Toggling from one bank to another?

[12VoltInstalls]

Why? Serious Question.....not being a smart-azz.
The switch is rated for 240A max 120x2...each pack gets one leg of DPDT of cutoff switch on hot side of inverter.

The switch is AC rated, not DC rated.

The arc extinguishing feature of dc switches is typically a ‘snap’ action that coincides with the ms data on your chart.

AC switches cannot necessarily provide the distance to exceed the arc length potential or the quick break of the continuity to assure personnel safety never mind fire safety.

able to afford an Edelbrock and dyno it against a stocker....Then go for it

 

[pullin_gs]

The switch is AC rated, not DC rated.

The arc extinguishing feature of dc switches is typically a ‘snap’ action that coincides with the ms data on your chart.

AC switches cannot necessarily provide the distance to exceed the arc length potential or the quick break of the continuity to assure personnel safety never mind fire safety.

AC-only rated switches DO NOT provide distance&quick-break as you stated. No argument from me on that.
But you did not answer question as to how my application will burn down my house @36V DC with quench of arc-length a non-issue (even at a slow-break as outlined per IEEE guidance for low DC voltages) with architecture provided by knife-switch.

Thanks for the feedback.

PS: Not really pertinent to this conversation, but have you ever seen a knife-switch application on high-voltage transmission lines? It is a 10-second process and is pretty wild to see....search youtube.

 

[timselectric]

My problem with that cheap knife switch is not while switching (voltage). But while operating (amperage).
If they get the slightest bit warm, the contacts spread apart and the knife doesn't make good contact. Which compounds the problem.
I actually purchased one (for an AC application) , but never installed it because of this reason.

 

[timselectric]

And it appears that the terminals are also problematic.

 

[pullin_gs]

My problem with that cheap knife switch is not while switching (voltage). But while operating (amperage).
If they get the slightest bit warm, the contacts spread apart and the knife doesn't make good contact. Which compounds the problem.
I actually purchased one (for an AC application) , but never installed it because of this reason.

Thanks the detailed explanation of your concerns.
Base material is ABS plastic, it will deform under higher temps and could result in failure as described.
An issue such as a loose lug, exceeding current capability of switch contacts, a partially closed switch, or corroded contacts/lugs would be concerning. A runaway heat condition will eventually result in a catastrophic failure....which is true of any switch no matter the base material, but ABS will give way much sooner than other materials.

I need 25A and 100A power cutoff switches rated for 36Vdc......what are your suggested products?

And it appears that the terminals are also problematic.

The terminals are basic box-style mechanical lugs.
Box lugs will come loose unless a deterministic process is adhered to when clamping down , especially with STRANDED wire.
Process includes twisting wire about 10-degrees several times as you lightly tighten, repeat several times increasing torque on clamp screw each time.
Unless this is done THEY WILL WORK LOOSE as stranded wire settles in to take form of the clamp's receptacle cavity.
Also wire MUST be clamped from underneath, NOT TOP AGAINST SCREW! This is an easy mistake to make and has very costly implications.

 

[12VoltInstalls]

But you did not answer question as to how my application will burn down my house @36V DC with quench of arc-length a non-issue (even at a slow-break as outlined per IEEE guidance for low DC voltages) with architecture provided by knife-switch

Because I didn’t think using the switch has any margin of safety and is pretty inexpensive compared to a house fire, discussing the viability of using an inappropriate AC switch of any design without insuring the circuit never sees voltage over 5% (the derate assumption for AC switches with no published DC voltage and Amp parameters by the manufacturer) seemed a fruitless endeavor.

 

[oldmaninsaline]

I wouldn't use these for any serious AC loads . If they get warm the contact points separate from the knife.
And definitely wouldn't use them for DC.

I've used one for several years, rated at 660 volts @ 65 amps which seems to be a pretty serious load from my point of view. I've used them in a 240 volt environment on a folder at work without issues, 8 hour duty cycle when the stock "no longer available" switch from 1971 gave up.

 

[pullin_gs]

pullin_gs said:
But you did not answer question as to how my application will burn down my house.

Because I didn’t think using the switch has any margin of safety and is pretty inexpensive compared to a house fire, discussing the viability of using an inappropriate AC switch of any design without insuring the circuit never sees voltage over 5% (the derate assumption for AC switches with no published DC voltage and Amp parameters by the manufacturer) seemed a fruitless endeavor.

Fair enough. You punted.
Having a thorough understanding of the issues (mainly having to do with disconnect arcing) and how it is mitigated by contact-design does indeed allow one to assess real-world performance vs apply the most general and conservative "fit-all" assumption.
P

 

[SamDeleted]

OK, so after some more time searching the internet and help from this forum I've put together the attached drawing. Should work, right?

Hi mate maybe it's just me but I'm a bit confused about how you're wiring that battery bank up , does that all make sense

 

[timselectric]

I need 25A and 100A power cutoff switches rated for 36Vdc......what are your suggested products?

ASI NDB1-125C100-2 DIN Rail Mount High Current Circuit Breaker, 100 Amp, 2 Pole, 240Vac, 60 Vdc, C Trip Curve, Miniature Circuit Breaker https://a.co/d/7flEflJ

DC Miniature Circuit Breaker, 2 Pole 1000V 25 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C25 https://a.co/d/3iwgVQ0

 

[featherlite]

ASI NDB1-125C100-2 DIN Rail Mount High Current Circuit Breaker, 100 Amp, 2 Pole, 240Vac, 60 Vdc, C Trip Curve, Miniature Circuit Breaker https://a.co/d/7flEflJ

DC Miniature Circuit Breaker, 2 Pole 1000V 25 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C25 https://a.co/d/3iwgVQ0

Thank you for taking the time to explain all you have explained in this thread, especially by posting links to those kind of breakers that I need to acquire for my install. Much appreciated!!

 

[RV10flyer]

I use these......DPDT. Great for low-voltage DC switching needs.
Down position is pack#1, up position is pack#2, middle position is "off"
Very simple COPPER knife switch.
"Swing" Knife is copper
Base knife receptacle is copper.
Hinge rivets are hardened bronze or brass?
Base is solid plastic block.
Screw-down wire mounts are "enclosed clamp" style copper w/steel screws.
I have two 36V 200Ah batteries.
This a 100A version which serves as my inverter DC-side disconnect.
I use two smaller 32A versions for my panel string DC-disconnects: My panel stings VOC is only 75V though.
I've used toggle switches like those posted above in past: Contacts WILL(!) weld shut when arcs occur for 120VAC designed switches.
The below switch you simply open and close a few times to clean off copper pitting if arcs occur. PS: I"m only running max 80V.....higher voltage DC arc-faults can destroy just about any switch that is not electronically mitigated for arc-fault shutdown.
View attachment 125068

I use the previous model from Amazon/China. It works great to switch a solar input between two separate scc. I stay under 100VDC and 10A.

 

[Philfr]

It does not look like the author ever got a fail-safe suggestion on his original request for a DC changeover/transfer switch. Any more ideas on this as I have the same issue.