UV Intensity Thresholds

The three key UV intensity levels used for compliance checking, operational targets, and lamp efficiency tiers.

The three UV intensity thresholds

All three values are defined in lib/constants.ts under THRESHOLDS.UV_INTENSITY:

Threshold	Value	Source	Purpose
IMO_MIN	252 W/m²	IMO G8 guidelines	Minimum for IMO D-2 compliance
USCG_MIN	530 W/m²	33 CFR Part 151	Minimum for USCG compliance
OPTIMAL	650 W/m²	System design spec	Full-rated output target

How 252 W/m² is used

The IMO_MIN value is the primary compliance gate. Any BALLAST or DEBALLAST operation where UVR_INTENSITY < 252 represents a D-2 non-compliance event. In the dashboard:

• Compliance tab: IMO D-2 item shows red (NON-COMPLIANT)
• Compliance tab treatment bar: fills to UVR_INTENSITY / 252 — when below 100%, compliance is at risk

How 530 W/m² is used

The USCG_MIN is the secondary compliance gate, relevant for vessels operating in US waters. Between 252 and 530, the system is in a “marginal zone”:

• IMO D-2 compliant ✅
• USCG non-compliant ⚠️

The Compliance tab shows the USCG item as WARNING (yellow) in this range. The USCG treatment bar fills to UVR_INTENSITY / 530.

How 650 W/m² is used

The OPTIMAL value represents the system’s full rated output under ideal conditions. It is used as:

• The denominator for efficiency calculations where intensity is expressed as a percentage of optimal
• The reference point for the UV Health component of the health score

Values above 650 W/m² are possible in cold, clear water conditions where UV transmittance is high.

Operating zones

0 ────── 252 ─────────── 530 ──────── 650+ W/m²
  FAIL    │  IMO ONLY    │  BOTH OK  │  OPTIMAL
          │              │            │

Lamp efficiency thresholds

Separate from UV intensity, individual lamp efficiency is tracked against these tiers, defined in THRESHOLDS.LAMP_EFFICIENCY:

Tier	Efficiency range	Colour	Recommended action
GOOD	≥ 90%	Green	No action
WARNING	70–89%	Yellow	Monitor, plan future replacement
DEGRADED	50–69%	Orange	Schedule replacement at next port
CRITICAL	< 50%	Red	Urgent replacement required

Lamp runtime thresholds

Defined in THRESHOLDS.LAMP_RUNTIME:

Threshold	Value	Action
WARNING	2,500 hours	Begin planning replacement
MAX	3,000 hours	End of rated lamp life

UV intensity vs lamp efficiency: the relationship

Individual lamp efficiency affects aggregate UVR_INTENSITY. As lamps degrade, the system cannot maintain the intensity setpoint without increasing UVR_POWER_OUTPUT.

POWER_COMPENSATION_PCT quantifies this: a value of 20 means the system consumes 20% more electrical power to achieve the same UV intensity that new lamps would produce at rated power. This is visible in the Trend Analysis tab’s runtime charts — the power line climbs as the efficiency line falls.

References

• IMO D-2 Regulation — regulatory context for the 252 W/m² threshold
• USCG Standards — regulatory context for the 530 W/m² threshold
• UV Disinfection Technology — physics behind intensity requirements
• Compliance Monitoring Tab — where these thresholds are applied in real time