Module 2 Test Questions Heating/Hot Water Boilers Flashcards
Copper-tube boilers typically have:
a. better heat transfer characteristics, & longer lifespans than cast-iron boilers
b. better heat transfer characteristics, & shorter lifespans than cast-iron boilers
c. worse heat transfer characteristics, but longer lifespans than cast-iron boilers
d. worse heat transfer characteristics, but shorter lifespans than cast-iron boilers
e. roughly similar characteristics to cast-iron boilers
better heat transfer characteristics, & longer lifespans than cast-iron boilers
Which of the following is a similarity between furnaces and boilers:
a. piping
b. low-level safety device
c. high-temp limit switches
d. pressure relief valve
high-temp limit switches
Heat exchanger diagnosis on boilers is easier than on furnaces b/c the heat exchanger will leak when it has failed. T/F
True
List 4 safety controls found on all hydronic systems.
- pressure relief valve
- high temp limit
- low-water cutout
- backflow preventer
What is the normal operating pressure in a boiler?
a. 2 to 5 psi
b. 5 to 9 psi
c. 9 to 12 psi
d. 12 to 15 psi
e. 15 to 18 psi
12 to 15 psi
What is the normal setting on the pressure-relief valve?
a. 10 psi
b. 20 psi
c. 30 psi
d. 40 psi
e. 50 psi
30 psi
Where is the pressure relief valve typically located? Also, where does it typically discharge?
pressure relief valve is located on top of the boiler, & typically discharges near the floor
Are we required to test the pressure-relief valve?
No
Is it possible to have a pressure-relief valve that is too small for the boiler?
Yes
What is the common temperature setting for the high temperature limit switch?
a. 180 degrees
b. 195 degrees
c. 210 degrees
d. 225 degrees
e. 240 degrees
210 degres
What is the purpose of the low-water cutout on a residential boiler?
Low water cut-out prevents boiler damage if the system loses its water for any reason, Cutout prevents boiler from firing
Why do we need a backflow preventer on a residential boiler?
prevent contaminated boiler water from flowing backwards into the domestic water piping if the domestic side loses pressure for any reason
What is the safety control that prevents us from getting superheated water in a boiler system?
a. circulator
b. pressure relief valve
c. backflow preventer
d. pressure reducing valve
e. heat exchanger
pressure relief valve
List 4 operating controls that we may find on a hydronic system
Thermostat; pressure reducing valve; primary control; pump control
What is the function of the pressure-reducing valve?
pressure reducing valve drops the domestic water pressure down to the pressure required in the hydronic system.
In a two-story Victorian home with a boiler in the basement you find a pressure-reducing valve set to 12 psi. Is there a possibility that this valve is set too low?
No
Is it possible for a boiler to function without a pressure-reducing valve?
Yes
You find a boiler with a low temp limit or primary control. What would be a typical setting for this control?
a. 50 degrees F
b. 100 degrees F
c. 140 degrees F
d. 180 degrees F
e. 220 degrees F
140 degrees F
List 3 ways that the system can control a circulator (pump)
pump can be controlled by water temperature, by the burner control including the thermostat, or be wired to run continuously when there is electrical power to boiler.
What are the 4 components in the distribution system for a hot water system?
- pump
- piping
- radiators
- convectors or baseboards & expansion tank
What is the basic difference between an open system and closed system?
open system operates at atmospheric pressure, the closed system is pressurized. the open system does not have a pump & does not need a pressure relief valve. An open system does not have automatic water make-up (pressure reducing valve)
Where is the expansion tank typically, in an open system?
above the highest level radiator
What is the function of the expansion tank in a closed water system?
expansion tank allows water to expand as it is heated, so that excess pressure will not build up in the system
Where is the expansion tank, typically, in a closed water system?
expansion tanks in closed systems are typically located near the boiler, often hung from the ceiling
List 3 styles of circulators
- pump & motor are mechanically coupled w/bearings that have to be oiled
- pump & motor are close-coupled w/permanently lubricated bushings
- pump & motor are close-coupled w/water lubrication
List 3 materials that have been used for distribution piping in hot water systems in the past.
Black steel, copper, cast iron, plastic
When a black steel pipe is extended with copper pipe, what can occur?
a. steel pipe may rust at the connection due to galvanic reaction.
b. circulator may not be able to overcome the pressure change at the junction.
c. copper pipe will wear through with the friction force of the water.
d. copper pipe will rust b/c of the galvanic reaction
e. nothing occurs when steel & copper piping are joined
steel pipe may rust at the connection due to galvanic reaction.
In a radiant hot water heating system, the pipes serve 2 purposes. What are they?
Distribute heated water to the room, transfer heat to the rooms & return the cooled water to the boiler to be reheated.
Mixing convectors and radiators in a single hydronic system will often result in uncomfortable heating. T/F
True
Where should a radiator be placed in a room?
a. interior wall
b. exterior wall
c. exterior wall below window
d. on ceiling
e. it doesn’t matter, the radiator radiates heat to the room from any location
exterior wall below window
Purpose of the bleed valve near the top of the radiator?
This allows the homeowner to remove trapped air from the radiator, letting the radiator fill w/water & heat the room effectively.
Why do balancing valves tend to leak when operated?
Because they are turned rarely, the valve packing dries out & shrinks. When the valve is disturbed, a leak occurs here.
What is the maximum ceiling temp you would want to have in an 8-foot room w/radiant pipe heating?
a. 70 degrees
b. 90 degrees
c. 110 degrees
d. 130 degrees
e 150 degrees
110 degrees
DO radiant piping systems need bleed valves, since there are no radiators?
Yes
What is the average lifespan of a cast iron boiler?
35 to 50 years
