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Monthly Tech Tips

Tech Talk Tip: Will the M500 help me in confirming an open winding?

The M500’s design is intended to measure the insulation resistance between 20 and 1,000 mega ohms.   It is a simple and effective way to monitor compressors and motors of almost any type.  The measurement indicates the degradation of a motor winding and will determine if a motor is about to fail or if there is moisture in the sealed system.  To do this the M500 is measuring the winding against ground.  A winding with weak insulation will indicate a level of resistance. 

However, your question is if our M500 Megohmmeter  (A.K.A. a “megger”) can measure an open winding.  An open winding would mean the motor has already failed.  The easiest way of testing for open motor windings is an Ohm check with a multimeter.  To use the M500 you would have to understand the different readings. Instead of connecting your M500 test leads to one load leg and ground, you would have to connect to the ends of your windings.

For example;

A 115 volt single phase motor, connect to “neutral” and “load”.

For a 115 volt multistage motor, it would be across the different speed legs to neutral, and so on.

The readings on the M500 would be opposite. For a bad winding, the M500 would read with the green LED “on” showing. For a good winding, the M500 would read with the green “on” and the red” bad” LED showing.

With this in mind, it can also be used to test transformers, contactors, and relays as well as 2 pole and 3 phase motor windings.

Tech Talk Tip: Locking Refrigerant Safety Caps

In March of 2009, the International Mechanical Code (IMC) and the International Residential Code (IRC) passed a law in each code book requiring the installation of locking caps on refrigeration systems on both residential and commercial air conditioning, heat pump, packaged, and ductless systems.

IMC code chapter 11- 1101.10 and IRC code chapter 14- 1411.8 reads as follows; Refrigeration circuit access ports located outdoors shall be fitted with locking type tamper-resistant cap or shall be otherwise secured to prevent unauthorized access.

Exception; This section shall not apply to refrigeration circuit access ports on equipment installed in controlled areas such as, on roofs with locked access hatches and doors.

Any locking cap can be circumvented with the right tools, but the deterrent of the SUPCO locking caps keeps your equipment in compliance without spending profits on expensive caps. You can’t put a price on safety, but the new SUPCO SFL14 series ¼ inch and the SLF516 series 5/16th inch caps can provide safety at a reasonable price. The SLF1402/SLF51602 (2 pack), SLF1410/SLF51610 (10 pack), and the SLF1450/SLF51650 (50 pack) are almost half the cost of competing caps. This can add up to quite a bit meeting the code requirements. No tools are needed for installation, and the removal can be performed with your 3/16th valve access hex key and are only required for removal. They simply tighten on by hand and are UV resistant composite to last the life of your equipment.

 SUPCO elected not to color code our caps. Color coded caps require stocking multiple types for service and could lead to mis-identifying the refrigerant type. Refrigerant type is well marked on the equipment and should be confirmed from the equipment tag before performing any system service.

This Tech Tip contains general technical information provided for educational use only. It is not intended to be technical advice and should not be treated as such, since situations, conditions, experience and skills are unique and vary widely. Information contained in this Tech Tips including, without limitation, all content, technical data, suggestions, ideas, services, features, functions and materials are provided "As Is," "As Available" without warranty of any kind, either express or implied including, without limitation, any warranty for information and any warranties concerning the accuracy, precision, correctness, thoroughness, completeness, usefulness, or content of the information. Supco® disclaims any and all liability and damages in connection with the providing or use of such technical information.