10 MW IT Load · Medium Voltage Distribution (11 kV) · Frankfurt, Germany
The commissioning documentation reviewed is substantially complete and the majority of test results meet specified acceptance criteria. However, four conditions must be resolved and evidence submitted to Criticon before energisation of the MV distribution system can proceed. These conditions relate to insulation resistance anomalies on Bus Duct B3, incomplete thermal imaging coverage, missing torque verification records on MV switchgear, and three open NCRs with no documented close-out plan.
Criticon was engaged by Nordheim Colocation GmbH to provide independent pre-energisation assurance for Phase 1 of the Nordheim Data Center facility in Frankfurt-Sachsenhausen. The facility comprises two 5 MW power halls with 11 kV medium voltage distribution, six 2,500 kVA dry-type transformers, 2N UPS architecture across four UPS rooms, and dedicated generator backup across six 2,500 kVA diesel generating sets.
The documentation package reviewed comprised 1,847 individual test records submitted by BauTech Infrastructure AG. Records were reviewed against IEC 60364, DIN VDE 0100-600, and project-specific commissioning specifications (Nordheim CxSpec Rev. 04, dated 08 February 2026). Test records cover electrical isolation testing, continuity and loop impedance, protective earth continuity, ductor (micro-ohm) testing of busbar joints and switchgear connections, thermal imaging surveys, FOD inspection sheets, and torque verification records.
The independent review identified five key risks, four evidence gaps, and six technical observations requiring attention. The overall commissioning programme is approximately 94% complete by record count. The outstanding items are not trivial — the insulation resistance anomaly on Bus Duct B3 requires physical re-inspection and the open NCR set has no documented closure plan. Energisation should not proceed until the four conditions stated in Section 5 are satisfied and written close-out evidence has been received by Criticon.
IR test results for Bus Duct B3, conductor-to-earth on sections 4 through 7, show values of 42 MΩ–68 MΩ at 1,000 V DC. Specified minimum acceptance criterion is 200 MΩ. Values are consistently below threshold across all four sections, suggesting systematic contamination, moisture ingress, or a connection defect rather than isolated measurement error. Re-inspection and physical investigation of the duct sections is required before energisation.
Ref: Test records IR-B3-004 through IR-B3-007 · Spec clause 4.2.1 · Acceptance: ≥200 MΩ @ 1,000 V DC
Thermal imaging surveys have been submitted for UPS Rooms A and B only. No thermal survey records have been provided for UPS Rooms C and D, which house the UPS B-train for Power Hall 2. Absence of thermal evidence means undetected hotspots on cable terminations, busbar connections, and UPS output switchgear cannot be ruled out. This is an evidence gap, not necessarily a defect — but energisation without this survey is unacceptable for an independent readiness sign-off.
Ref: Thermal surveys TI-UPS-A and TI-UPS-B submitted; TI-UPS-C and TI-UPS-D absent from documentation package
Torque verification records for MV switchgear bus section joints are absent from the documentation package. The test specification (Nordheim CxSpec, Section 7.4) requires post-assembly torque verification at manufacturer-specified values for all MV bus joint connections. Fourteen joints are in scope. Zero records have been submitted. Unverified torque on MV bus joints presents an arcing risk during energisation.
Ref: CxSpec Rev.04 §7.4 — no corresponding records received in submission package dated 14 April 2026
NCR Register v11 (submitted 16 April 2026) lists three open Non-Conformance Reports: NCR-2026-031 (earth bar connection defect, LV DB-12), NCR-2026-038 (cable tray bonding continuity failure, Zone B corridor), and NCR-2026-044 (incorrect cable lug sizing, UPS Room A, position UPS-A3-OUT). All three were raised over 30 days ago. None have a documented corrective action, responsible party, or target close-out date. Open NCRs against safety-critical systems with no closure plan are not acceptable at energisation.
Ref: NCR Register v11 — NCR-2026-031, NCR-2026-038, NCR-2026-044
Micro-ohm resistance measurement for Transformer T4 LV busbar joint (phase L2) returned 98 µΩ against a specified limit of ≤45 µΩ. The outlier value is more than double the acceptance limit and is inconsistent with the six other measured joints on the same transformer (range: 28–41 µΩ). The test was not repeated and no comment was recorded by the commissioning engineer. Elevated joint resistance indicates a potential connection quality issue that could result in thermal overload under full load conditions.
Ref: Ductor record DT-T4-LV-L2 · Spec limit: ≤45 µΩ · Measured: 98 µΩ
The following records were expected per the commissioning specification but were either absent from the submitted package or incomplete. Energisation conditions are indicated where applicable.
| Document / Record Type | Scope / Location | Status | Condition |
|---|---|---|---|
| Thermal Imaging Survey | UPS Room C & D | Missing | Condition 1 |
| Torque Verification Records — MV Bus Joints | MV Switchgear, all 14 bus section joints | Missing | Condition 2 |
| NCR Close-Out Evidence | NCR-2026-031, -038, -044 | Missing | Condition 3 |
| IR Test Repeat — Bus Duct B3 Sections 4–7 | Bus Duct B3, conductor-to-earth | Missing | Condition 4 |
| Ductor Test Repeat — Transformer T4, LV L2 | T4 LV busbar joint, phase L2 | Missing | Advisory |
| FOD Inspection Sheets — Generator Compound | Gen sets G5 and G6 (intake areas) | Partial | Advisory |
| Cable Test Certificates — LV Distribution | Power Hall 1 & 2 LV distribution | Complete | — |
| Protective Earth Continuity Records | All distribution boards (48 of 48) | Complete | — |
| Insulation Resistance — HV Cable System | 11 kV incoming cables (3 circuits) | Complete | — |
Systematic IR test failure across Bus Duct B3 sections 4–7 is inconsistent with random measurement error. The values show a monotonic decrease from section 4 (68 MΩ) to section 7 (42 MΩ), which is characteristic of moisture ingress with the gradient correlating to the duct run direction (sections 4–7 traverse the external plant room wall at column grid E7). This section was exposed during the construction phase when the plant room roof membrane was incomplete.
Section 4 (IR-B3-004): 68 MΩ @ 1,000 V DC · Limit: ≥200 MΩ · FAIL
Section 5 (IR-B3-005): 61 MΩ @ 1,000 V DC · Limit: ≥200 MΩ · FAIL
Section 6 (IR-B3-006): 54 MΩ @ 1,000 V DC · Limit: ≥200 MΩ · FAIL
Section 7 (IR-B3-007): 42 MΩ @ 1,000 V DC · Limit: ≥200 MΩ · FAIL
Adjacent sections (B3-003, B3-008): 410 MΩ, 385 MΩ · PASS
Finding: Physical inspection of duct sections 4–7 required. Likely moisture ingress at column E7 wall penetration. Do not energise Bus Duct B3 until values ≥200 MΩ achieved after investigation and any required remediation.
The micro-ohm resistance reading for the T4 LV busbar joint (phase L2) is anomalous. All other measured joints on T4 and on the three adjacent transformers (T1, T2, T3) are within the specified limit. The L2 joint is at the lower busbar connection to MLVDB-4. A visual inspection at the time of testing should have been triggered — no photographic or visual inspection record is present in the submission.
T4 LV L1 joint (DT-T4-LV-L1): 34 µΩ · Limit: ≤45 µΩ · PASS
T4 LV L2 joint (DT-T4-LV-L2): 98 µΩ · Limit: ≤45 µΩ · FAIL
T4 LV L3 joint (DT-T4-LV-L3): 41 µΩ · Limit: ≤45 µΩ · PASS
T4 LV N joint (DT-T4-LV-N): 28 µΩ · Limit: ≤45 µΩ · PASS
Finding: Advisory — repeat the ductor test on T4 LV L2 and conduct a physical inspection of the busbar joint (torque verification, contact surface condition). Advise before energisation; risk is elevated joint resistance under full load causing thermal overload at MLVDB-4.
Loop impedance measurements for 14 final circuits in Power Hall 2, Zone B show values 15–22% higher than the equivalent circuits in Zone A of the same distribution board. This is not a specification failure — all values pass the calculated Zs limits — but the systematic uplift is unusual and warrants an explanation. Possible causes include inconsistent cable termination quality, higher-resistance cable runs routed via an alternative path, or temperature differential during testing.
Zone A circuits (14): Zs range 0.38–0.44 Ω · All within limits
Zone B circuits (14): Zs range 0.46–0.54 Ω · All within limits
Variance between zones: ~15–22% uplift · No technical explanation noted in records
Finding: Advisory — request the commissioning engineer's note on the Zone B loop impedance uplift. If no explanation is available, conduct targeted visual inspection of Zone B cable terminations at MLVDB-5 Zone B busbars.
NCR-2026-038 was raised against cable tray bonding continuity in the Zone B corridor. The commissioning record for this circuit (PE-TRAY-B-007) shows a measured resistance of 4.1 Ω between tray sections at the mid-point of the run. The specified limit is ≤0.5 Ω. This is an eight-fold exceedance. The likely cause is a missing or incorrectly installed earth bond strap at one of the cable tray expansion joints. The remedial fix is straightforward (install or replace bond strap) but close-out evidence is required.
PE-TRAY-B-007: Measured 4.1 Ω · Limit: ≤0.5 Ω · FAIL — NCR-2026-038 raised 18 March 2026
Status as of documentation package date (16 Apr 2026): Open, no corrective action recorded
Finding: NCR-2026-038 must be closed with a post-remediation test result (≤0.5 Ω) before energisation. See Condition 3.
Based on the documentation reviewed, the commissioning programme for Nordheim Data Center Phase 1 is substantially complete and the large majority of test results meet acceptance criteria. However, the findings documented in Sections 2–4 are not trivial and include a critical IR failure on a primary distribution path, absent thermal surveys for 50% of UPS rooms, and three unresolved NCRs against safety-critical earthing and bonding systems. These items must be resolved before Criticon can provide an unconditional readiness sign-off.
The four conditions listed below must be satisfied. Written close-out evidence for each condition must be submitted to Criticon for independent verification. Upon receipt and acceptance of satisfactory close-out evidence, Criticon will issue a Readiness Confirmation letter and the project may proceed to energisation.
Physically open and inspect duct sections 4–7 at the column E7 wall penetration. Check for moisture ingress, contamination, or connection defects. Dry out or replace affected sections as required. Retest to ≥200 MΩ before closing out.
Owner: BauTech Infrastructure AG (Electrical Commissioning Team) · Target: Before energisation · Condition 4
Engage a qualified thermography contractor to survey UPS Rooms C and D under representative load conditions. Provide full report with thermal images, temperature readings, and any findings. Submit to Criticon for review.
Owner: Nordheim Colocation GmbH (Project Manager) · Target: Before energisation · Condition 1
Verify torque on all 14 MV switchgear bus section joints using a calibrated torque wrench at the manufacturer's specified value. Complete the torque verification record for each joint and submit to Criticon.
Owner: BauTech Infrastructure AG (HV Commissioning Supervisor) · Target: Before energisation · Condition 2
Assign corrective actions, responsible parties, and target dates to each open NCR. Complete the remedial works. Retest and obtain a passing result for each. Provide close-out documentation with photographic evidence and post-remediation test certificates.
Owner: BauTech Infrastructure AG (Commissioning Manager) · Target: Before energisation · Condition 3
Re-measure the micro-ohm resistance of the T4 LV L2 busbar joint. Inspect the joint for correct contact surface preparation and torque. If value remains above 45 µΩ, disassemble and re-make the joint. Target value: ≤35 µΩ.
Owner: BauTech Infrastructure AG · Target: Advisory — before energisation recommended · Risk: R-05
Request a written technical note from the commissioning engineer explaining the 15–22% higher loop impedance readings in Power Hall 2 Zone B. If no explanation can be provided, conduct targeted visual inspection of terminations at MLVDB-5 Zone B busbars.
Owner: BauTech Infrastructure AG · Target: Advisory — before energisation · Risk: OBS-03
Verification & Close-Out Upon submission of close-out evidence for all four conditions, Criticon will review the documentation and, where satisfactory, issue a Readiness Confirmation letter within 2 business days. Advisory actions (A-05, A-06) are strongly recommended but are not blocking conditions for the Readiness Confirmation. The assessment in this report is based solely on the documentation submitted to Criticon as of 21 April 2026. Criticon accepts no liability for defects not evidenced in the reviewed documentation set.