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PT-500 Pump-Protection Application Note

Dry-run & dead-head protection with the PT-500 transmitter

Category
Application note
Model
AN-PT500-07

A centrifugal pump run dry or against a closed valve overheats within seconds. This note shows how a single PT-500 discharge-pressure transmitter, wired to the drive's analogue input, protects the pump by detecting both low-pressure (dry-run) and high-pressure (dead-head) conditions without extra flow switches.

Application scenario

A centrifugal pump run dry or against a closed valve overheats within seconds. This note shows how one PT-500 discharge-pressure transmitter, wired to the drive, protects the pump from both dry-run and dead-head without extra flow switches.

Recommended approach
  1. Mount the PT-500 on the pump discharge, downstream of the check valve.
  2. Wire the 4–20 mA output to the drive's analogue input AI1.
  3. Set a low-pressure trip below minimum running head and a high-pressure trip above dead-head.
  4. Add a short trip delay to ride through start-up transients.
Expected trip settings
Sensor range0–16 bar
Dry-run trip (low)< 1.2 bar for 3 s
Dead-head trip (high)> 12.5 bar for 2 s
Output4–20 mA to drive AI1
RestartManual reset after trip
Response time< 50 ms
References
PT-500 data sheet
DS-PT500
Pump protection guide
TN-PUMP-02
Product specifications and information are subject to change without notice, and State & Lake assumes no liability for errors, omissions, or the suitability of products for any specific application.
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