Two 80 amp 3-pole breakers instead of a (1) 160 amp 3-pole breaker

Status
Not open for further replies.
cottora said:
First, thank you to the members for providing insight. What we are putting together is new, and while we have hired an engineer, many of the ideas from this board are being incorporated and have helped us reduce the cost to hopefully make this venture a reality (we are a small business).

Below is the schematic for a PDU that will work for our installation. Here is the problem, the total amp for the PDU is 183 amps (single-phase amps derived from a four-wire setup @100 rated).

We have a 400 amp square D Panel. Ideally, we would install a 160 amp breaker and the world would be perfect. However, Square D seems to max out at 100 amp 3-pole.

Can we install two 80 amp three pole breakers with two 80 amp wire runs that land together in the PDU?

Thanks

*** The below pictures are of the manufacturers 5 wire system, we would receive the 4 wire for 208Y per the below schematic ***



Click to expand...

First, you can't parallel those breakers unless it is part of a listed assembly. I think you have been told code reference in other posts.

Second 160 amps is not a standard size, if you can get such a thing it would be special order - something like an OEM would place orders for, if doing that you would be specifying 160 amps and not trying to cobble together standard items to get what you want.

Third (assuming you are talking about QO series breakers) you can get over 100 amp breakers but they are not the typical ones you see 100 amp and less, they take up two panel spaces per pole, and are not cheap in comparison to those 100 amp and under either.

If you have existing panel to come from might still be the way to go, but often adding such sized circuits means you probably need to increase the feeder or already had under utilized capacity available. If new install would probably be better to use I-line panel or even one of their combo panels that has both I line and QO breaker spaces.
 
ptonsparky said:
I am thinking you should not be building to the NEC. This will need some testing lab input. UL, etc.
Click to expand...

We could modify the unit and basically feed each breaker within the unit. But we then void certifications. Fundamentally there is no issue with that, but the insurance man will probably disagree.
 
kwired said:
First, you can't parallel those breakers unless it is part of a listed assembly. I think you have been told code reference in other posts.

Second 160 amps is not a standard size, if you can get such a thing it would be special order - something like an OEM would place orders for, if doing that you would be specifying 160 amps and not trying to cobble together standard items to get what you want.

Third (assuming you are talking about QO series breakers) you can get over 100 amp breakers but they are not the typical ones you see 100 amp and less, they take up two panel spaces per pole, and are not cheap in comparison to those 100 amp and under either.

If you have existing panel to come from might still be the way to go, but often adding such sized circuits means you probably need to increase the feeder or already had under utilized capacity available. If new install would probably be better to use I-line panel or even one of their combo panels that has both I line and QO breaker spaces.
Click to expand...

Thanks! You are right, there is a big line once you jump above the "standard" panels/breakers.
 
cottora said:
We could modify the unit and basically feed each breaker within the unit. But we then void certifications. Fundamentally there is no issue with that, but the insurance man will probably disagree.
Click to expand...

I'm not seeing from the schematic why you would need a 160A c/b to supply it. 100A ought to be sufficient.
 
My first thought was if the panelboard had subfeed lugs(or a means to replace the incoming lugs with a type with more wire holes), you could use the tap rule to come off the lugs to an appropriately sized fused disconnect located adjacent to the panelboard.
 
Cow said:
My first thought was if the panelboard had subfeed lugs(or a means to replace the incoming lugs with a type with more wire holes), you could use the tap rule to come off the lugs to an appropriately sized fused disconnect located adjacent to the panelboard.
Click to expand...
And if he needs 160 amps minimum, he still going to go to next standard size up if using standard items which will be 175 amps. He still can use a conductor that has or is adjusted to an ampacity of 160 amps though.
 
david luchini said:
I'm not seeing from the schematic why you would need a 160A c/b to supply it. 100A ought to be sufficient.
Click to expand...

The three-phase wiring input is broken out into (3) single phase 63 AMP banks (100% rated). If I am correct, I believe that the 100 amp 3-pole will have to be derated to 80% because of the full load.
 
Seems to me the feeder breaker just needs to be large enough for the connected load. So feed the PDU with a 100A feeder, and only connect 80A continuous worth of miners to the PDU.

Why 63A? 63 * sqrt(3) = 109

Are those C14 inlets, the cords, and the miners really rated to be protected at 63A?

Cheers, Wayne
 
I'm still trying to figure out where the individual protection is for the individual 120v outlets.

To me, the OCPD set at 40 amps for the individual plug strips is severely oversized.

JAP>
 
wwhitney said:
Seems to me the feeder breaker just needs to be large enough for the connected load. So feed the PDU with a 100A feeder, and only connect 80A continuous worth of miners to the PDU.

Why 63A? 63 * sqrt(3) = 109

Are those C14 inlets, the cords, and the miners really rated to be protected at 63A?

Cheers, Wayne
Click to expand...

The cord will not but the miner is listed at 83 amps with overcurrent protection.
 
There is no way that PDU is going to receive a UL (or other NRTL) listing. What is the 'certification' it is undergoing?

Also, I am 98.5% sure you cant have a hardwired pdu with IEC receptacles. My logic is that if its hardwired then its part of the structure and is permanently installed. Cant permanently install IEC receptacles due to their use on multiple voltages. Someone please correct me if I am wrong here.
 
Status
Not open for further replies.
Top