national codes, as well as DoD rules concerning safety, must be observed. Some of the more important safety steps that are often overlooked are as follows:

Protective equipment, such as eye protection, gloves, hard hats, and so forth, must be available and worn.

Fire extinguishers must be readily available, in good working order, and adequate for the situation.

Safety tags with such notations as "Danger," "Hands Off," "Do Not Operate," and "Do Not Throw Switch" should be attached to valves, switches, and at other strategic locations when servicing or making repairs.

Install machinery guards properly before operating machinery.

The above is only a short list and not intended to be all-inclusive. You will also find table W, appendix II, "Troubleshooting - Industrial Refrigeration," and table Y, appendix II, "Troubleshooting - Domestic Refrigerators and Freezers," useful guides for locating and correcting different troubles in refrigeration equipment.

Q46. Most problems with electrical motors for refrigeration system compressors fall into what classes?

Q47. How often is the coupling on the shafts of direct drive motors realigned?

Q48. What piece of equipment is installed in a refrigeration system just before the expansion valve to remove moisture?

Q49. Manually defrosting is normally required on refrigeration units that operate at what temperature?

Q50. If you suspect a component is open, you should test the source in what way?

Q51. What unit of measurement on a multimeter do you use to test for a short?

Q52. When checking for a ground, you use the same troubleshooting procedure as used for what other problem?

Q53. Troubleshooting a refrigeration system depends partly on your knowledge of how the equipment runs normally. True/False.

LOGS

Learning Objective: Understand the importance and use of maintaining, operating, and inspecting logs for refrigeration equipment.

When maintaining, standing watch, operating, or inspecting refrigerating and air-conditioning equipment, the Utilitiesman may be responsible for keeping operation, inspection, or maintenance logs on the equipment. Try to keep the logs neat and clean. You must ensure that any information recorded in them is accurate and legible.

Operation and maintenance logs may help to spot trouble in the equipment. They also aid in ensuring proper periodic maintenance and inspection are performed on the equipment. Logs may provide a means of self-protection when trouble occurs and the cause can be placed on an individual.

Good judgment must always be used in analysis of service troubles and specific corrections should be followed whenever possible. One of the methods for determining when and what corrective measures are necessary on equipment or a plant which is not operating properly is to compare the pressures and temperatures of various parts of the system with corresponding readings taken in the past when the equipment or plant was operating properly under similar heat load and circulating water temperature conditions.

A typical operating log may contain entries such as the following:

Date and time of readings

Ambient temperature

Suction pressure and temperature readings

Discharge pressure and tem perature readings

Condenser pressure and temperature

Evaporator pressure and temperature

Oil level in the compressor

Operating hours

These types of readings give a complete picture of the current and past operating conditions of the equipment or plant and can assist the Utilitiesman in keeping the equipment or plant at its maximum efficiency.

Maintenance logs contain entries of when, what, and who performed routine periodic maintenance on