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SPX Cooling Technologies Marley NC Cooling Tower

Operation, maintenance, and water treatment guide for Marley NC series induced draft cooling tower. Covers mechanical maintenance, water treatment, and Legionella prevention per ASHRAE 188.

SPX Cooling Technologies Marley NC8403

Safety Warnings

  • •LEGIONELLA RISK: Aerosol from cooling towers is a public health hazard
  • •Follow ASHRAE 188 Water Management Plan at all times
  • •PPE: N95 respirator, goggles, waterproof gloves when working near tower
  • •Never enter operating tower without proper confined space permit

ASHRAE 188 Compliance

A written Water Management Plan is required. Key elements:

  1. Describe system in detail with P&ID
  2. Identify control points and monitoring parameters
  3. Assign responsibility for each control measure
  4. Define corrective action triggers
  5. Document all testing and treatment

Water Treatment Targets

| Parameter | Target | |-----------|--------| | pH | 7.2 – 8.5 | | Conductivity | 1200 – 2000 µS | | Total Hardness | 100 – 300 mg/L | | Chlorine (biocide) | 0.5 – 1.5 ppm free | | Scale inhibitor | Per program | | Legionella (quarterly) | < 10 CFU/mL |

Monthly Mechanical Inspection

  • Fan blades: Check for balance, erosion, or cracks
  • Gearbox oil level: Change annually, SAE 90 gear oil
  • Drive shaft couplings: Check alignment and condition
  • Fill media: Inspect for scale or biological fouling
  • Basin: Remove debris, check float valve

Seasonal Startup (After Winter Shutdown)

  1. Flush and drain basin completely
  2. Clean basin and remove sediment
  3. Fill with fresh water
  4. Shock dose with biocide (10-20 ppm chlorine)
  5. Run and test water chemistry before connecting to chiller

Structured Troubleshooting

Common problems, likely causes, diagnostic steps, and safe resolution paths.

Cooling tower — elevated Legionella risk indicators

High confidence
Likely Causes
  • Water temperature in optimal Legionella growth range (68–113°F) without adequate biocide
  • Biocide dosing system malfunction — chemical not being added
  • System stagnation — areas of low or no flow providing growth sites
  • High turbidity or biofilm visible on surfaces
Diagnostic Steps
  1. Test free biocide residual immediately — chlorine should be 1–3 ppm; bromine 2–4 ppm
  2. Inspect biocide dosing pump operation and chemical supply level
  3. Check all water circulation paths — identify and eliminate dead legs
  4. Inspect basin surfaces, fill media, and drift eliminators for biofilm
Resolution Paths
  • Shock treat with biocide per ASHRAE 188 and system water treatment provider guidance
  • Service or replace failed dosing pump
  • Flush dead leg sections and increase circulation
  • Clean biofilm surfaces and increase biocide concentration temporarily

Cooling tower water — scale buildup or system fouling

Medium confidence
Likely Causes
  • Cycles of concentration too high — dissolved solids concentrating
  • Makeup water hardness not being compensated with scale inhibitor
  • pH not being maintained — outside 7.0–9.0 range
  • Blowdown not functioning — conductivity setpoint not achieved
Diagnostic Steps
  1. Test water hardness, alkalinity, and conductivity — compare to treatment provider target ranges
  2. Verify blowdown valve is operating and opening at conductivity setpoint
  3. Measure scale inhibitor residual against target concentration
  4. Inspect fill media and heat exchanger for scale deposits
Resolution Paths
  • Adjust blowdown setpoint to reduce cycles of concentration
  • Increase scale inhibitor dosage in consultation with water treatment provider
  • Correct pH using acid (to lower) or alkali (to raise) per treatment program
  • Descale fill media or heat exchanger with approved chemical treatment
cooling towermarleySPXwater treatmentLegionellaASHRAE 188condenser water