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chapter 6
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Indicate whether the statement is true or false.
1. A nonlinear relationship between heat output and flow rate represents a more challenging design condition than a linear
relationship.
a.
True
b.
False
2. Varying either water temperature or flow rate are two primary methods of controlling the heat output of hydronic heat
emitters.
a.
True
b.
False
3. Temperature sensors mounted to the external surface of a pipe should not be insulated so as to provide accurate
temperature measurements.
a.
True
b.
False
4. Oversizing a modulating heat source relative to the design heating load will minimize short cycling.
a.
True
b.
False
5. The reset ratio for a given system depends on the temperature units chosen.
a.
True
b.
False
Indicate the answer choice that best completes the statement or answers the question.
6. What are the two major subassemblies within a relay?
a.
spring and contacts
b.
coil and contacts
c.
coil and spring
d.
pendulum and terminals
7. Which of these is a common type of solid-state sensing element?
a.
positive temperature coefficient thermistor
b.
negative temperature coefficient thermistor
c.
k-type thermocouple
d.
j-type thermocouple
8. Which type of control is typically used with a room thermostat?
a.
on/off control
b.
floating control
c.
modulating DC output control
d.
differential control
9. Which type of relay contact will allow the signal to pass when the coil is off?
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chapter 6
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a.
normally closed
b.
normally open
c.
center-off
d.
center-on
10. What is an example of a modulating DC output signal?
a.
an on/off signal
b.
a digital signal
c.
2 to 10 volts DC
d.
2 to 10 volts AC
11. Which term describes the number of independent, simultaneous electrical paths through a switch?
a.
throws
b.
lines
c.
rungs
d.
poles
12. Which time delay relay operating mode prevents contacts from moving until the specified delay period has elapsed
from when the input signal is turned on?
a.
delay-on-break
b.
delay-on-make
c.
interval timing
d.
repeat cycle
13. In which type of control is the rate of heat delivery modified with changes in outdoor temperature?
a.
variable control
b.
on/off control
c.
outdoor floating control
d.
outdoor reset control
14. Which term best describes the actual variation in the controlled variable as the system operates?
a.
control differential
b.
operating differential
c.
exact differential
d.
overshoot
15. Which is the most accurate approach to heat metering?
a.
determining the heat load and periodically adjusting the reset ratio
b.
setting the on/off differential to a relatively large value
c.
measuring instantaneous values of flow rate, temperature, and fluid properties and integrating them
d.
estimating flow rate while measuring temperature to allow a quick response to temperature changes
16. Which type of control is most typically used with 3-way mixing valves that have an electronically controlled mixing
assembly?
a.
on/off control
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b.
floating control
c.
mixing proportional control
d.
no control is necessary with this type of valve
17. Strong inductive loads can produce what undesirable condition in a sensor circuit?
a.
electrical noise
b.
cavitation
c.
short cycling
d.
overshoot
18. Where is the line voltage section represented on a ladder diagram?
a.
at the top
b.
at the bottom
c.
on the left side
d.
on the right side
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chapter 6
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Answer Key
