Infrastructure Engineering · Lesson 13 of 24 · 25 minutes

Build an evidence-controlled load ledger

Begin where the original course leaves off: not with a bigger battery, but with a more disciplined definition of demand. A facility total is meaningful only when every term belongs to the same boundary and operating condition. In this lesson, a 20 MW IT allocation becomes a traceable facility ledger, while a second example demonstrates why conflicting source values must remain visible.

Learning objectives

• Separate connected ratings, coincident demand and future reservation.
• Reconcile IT, cooling electricity, other loads and losses without duplication.
• Distinguish an assumed design-point ratio from an interval energy PUE.

Predict → run → explain

1. Read the declared boundary and units. Predict the selected result before calculating.
2. Run the starting case and inspect the ledger, assumptions and model limits.
3. Apply the challenge, run again, and explain the difference. Export only the last completed inputs and results.

IT kW = racks × rack kW × demand factor × (1 + growth); facility kW = IT kW × design ratio; residual kW = facility − IT − cooling; S(kVA) = facility kW / pf; I(A) = S(kVA)/(√3 × V(kV)).

Declared starting inputs

{
  "racks": 2500,
  "rackKW": 8,
  "demandFactor": 1,
  "growth": 0,
  "designRatio": 1.35,
  "coolingKW": 6200,
  "pf": 0.9,
  "voltageKV": 13.8
}

Challenge

Keeping 6.2 MW cooling unchanged, can the revised design ratio accommodate the ledger?

{
  "designRatio": 1.25
}

Facility demand becomes 25 MW and the residual becomes −1.2 MW. This is an inconsistent set of assumptions, not negative physical losses.

The transparent facility ledger — static equivalent

1. Reveal the rack field and its IT boundary.
2. Lift four separately labelled ledger slabs: IT, cooling electricity, conversion loss, other.
3. Join the slabs into one facility total; a second cooling slab is flagged as duplication.
4. Switch to a matched-interval energy view without relabelling power as energy.

An accessible table of load terms, units, evidence labels and inclusion rules.

Keyboard-select each ledger term; change the design ratio and expose a negative residual.

Narrative steps are not physical seconds. Essential states and quantities remain available without animation.

Assessment and answer criteria