DC & AC Disconnect for GridTied Inverter

quique

Im getting a head start on setting up the connections for my grid tied inverter.

I was wondering if i should get a DC Disconnect from a place like altestore.com or just buy a small breaker box from a local hardware store?

Found this one here:

http://www.affordable-solar.com/store/ac-dc-disconnect-enclosures/dc-disconnect-30a-600vdc-sunny-boy

BB.

Re: DC & AC Disconnect for GridTied Inverter

Looks OK. If you pull up the specs it is rated to 10-15 HP at 600 VDC.

You have to check the array voltage ratings (current, voltage, etc.) to make sure it meets the disconnect requirements. Or, many GT inverter manufacturers have a DC disconnect--sometimes it is an option.

You don't need a circuit breaker, and it will be hard to find a high voltage DC breaker that meets those ratings and will be cost effective.

Our host also has a SquareD disconnect--I have not checked the specifications closely--Call NAWS/double check if it will meet your needs (I don't work for NAWS, I am not in the solar business, and I am not "your" solar engineer):

http://www.solar-electric.com/sqd600vodcar.html

Have fun!
-Bill

solarix

Re: DC & AC Disconnect for GridTied Inverter

Ya, the HU361.. is the proper switch to use on the DC side. DC current is much harder to switch cause it doesn't self extinguish and the ratings on even this unit are for AC. The DC rating is substantially less. Usual practice is to put a couple of the switch poles in series to increase the rating. This is why most inverter manufacturers build in the DC switch using expensive special switches made for DC. Most AHJs have gone away from the requirement for an additional DC disconnect - are you sure you need this switch? In any case you won't find any suitable breaker box locally. They are all made for AC.
Also, the disconnect switch built into most GT inverters does not switch the AC side however and most AHJs will want you to add an AC disconnect switch (even though all GT inverters can't run when the grid is down. A basic DU221RB (30amp) or DU222RB (60amp) or actually the 3ph DU321RB is cheaper and more available. Some AHJ's don't like the SQ-D switches however as the AIC rating is dependent on being in line with fuses not breakers (read the fine print on the label) so use Eaton switches there. You won't find any of these switches locally either.

quique

Re: DC & AC Disconnect for GridTied Inverter

No I don't need this one. That's what I'm trying to figure out. I'm looking for the best dc and AC disconnect.

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok so I can use this for the DC Disconnect side. What about for the AC disconnect side?

Remember I will have to look for this stuff here in Honduras.

BB.

Re: DC & AC Disconnect for GridTied Inverter

Do you need a"lockable" AC disconnect?

In many places, the utility requires a disconnect the line man can access when nobody is home. Or they would just pull the meter.

-Bill

quique

Re: DC & AC Disconnect for GridTied Inverter

Not really. I just need both AC/DC disconnects to be easily found in my market, this will mean common products of big name lines such as SquareD or Schneider.

BB.

Re: DC & AC Disconnect for GridTied Inverter

If you don't need a GT AC disconnect, just the standard circuit breaker in the main panel is fine.

-Bill

quique

Re: DC & AC Disconnect for GridTied Inverter

Right because the GT inverter connects to the main panel anyway right? So pulling down the main breaker in the main panel we cut off power from the grid side to the GT Inverter, right?

Ok so I need to get a DU321RB or DU221RB...

BB.

Re: DC & AC Disconnect for GridTied Inverter

Yep--In (parts?) of California, I believe our utility no longer requires external AC disconnects--They trust the modern UL/NRTL Listed GT inverters will not back drive a "dead/failing" grid.

-Bill

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok im looking at the specs and it says that:

DU221RB is for 240VAC whereas

H361RB is for 600VAC.

Would this be a problem if my pv arrays may grow to be up to 600V?

Should I buy a H361RB for the DC side which incidentally is rated up to 600VDC and then a DU221RB for the AC side?

BB.

Re: DC & AC Disconnect for GridTied Inverter

You have to look at the VDC rating... VAC and VDC will (usually) have different maximum voltage and current ratings.

-Bill

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok the local guys have a d221nrb but they told me it wouldn't work because it's rated for 240vac where we will be using 600vdc.

They also told me it would need special dc fuses that they don't have.

Also, the hu doesn't have fuses, what would the need for them be.

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok, I got the electrician over and had him install the Disconnects. Here is a picture of the AC Disconnect. Its an HRU361rb:

Attachment not found.

Please disregard the fact that all 3 wires are green. I told him to buy the right color wires and replace it. But basically this would connect to the 2 hot and 1 neutral going into the Main AC Breaker panel, correct?

solar_dave

Re: DC & AC Disconnect for GridTied Inverter

Is a permitting agency involved? You are going to need to run conduit and a ground wire if they are. I would be doing the ground wire anyway.

SkiDoo55

Re: DC & AC Disconnect for GridTied Inverter

My comment on that is if that was a licensed electrician he needs it revoked. What's all of the Green wire for. No clamps chafe protection on box penetration. No clamps securing wire to wall etc.

quique

Re: DC & AC Disconnect for GridTied Inverter

Agree (SkiDoo55 & solar_dave)!

The green wire was the first mistake I called him on as well as the conduit. I didn't know about the chafing protection for the wires but it makes total sense and Ill be getting that with the conduit tomorrow. Therefore the clamps will be holding the actual conduit to the wall.

Thx guys!

DanS26

Re: DC & AC Disconnect for GridTied Inverter

If the green wires are coming from the inverter, then this switch is wired backwards. The blades will be energized in the open position. Not good!

Also, since the grid tied inverter is not a separately derived system, then the neutral should not be switched.

bill von novak

Re: DC & AC Disconnect for GridTied Inverter

quique wrote: »

The green wire was the first mistake I called him on . . .

Sounds like it's time for a new electrician. At this point you' might even be better off doing it yourself.

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok 2 important questions:

1) Why would the wires from the switch be wired backwards? The switch completes the circuit when in the closed position. But when open, as in the picture, it doesn't matter who is where, the circuit is open, isn't it? Isn't that the purpose of the disconnect? What am I not seeing here?

2) As for switching the neutral, so if I don't switch the neutral, then the neutral should go directly from the Main AC Breakers panel to the inverter?

DanS26

Re: DC & AC Disconnect for GridTied Inverter

quique wrote: »

Ok 2 important questions:

1) Why would the wires from the switch be wired backwards? The switch completes the circuit when in the closed position. But when open, as in the picture, it doesn't matter who is where, the circuit is open, isn't it? Isn't that the purpose of the disconnect? What am I not seeing here?

2) As for switching the neutral, so if I don't switch the neutral, then the neutral should go directly from the Main AC Breakers panel to the inverter?

1)The danger is that the blades in that switch in the open position are exposed. The exposed blades should not be energized because they could be a shock hazard. The lines from the utility should be connected to the top of the switch and lines from inverter should be connected to bottom (ie exposed blades) portion of the switch. In the open position the inverter has to shut down thus de-energising the exposed blades.

2) The grounded conductor (ie neutral) should always travel with the matching ungrounded conductors. Therefore make a continuous neutral connection in the switch box.

These are NEC rules. I see you are in a foreign country and probably do not have to comply with these safety rules. In any case you should make your installation as safe as possible.

quique

Re: DC & AC Disconnect for GridTied Inverter

Thanks for the exposed switch blade bit. I'll switch that over.

I don't have a comply agency but I still want to comply. :-)

About the neutral conductor, how would I make a direct connection? Inside the switch somehow or do I take it outside the switch to a block?

DanS26

Re: DC & AC Disconnect for GridTied Inverter

quique wrote: »

Thanks for the exposed switch blade bit. I'll switch that over.

I don't have a comply agency but I still want to comply. :-)

About the neutral conductor, how would I make a direct connection? Inside the switch somehow or do I take it outside the switch to a block?

You make that connection inside the switch box with an approved connection device rated for the wires being connected. There are grounding issues here which have also not been addressed.

You really should be working with a knowledgeable electrician who can make a safe installation compliant with local codes.

quique

Re: DC & AC Disconnect for GridTied Inverter

I already called for a new electrician.

Yes the chassis needs to be grounded as well.

Thanks for all the pointers.

quique

Re: DC & AC Disconnect for GridTied Inverter

DanS26

Could you point me to a place online where I could find those pieces that directly connect one side of the neutral with the other inside the switch? I need to find it for my "new" electrician so he can make the adjustment.

Thx

BB.

Re: DC & AC Disconnect for GridTied Inverter

They will look like this... This is a non-insulated version:



Or like this insulated version:



These are not the "right ones" per code... You should find some that are rated for use in an AC panel. You might get into an issue here--Generally, a knife switch would not have "multiple connections" inside the switch box, so I am not even sure if a Neutral (grounded or floating) is even legal/appropriate here.

The Neutral, not switched, should just pass directly through the box unbroken to the sub panel and connected to an isolated neutral bus there.

-Bill "not an electrician" B.

quique

Re: DC & AC Disconnect for GridTied Inverter

ok so in the worst case scenario I can just buy a small box with a bus and plug both neutrals into the bus, right?

DanS26

Re: DC & AC Disconnect for GridTied Inverter

or this:

http://www.amazon.com/Gardner-Bender-HSB-28-Butt-Splice/dp/B001AWP7OG/ref=sr_1_fkmr1_2?ie=UTF8&qid=1390426552&sr=8-2-fkmr1&keywords=underground+connector+%236+with+heat+tape

quique

Re: DC & AC Disconnect for GridTied Inverter

Ok so this is like just a splice with an insulation sleeve...

DanS26

Re: DC & AC Disconnect for GridTied Inverter

quique wrote: »

ok so in the worst case scenario I can just buy a small box with a bus and plug both neutrals into the bus, right?

No, do not do that. The neutral should pass thru the switch box.

Somehow I get the feeling you want to do this without hiring a qualified electrician. For your own safety and the safety of your family and property spend a few bucks and get a qualified electrician to make these connections. You will sleep better at night!!

quique

Re: DC & AC Disconnect for GridTied Inverter

It's not that, it's just that there are few qualified electricians here. I will hire one but I'd will always want to check with you.

I do plan to pass it through the switch box.