--- title: "RDF 18 Series Evaporative Air Cooler — Bottom Discharge" url: https://tiercooling.com/product/rdf-18-series-evaporative-air-cooler-bottom-discharge/ date: 2026-09-07 modified: 2026-10-09 lang: en author: "info@tiercooling.com" description: "RDF18 — RDF evaporative air cooler for factories, workshops and warehouses — high-airflow water-evaporative fresh-air cooling at low running cost. Request a quote for quantity and project pricing." image: https://tiercooling.com/wp-content/uploads/2026/09/RDF-180A-G-9.jpg word_count: 904 --- # RDF 18 Series Evaporative Air Cooler — Bottom Discharge The **bottom-discharge (B) RDF18 series** pushes 18,000 m3/h straight down from elevated positions - roof risers, mezzanines and platform decks - into the occupied zone. It shares the 1.1 kW, 5090-pad platform of the family and is offered with 25 L or 35 L tanks and a 670x670 mm outlet across 220 V and 380 V versions. ## Why factories choose RDF evaporative cooling - **Proven cooling pad.** 100 mm Type-5090 cooling pad with evaporation efficiency above 80%; corrugated cellulose gives roughly 100x the water-to-air heat-exchange area of a flat surface. - **Real temperature drop.** 4-10 C cooler supply air in humid climates and 4-15 C in hot, dry climates, with continuous fresh air instead of recirculated indoor air. - **About 1 kWh per hour.** A typical RDF unit uses roughly one unit of electricity per hour - about one fifth of the capital cost and one tenth of the running cost of compressor air conditioning for the same area (manufacturer figures). - **Clean, low-maintenance water system.** Open water distribution is easy to inspect and resists clogging; Class-I anti-algae pad treatment, low-water protection and RoHS/REACH compliant contact materials. - **Cooling, ventilation and filtration in one.** Slight positive pressure pushes hot, dusty or odorous air out through doors and vents - ideal for open or semi-open production spaces. - **Central control ready.** The GK800 system links up to 32 units over RS485/Modbus with zoning, scheduling and fault indication for factory-wide installations. ## Technical specifications | Model | Voltage | Max. airflow (m3/h) | Std. airflow (m3/h) | Current (A) | Power (kW) | Dimensions LxWxH (mm) | Air outlet (mm) | Weight (kg) | Tank (L) | Panel | | ----- | ------- | ------------------- | ------------------- | ----------- | ---------- | --------------------- | --------------- | ----------- | -------- | ----- | | RDF18A-11 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1000 | 670x670 | 60 | 25 | LCD | | RDF18A-11S | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1000 | 670x670 | 60 | 25 | LED | | RDF18A/BT | 220V/50Hz | 18,000 | 11,500 | 4.8 | 1.1 | 1100x1100x1000 | 670x670 | 60 | 25 | LCD | | RDF18B-11 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1120x1100x1000 | 670x670 | 56 | 35 | LCD | | RDF18B-11S | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1120x1100x1000 | 670x670 | 56 | 35 | LED | | RDF18B/BT | 220V/50Hz | 18,000 | 11,500 | 4.8 | 1.1 | 1120x1100x1000 | 670x670 | 56 | 35 | LCD | | RDF18C-11 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1025 | 730x730 | 62 | 35 | LCD | | RDF18C-11S | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1025 | 730x730 | 62 | 35 | LED | | RDF18C/BT | 220V/50Hz | 18,000 | 11,500 | 4.8 | 1.1 | 1100x1100x1025 | 730x730 | 62 | 35 | LCD | | RDF18A-12 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1000 | 670x670 | 60 | 25 | LED | | RDF18B-12 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1120x1100x1000 | 670x670 | 56 | 25 | LED | | RDF18C-12 | 380V/50Hz | 18,000 | 11,500 | 2.8 | 1.1 | 1100x1100x1025 | 730x730 | 62 | 25 | LED | | RDF20A/SF | 220V/50Hz | 20,000 | 13,500 | 3.7 | 1.1 | 1100x1100x1000 | 670x670 | 53 | 35 | LCD | | RDF20B/SF | 220V/50Hz | 20,000 | 13,500 | 3.7 | 1.1 | 1120x1100x1000 | 670x670 | 50 | 35 | LCD | | RDF20C/SF | 220V/50Hz | 20,000 | 13,500 | 3.7 | 1.1 | 1100x1100x1025 | 730x730 | 56 | 35 | LCD | Standard airflow measured under GB/T conditions; maximum airflow in free discharge. A = side discharge, B = bottom discharge, C = top discharge; 11/12 suffixes mark outlet-ducting variants; /BT = single-phase; /SF = high-airflow PMSM version. ## When bottom discharge is specified B-units are chosen when the cooler sits on an elevated platform or roof frame and air must drop vertically into a double-height production hall, warehouse aisle or atrium before spreading horizontally. The discharge geometry lets the cooled column reach floor level before mixing - useful in spaces over 6 m. The same low-water protection, open distributer design and optional GK800 group control apply; if the project needs high static pressure for metal duct runs, look at the centrifugal B-series (25,000-60,000 m3/h) rather than the axial RDF18B. ## Backed by a specialist air-treatment manufacturer - 20+ years focused on evaporative cooling and large industrial fans; National High-Tech Enterprise and CRAA-listed manufacturer. - Deputy Director Unit of the national evaporative-cooling industry committee, with 40+ patents and self-developed, patented molds. - Product liability underwritten by CPIC (policy ADNGD0207121Q000109N); type-test, protection-grade and CE motor-conformity documentation supplied with export orders. - RDF equipment is published in service with automotive, food and electronics manufacturers including SAIC-GM-Wuling, FAW-Volkswagen, GAC Toyota/Honda, PepsiCo, Foxconn, Panasonic, Gree, Midea and Haier. ## Ordering the RDF18/RDF20 series bottom-discharge evaporative cooler (18,000-20,000 m3/h) - **MOQ:** 10 units - **Lead time:** 10 units ex stock; 100 units in about 7 days; 500 units in about 20 days (larger orders confirmed case by case) - **Trade terms:** FOB Shenzhen - **Payment:** T/T - 35% deposit, 65% balance paid before shipment - **Warranty:** 2-year warranty on the complete unit per the factory's warranty policy: motor 2 years, controller 2 years, cooling pad 2 years, water pump 1 year. Overseas spare-parts support (wear-parts list, quotation and dispatch lead time) is confirmed with your order. - **Documentation:** Factory inspection reports, RoHS/REACH pad-compliance documentation and the evaporative-cooler design patent certificate are available. Complete-unit CE/SASO certificates can be arranged for export orders upon request; motor-level CE (LVD), EMC/RoHS reports and national-lab complete-unit inspection reports are on file. Send your floor dimensions, ceiling height and heat-load description (a sketch or photo is enough) - we reply with a model recommendation, layout and quotation within one business day via the [contact page](/contact/). ## Frequently asked questions ### How much can an evaporative cooler lower the temperature? Brochure figures are 4-10 C in humid climates and 4-15 C in hot/dry climates. The closer the outdoor air is to saturation, the smaller the drop - ventilation benefit remains. We size from your local temperature and humidity data. ### Does it work when it is humid? Yes - the mechanism shifts toward ventilation and air movement. The large fresh-air volume keeps workshops acceptable even at 70-80% RH; for sealed spaces the compressor-based RDF low-carbon range is the alternative. ### What is the difference between an axial RDF18B and the centrifugal B-series? RDF18B is an axial-fan unit with a bottom outlet for vertical free discharge. The centrifugal B-series (RDF25B-RDF60B) are much larger high-static machines for ducted systems. This table lists the RDF18/20 axial configurations; the centrifugal family has its own series page. ### How much water and electricity does it use? Power is roughly 1 kWh/h for the 18,000-26,000 m3/h axial platforms; water use varies with humidity and bleed settings. Nominal water consumption per the manufacturer's Chinese-market data: about 60 L/h for the 18,000 m3/h class and about 100 L/h for the 23,000 m3/h class. ### How often must the cooling pad be replaced? With normal water quality and Class-I anti-algae treatment the 5090 cellulose pad lasts multiple seasons; replacement is a tool-free panel job. Maintenance schedule and pad pricing ship with the quotation. ## Related products - [RDF 18 Series - Side Discharge](/product/rdf-18-series-evaporative-air-cooler-side-discharge/) - [RDF 18 Series - Top Discharge](/product/rdf-18-series-evaporative-air-cooler-top-discharge/) - [Centrifugal Fan Evaporative Air Cooler](/product/centrifugal-fan-evaporative-air-cooler/) - [Axial Fan Evaporative Air Cooler](/product/axial-fan-evaporative-air-cooler/) ## More from TierCooling - [View installed project references](/projects/) - [About the manufacturer](/about/) - [All products in this category](/product-category/evaporative-air-coolers/) ## FAQ ### How does an evaporative air cooler work? Evaporative cooling pulls hot outside air through water-wetted pads; evaporation removes heat from the air, delivering cooled airflow into the space. It works best in hot, dry climates where the evaporation effect is strongest. ### What is the difference between side, top and bottom discharge? Discharge direction decides installation: side-discharge units mount on walls and blow across or into ducting, top-discharge units suit roof mounting with downward delivery, and bottom-discharge variants feed airflow through a raised plenum. The right choice depends on building structure and airflow path. ### What maintenance does an evaporative cooler need? Routine care means keeping the pads and water system clean, checking the pump and drain, and winterising the unit in cold regions. Maintenance frequency rises with dust levels in the workshop. ### Do evaporative coolers work in humid climates? Cooling effect depends on the gap between air temperature and wet-bulb temperature, so output drops in very humid weather. In mixed climates they are often sized as part of a hybrid system with HVLS fans or low-carbon air conditioning.