Section 3 060203a-db Flashcards

(88 cards)

1
Q

Name the two types of hydronic systems

A

Gravity systems
Forced flow systems

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2
Q

How do gravity systems work

A

Circulation relied on natural convection with the heated water rising in the supply and the denser, cooler water dropping in the return piping

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3
Q

What are the 2 major drawbacks to gravity systems

A

Large diameter piping
Slow response time

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4
Q

What are forced flow systems

A

Addition of circulator

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5
Q

What are the two advantages to forced flow systems

A

Very Efficient
Smaller pipe diameters

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6
Q

What are the 4 types of forced flow systems

A

Monoflow systems (one pipe system)
Reverse return (two pipe systems)
Direct return (two pipe systems)
Series loop (one pipe system)

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7
Q

What does a monoflo system have that others don’t

A

Venturi tee

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8
Q

What does a Venturi tee do?

A

Reduces pressure at the outlet of the Venturi causing a flow of fluid from the convector into the header (typically on the outlet side)

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9
Q

What are the advantages and disadvantages of monoflo systems?

A

ADVANTAGES: less piping, and each unit can be controlled individually.
DISADVANTAGES: limited sizes of Venturi tees,temp of fluid decreases after each unit, and heat transfer units with high resistance don’t work well with this system

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10
Q

What is a direct return system

A

First supply, first return

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11
Q

What are the advantages and disadvantages of direct return systems

A

ADVANTAGES: all units get the same temperature, and size of piping can be reduced as flow requirement is reduced.
DISADVANTAGES: unequal length of each circuit, prone to short circuits, and must have balancing valves.

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12
Q

What is a reverse return system

A

First supply last return

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13
Q

The distance for each unit on a reverse return is the nearly the same (true/false)

A

true

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14
Q

What are the advantages and disadvantages of a reverse return system?

A

ADVANTAGES: easy to balance, individual units can be controlled.
DISADVANTAGES: more piping, expensive to install.

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15
Q

What is a series loop?

A

All fluid flowing through the circuit flows through each series-connected baseboard.

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16
Q

What are the advantages and disadvantages of a series loop?

A

ADVANTAGES: reduces the amount of piping.
DISADVANTAGES: first convector gets the highest temperature fluid, downstream units may have to be increased.

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17
Q

What kind of valves are used for isolation

A

Gate and ball valves are a good choice

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18
Q

What valve is used for balancing

A

Globe valve

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19
Q

Where are balancing valves installed in a heating system?

A

Either the supply or return (preferably on the return)

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20
Q

Stem on valve has to be installed with the valve stem in a ___________ position to prevent air from being trapped.

A

Horizontal

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21
Q

What is a wild loop

A

A connection between the supply and return piping that allows for continuous flow

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22
Q

When using a wild loop what is required to prevent dead-head

A

A bypass

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23
Q

What are radiator valves

A

Used to stop or reduce circulation at each heat emission unit.

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24
Q

What are zone valves

A

Allow flow to specific areas or zones

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25
A zone valve is usually normally closed (true/false)
True. But can be either normally open or normally closed
26
Trapped air in a heating system can cause poor ___________.
Circulation
27
What is entrained air
Trapped air
28
What makes it easier for air to be released from fluid
Higher temperature, lower pressure
29
What do boiler fittings do
Direct air that is collected at the top of the boiler to a cushion tank
30
What are the three types of air elimination devices
Boiler fittings Air scoops Auto and manual air vents
31
How much piping is required to create laminar flow
4x pipe diameter
32
What are auto air vents
Float operated devices that allow for air to be vented from the system at any point of accumulation
33
What are manual air vents
A vent that is manually opened to vent air out of the system at high points (normally closed)
34
Where is a vent placed if piping drops
At the top just before it drops down
35
How many dual purpose appliances can be used in a heating system
1
36
How often should a dual purpose recycle water to prevent stagnation of water?
Every 7 days
37
Every boiler must have at least __ temp-actuated control (also known as safety shut off)
1
38
What are the two types of water boilers
High temp Low temp
39
BHP
Boiler horsepower
40
What is equal to 1 BHP
34.5 lb
41
What is Net rating
75% of gross
42
How do you find efficiency
Gross/Netx100
43
1 BTU=____ F
1
44
How do you calculate BTU
BTU= EDR x 150BTU/hr
45
How do you calculate EDR
EDR= BTU / 150BTU/hr
46
What is the max pressure for cast iron boilers
207 kpa (30 psi)
47
What is the max temp and pressure for low temp boilers
120 C (250F) 1100kpa (160psig)
48
What are the three types of boilers
Fire tube boilers (high mass) Water tube boilers (low mass) Cast iron sectional boilers (high mass)
49
What is critical when boilers are fired
Continuous flow through heat exchanger
50
What are the advantages and disadvantages of high-mass boilers
ADVANTAGES: stable supply temp, reduces susceptibility to thermal shock. DISADVANTAGES: slow recovery rate, risk of explosion, require low water cut off if over 400000 BTU
51
What are advantages and disadvantages of low mass boilers
ADVANTAGES: directly heat domestic water, quick recovery rate, higher velocity DISADVANTAGES: susceptible to damage in case of no flow or low flow conditions,
52
What is used to prevent boiler from firing in case of no flow through heat exchanger
Flow switch
53
What is the most important when installing a boiler
Clearance to combustibles
54
What must installation of a boiler conform to
1- authority having jurisdiction 2- CGA B149 natural gas and propane code 3- CSA standards B214-01 installation code for hydronic heating systems 4- manufactures recommendations
55
What does VI and I mean
ASME stamps
56
What is a pressure relief valve set to go off at
30 psi
57
What is a limit control
A redundant control that only operates if the operating control fails
58
What is an operating control
Set to cut off fuel supply when the liquid temp reaches operating limit
59
What are pressure gauges used for
Determining pressure drop over the system and the flow characteristics of the circulator
60
What do all boilers need to have
1 pressure gauge and 1 thermometer
61
What are flow control valves used for
Preventgravity circulation from occurring within the piping system
62
What are expansion tanks
Allow for continuous expansion and contraction of fluid
63
What cross-connection is always the case for boilers
Severe (due to the use of chemicals)
64
What is used to prevent cross-connection
RP or air gap
65
What is the size for an air gap
1" or 2 times the pipe opening whichever greater
66
How often is an RP tested
Annually
67
PRV
PRESSURE REDUCING VALVE
68
How much psi do you lose for every foot of height
0.433 psi
69
What is the final form of protection
Safety relief
70
A PRV is installed ________ a boiler
above
71
What are the 2 types of switches
Float-activated Probe-type
72
_______ and _________ can be damaged from condensate
Cast and copper
73
What does a condensate neutralizer do
Reduces acidity before draining into sewer
74
What must you do to all valves regularly
Exercise
75
If a safety relief valve is faulty what would happen
Leaking due to overpressure
76
What is the most common form of energy used to move a liquid
Pressure
77
Feet of head
Height of a column
78
What is the ideal velocity in a heating system
2-4 ft per second
79
What is the best type of flow
Laminar
80
What causes friction in a pipe
Viscosity Pipe wall Size and type of pipe Number and type of fittings Temperature Velocity
81
What is erosion
Wearing away a metal due to the high temp, high pressure, and high velocity
82
If the velocity nis doubled what happens to the head pressure
Increases about 4 times
83
If the flow rate is halved what happens to the head pressure
Goes way up
84
Where is the expansion tank located
Upstream of the circulator
85
What is cavitation
Water changing to steam
86
How is the total equivalent length calculated
Total distance times 1.5
87
How is a wet rotor line-mounted circulator lubricated
Internal circulating liquid
88
How often and what do you do when you check a circulator
Annually check for leaks and unusual noise