F4: Hydronic Control System

Question 1

What is the point of a second heat exchanger in a boiler?

Answer 1

It scrubs the latent heat from the flue gases = increases AFUE / allows to operate at a lower temp

Question 2

What does AFUE stand for?

Answer 2

Annual Fuel Utilization Efficiency

Question 3

Primary / Secondary piping have replaced what types of piping?

Answer 3

Series loop
2 - pipe direct / reverse return piping
Monoflow tee

Question 4

How does a primary / secondary system operate?

Answer 4

through the principle of hydraulic separation for proper flow rates

Question 5

Why are closely - spaced tees / hydraulic separators used?

Answer 5

So that pumps that are connected to the same water system won’t have an effect on each other.

Question 6

What ensures min pressure drop between the tees?

Answer 6

Placing tees no farther than 4 pipe diameters from each other

Question 7

What are parallel - multizone / zone valves?

Answer 7

Same heating fluid temp to all zones
- Common supply / return piping are used
- One circulator for all zones

Question 8

How does a 2 pipe direct return system move water?

Answer 8

By one pump

Question 9

How are zone valves controled?

Answer 9

Through a thermostat

Question 10

What senses domestic hot water

Answer 10

an aquastat

Question 11

How does a pump and boiler burner operate on a Low mass boiler?

Answer 11

Circuit only energized if a zone valve proved open

Question 12

How does a pump and boiler burner operate on a High mass boiler?

Answer 12

does not need flow through it / burner circuit could always be energized

Question 13

What does cold start mean?

Answer 13

Can’t fire to keep it self hot unless there is a call for heat from the system

Question 14

What does a schematic diagram show?

Answer 14

Shows the components as they might appear physically

Question 15

What does a ladder diagram show?

Answer 15

Only electrical symbols for components

Question 16

What does the R terminal indicate?

Answer 16

external power supply to the thermostats / end switches

Question 17

What does C terminal indicate?

Answer 17

Connects internally to neutral side of the 24V AC transformer
is also the external ground connection for burner / zone valve circuits

Question 18

What does the G terminal do?

Answer 18

outlet sides of end switches connects to it
feed internal relay coil / externally feeds power to burner circuit

Question 19

What would W and Y terminals indicate?

Answer 19

There is another internal relay for control of other devices (AC or furnace fan)

Question 20

What water temp feeds Radiant floor panels?

Answer 20

90 F - 140 F
depending on the BTUH / ft2 and R value of floor coverings

Question 21

What is a mixing valve?

Answer 21

has tempering of water through it

Question 22

Are diverting valves installed in the same location as mixing valves?

Answer 22

No

Question 23

Where are diverting valves located?

Answer 23

mounted on the return piping.

Question 24

How many inlets does a mixing valve have?

Answer 24

2 inlets
1 outlet

Question 25

How many inlets / outlets does a Diverting valve have?

Answer 25

1 inlet
2 outlets

Question 26

True or False: diverting valves have less head loss than mixing valves.

Answer 26

True

Question 27

What is a 2 way valve?

Answer 27

a throttling valve w/ a low head loss
controlled by a capillary tube connected to a bulb

Question 28

What does the bulb do on a 2 way valve?

Answer 28

sense the temp in the radiant circuit

Question 29

Why is a 4 way mixing valve a superior choice for tempering water?

Answer 29

has very low head losses through them

Question 30

What does a heating curve calculate?

Answer 30

How much hotter the supply water will need to be as outdoor temp drops

Question 31

What is thermal equilibrium?

Answer 31

Where indoor and outdoor temperatures are equal

Question 32

What does WWSD stand for?

Answer 32

Warm Weather Shutdown Point

Question 33

What does a Voltmeter containing VOM (volt-ohmmeter) tell us?

Answer 33

Where voltage is or isn’t present / its value

Question 34

A voltmeter will always tell us the difference in what?

Answer 34

in volts between the two meter leads

Question 35

Why would a voltmeter read 0?

Answer 35

1) no voltage present at all at either of the leads
2) 2 leads are being exposed to the same voltage
3) meter isn’t working properly

Question 36

a minus sign appearing in front of the voltage measured on a digital multimeter would indicate what?

Answer 36

leads are reversed in polarity
No action needed –> meter isn’t being harmed

Question 37

What does a tap test ensure?

Answer 37

the polarity is correct
meter pointer moves to the right = polarity is correct

Question 38

Do the wires have to be disconnected when measuring voltage?

Answer 38

No
Voltmeter is used in parallel w/ circuit being tested

Question 39

Ammeters must be installed is a what?

Answer 39

in a series with the circuit or components being checked
remove a wire and place meter leads to each end of wire

Question 40

True or False: Wire leads must be at least as heavy in wire gauge as the wiring in the circuit being checked

Answer 40

True

Question 41

What is the easiest way to check for amperage (current flow)?

Answer 41

use a clamp on ammeter