YS620 Altitude and Temperature Derating for Pump VFD Projects

The YS620 manual specifies installation below 1,000 m without altitude derating and states a 1% capacity derating for each additional 100 m. It specifies an ambient range of -10°C to +40°C at normal capacity and a 4% capacity derating for each 1°C from 40°C to 50°C. These rules must be applied to the actual air around the drive, with enclosure heating, ventilation, dust and simultaneous altitude effects reviewed before model selection.

Why This Application Needs Pump-Specific Engineering

Environmental derating is often discovered too late because buyers provide motor kilowatts but omit the site elevation and enclosure temperature. A 40°C outdoor weather report is not necessarily the drive ambient: solar gain, a sealed cabinet, pump heat and recirculated exhaust can make local air hotter. At high altitude, thinner air reduces cooling performance. Dust can block passages, while direct sunlight, corrosive gas, oil mist, steam and water drops fall outside the manual's stated installation conditions. A professional quotation therefore records the site, calculates the required capacity margin and states assumptions instead of silently selecting the same model used at sea level in an air-conditioned room.

Engineering Decisions and Evidence

Use site elevation, not nearest-city elevation

Mountain projects can vary hundreds of metres across a short distance.

Evidence to collect: GPS or surveyed equipment elevation in metres above sea level.

Risk if ignored: An incorrect altitude assumption removes intended thermal margin.

Engineering decision: Record the equipment location and apply the manual's rule above 1,000 m.

Measure the drive's cooling air

Ambient means the air experienced by the installed drive, not an outdoor forecast or control-room average.

Evidence to collect: Temperature at the drive air inlet during worst credible operation.

Risk if ignored: A cabinet hotspot can exceed the allowed condition while the room sensor remains acceptable.

Engineering decision: Design ventilation from measured or calculated enclosure heat and verify after commissioning.

Apply temperature derating transparently

The manual calls for 4% capacity derating per 1°C above 40°C through 50°C.

Evidence to collect: Worst local ambient, load profile and selected drive capacity calculation.

Risk if ignored: Ignoring a few degrees can create repeated overheating or shortened component life.

Engineering decision: Show the derating calculation in the technical offer and review a larger rating where required.

Apply altitude derating transparently

The manual states 1% capacity reduction for every 100 m above 1,000 m.

Evidence to collect: Exact elevation and resulting capacity multiplier.

Risk if ignored: A drive selected only on nominal motor power may lack sufficient capacity at altitude.

Engineering decision: Have Ausenist confirm the final model after all motor and environment data are supplied.

Do not add percentages casually

Temperature and altitude can occur together, but the correct combined selection should be confirmed by the manufacturer rather than improvised.

Evidence to collect: Both derating factors, motor current, duty cycle and enclosure condition.

Risk if ignored: A simplistic arithmetic shortcut can under- or overstate available capacity.

Engineering decision: Submit the combined case to Ausenist engineering and document the approved basis.

Control contamination and airflow

The YS620 manual excludes direct sunlight, dust, corrosive or flammable gas, oil mist, steam and water drops from normal installation conditions.

Evidence to collect: Site photos, contaminant type, cleaning practice, filters and maintenance access.

Risk if ignored: Blocked or corrosive cooling paths can defeat a correct electrical selection.

Engineering decision: Use a suitable protected installation and maintain airflow without exposing the drive to prohibited conditions.

Check the motor by current

Motor kW alone does not define VFD loading, especially across voltages or motor efficiencies.

Evidence to collect: Rated voltage, current, frequency, speed, service factor and actual pump duty.

Risk if ignored: A derated drive may no longer cover the motor current even when kW labels appear equal.

Engineering decision: Select from documented model current and application review, not a kW-only table.

Validate the hot operating point

A cold workshop test cannot prove a high-altitude or hot-enclosure installation.

Evidence to collect: Drive temperature indication, motor current, frequency and enclosure ambient at maximum credible duty.

Risk if ignored: Thermal alarms may appear only after hours of peak pumping.

Engineering decision: Run a controlled heat-soak test and retain readings as an acceptance baseline.

Verification Workflow

Stage	Action	Acceptance evidence
Locate	Record elevation and climate	Site data verified
Thermal	Calculate enclosure temperature	Worst ambient established
Load	Collect motor current and duty	Electrical demand known
Derate	Apply manual rules	Capacity review documented
Protect	Design airflow and contamination control	Installation conditions met
Prove	Perform hot-duty test	Temperature trend accepted

Information Buyers Should Send With the RFQ

• Equipment elevation above sea level
• Minimum and maximum ambient temperature
• Cabinet dimensions, ventilation and heat sources
• Direct sun, dust, moisture, gas or chemical exposure
• Motor nameplate and pump curve
• Continuous and intermittent duty profile
• Supply voltage tolerance and generator use
• Required enclosure or oem mounting arrangement

Illustrative calculation discipline

For a site at 1,800 m, the elevation is 800 m above the manual's 1,000 m threshold, so the stated altitude capacity reduction is 8%. For a measured drive ambient of 43°C, the stated temperature reduction is 12%. These two figures describe separate stresses; do not invent the combined model rating from the example. Provide them with motor current and enclosure data to Ausenist for an approved selection. The example explains the method, not a universal product recommendation.

Commissioning evidence

Place the temperature probe where the YS620 receives cooling air, not against a cool cabinet wall. Record inlet ambient, displayed internal temperature, output current and frequency at intervals until values stabilize. Repeat at the highest expected pump load and with the final enclosure closed. Check that filters and cable entries match production construction; a temporary open door invalidates the result.

Procurement wording

State elevation, design ambient and enclosure explicitly in the RFQ. Ask the supplier to identify the derating basis and exact drive model in the quotation. If environmental data are provisional, mark the recommendation provisional. This approach protects both buyer and supplier from a nominal selection that later fails when installed in a hot rooftop cabinet or remote highland pump station.

Frequently Asked Questions

Does a 1,500 m site require derating?

Under the YS620 manual rule, altitude above 1,000 m requires capacity derating; submit the full motor and environment case for model confirmation.

Can a fan cancel temperature derating?

A fan may reduce local ambient if correctly designed, but selection must use the verified air temperature at the drive and account for contamination.

Is outdoor installation allowed without an enclosure?

The manual's normal conditions exclude direct sunlight and water drops. Use a complete suitable protective installation and confirm the exact product arrangement.

Should I size from motor kW or current?

Provide both, plus voltage, frequency, speed, pump duty and derating conditions. Current is essential for checking VFD loading.

What happens above 50°C?

The cited normal derating range ends at 50°C. Do not assume operation beyond documented limits; redesign the environment or request engineering review.

Ask Ausenist for an Application Review

Send Ausenist the project elevation, measured or design ambient, enclosure details, motor plate, pump curve, duty cycle and contaminants. We can review the documented YS620 derating conditions and recommend an appropriate model or installation adjustment.