Watlow Mercury Relay or MDR Retrofit User Manual
Using this retrofit guide
Using This Retrofit Guide
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Additional information on other Watlow products may be obtained by visiting
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If there are multiple listings, then the retrofit is conditional upon field use. Select the appropriate selection. The User’s
Manual is included at the bottom of this document when available.
Before selecting a replacement controller:
1. Know the application.
• Temperature range
• Sensor type
• Is the sensor upgradable if required?
• Additional input requirements – remote set points, secondary sensor or events
• Output required – control, alarm, event
• Is the power-switching device upgradable?
• Operating voltage of controller
• Mounting requirements – panel space
• Is a safety limit device required?
2. Know the product.
• Inputs – type and number of
• Control function – direct (cool) or reverse (heat)
• Outputs – switched DC, SSR, or mechanical relay
• Communication requirements
• Which control features are required? (cascade, slidewire, differential, remote control, other)
3. Use your best judgment for selecting a replacement controller. All applications require close examination of input,
output and the control mode needs to have the controller function properly.
4. Safety: Remember to make sure all redundant safety equipment is in place and working when retrofitting equipment.
If a system has been retrofitted without the proper safety equipment, you could be liable if an accident occurs.
This is only a guide to replacement controllers. If you have doubts, please call (507) 454-5300
and ask for technical support or email [email protected]. We’re here to help. The
suggested replacement will differ in fit and form. Please review the replacement controller
specifications for suitability. Carefully check the notes for additional information that may
apply.
Your comments or suggestions on the Retrofit Guide are welcome. Please send comments or corrections to: Technical
Writer, Watlow Controls, 1241 Bundy Boulevard, P.O. Box 5580, Winona, MN 55987-5580; phone (507) 454-5300; fax
(507) 452-4507.
This Retrofit Guide is copyrighted by Watlow Winona, Inc., © February 2004 with all rights reserved. (1455)