feeding (2) LV6548s

In some of Will's videos I see an enclosed DIN Breaker PV Disconnect, many others have recommended IMO units and I've seen a few Square D H361s mentioned as well. I will be in a non-grid feeding setup but will access grid power for low PV days to charge 48v battery system.

IMO style PV disconnect on roof at each string of panels?

DIN Breaker style disconnect mounted near LV6548s?

Square D H361 mounted near LV6548s?

Something else? Both? All of these lol???

Thanks

 

[pvgirl]

Roof top panels will most likely need panel level rapid shutdown. For NEC code compliant install you will need something listed, which many of the random breakers, and din boxes on amazon are not. The IMO disconnects are a low cost option that can disconnect up to 4 strings with one switch, the disadvantage is that these are plastic and generally can't be used indoors. Metal disconnects such as the square D, can be used indoors, but only disconnect one string. Midnite solar has breakers and metal boxes that can also be used as disconnects.

 

[TheHappyNomads]

You know what, I'm an idiot, I looked back at the permit sheet from the city and I have my answer. I'll need a rooftop PV disconnect like the IMO at the strings and then another disconnect by the LV6548s.

I suppose my answer is IMO\some variation on the roof.

 

[MaikaiLifeDIY]

In my setup, I use the Chatixi brand mini DC breakers for each string of panels.

I have 30 panels 5 in each series string and I use one of these breakers for each string. Do I believe they're the best on the market and will protect me from everything??? No, they're simply a switch for me to turn the power off per string for isolation/testing purposes and they have the added benefit of tripping if there is an over-current situation.

There are lots of people who will go into analysis paralysis over engineering specs, certifications, etc, and at the end of the day, it's about code compliance, and mostly your budget/risk ratio, which differs per individual.

As @pvgirl mentioned they do not suffice for rapid shutdown, those systems to be 50 state compliant must shut the power down at the panel and require communication between wherever the button is and the panels. Tigo comes to mind as a very common solution that has the optional benefit of optimizers that work great when building a heterogeneous system.

 

[EJansen]

The IMO disconnects are a low cost option that can disconnect up to 4 strings with one switch, the disadvantage is that these are plastic and generally can't be used indoors.

This is interesting and the first i've read of this. Why can't they be used indoors? Is it because all DC conductors are supposed to be in metal conduit?

The more I read your posts, the more I find wrong from a code compliance perspective with my system - as seen between my old inverters.



Since the EG4 18KPv has a PV Disconnect, I assume I don't need those anymore, but I do like the additional disconnect between the arrays and the inverter.

Even if I didn't need them there, and would be compliant with just the 18KPv's disconnect, I'm guessing just because they're there, they would cause a failed inspection?

 

[pvgirl]

This is interesting and the first i've read of this. Why can't they be used indoors? Is it because all DC conductors are supposed to be in metal conduit?

The more I read your posts, the more I find wrong from a code compliance perspective with my system - as seen between my old inverters.

View attachment 176013

Since the EG4 18KPv has a PV Disconnect, I assume I don't need those anymore, but I do like the additional disconnect between the arrays and the inverter.

Even if I didn't need them there, and would be compliant with just the 18KPv's disconnect, I'm guessing just because they're there, they would cause a failed inspection?

The PV DC circuits inside buildings, must be in metal conduit, raceway, or enclosures, for the whole run under NEC 2020 and later, NEC 2017 only requires metal to the first disconnect, which should be metal as well. The DC disconnects built in to inverters will provide the required disconnect so no other disconnect is needed at the inverter.

 

[EJansen]

The PV DC circuits inside buildings, must be in metal conduit, raceway, or enclosures, for the whole run under NEC 2020 and later, NEC 2017 only requires metal to the first disconnect, which should be metal as well. The DC disconnects built in to inverters will provide the required disconnect so no other disconnect is needed at the inverter.

OK, so in retrospect, if I ran the conduit all the way to the trough, and put the IMO Disconnects in there, then I assume, technically it would be good to go; Pending AHJ ruling of course.

I'm pretty sure the IMO switching part can actually come out of the plastic housing since I think it mounts to a DIN rail inside of the housing.

 

[pvgirl]

OK, so in retrospect, if I ran the conduit all the way to the trough, and put the IMO Disconnects in there, then I assume, technically it would be good to go; Pending AHJ ruling of course.

I'm pretty sure the IMO switching part can actually come out of the plastic housing since I think it mounts to a DIN rail inside of the housing.

With the disconnects in the trough, they might not comply with rules in the code for access to disconnects to not expose the operator to exposed live parts.

 

[TheHappyNomads]

As @pvgirl mentioned they do not suffice for rapid shutdown, those systems to be 50 state compliant must shut the power down at the panel and require communication between wherever the button is and the panels. Tigo comes to mind as a very common solution that has the optional benefit of optimizers that work great when building a heterogeneous system.

I don't think I necessarily have to have a rapid shutdown considering the permit app says "if another means of rapid shutdown is not available use dc disconnects within 3' of panel"

Am I reading that correctly?

 

[pvgirl]

I don't think I necessarily have to have a rapid shutdown considering the permit app says "if another means of rapid shutdown is not available use dc disconnects within 3' of panel"

Am I reading that correctly?

Per that document, local requirements would allow you to use a disconnect within 3 feet of the panel, as an alternative to a rapid shutdown system.

 

[TheHappyNomads]

How many amps do I need per disconnect?

 

[Jim in Florida]

My question would be how far off the ground would a cutoff switch need to be for a rooftop panel install assuming the panels went right to the roofs edge. Could it be reached without a ladder?

 

[pvgirl]

How many amps do I need per disconnect?

Amp rating should be greater then: Isc of the panels * number of strings in parallel * 1.56

 

[pvgirl]

My question would be how far off the ground would a cutoff switch need to be for a rooftop panel install assuming the panels went right to the roofs edge. Could it be reached without a ladder?

Disconnect switches generally aren't required at or adjacent the roof, outside of special local requirements like ones in Hayward, CA mentioned earlier in the thread. Their are restrictions in IRC(International residential code) on panel placement to insure there are paths for firefighter access to the roof.

 

[Jim in Florida]

Disconnect switches generally aren't required at or adjacent the roof, outside of special local requirements like ones in Hayward, CA mentioned earlier in the thread. Their are restrictions in IRC(International residential code) on panel placement to insure there are paths for firefighter access to the roof.

Going back to the disconnect needing to be within 3 feet of the panel and originally stated a rooftop array. It would seem a manual disconnect would be impractical for this setup unless you had a really low roof structure.

 

[pvgirl]

Going back to the disconnect needing to be within 3 feet of the panel and originally stated a rooftop array. It would seem a manual disconnect would be impractical for this setup unless you had a really low roof structure.

In that case the disconnect, allowed as an alternative to rapid shutdown in Hayward, CA, is on the roof so firefighters on the roof can shutdown the array.