Calculating and Spec a disconnect

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samvivi7

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Hi guys,

need some help with selecting a disconnect.

here is the system ---->> 20Ah battery powering up a control panel, protected by an 80amp circuit breaker.
i would like to add the disconnect, so---->> Disconnect ---- 80amp breaker ----- battery.

how do i calculate what amp rating disconnect is needed? (need a small form factor).

this is a 48VDC panel.

Thanks for the help and sorry if i made it confusing.
 
samvivi7 said:
Thank you for the reply, is there a calculation or if you can point me where I can find it.
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The code has some requirements for disconnects. I forget what article it is in but there is an article about batteries and you might find it there.

Incidentally, circuit breakers can be used as disconnects. Is there some reason you want an extra disconnect?
 
We need the disconnect to meet the logout tagout requirements. Do you remember if it was in UL508A , NFPA 70-79, or UL 3100. Sorry to bother you but I have to show where I got my numbers from.
Thank you 🙏
 
samvivi7 said:
We need the disconnect to meet the logout tagout requirements. Do you remember if it was in UL508A , NFPA 70-79, or UL 3100. Sorry to bother you but I have to show where I got my numbers from.
Thank you 🙏
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I think there is an article dealing with batteries in the nec. I would start there.
 
samvivi7 said:
Hi guys,

need some help with selecting a disconnect.

here is the system ---->> 20Ah battery powering up a control panel, protected by an 80amp circuit breaker.
i would like to add the disconnect, so---->> Disconnect ---- 80amp breaker ----- battery.

how do i calculate what amp rating disconnect is needed? (need a small form factor).

this is a 48VDC panel.

Thanks for the help and sorry if i made it confusing.
Click to expand...
I'm confused. Are you trying to disconnect, the AC power before the circuit breaker and the battery, or the control panel after the battery? Sizing shouldn't be that difficult. You don't need fusing, so a disconnect with a higher voltage rating than the supply, DC or AC as required and an amperage higher than the breaker.
 
Strathead said:
I'm confused. Are you trying to disconnect, the AC power before the circuit breaker and the battery, or the control panel after the battery? Sizing shouldn't be that difficult. You don't need fusing, so a disconnect with a higher voltage rating than the supply, DC or AC as required and an amperage higher than the breaker.
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Control panel after the battery, any suggestion on where i can find any standards, codes or calculations on sizing ??

or do you suggest taking the highest breaker value for amperage?
if higher than the breaker, what % do i go higher by?

Thank you for the help.
 
samvivi7 said:
Control panel after the battery, any suggestion on where i can find any standards, codes or calculations on sizing ??

or do you suggest taking the highest breaker value for amperage?
if higher than the breaker, what % do i go higher by?

Thank you for the help.
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I should have said equal to or higher than the breaker, ditto with the voltage. Sorry I misspoke.
 
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