Rooftop Water Tank Float Switches in Vietnam: 220 V Pump-Up Control, Dry-Run Protection & Cable Length
A specifier's guide for Vietnamese pump packagers, control-panel builders and plumbing wholesalers: the two level points a rooftop tank actually needs, how to wire one 3-core float for either duty, and how to choose a cable length that survives the monsoon season.
Rooftop and overhead storage tanks (bồn nước) are standard on Vietnamese houses, shops and small factories. Mains supply can be intermittent, so the tank is filled by a transfer pump rather than simply left on line pressure. That arrangement creates two separate failure modes: the tank overflows when the fill pump is not stopped, and the pump runs dry when the source tank, well or mains feed runs empty. Both are level-control problems, and both are solved with a cable float switch — but not with the same single switching point. This guide maps the two level points to an actual float bill of materials so the RFQ is right the first time.
1. Define the two level points before ordering anything
A fill-control scheme normally needs a high-level stop (pump switches off when the rooftop tank is full) and a low-level / dry-run stop (pump switches off when there is no water to draw). A single cable float gives one switching point. The practical minimum is one float for tank high level, plus either a second low-level float at the source, a controller with a low-level input, or a dry-run relay. In projects with an alarm requirement, add a third independent high-high float feeding the alarm circuit rather than the pump circuit. Write down the number of switching levels and the panel's available inputs before choosing models.
2. One 3-core float, two wiring directions
The UKY cable float uses a 3-core cable — black, blue and brown — around a changeover microswitch. Wire it one way for pump-down (empty a pit: pump starts at high level, stops at low level) and reverse two cores for pump-up (fill a tank: pump starts at low level, stops at high level). The same part number therefore covers both rooftop fill and sump drainage, which lets a Vietnamese OEM keep one stocked SKU for two product lines. The switching level is set by sliding the polypropylene counterweight along the cable — one screw, no tools — so the installer can fine-tune the level after the tank is in place.
3. Select cable length from the installed geometry, not the tank capacity
Length is driven by the distance from the fixing point to the lowest switching level, plus the float's swing radius and the run back to the junction box — not by how many litres the tank holds. Standard factory-fitted lengths are 2, 3, 5, 10 and 15 m. A shallow plastic rooftop tank is usually a 2 or 3 m job; an underground concrete cistern, a deep stormwater pit or a pond intake may need 10 or 15 m. Leave enough slack for the float to swing freely, keep the counterweight clear of the inlet stream, and never coil the spare cable inside the tank where it can snag. Custom lengths are available for repeat OEM volumes.
4. Respect the 220 V / 50 Hz electrical boundary
Vietnam's domestic supply is 220 V / 50 Hz single-phase; industrial sites commonly use 380 V three-phase. ELEHPD cable floats are rated 250 V AC with 380 V maximum isolation (120 V AC versions for 110/120 V export markets), in 16 A (8 A), 10 A (8 A) or 10 A (4 A) versions. That is a signal rating. A 750 W / 1 HP pump and anything larger, plus every three-phase motor, should be switched by a contactor or control panel: the float feeds the panel input, the panel switches the motor. Fixed 220 V wiring belongs with a qualified electrician. Treating the float as a direct motor switch is the most common cause of welded contacts and premature failure.
5. Heat, humidity, dirty water and switching cycles
Sealed polypropylene with an IP68CS rating is designed for permanent immersion; the range is rated 0–70 °C, with PVC or HO7RN-F cable resistant to wastewater and oil — relevant for monsoon drainage and aquaculture ponds where the cable may sit in warm, silty water for months. Mechanical endurance is over 100,000 cycles and electrical endurance over 50,000 cycles. Domestic-grade switches are often specified with only a few thousand cycles, so for commercial buildings and contractor projects, ask for the endurance figure and the cable material in writing rather than comparing only the IP number. Standard models are not Ex / intrinsically safe, and highly viscous or solids-heavy media need a separate assessment.
6. RFQ checklist and project documentation
Send these six lines and we can confirm the closest catalogue model without a second round of questions:
- Tank or pit depth, and the height of the fixing point above the lowest switching level.
- Number of switching levels (stop / start / alarm) and the control panel's input count.
- Pump-up or pump-down duty, or both on the same SKU.
- Supply: 220 V single-phase or 380 V three-phase via contactor; pump power in kW or HP.
- Medium: clean water, wastewater, greywater, pond water, mild acid/alkali.
- Quantity, cable length, and whether private-label markings or Vietnamese labelling are required.
For contractor submissions we supply English datasheets, wiring diagrams and the technical file, with CE / RoHS documentation under an ISO 9001 quality system; Vietnamese labelling can be coordinated with the importer for CO/CQ and project acceptance. Note: whether the finished assembly falls under Vietnam's mandatory CR certification (QCVN / TCVN) depends on its HS code and the applicable regulation, and must be confirmed by the Vietnamese importer or panel builder — ELEHPD does not claim a Vietnamese CR certificate. Spares and documentation ship factory-direct; we do not operate a local repair centre or spare-parts warehouse. For the wider electrical and application context see our Vietnam market page.
FAQ
Can one float switch handle both overflow and dry-run protection on a rooftop tank?
Not by itself. A single cable float gives one switching point. A typical fill-control arrangement uses one float to stop the pump at high level, plus either a second low-level float, a controller with a low-level input, or a dry-run relay to stop the pump when the source tank or well runs empty. Vietnam's intermittent mains supply makes the low-level/dry-run side the one most often forgotten.
Can the float switch a 1 HP / 750 W pump directly?
Do not rely on it. A float switch is a signal device with a limited contact rating - 16 A (8 A), 10 A (8 A) or 10 A (4 A) at 250 V AC depending on version. Motor starting current and 380 V three-phase loads belong in a contactor or control panel. The float feeds the panel input; the panel switches the motor. Fixed 220 V wiring should be installed by a qualified electrician.
Does ELEHPD hold Vietnamese CR certification for these switches?
ELEHPD does not claim a Vietnamese CR certificate. The float is a control component supplied to OEMs and panel builders; the importer or the assembler determines the applicable QCVN / TCVN requirements for the finished assembly based on its HS code. We provide CE, RoHS and ISO 9001 documentation, datasheets, wiring diagrams and the technical file the importer needs for that assessment.
Related ELEHPD products
- UKY cable float switch, 2 m cable
- UKY cable float switch, 3 m cable
- UKY cable float switch, 5 m cable
- UKY cable float switch, 10 m cable
- UKY cable float switch, 15 m cable
- Water level controller for pump
Related guides
- Rooftop water tank float switch Vietnam
- Rainwater tank float switch Australia
- Stormwater pit float switches: duty/standby & high-level alarms
- How to wire a cable float switch to a pump
- Float switch selection guide
- Cable float vs electrode level switch
Supplying the Vietnamese market
ELEHPD manufactures and wholesales float switches and level controllers to Vietnamese OEMs, pump packagers, control-panel builders and distributors. Vietnam already has established local float brands, so we position ourselves upstream: factory-direct sealed float elements, custom cable lengths, private-label markings and the documentation the importer needs. We do not compete with local retail brands and we do not maintain a local warehouse. See our Vietnam market page for voltage, compliance and application notes.
Talk to us about your specification
Send the tank depth, the number of switching levels and the pump power, and we will confirm the closest match from the ELEHPD catalogue, the documentation available for it and the lead time. OEM branding and buyer-specific cartons are available on qualified volumes.