351 REVIEW QUESTIONS 1. Why is a low-voleage thermostat normally more accu 26. D

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351 REVIEW QUESTIONS 1. Why is a low-voleage thermostat normally more accu 26. Describe two methods for cooling an overheated rate than a high-voltage thermostat? 2. The three kinds of switching mechanism used in kow 27. How can an electronic thermometer be used in a well to voltage thermostats are and obtain an accurate response? 28. A trmperature-sensing device used in measuring airflow 29. How does a thermocouple change with a temperature The temperature drop below the thermo- 30. Name two methods ased to convert pressure changes 31. Name two actions that can be obtained with a pressure 3. What does a heat anticipator do 4. What does a cold anticipator do 5. Define system overshoot when dealing with thermostats 6. True or False: 7. What S. Describe the method a service technician should fo 32. True or Falses Pressures below atmospheric pressare 9, Explain how star's set point is referred to as system lag. to setting a heating anticipator? low when measuring the current that normally travels is meant by the steady-state condition with regard cannot be detected. 33. Name one function of the low pressure control. through a heating anticipator. microelectronic or electronic thermostats 34. Whach is true of a high-pressure controla handle system overshoot and system la 10. Describe how a bimetal funcrions 11. What component steps down the voltage to the low 1ow wolage is desirable for tresideaial control vole A. le closes on a rise in pressure. B. It opens on a fall in pressare. C. It is located on the evaporator voltage value? s. tes of water presure control 36, why should a safety control not be adusted ages because e ot ·?????????????and if it has a cal to prevent tampering? 13. What is the maximum amperage usually encounsered 37. True or False: If the differential of a motor control is set by a low-voltage thermostat? too small, the moeoe may short cycle. automatically change the cut-in point of the control. will always change the range of the control. 14. A heating thermostat- 15. A cooling thermostatn a rise in temperature. -on a rise in temperature. 38. True or False: A change in the differential setting will 16. What two types of switches are normally found in the 39, True or False: A change in the differential of a control subbase of a low-voltage thermostat? 17. When is a line-voltage thermostat used? 40. True or False Changing the cur-out adjustment without 18. The three sensing elements that can be used with achanging the differential adjustment will automatically line-voltage thermostat are and change the cut-in setting. control or pressure control. a cut-in of 450 psig, what would be the differential of 41. Explain what is meant by the range of a temperature 19. What is the maximum amperage generally encountered 20. Why is a line-voltage thermostat mounted on an electri 21. Why do motors build up heat? 22. The trwo types of motor temperature-sensing devices are in a line-voltage thermostat? 42. If a high pressure control has a cut-out of 500 psig and cal box that has conduit connected to it? 43. Explain the function of a pressure transducer, and give an example of where one would be used in the HVAC/R 23. What is the main precaution for an externally mounted 44. List two advantages an electronic odl safety control- motor temperature protector? ler has over a mechanical, bellows-operated oil safety 24. What is the principle of operation for most externally controller 25. Describe a method for speeding up the cooling of an mounted overload protection devices?

Explanation / Answer

1) Low voltages thermostat are more accurate than high voltage thermostat because high voltage thermostat usually operate at high voltage(240V) due to which high current will flow through the thermostat causing it to heat up thus thermostat may sense up its own heat and hence lowering the accuracy of high voltage thermostat wheras in low voltage thermostat low voltage causes less current to flow through the thermostat causing it not to heat up and hence having more accuracy.

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