Sanity check on those PV solar (high voltage) disconnect switch - located in US

[Zucca]

System was installed in my home by a solar company 3 effing years ago.
I did most of the design, they were responsible manly to go on the roof (5 PV strings), put the solar panel and bring the cables down.

I am from Europe and had not too much experience with US residential breakers.

They told me they will install PV disconnect switch. I was fine with that. They looked OK from far away okay, big (to sustain a VDC arc opening) and 15A.
PV spec needed: VDC 500V and 8ADC min, in each PV string.

Two days ago I got one of my worst "wait a minute moment", are those 15A split phase US residential AC breaker?






What do you think I should do? Yes I will forward this thread to them (if they are still in business)...

[Psi]

[synccond]

QO breakers are listed for DC up to 125V (if you buy the product with that label).  However, you are stating 500V.
Would have to install a J-frame for 500V applications.  Significantly larger and big bucks.
You might be better off going with fused disconnects.

[Psi]

You might be better off going with fused disconnects.

Considering how rarely they would blow, yeah, fuses does sound better. Assuming that is legal where OP is.
I'm assuming DC breakers are really expensive, but perhaps with so many solar setups they aren't. dunno.

[Monkeh]

Solar systems don't generally need DC breakers - under what condition is a series string going to produce an overcurrent fault?

Solar systems do need some point of DC isolation. Those are not it. DC rated rotary isolators are easily obtained, at least in the EU, and under no-load conditions (Turn the inverter off. You can do that via the AC isolator.) you can simply disconnect the panels directly.

Those, obviously, are not DC rated breakers or isolators. They'll probably stand off the OCV when open, but opening them under load might not work out.

[nctnico]

Solar systems don't generally need DC breakers - under what condition is a series string going to produce an overcurrent fault?

Solar systems do need some point of DC isolation. Those are not it. DC rated rotary isolators are easily obtained, at least in the EU, and under no-load conditions (Turn the inverter off. You can do that via the AC isolator.) you can simply disconnect the panels directly.

Those, obviously, are not DC rated breakers or isolators. They'll probably stand off the OCV when open, but opening them under load might not work out.

The best option is to remove these breakers. If one trips under load, it could (very likely) arc over and start a fire. But realistically I don't see how a solar panel can generate more current than it's maximum spec. So having breakers on solar panels is moot. It can help to have DC GFIs though for safety reasons. For DC breakers: check if there isn't one in the inverter already. My Growatt inverter has both a DC breaker and GFI built in. Remember that having more stuff installed, more things can go wrong. Australia used to have the requirement of a DC switch but that backfired badly. Literally.

[Psi]

My gut says a 10kA AC breaker will be able to stop DC 500V limited to 8A without instantly failing, but that it will severely shorten the lifespan before catastrophic melting/failure/fire.  But I wouldn't what them in my house even if they could survive a few trips.

I'm not sure what your house insurance would do if one did start a fire, you could sue the company that installed them but that is probably way more annoying than just sorting this out now.

[nctnico]

My gut says a 10kA AC breaker will be able to stop DC 500V limited to 8A without instantly failing, but that it will severely shorten the lifespan before catastrophic melting/failure/fire.  But I wouldn't what them in my house.

I've seen DC arc over at much lower voltages and currents. Switching DC is nasty. Check the DC derating graphs on relays for example.

[Psi]

My gut says a 10kA AC breaker will be able to stop DC 500V limited to 8A without instantly failing, but that it will severely shorten the lifespan before catastrophic melting/failure/fire.  But I wouldn't what them in my house.

I've seen DC arc over at much lower voltages and currents. Switching DC is nasty. Check the DC derating graphs on relays for example.

yeah. I think we can all agree DC is nasty and AC only switches do not belong in DC circuits.

[Zucca]

Thanks for confirming that those can't be installed for DC disconnecting/isolation. Thinking who did that was a hired solar company makes me scream. How many many other customers are not aware about the risk of operating them when the sun is out?

As long you keep them close, I suppose there is no risk of smoking anything out.

Anyway let's fix this madness, DIN rail mount please.I was tempted by this

https://www.ebay.com/itm/114252077692

but it looks cheap scammy chinesium stuff. No bueno.

Lately I am more and more attracted by ABB products, so I got three OTDC16F4


https://new.abb.com/products/1SCA121461R1001/otdc16f4

Will report once I have them. Meanwhile I need to find a decent din rail enclosure, they are tall guys...

[Someone]

Thanks for confirming that those can't be installed for DC disconnecting/isolation. Thinking who did that was a hired solar company makes me scream. How many many other customers are not aware about the risk of operating them when the sun is out?

Find the compliance/safety certificate for the work and take it up with the regulator, that is what the lodgement of certificates is supposed to be for.

[Zucca]

Solar systems don't generally need DC breakers - under what condition is a series string going to produce an overcurrent fault?

Solar systems do need some point of DC isolation.

This, 110% this. It is nice to be able to turn the panels off if necessary, it is much harder to remote control the sun. 

[synccond]

Solar installs are subject to permitting and inspection.  Did you pull a permit?  An inspector would have flagged this immediately.  If not, who is ultimately at fault?

[Zucca]

quick fix for now:




I still have no idea how thing works here in South Carolina. I had a gentleman agreement with the solar company, once I was done with my final touches (48VDC batteries) I would have informed them and they would have send out the inspector. I did notified them when the system was working but nobody showed up. Since I was feed up with them (I corrected myself some other flaws in the installations....) I did not follow up. Here the contract I signed:

Contractor warrants that the will be constructed and installed in a good workmanlike manner
according to the standards of care and diligence generally practiced by solar engineering,
construction, and installation companies when installing residential photovoltaic solar power
systems of a similar size and type as the System in the geographic region where Buyer’s
Property is located, and pursuant to (i) good engineering design practices, (ii) manufacturer’s
instructions, (iii) applicable law (including local codes and standards), (iv) required
governmental approvals and permits, and (v) applicable requirements of the local utility. This
5-Year Limited Workmanship and Installation Warranty will extend for a period of five (5)
years from the date installation of the System is completed by Contractor.

but it looks like I am/was responsible to get the permit

Scope of Work/Permits: Contractor shall perform the installation of
the specified project. Buyer acknowledges that Contractor does not provide, or arrange for or
assume any responsibility for, architectural/engineering services or structural changes to
dwellings or buildings unless otherwise noted in the Contract. Contractor shall have the right
to determine method, details, and means of performing the work. Contractor and/or its
subcontractor(s) shall obtain the necessary building and electrical permits (“Permits”), and
ensure code compliance associated with the installation of the specified project. Buyer shall
cooperate with Contractor and/or its subcontractor(s) to obtain the Permits and meet code
compliance for the installation of the specified project. Buyer shall be solely responsible, at
the Buyers’ own cost and expense, to obtain any and all necessary zoning permits/licenses,
variances, special exceptions, easements, or any other governmental or nongovernmental
zoning-based requirements if required by Buyer’s municipal, state, federal or local
government or Buyer’s property owners association or similar organization.

Once I am done with my new transfer switch panel, I will make some calls to get the situation rectified.

[floobydust]

What is the welding cable for?
I'd get in trouble using that wire indoors - check its ratings for flammability, as well it's not in conduit and against a combustible (wood) surface, no cable clamps etc.

[Zucca]

What is the welding cable for?

1/0 AWG (100A fused) to feed the 48VDC batteries from the MPPT Victron RS. Should be fine.

[Psi]

yeah, around here all DC solar wires need to be in conduit.
But yeah, that's here, not where OP is.

Ah true, it's the Batteries to MPPT.  No idea what rules there are for charger to batteries.

[Zucca]

yeah, around here all DC solar wires need to be in conduit.
But yeah, that's here, not where OP is.

Ah true, it's the Batteries to MPPT MPPT to Batteries.  No idea what rules there are for charger to batteries.

FFY.

Absolutely the High VDC from the roof needs to be in a conduit. No discussion here, don't care about the code or where I am on this planet.

Now my concern shift to the "rapid shut down" button feature. What I was told/heard not sure if it is a legend or not: home is on fire,  the fireman would come they need to press the button to make sure the roofs gets shut down...
I did not install such thing and I don't want to.

I hope the inspector will not argue....