32.3 Cleaning Towers, Condensers, Foreign Matter & Condensate Drains
Key Takeaways
- FBC Mechanical 307.2.1 slopes condensate not less than 1/8 inch per foot to an approved disposal; 307.2.1.1 forbids a direct sanitary DWV tap. Table 307.2.2 sizes the drain at 3/4 inch through 20 tons. F.S. 489.105 lets Class A/B run condensate only to an existing safe waste.
- Where overflow would damage the building, 307.2.3 requires an auxiliary pan with a conspicuous drain, an equipment overflow drain, an auxiliary pan with a UL 508 shutoff, or a UL 508 water-level device. Downflow coils (307.2.3.1) take the device in the primary pan — not in the drain line. 307.2.5 wants the line clearable without cutting.
- Florida condensate fails on algae, biological slime, and scale. Service is flush, trap cleanout, listed pan treatment that does not plug the outlet, and a float switch that actually lifts. A secondary pan full of sludge is not overflow protection.
- Cooling-tower service is fill, basin, strainers, and drift eliminators plus bleed-off (blowdown) to control cycles of concentration. Legionella awareness is real because towers aerosolize water; follow the water-treatment specification and the listing. Do not invent an unpublished ppm as the CILB answer.
- A water-cooled condenser that is fouled shows a rising approach (saturated condensing temperature minus leaving condenser water). Clean tubes mechanically or chemically after LOTO. Foreign matter also lives in strainers, air-cooled fins, and pump screens. Class B still cleans these components on legal systems; a 40-ton tower loop is Class A to contract.
32.3 Cleaning Towers, Condensers, Foreign Matter & Condensate Drains
The last Trade F cluster in this chapter is cleaning cooling towers, cleaning foreign matter from systems, cleaning water-cooled condensers, and cleaning condensate drain lines. Installing towers and condenser barrels was Chapters 21.2 and 23.1. Installing the drain pan was Chapters 19.4 and 20.1. This section is service: Florida algae and scale in a 3/4-inch drain, a float switch that never lifts, a secondary pan full of sludge, a tower basin that smells like a swamp, and a water-cooled barrel whose approach has doubled. FBC Mechanical 2023 (8th Edition — the 2026 CBT edition) Sections 307 and 908, Refrigeration & Air Conditioning Technology, 9th Edition (2021), and OSHA 29 CFR 1926 are the books. F.S. 489.105 still lets Class A and Class B run condensate only to an existing safe waste, not a new sanitary tap, and still caps Class B at 25 tons / 500,000 Btu for the connected system. Cleaning a 20-ton tower loop can be Class B. Cleaning a 40-ton plant does not turn that plant into a Class B system.
Quick Answer: Condensate: 1/8 in/ft, 3/4 inch through 20 tons, no direct sanitary, plus a 307.2.3 overflow method over finished space — UL 508 float or a secondary pan. Florida plugs drains with algae and slime; clean so 307.2.5 is true (clear without cutting). Towers: clean fill and basin, keep bleed-off working, treat the water. Legionella is a cooling-tower risk because the fan aerosolizes water — follow the treatment spec; do not invent a ppm. Water-cooled condensers: clean tubes when approach rises.
Condensate drain lines — Florida algae, floats, and the secondary pan
Florida latent load keeps evaporator pans wet for months. Warm, dark, 45–55°F pans grow biological slime and algae; makeup and coil carryover leave scale. The exam still wants the code drain, not a shop towel in the pan.
FBC Mechanical 307.2.1: convey condensate to an approved place of disposal at a horizontal slope of not less than 1/8 unit vertical in 12 units horizontal (1 percent). Do not dump it into a street or alley as a nuisance. 307.2.1.1: no direct connection to the sanitary DWV. Indirect to a floor sink, hub drain, standpipe, or similar receptor. That matches the HVAC license fence: existing safe waste, not a new sanitary wye.
307.2.2 / Table 307.2.2: drain not smaller than the pan outlet and not less than 3/4 inch through 20 tons; 1 inch from 20 to 40 tons; 1-1/4 inch from 40 to 90 tons. Never reduce downstream. Class B’s 25-ton cap already sits on the 1-inch row once you manifold over 20 tons.
307.2.3 — overflow protection where damage to building components could occur (Florida attics and second-floor air handlers are the default): one of (1) auxiliary drain pan with a separate drain to a conspicuous point, pan 1-1/2 inches minimum depth and 3 inches larger than the unit, 24-gage galvanized or 0.0625-inch nonmetallic; (2) equipment overflow drain from a higher pan connection to a conspicuous point; (3) auxiliary pan without a drain but with a UL 508 water-level device that shuts the equipment off; (4) a UL 508 device in the primary pan, overflow line, or primary line as the item allows. 307.2.3.1 (downflow and coils with no secondary-pan provision): the water-level device goes inside the primary drain pan. Devices installed in the drain line shall not be permitted on those units.
307.2.4: trap as the manufacturer requires. 307.2.5: configure the line so you can clear blockages without cutting the pipe. That single sentence is the service exam item: cleanouts, unions, or a removable trap — not a glued 20-foot run of 3/4-inch PVC with no access above a finished ceiling.
Service that actually matches 307. Vacuum or flush the primary line from an accessible cleanout. Pull the trap and dump the algae plug — the usual Florida no-cool call in August. Listed pan-treatment tablets control biological growth; a whole puck jammed in the outlet is a new blockage, and some treatments attack aluminum pans — follow the listing. Prove the float switch (or pan sensor) by lifting it: the equipment must stop. Sludge that holds the float up causes nuisance trips; sludge that cements it down is no protection at all. A secondary pan that has become a planter is not 307.2.3 Item 1 — clean it, confirm the conspicuous drain still spills where someone will see it, and never pipe the secondary back into the primary. Condensate pumps still need a float and a lockout on pump failure (307.2.5.2 family on attic pumps). Low-voltage float cable is HVAC work on both licenses.
Cooling towers, bleed-off, and Legionella awareness
A cooling tower rejects condenser heat by evaporative cooling (Chapter 21.2). Service dirt is scale on fill, algae and biofilm on wet surfaces, sludge in the basin, and foreign matter — leaves, birds, cooling-tower drift, and construction debris — on strainers and screens. FBC Mechanical 908 still wants the appliance installed and listed (UL 1995 or UL/CSA 60335-2-40). Cleaning does not waive the listing, the fan guard, or LOTO on the tower fan and condenser pump before anyone leans into the fill.
Bleed-off (blowdown) dumps a fraction of circulating water so dissolved solids do not concentrate until everything scales. Cycles of concentration compare makeup-water dissolved solids to circulating-water solids. The water-treatment specification sets the target cycles for that makeup water and that tower. A common comfort-cooling conversation is a few cycles, not an infinite closed loop with no bleed. Too little bleed: scale and a high condensing temperature. Too much bleed: wasted water and treatment chemical. Do not treat an unpublished ppm (free chlorine, bromide, or otherwise) as a CILB exam number unless the item prints the spec. The outline asks you to clean the tower and keep bleed-off and treatment working, not to recite a forum residual.
Legionella. Cooling towers aerosolize water. Legionella bacteria can colonize warm basins and biofilm; the drift can carry them. ASHRAE Standard 188 and public-health guidance describe a water-management program: keep the basin clean, keep treatment in spec, keep drift eliminators in place, and do not leave a tower stagnant then shock it into occupied air. That is awareness for the contractor exam, not a license to invent a Florida statutory ppm. Follow the treatment vendor, the listing, and any building water-management plan. Use SDS and PPE for biocides and descalers (Chapter 33). Some basins are confined spaces — do not treat a tower like a kiddie pool.
Cleaning sequence (service, not a shutdown dare): LOTO fan and pumps. Isolate makeup and bleed as the spec requires. Remove foreign matter from screens and the basin. Clean fill and drift eliminators so air and water actually meet. Flush sludge; do not wash it into the condenser barrel. Restore treatment and bleed. Bump the fan for rotation (swap two leads if three-phase is backward — Section 32.1) only after guards are on and windings are not being serviced live.
Water-cooled condensers and foreign matter
A water-cooled condenser (shell-and-tube or coaxial) rejects heat into condenser water. Approach on this heat exchanger is saturated condensing temperature minus leaving condenser-water temperature. Clean tubes show a small approach. Fouled tubes (scale, rust, biological film, mud) make refrigerant sit hotter than the leaving water: approach rises, head pressure rises, capacity falls, and the compressor amps climb. That is the diagnostic that says clean the condenser, not replace the TXV.
Worked approach. Design is 95°F condensing with 85°F leaving condenser water — 10°F approach (numbers from the schedule, not a law of physics). After two untreated Florida summers the same machine shows 110°F condensing with 86°F leaving water — 24°F approach. The tower is making water; the barrel is dirty. LOTO the compressor and pumps. Isolate, drain, remove heads on a shell-and-tube, brush the tubes, or chemically descale per the manufacturer and the SDS. Do not rod out tubes with a tool that cuts tube wall. Coaxial coils follow the listing — often chemical or replacement, not a shop brush. Flush foreign matter from strainers and pump screens before you restart so you do not pack the last of the mud into the tubes you just cleaned. Air-cooled coils are the other foreign-matter job: cottonwood, sand, and kitchen grease on fins — coil-clean, straighten, do not chew the aluminum with a pressure washer at point-blank range.
Class A / Class B. A 20-ton water-cooled package with a small tower is inside Class B tons if heat is under 500,000 Btu. An 80-ton barrel and tower are Class A. Both candidates still read approach, still clean strainers, and still know that plastic pipe belongs on the water side, never on the refrigerant circuit (Chapter 23.1).
| What you are cleaning | Dirt that shows up in Florida | Field flag | Code / service rule |
|---|---|---|---|
| Condensate drain and pans | Algae, slime, scale | Overflow, no-cool, wet ceiling | FBC 307: 1/8 in/ft, Table 307.2.2 size, no direct sanitary, UL 508 float or secondary pan, clear without cutting |
| Cooling tower | Biofilm, scale, leaves, sludge | High head, dirty basin, closed bleed | 908 listing; LOTO fan/pump; restore bleed-off and treatment; Legionella awareness — no invented ppm |
| Water-cooled condenser | Tube scale, rust, mud | Approach rises (SCT minus leaving water) | LOTO; brush or chemical clean per listing; flush strainers first |
| Foreign matter elsewhere | Fins, pump screens, construction debris | Low CFM, tripped strainers | Clean screens and coils; do not pack debris back into the barrel |
Florida scenario
Coastal Comfort, certified Class B in Broward County, has two Monday calls. Call one: a second-floor 3-ton air handler over finished space, no cooling, pan overflowing. The primary 3/4-inch line is a glued run with no cleanout, sloped backward in one bay, packed with algae. The secondary pan is full of wet insulation and the float is cemented down, so the unit never shut off. Service that matches 307: add access so the line clears without cutting, restore 1/8 in/ft, flush the algae, replace the float, clean the auxiliary pan, and keep the conspicuous secondary drain. Do not tee into the sanitary stack. Call two: a 40-ton water-cooled loop the owner wants Class B to take over because we already clean the 3-ton drains. Tower fill is slimy, bleed-off is valved off to save water, and condenser approach has gone from about 10°F to the mid-20s. Cleaning and restoring bleed-off is the right mechanical work. Contracting the 40-ton plant is Class A. Legionella awareness means you do not start that fan over a dirty stagnant basin without the water-management program; it does not mean you quote a ppm the outline never published.
Traps: (1) Direct sanitary condensate. (2) Drain-line-only float on a downflow coil. (3) Secondary piped into primary. (4) Cutting the drain every clog because nobody installed a 307.2.5 cleanout. (5) Valving off tower bleed to save water. (6) Inventing a chlorine ppm as the exam answer. (7) Calling a high-approach barrel a bad TXV. (8) Class B taking the 40-ton tower because the drain call was 3 tons.
A Broward County attic air handler over finished space has stopped cooling. The 3/4-inch primary drain is packed with algae, the secondary pan is full of sludge, and a float taped only in the primary drain line never shut the unit off. Which service-and-code statement is correct?
A cooling tower serving a legal Class B 20-ton water-cooled unit has slimy fill, a basin full of leaves, and the bleed-off valve closed to save water. Which cleaning statement matches Trade F without inventing a chemistry number?
A water-cooled condenser that used to run about 10°F of approach now shows 24°F of approach (saturated condensing temperature minus leaving condenser water) with a clean tower and design flow. Which statement is correct?