... two options, one is single speed, one is variable speed circulation.Product descriptionStainless steel casing, big air ... performance, low noise, low power consumptionSingle and variable speed models are available.NameModelVoltageFrenquencyPowerRMPAir flowFLC circulation fan ... Circulation fan variable speed ZLFJ500T 220V/110V 50HZ 45-100W 950*1400r/min3900 - 5800m3/h ZLFJ400 Voltage:220V, Frequency ...