This is SideRiser's unedited output for a commercial building's one-line diagram, checked against the firm's own design rules and the NEC. Filter the findings by kind, or open the components tab for the full inventory with what feeds what.
Drawing
One-line, 48 × 36 in, with a cover sheet
Company rules
4: bus ratings, breakers, feeders, transformers
Components
77
Findings
13
Time
About 4 minutes
No title block found (one-line.pdf has no title block; cover.pdf holds only the symbol legend, abbreviations and line types)
The service comes from an overhead pole utility transformer (primary voltage TBD, 480/277V secondary) through 5 sets of 4-500kcmil to a new 2000A, 480/277V, 3PH 4W, 200kAIC MSB with a 1600A/3P LSIG main. The MSB distribution section feeds: T-DP-S (300 kVA, 480-208/120V), which feeds DP-S (1200A, 65kAIC, 1200A LSIG main) and its 10 branch feeders; three RTUs through fused disconnects; T-AV (75 kVA K-13), which feeds PP-AV; DP-S1; MPH-LS, which feeds T-HV and then MPL-LL; and LP-LS and LP-TT. The cover legend sets line weight: 1.68pt heavy is new, 0.72pt thin is existing. EX/R tags mark the existing and relocated panels.
Main findings:
- Errors: T-HV has no primary or secondary overcurrent protection drawn. The T-AV secondary EGC is #4 where Rule 4 calls for #2. The two T-AV secondary callouts don't agree with each other (4#4/0 vs 3#4/0, both with 2 neutrals). The existing 1P3W SITE PANEL is fed by a 3-pole breaker with 4 wires.
- Missing information: DP-S1, MPH-LS, LP-LS, LP-TT and MPL-LL have no ratings. Main breaker or MLO isn't stated on any panel. CS-101 and the T-AV disconnects have no switch, fuse or AIC ratings. The service GEC has no size.
- To confirm: several feeders are larger than Rule 3 requires (voltage drop?). 42kAIC disconnects are fed from a 200kAIC switchboard. The utility voltage is TBD.
Everything else checks out against Rules 1-4: T-DP-S and T-AV primary, secondary and GEC sizing, the DP-S feeders, GFPE on the 1600A and 1200A mains, and LSI on the MSB distribution breakers.
Limits: there is no title block, so project, sheet, date and revision are unknown. Available fault current, feeder lengths and transformer impedances aren't given, so I couldn't check AIC adequacy, voltage drop or tap lengths under 240.21(C). The note "REFER TO E-002" points to a sheet that wasn't provided. Conductor material and insulation aren't stated, so I assumed copper at 75C to match the rule tables. Both pages have a text layer.
01
T-HV has no primary or secondary overcurrent protection
Rule 4; NEC 450.3(B), 240.21(C)Error
MPH-LSMPH-LS -> T-HVT-HVT-HV -> MPL-LLMPL-LL
Fix: Show a 150A/3P primary breaker in MPH-LS and a 225A secondary OCP (MPL-LL main or a disconnect)
Analysis
Rule 4 for 75 kVA calls for a 150A primary OCP and a 225A secondary OCP. The drawing shows no breaker in MPH-LS for 3#1/0 to T-HV, and no device between T-HV and MPL-LL (4#4/0, 1#2G). As drawn, neither the transformer nor its secondary conductors are protected.
Rule 4 for the 75 kVA secondary: 4#4/0, #2 G, 2-1/2"C. Both secondary callouts show 1#4G. #4 meets NEC 250.122 for 225A, but the rule is stricter and governs.
03
T-AV secondary callouts contradict: 4#4/0 vs 3#4/0
Fix: Make both callouts read 3#4/0 + 2#250kcmil neutral, 1#2G, 3"C (or as intended)
Analysis
T-AV to the disconnect reads "4#4/0, 2 SETS(1# 250kCMIL NEUTRAL) 1#4G, 3"C". That would be four #4/0 plus two 250kcmil neutrals on a 3-phase 4-wire circuit. Disconnect to PP-AV reads "3#4/0, 2 SETS(1# 250kCMIL NEUTRAL)". The same circuit should carry the same conductors.
04
1P3W SITE PANEL fed by 3-pole breaker, 4 wires
Error
DP-S 100A/3P breaker (to SITE PANEL)DP-S -> SITE PANELSITE PANEL
Fix: Change to a 2P breaker with 3#1/0 + G, or confirm SITE PANEL is actually 3P4W
Analysis
The existing SITE PANEL is labeled 100A, 208/120V, 1P3W. The new feeder is a 100A/3P breaker with 4#1/0, 1#6G, 2"C. Pole count and wire count don't match a single-phase 3-wire panel.
05
DP-S1, MPH-LS, LP-LS, LP-TT, MPL-LL have no ratings
Rule 1Missing
DP-S1MPH-LSLP-LSLP-TTMPL-LL
Fix: Add bus rating, voltage, phase/wire, main or MLO and AIC to each
Analysis
Each is shown only as a tagged box. Without a bus rating, bus >= OCPD can't be checked: DP-S1 on 400A, MPH-LS on 250A, LP-LS and LP-TT on 60A, MPL-LL unprotected. Voltage isn't shown either, so I couldn't confirm MPL-LL is 208/120V.
06
Main breaker or MLO not stated on rated panels
Rule 1Missing
RP-LL1RP-LL3RP-LL4RP-UL2RP-UL3PP-SL-101PP-AV
Fix: State MCB or MLO for each panel
Analysis
These panels give a bus rating (RP-LL1 200A, RP-LL3 125A, RP-LL4 200A, RP-UL2 100A, RP-UL3 100A, PP-SL-101 200A, PP-AV 225A) but not whether they have a main breaker or are MLO. Each is protected by an upstream device no larger than its bus, so MLO is acceptable, but it must be stated.
07
CS-101 fused disconnect has no switch, fuse or AIC rating
Missing
CS-101
Fix: Add switch amps, fuse size and AIC (e.g. 200AS/200AF)
Analysis
CS-101 is drawn with the fused disconnect symbol on a 200A/3P feeder (4#3/0) but has no ratings. Fuse <= switch and the AIC can't be checked.
The RTU disconnects are marked 42kAIC. The T-AV primary disconnect (200AS/150AF, fed from the 200kAIC MSB) and secondary disconnect (400AS/225AF) have no AIC rating.
09
Service grounding electrode conductor size not shown
NEC 250.66Missing
MSB
Fix: Size the MSB GEC and bonding jumper (5 sets 500kcmil Cu -> 3/0 Cu min)
Analysis
A grounding electrode is drawn at the MSB but has no conductor callout. The separately derived systems give theirs (#3/0, #2). For 2500kcmil of Cu service conductors, Table 250.66 requires at least 3/0 Cu.
10
Service conductors larger than Rule 3 for 1600A
Rule 3Confirm
UTILITY XFMR -> MSB
Fix: Confirm 5 sets 4-500kcmil is for voltage drop or utility requirements
Analysis
Rule 3 F1675G for 1600A: 5 SETS (4-400KCMIL, #4/0 G, 3-1/2"C). Drawn: 5 sets (4-500KCMIL in 4" PVC). Larger than required.
Fix: Confirm upsizing is for voltage drop; if not, reduce to Rule 3 sizes
Analysis
RTU-2B 150A: rule 4#1/0, #6G, 2"C; drawn 4#3/0, 1#6G, 2-1/2"C. RTU-3A 175A: rule 4#2/0, #6G, 2"C; drawn 4#4/0, 1#4G, 2-1/2"C. SITE PANEL 100A: rule 4#2, #8G, 1-1/2"C; drawn 4#1/0, 1#6G, 2"C. RP-UL2 and RP-UL3 100A: rule 4#2, #8G, 1-1/2"C; drawn 4#1, 1#6G, 2"C. If the phase conductors were upsized for voltage drop, check that each EGC is increased in proportion (250.122(B)).
12
42kAIC RTU disconnects fed from 200kAIC switchboard
NEC 110.9, 110.10Confirm
RTU-1ARTU-2BRTU-3A
Fix: Provide available fault current at the RTUs, or a series rating, showing 42kAIC is adequate
Analysis
The MSB is rated 200kAIC, which implies high available fault current. The RTU fused disconnects are 42kAIC. Available fault current isn't given on the drawing, so adequacy can't be verified.
13
Utility primary voltage to be confirmed
Confirm
Overhead pole utility serviceUTILITY XFMR
Fix: Confirm the utility primary voltage and available fault current; provide sheet E-002
Analysis
The drawing says "VOLTAGE TO BE CONFIRMED" and "PRIMARY VOLTAGE TBD / 480/277V SECONDARY", and refers to E-002 for primary feeder modifications. E-002 wasn't provided.
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