I have a client who wants to back up the entire facility, on top of the typical Life Safety, Critical, and Equipment branches.

We're talking about kitchen loads, common receptacles for entertainment rooms, all lighting (rather than just the EM lighting).

Should all of these nonessential loads be on a fourth branch of the emergency system, the 'Optional' branch, or can all of these loads go on the least-important 'Equipment' branch of the emergency system?

2014 NEC, Phoenix AZ

Thanks! ]]>

The feeds are:

(1) 400 A / 3 ph / 400 V

(1) 250 A / 3 ph / 400 V

(1) 100 A / 3 ph / 400 V

The trench is 12" wide and 8" deep with a cover on top.

Is there an easier way of running the wiring in the trench without using conduit? I assume I cannot just put THHN in the trench?

Is there trench rated cable or wire? ]]>

a) is this true and b) is it true even if the later version of NFPA 99 is not adopted by the states fire safety code? ]]>

There is currently a 1600A Service entrance switchboard with only a 1600A main breaker which feeds another downstream 1600A MLO switchboard. This existing service entrance switchboard is being upgraded to a 2000A switchboard in order to re-feed the downstream switchboard as well as feed a new 1200A Chiller Switchboard.

Because of space constraints it was proposed that the new service entrance switchboard only have a single 2000A Main breaker and then off of that main breaker there will be two taps to feed the existing downstream switchboard as well as the new 1200A switchboard.

The new 1200A switchboard will have a 1200A main so as long as the feeder cables from the tap are (3) sets of 600MCM (1260A ampacity) then this feeder tap is o.k.

The issue I see is with the feeder to the existing downstream 1600A Switchboard. Because this existing switchboard is a 1600A MLO switchboard the switchboard itself and the existing (5) sets of 500MCM would not be adequately protected by the new 2000A main breaker in the service entrance switchboard. In order to be adequately protected under this arrangement a 1600A main breaker would need to be added to the existing switchboard. Is this correct?

Of course the best solution would be to add two feeder breakers to the new service entrance switchboard but this may not be possible due to switchboard footprint available. All of these switchobards and feeders are located outdoors so they fall under 240.21(B)(5). ]]>

A new 480V 1200A Switchboard is being provided which will feed a 235kW chiller along with some small auxiliary pumps that will support the chiller system. There will be a feeder breaker in the Switchboard to feed the Chiller directly and there will be another feeder breaker which will feed a small MCC which contain the small pump starters.

The Chiller schedule from the manufacturer shows the chiller as having an "MCA" of 530.6A, a "MOCP" of 700A and an "IF" of 2028.6A. It also lists a "IPLV/EER" of 12.29/10.08. I'm not sure what the "IF" and "ILPV/EER" are?

In terms of the feeder calculation for this chiller do I simply use the 700 listed OCPD to size the feeder breaker at 700A and have (2) sets of 500MCM cables for the feeder? I'm assuming that the listed MOCPD and MCA already factor in the requirements of 440.22 and 440.33 and thus there are no further multiplying factors needed for these (the manufacturer already did these calcs for us)

In terms of the load calculation for the switchboard would I simply use the MCA (530.6A) value for the chiller load or do I need to add any adjustment factors to this for the load calc.

There will be four small 10hp pumps connected to a small MCC which if fed from the switchboard. For the load calcs for these pumps I simply use 4 x 14A (FLA) plus 25% of 14A (largest FLA) to come up with 59.5A. I then add this 59.5A to the 530.6A chiller value above to come up with the total Switchboard calculated load. Am I on the right track here? ]]>

Thanks for the help. ]]>

A 2000 kVA 34.5/480 V Delta - Wye transformer will carry mostly (>95%) three phase loads connected only by three phases, not using the neutral. By system design, some lighting panels will be connected L-N in this arrangement.

My question is: How do you properly size the conductors that go from to the transformer's X0 to the main switchgear neutral busbar?

Best regards and thanks in advance.

Pablo. ]]>

that has 480v, 3- wire service and a 240vv, 1 ph., 3 wire service available

( no nuetral or return leg in none of them).

and gives out a nuetral terminal that can be used for both types of load (120v or 277v) ????????

for voltage drop. The plans call for a #4 grounding conductor with the 350's. I'm calculating something different.

#350 MCM 350,000CM Upsized conductor

#3 52,560CM 100 amp conductor

#8 16,510CM ground

350,000/52,560*16,510 = 109.941CM

#1/0 105,600CM

#2/0 133,100CM

Do I need to use a 2/0 for this run? Seems huge so I'm wondering if I'm doing the calculation incorrectly. ]]>

I have a two quick questions...

- With a standard load calculation format, please explain to me how one would account for a range load for a 15 unit apartment complex with the each range at 13 KW? I am a little unclear as to using column "C" of T250.55, whether I would use the 30KW as the total load or whether I would calculate the load at 5% over 12KW (1KW * 5%=5%) then (.05 * 8KW = 400) thus (8KW + 400 = 8400W) and this lands me in column "B" which would be total range load at 32 KW for a 15 unit multi family dwelling with 13KW range load for each unit.
- 220.53 Appliance Loads, demand factor of 75% to the name plate of four or more connected appliances. Does this also include the hot water heater? I believe that the hot water heater is a fastened in place appliance and thus falls under this category.

Does anyone have a process for load calculations, whether standard or optional, that they like to use and would like to share?

Thanks for your time, first time poster long time reader! Glad to be apart of the group! ]]>

Right now, there is a 20A, 2-pole non-fused disconnect feeding the condensing unit. Is there a product out there that could maybe mount to the side of the N/F disconnect and connect to the line side of the disconnect? Something approved specifically to protect a single piece of equipment retroactively. This is kind of tough because normally the manufacters data recommends #10 wire with a 30A circuit breaker but I only have a 20A probably fed with #12s.

I dont really like this whole idea. Maybe its just better to advise him to install at the panel? Either way, curious to know. ]]>