Heating / Cooling Systems (B - books) Flashcards
One BTU is described as what?
The amount of energy it takes to raise 1 lb of water 1 degree Fahrenheit
What is the metric unit of energy
Joule (J)
Kilojoules (kJ)
1 BTU = how many kJ?
1.054
What is the metric equivalent of BTU?
Kilowatt (kW)
1 kilowatt = how many BTU/h?
3412 BTU/h
What are the 3 main processes of heat transfer?
1) Conduction
2) Convection
3) Thermal radiation
Heat transfer units (emitters) use the process of what to transfer heat to rooms or zones?
Conduction, convection and radiation
How does heat transfer between 2 materials (that are touching) with different temperatures?
Through conduction: Heat from warm material is conductive to cool material
What else is Convection called?
Gravity circulation
How does Radiation heat transfer occur?
Through electromagnetic heat rays emitted directly from a heat source –> receiving material
The amount of heat transfer by a radiator depends on what?
It’s surface area / temperature
What is the best type of radiators of heat?
Rough and black –> cast iron stoves
Light-coloured, smooth / shiny materials –> reflect heat
As the temp of radiating material increases, what happens to the amount of radiation?
Increases
In domestic / small commercial buildings, what is the max PRESSURE of steam?
Less than 15psig (200 kPa)
House Steam systems should not operate at pressures higher than what?
2 psi
What is a Hartford Loop?
A piping arrangement designed to prevent complete drainage of boiler should a leak develop in wet return.
What is the pitch in a counterflow system?
Pitch must be at least 1” in 10 feet
What is an advantage of forced-air system?
The movement of the return air via a filter that removes dust / airborne particles
What is the downside of forced air heating?
The difficulty in maintaining a comfort level in all areas of the house.
All furnaces consist of what?
- air filter
- blower
- heat exchanger/element/coil
- ductwork
- various operating / limit controls
All new installations of residential furnaces must have a min efficiency of what?
(As per the Canadian federal efficiency guidelines)
90%
Mid-efficiency furnaces have a category of what and use what type of venting material?
Category 1
Type B venting material
What category are High-efficiency furnaces and what type of venting material is used?
Category 4
Plastic Type BH Venting material
In-shot orientation allows mid/High-efficiency furnaces to be installed which way?
Upflow - common for multi-level homes
Downflow- rancher style w/ crawl space
Horizontal flow - mounting in a crawl space or attic
Known as convertible or multi position furnaces
All forced air furnaces require what?
Air filtration to operate safely / efficiently
How does a Heat pump extract heat from the environment?
By either the ground or outside air as the source through refrigeration
What does a Heat coil combine with?
Hydronic (hot water) heat source w/ forced air delivery
What is a Plenum?
It is the duct that connects directly to the furnace
True or False: There is a supply plenum and a return plenum.
True
What 2 places can an air filter be mounted
1) Inside the blower compartment
2) Onto the return air plenum (where it attaches to the furnace)
What are the different thermostate options?
- heat only
- heat / cool
- analouge
- digital
- digital/ programmable
- wi-fi enabled aka smart
Why are programmable thermostates the popular choice?
Due to air’s low thermal mass
What removes the heat in a Hydronic cooling system?
Cooling tower and Chiller
Why is Water ideal for heating and cooling?
It is non-toxic, non-flammable / readily available.
has a high heat storage capability
What princible did the early hydronic heating system use?
Eary hydronic heating system also called Gravity System
principle of buoyancy
How are convection currents created in boilers?
- water becomes less dense when heated
- The density differential (bn supply / return) creates a convection current
- Hot water gets carried up and through pipes –> Heat transfer unit (HTU)
How did electricity help with moving water?
Electricity created pump (eye roll) with helped move water bn heat source / emitters.
Resulted in better control / smaller diameter piping
What % of a person’s body heat is released by thermal radiation –> colder surface?
48%
What uses less energy: Hot water heating system or forced air heating system?
Hot water heating systems
What 2 categories do boilers fall under?
Low temp boilers
High temp boilers
What is the max temp and pressure of a low temp boiler?
Max temp = 120C / 250F
Max pressure = 1100kPa (160 psig)
Exception: cast iron boilers = max pressure: 207 kPa (30psig)
What is the max pressure / temp of a High temp boilers?
Everything that exceeds the low temp boilers max rates
What are the 2 types of boilers?
1) hot water
2) steam
What other classifications do boilers have?
(theres’s 5)
Heating method - fire tube / water tube
Material used in construction
High mass or low mass
non-condensing or condensing
high pressure and low pressure
True or False: Steam boilers need a pump.
False
but pumps are installed to return condensate back to boiler
What is the operating pressure of a low-pressure steam boiler?
105 kPa (15 psig) or less
In order to stay below water’s atm boiling point what temp do Hot water boilers normally operate at?
82 C (180 F)
What does a pressure reducing valve do and where is it located?
- maintains set pressure
- installed on boiler’s inlet water makeup
Steam creates what…
Pressure
What does ASME stand for?
American Society of Mechanical Engineers
Steam for heating does not exceed what pressure?
105 kPa (15 psig)
How are fire-tube boilers identified?
By the number of “passes” that the heated gas makes
Ex: Three pass boiler = flue gases pass via firebox once / water chamber twice
What are cast iron boilers classified as?
High mass boilers (dt large water vol)
Holds 40-64L (10 - 16 gal)
Weighs 130 - 180kg (300 - 400 lb)
What temp do boilers heat water to?
bn 77 - 88 C (170 - 190F)
What temp does water drop to before returning to boiler?
6.5 C (20 F)
a non-condensing boiler cannot have return water be at what temp?
It cannot be any lower than 60 C (140 F)
What is the returning temp of a condensing boiler?
below 60 C (140 F)
Modern condensing boilers are designed to function how?
with low return water temp that condenses w/in combustion chamber of the boiler
What is the condensate put through before being drained via sanitary drainage system?
Acid neutralizer
Packaged boilers can be made out of what?
Cast iron
copper tube
steel tube
stainless steel
Packaged boilers come with what?
- Insulated jackets
- min size circulator
- electrical controls (all ready to go)
A circulator is removed from a packaged boiler and installed where?
Page 18
On the supply piping downstream on the expansion tank.
What is the formula for efficiency?
(output / input) x 100
Remember: you cannot have more than 100% efficiency
What are chillers in Commercial Cooling Equipment?
(pg 25)
Chillers are the heart of commercial cooling systems
True or False: In cooling systems: the refrigerant mixes with the cooling medium (aka chilled water)
False: refrigerant / colling medium never mix
The chilling of water (in a refrigerant system) is done how?
Done by the evaporator, once now chilled refrigerant, is pulled into a compressor where the temp and pressure is increased.
(page 25)
Air-to-water heat pumps require controls that monitor what?
The dew point –> in order to avoid condensation forming on cool surfaces (can create dampness –> mould)
What is another term for water-to-water heat pump?
ground source heat pump or Geothermal
What is the difference bn geothermal and ground source heat pump?
True geothermal = taps into heat emitted from underground hot springs
Ground source heat pump = conducts latent heat from below earth surface
What is a water-to-air heat exchanger?
Hot boiler water gets piped into W2A heat exchanger –> water circulates via heat exchanger –> fan pushes air via finned coils
(Acts like a radiator in a car)
What is the CSA B214 Code ?
It is the installation code for hydronic heating systems in Canada
Section 5 = heating equipment
All heating equipment must be installed according to what?
Codes / regulations specified by the region in which they were installed.
True or False: Multiple codes will have to be used when installing heating equipment.
True: Boilers must meet the requirements of applicable boiler / pressure vessel regulations (as well as boiler, building, plumbing, electrical , gas / fire codes)
page 42 B-2
What does the Canadian Electrical code state in regards to a branch circuit?
That all heating equipment must have a dedicated branch
How high does a boiler heater water to?
To temps as high as 88 C (190 F)
What are the 4 groups of emitters?
1) gravity circulating convectors
2) forced circulating convectors
3) Radiators
4) Radiant panels (in-floor heating)
How are gravity circulators installed?
- surfaced mounted
- recessed into the wall
(insulation installed behind prevents heat loss through wall)
How are gravity circulation convectors installed?
- Surfaced mounted
- Recessed into the wall
(installing insulation behind the wall –> prevents heat loss)
How are residential circulating convectors installed?
Mounted at baseboard level beneath windows
Where are commercial grade convectors located?
Normally found in stairwells / common areas
What happens to the cold air that moves downward from the window towards a convector?
The cool air mixes with the warm air from the convector => both drafts produce a more even room temp.
What is a Convector?
Baseboard heater…
Commercial wall mounted convectors are the modern day what?
Are the modern day cast iron radiator
Gravity convectors rely on what to transfer temp?
temp differences / air densities to create convection
Forced flow systems combine what 2 things to move air?
heating element and a fan (or blower)
What are the different names for a fan coil?
Unit heaters, duct heaters and kickspace heaters
How does a fan coil work?
The fan (placed on the upstream side of coil) pushes air across the coil –> air picks up heat and is pushed out towards room.
Where are unit heaters and overhead fan coils mainly used?
In commercial buildings (where its advantageous to deliver heat from above)
What is another name for vertical unit heaters?
Projection unit heaters
How do vertical unit heaters work?
They push air downwards
Are mounted near the ceiling
Deflecting louvers (below fan) can do what?
can be adjusted to direct the air
Diffuser cone can be used to decrease drafts
What do Horizontal unit heaters do?
Move air at lower velocity than vertical unit heaters
How do horizontal units provide more comfort?
through their ability to direct airflow through adjustable discharge deflectors.
What is another name for a Kick-space heater?
Under-cabinet fan coils
Where are kick-space heaters normally located?
kitchen or bathroom in the “kickspace” below cabinets
What can Forced-flow wall mounted convector unit be referred as?
a wall mounted fan coil
What does the term radiator refer to?
Both freestanding cast-iron radiators / baseboard radiators
How does heat transfer happen for radiators?
Conduction –> hot water inside radiator warms outside
Radiation –> warm outer surface of radiator emits heat to objects in the room.
How does a free standing cast iron radiator emit heat?
60% via radiation
40% via convection
What are the general measurements of a freestanding radiators
They are constructed to be no wider than a window
(in order to maximize the use of convection currents w/in the room)
What do the end sections of baseboard radiators have?
tappings (female threaded connections) for connecting supply / return piping
Where are baseboard radiators located?
On outside walls (like baseboard convectors)
How do radiant baseboard transfer heat?
Hot water runs through a copper tube w/in the housing / heats the front panel (does not contain fins)
If a Panel radiator transfers heat via convection, how would that happen?
Fins would be included in its set-up –> it would capture heat –> create convection currents
What is a benefit of panel radiators?
it is relatively small amount of wall or ceiling space they require.
What is the main benefit of radiant floor panels?
An increased level of comfort
What is considered a comfortable room?
One in which the temperature in the room matches human body requirements
What is the temperature of boiler water used in radiant panel flooring systems?
Max 49 C (120 F)
–> Prevents floor/ occupants from getting too warm
What are the ups and downs for radiant systems? (in regards to economy)
Plus = are least expensive to operate
Not so plus = Initial install cost is bad
Hotter water means what?
Less area of transfer unit needed
Greater arear of transfer units = use of lower temp heat sources (heat pumps + condensing boilers)
What does design temperature difference mean?
It is the water temperature drop
Most systems are designs to release how much temp from water?
11 C (20 F)
If one room has a high heat transfer unit, what does that mean for the rest of the rooms?
Other rooms may receive less heat than needed
What is the primary function of air vents?
To rid the system of trapped air
Where must air vents be places?
at all the high points in a piping arrangement + be accessible for servicing
How much will baseboards expand when heated?
5 mm per 3m (3/16” / 10’) when temperatures= 4 - 93 C (40 to 200F)
What must you do to allow for piping mvmt / coming through floors?
Drill larger holes (if you do not, pipes rub against floor / squeak loudly)
What is important to not for rods on unit heaters?
Rods should be double nutted at each connection to ensure that vibration won’t loosen them
–> May also be seismically restrained
Counterflow piping direction is best for?
Most heat exchangers
Isolation valves should be installed where?
On both supply / return piping connections
Unit heaters are well suited for what locations?
Where there is a need for quick heat recovery (service station or buildings w/ frequently opened doors)
Vertical heaters should be spaced how far apart?
17m (50’) for best performance
What is a circulating pump’s job?
to pump liquid through piping system
heat source –> heat emitter –> return heat source
A centrifugal pump can be found where?
On a hot-water system
What does a centrifugal pump consist of?
Page 8 B-4
- electric motor spinning an impeller w/in a housing (aka Volute) containing liquid
What is the preferred location of a pump?
on the supply main immediately downstream of compression tank
what is the “point of no pressure change” concept?
When a system is drained, whatever the pressure is in the air side of expansion tank = the pressure at the point of no pressure change at the water side of the expansion tank…
Why is it important to mount larger pumps on vibration mount brackets?
Pumps vibrate when operating, mounting brackets help keep pumps in place
What is included in an isolation flange?
Flange and ball valve
Where should a strainer be installed?
Upstream of the pump in order to pick up any solids that are in the system
What 2 factors determine the selection of a centrifugal pump?
1) flow rate
2) head pressure
What does feet of head refer to?
Pressure
What is feet of head expressed in?
pounds per square inch
psi
What does 1 foot of head =?
1 foot of head = 0.433 psi
(1 psi = 2.31 feet of head)
What is flow measured in?
US gallons / min (USGPM)
What is dewpoint temp at atm pressure?
53 C (127 F)
What is a safe temperature drop that avoids the dewpoint (in non-condensing boilers)?
11C (20F)
Why don’t you want water returning to a boiler lower than the dewpoint?
Causes condensation / corrosion of the boiler’s heat exchanger surface
Return water temp to a non-condensing boiler should never be lower than what?
60 C (140 F)
What is the USGPM flow rate formula?
USGPM = delta T x 60 x 8.33
delta T = temp drop desired (usually 20 F)
60 = number of min in an hour
8.33 = mass in lbs of US gallons of water
1 USGPM = how many BTU/h?
10 000BTU/h
When manufactures publish charts, what does the curve represent?
the capacity of the pump (pg 20)
What are 6 problems of air being trapped in an hydronic heating system?
1) Noisy flow
2) Increased corrosion
3) poor or possibly no flow
4) poor heat transfer
5) Cavitation leading to circulator damage
–> dt above reasons air removal must be a priority in system design
Where is a central air separator located?
on the supply piping leaving the boiler
- DT air being most easily removed from water whenever it is hottest / slowest
What else are Manual air vents referred to as?
Coin vents or bleeders
Where is the most common location for a Manual air vent?
Downstream (return) end of heat transfer units
The slotted steam air vent is also referred to as what?
Coin vent
When do automatic air vents open and close?
Open = automatically when air is present
Close = automatically what water is present
Automatic air vents should be installed with which other vent?
Isolating valve –> so that repairs or replacement can occur
What else is an Air Purgers called?
Air separators or Air scoops
Where are air scoops installed?
Horizontally on the main as close to the boiler as possible
What can be installed at the bottom of an air scoop?
Diaphragm compression tank
Why are microbubble resorbers perferred choice for air removal?
Preferred when there is not enough room to install 18” of straight horizontal piping on the inlet side
A properly sized / placed expansion tank allows room for what?
Water to expand / contract
What are some factors that need to be considers when selecting an expansion tank?
(page 33)
1) total vol of water in the system
2) Min system temp
3) Max system temp
4) Min operating pressure
5) Max operating pressure
6) Presence of glycol in the system
Commercial / industrial hot water heating systems may require chemicals, why? (4 points)
1) Degrease the system
2) Inhibit corrosion
3) Lubricate components
4) Prevent freezing
What safety device is required on some hot-water boiler and all steam boilers?
A low-water cutoff (LWCO)
What does a Low water cut off do?
is a safety guard against low water condition in the boiler
What are common valves found in hydronic piping systems?
1) Gate Valves
2) Globe Valves
3) Ball Valves
4) Check valves
What valves are considered manual valves that can be used for isolation?
- Gate
- Globe
- Ball
Which valves will air flow freely through?
Gate or Ball Valves
How are Globe valves special?
- Provide throttling or isolation on feedwater lines
What type of valve is a Balancing valve / what is it used for?
- Globe valve
- Used for throttling flow in hydronic systems
Where can Check valves be used for?
Wherever reverse flow is unwanted
Water makeup to a boiler has 4 components, what are they?
(MBFB)
1) Main stop valve
2) backflow preventer
3) feedwater valve (pressure - reducing valve)
4) bypass valve (quick fill)
A dual check with atm port is considered what?
Backflow preventer
(seen on residential hydronic system)
A feedwater valve is also known as what?
Pressure - reducing valve
What is the working pressure of a PRV?
12 psig - 20 psig (84kpa - 140 kpa)
The backflow preventer is located where?
On the feedwater line in series w/ feedwater valve
(sometimes comes in a packaged unit)
Where is the purge valve located?
on the return piping near the boiler
PRV has a rating plate that identifies what?
- relief pressure setting
- relieving capacity
- size of valve
Where must the PRV be installed?
Directly on the boiler
Can there be another valve bn the PRV and boiler?
NO
How is water safely relieved on a PRV?
page 47
By discharging water through a pipe to a drain or safe location
Piping used for discharge outlet?
1) same size as PRV
2) as short as possible
3) sloped down / away from the valve to prevent a buildup of back pressure
What does a zone valve do?
permits or prevents the flow of water through the zone they control
What happens when a thermostat senses the need for heat?
Signal to control valve for that zone to open is sent
Zone valves are normally operated by what?
electric motors
activated by a 24 volt signal from thermostat in that zone
Zone valves are normally installed where?
On the supply side of each zone circuit
A balancing valve is a type of globe valve that has much less what?
flow restriction
How can you ensure accurate flow measurement at a balancing valve?
Install a straight pipe line a min 5 pipe diameters upstream of the valve + 2 pipe diameters downstream
A diverting valve is located where?
on the return side of the system similar to a mixing valve
flow coming into valve = return water from system
A 3 way diverting valve will divide what?
the cooler system return water into 2 flows
25% of the flow goes to the boiler to be reheated
75% bypasses the boiler to meet /mix w/ the heated water from the boiler
What is the difference bn a 3 way and 4 way mixing valve?
4 way mixing valve = can control water temp / flow rates –> supply piping / return piping to the boiler
What is the rule of thumb when it comes to BTU/h and circuit units?
No more than 60 000 - 70 000 BTU/h should be allocated to each circuit in the system
How many loops can there be in a split series loop system?
There can be more then just 2 loops
Heat source = sized to supply all the loops
How many pipe system is a diversion Tee or Monoflo system?
A one-pipe system
What principal does the Monoflo operates under?
page 66
Bernoulli’s principal –> Where velocity is greatest, pressure is least
(operates via use of a venturi)
2 pipe systems are categorized as what? and where is this system foud?
1) direct or reverse return
2) found in large commercial or industrial buildings
Why is the direct return system unpopular for residential systems?
- Difficult to balance
- Expensive to install b/c of balancing components
- Expensive to maintain b/c of balancing components
The 2 pipe reverse return system is also called?
- First fed, last return system
- Most common system installed in commercial buildings
What are some benefits of a home-run system?
- Heat output of each room can be individually controlled (via flow rates)
- Water is delivered to each heat emitted at roughly the same temp
- Manifolds can be used in conjunction w/ variety of heat emitters
- Balancing vales can be used to regulate flow via each separate home run.
What does head loss mean?
pressure loss
How do circulators interact with each other?
through head loss
What is needed in order to create flow in a system?
a pressure differential
What happens if there is low flow resistance in a system?
very little head or pressure loss occurs
What is the main purpose of a primary circuit?
To keep a hot supply of water flowing through it.
Piping / pump need to be large enough to carry heated water / long enough to have space for the closely spaced tees for the secondary unit.
How else can hydraulic separation be accomplished?
By using a hydraulic separator or low loss header.
Both use a large diameter vertical chamber to slow down water flow rates.
Slowing water down does what?
- Creates little head loss via the chamber
- Creates hydraulic separation needed bn systems in order to be effective
What terms are used in a Hydronic system?
- supply main
- return main
- branch or spring piece
- riser
- runout
- stub
- drop
What can cause stress in a hot-water piping system?
- Fluid surges
- pipe misalignments
- impacts
- mvmt during earthquakes
How are stress impacts prevented?
- swing joints
- expansion loops
- expansion bellows
- oversized holes via building structures
What is another name for Swing Joint?
How do swing joints work?
- Spring piece
- allows for stresses / for grade
- consists of adding three or more elbows / connecting pipes w/in a piping run.
What kind of elbows are used in a swing joint?
90 degree or a combination of 90 and 45 degree
Pipes can expand which way?
in diameter + length
How do you allow for pipe expansion in holes either in walls or floors?
Drill all holes a min of 12mm (1/2” larger) than the size of pipe
The hole has to be sealed after to prevent air leaks / create fire stops
How can holes be sealed but still allow for movement?
Grommets or silicone caulk
Why must a system be entirely full of water?
So that a pump does not have to lift water, only move it
What is a zone?
a heating area that is controlled separately from other heating areas
True of False: Each zone has it’s own thermostat.
True
What does zone controlled area allow for?
Greater comfort
Lower operating cost
Better temp control in building w/ areas difficult to heat
How does the orientation of a house determine the temperature of the rooms?
By which side the sun will hit / heat the rooms
True or False: Rooms on the southeast receive more sunlight than those on the southwest.
True, it’s alll true
What type of material is good to use for radiant floor heating in different zones?
Concrete and wood –> allows for passage of heat but at different rates
How do high storeys require less heat than lower storeys?
Because of the stack effect
What is the stack effect?
Refers to the mvmt of heat upwards in a multi-storey building
(heat moves up elevator / staircases and through floors)
What are the different heat gain via windows based on direction?
North = no heat gain
South = significant solar heat gain
East = can contribute some heat gain
West = Also can contribute some heat gain
Why is balancing zones necessary?
1) To obtain design flow in the boiler
2) fluctuations in flow = reduce efficiency of heat transfer units / make control difficult
3) in order for zones to get heat flow
4) control loops necessary to make control valves work / make primary / secondary flows compatable
