practice pe exam hvac breadth and depth

8/18/2019 Practice PE Exam HVAC Breadth and Depth

1/15

Practice PE Exam: HVAC Breadth and Depth

The following is a practice PE exam for the HVAC Breadth part of the PE test. I chose not tomake this a multiple choice format. ne the indi!idual answer page I will show "ou the workedout pro#lem and "ou can deride if "ou got the correct solution. The reason I did this is when "ouare looking on charts for num#er or multipl"ing #" num#ers that ma" ha!e #een rounded off"our answer can !ar". The wa" I see things is that if "ou can get the pro#lem done correctl". Thistest should take $ hour

Question 1

A mechanical room has %&' () kilowatt electric water heaters and %$' *+++ ,BT-H natural draftgas fired #oiler. ou are looking to use the one permanent opening method for the com#ustion air opening. /hat area should the com#ustion air opening #e0

Question 2

A water cooled chiller uses 12$*(a as a refrigerant. The refrigerant flow rate through thecondenser is $++3+++ l#m4hr with the entering pressure of $++ P5IA and lea!es the condenser ata temperature of 6+7 8 and is a saturated li9uid. The refrigerant then passes through thee!aporator and lea!es as a gas at $+7 8 . /ater from a cooling tower is used to a#sor# the heatgi!en off #" the condenser. The cooling tower water enters the condenser at ):7 8 and lea!es at;67 8.The Coefficient of Performance for this chiller is (.+. /hat is the flow rate in gpm of thecooling tower water0

Question 3

A client is asking to use a solar energ" collector to collect energ" for a solar powered pump. Thesolar panels ha!e an o!erall efficienc" of $&


2/15

ou ha!e #een asked to e!aluate two chillers using the coefficient of performance. Both chillersare a#out the same tonnage and "our client would like to use the more efficient chiller.

Chi er !1

•

8low rate of ::+ @P,

• Entering Temperature :67 8

• ea!ing /ater Temperature (:7 8

• Compressor input &: Tons

Chi er !2

• 8low rate of :++ @P,

• Entering Temperature :67 8

• ea!ing /ater Temperature ((7 8

• Compressor input &: Tons

Question "

An air handler has $:3+++ cfm of air passing through the coiling coil. The !elocit" across the

face of the cooling coil has a maximum !elocit" of :++ fpm. The air then passes through the faninlet section of the air handling unit and then passes into a $6? diameter plug fan. If a pressuresensor records a pressure of 2*.+ inches immediatel" downstream of the cooling coil3 what is the

pressure when the air enters the plug fan0

Question #

The design conditions for a dining room at a pu#lic school are ):7 8 dr" #ul# and =&.:7 8 wet #ul#. -sing A5H1AE =&.( to calculate the outdoor air re9uirement3 it was calculated that the!entilation re9uirement for the dining room would #e $3(++ cfm. The temperature outside has amaximum range of ;:7 8 dr" #ul# and 6$7 8 wet #ul#. /hat is the !entilation load the cooling

coil will see from the outside air0

Question $

A fuel depot at the airport has %*' ): horsepower pumps that can each deli!er :++ gpm of et fuelto the holding tanks. All three pumps operate at =:< efficienc". The total d"namic head neededfor each pump is (++ feet


3/15

The fuel depot is getting read" to #e retrofitted. our #oss wants to know what is the maximumthroughput "ou can attain with the current pumps.

Question %

An architect has asked "ou to get an estimate of the fuel that would #e needed to heat an exteriorwall per "ear. The wall has an area of $:+ s9uare feet. The thermal conducti!it" of the wall is+.+6 BT-4%ft>& D h D8 '. uring the heating season this wall will see a#out *&++ degree da"s.

/hat is the total amount of heat lost in a "ear

Question 1&

A &+ ton air conditioning unit has an a!erage electrical load of *+ Fw. /hat is the EE1 rating0

Practice PE Exam: HVAC Breadth and Depth

Practice Exam #1

8or a complete list of the 9uestions please go to the HVAC Practice Exam G$ Page

Problem 1The area needed is $+++ s9uare inches

5olution for HVAC uestion G$

Combustion Air Opening

Problem #1A mechanical room has %&' () kilowatt electric water heaters and %$' *+++ ,BT-H natural draftgas fired #oiler. ou are looking to use the one permanent opening method for the com#ustion air opening. /hat area should the com#ustion air opening #e0

Ans erTo sol!e this 9uestion "ou need to #e familiar with the ational 8ire Protection AssociationJsCodes % 8PA' The re9uirements for com#ustion air openings are dictated in 8PA :(.

Per the &++; Edition of 8PA :( 5ection ;.*.*.&

http://www.peexamquestions.com/pe-exam-hvav-1/http://www.peexamquestions.com/hvac-1/http://www.peexamquestions.com/hvac-1/http://www.peexamquestions.com/pe-exam-hvav-1/


4/15

ou will need $ in & of open area for each *+++ BT-H. Also pa" attention to the difference #etween ,BT-H3 which "ou ma" #e gi!en3 and BT-H which is what is needed for hecon!ersion.

8or reference $ ,BT-H is e9ual to $+++ BT-H

5ince the water heaters are electric the" will not re9uire an" extra com#ustion air.

To meet 8PA standards "ou would need a com#ustion air opening of at least $3+++ s9uareinches or ) s9uare feet

Problem !The mass flow rate of water to the cooling tower is :;+ gpm5olution for HVAC uestion G&

"lo ate $hrough the Condenser

ProblemA water cooled chiller uses 12$*(a as a refrigerant. The refrigerant flow rate through thecondenser is $++3+++ l#m4hr with the entering pressure of $++ P5IA and lea!es the condenser ata temperature of 6+7 8 and is a saturated li9uid. The refrigerant then passes through thee!aporator and lea!es as a gas at $+7 8 . /ater from a cooling tower is used to a#sor# the heatgi!en off #" the condenser. The cooling tower water enters the condenser at ):7 8 and lea!es at;67 8.The Coefficient of Performance for this chiller is (.+. /hat is the flow rate in gpm of thecooling tower water0

%olutionThis pro#lem re9uires a little #it of knowledge a#out the Vapor Compression 1efrigerationC"cle. The wa" I find that is easiest to sol!e these is to set up a ta#le for the set points "ou ha!e

#een gi!en. This wa" "ou can see which points "ou are missing still. I ha!e created a !aporcompression refrigeration c"cle cheat sheet to help

To find the flow rate of the condenser water we need to find the total heat re ected to thecondenser water which is the sum of the refrigeration and work done #" the pump.

8irst we look at the e9uation for the Coefficient of Performance %C P'

http://www.peexamquestions.com/hvac-2/http://www.peexamquestions.com/wp-content/uploads/2013/04/Vapor-Compression-Cycle-Cheat-Sheet.pdfhttp://www.peexamquestions.com/wp-content/uploads/2013/04/Vapor-Compression-Cycle-Cheat-Sheet.pdfhttp://www.peexamquestions.com/hvac-2/http://www.peexamquestions.com/wp-content/uploads/2013/04/Vapor-Compression-Cycle-Cheat-Sheet.pdfhttp://www.peexamquestions.com/wp-content/uploads/2013/04/Vapor-Compression-Cycle-Cheat-Sheet.pdf


5/15

5ince we onl" ha!e the C P we will stat #" calculating the heat a#sor#ed #" the e!aporator #"using the following e9uations.

The pro#lem states that the refrigerant passes through the e!aporator at $+ 7 8 and lea!es as agas3 the enthalp" for h$ can #e found.

h$ K $=6.+= #tu4l#m

The next clue we ha!e is that the refrigerant lea!es the condenser as a li9uid at 6+ 7 8. 5ince therefrigerant is not su#2cooled we can find the pressure. The e!aporation process is isothermal so

with the pressure and temperature we can find the enthalp" for h(

h( K $+$.66 #tu4l#m

The mass flow rate is gi!en in the pro#lem.

ow putting it all together gi!es

ext step is to find the work done #" he compressor3 which can #e done & different wa"s

ow that we know what the heat in % in' and work in %/ in' are we can find the heat out % out '

ow that we know the heat that would #e a#sor#ed #" the cooling tower water we can find the!olumetric flow rate #" using the following e9uation


6/15

ow to con!ert from cu#ic feet per hour to gallons per minute

The mass flow rate of water to the cooling tower is )$; gpm

Problem &

5o in order to run the $.*( horsepower pump "ou would need ::= s9uare feet of solar collectors.5olution for HVAC uestion G*

%olar Po ered Pump

ProblemA client is asking to use a solar energ" collector to collect energ" for a solar powered pump. Thesolar panels ha!e an o!erall efficienc" of $&


7/15

The pump would re9uire $+++ watts to run. ow to siLe the energ" collector

5o in order to run the $.*( horsepower pump "ou would need ::= s9uare feet of solar collectors.

Problem 'The total load seen #" the coil is :*= ,BT-H5olution for HVAC uestion G(

%ensible Heat atio

ProblemAn air handler has a & $4&? diameter chilled water #ranch piping that supplies water to a )&? x(6? cooling coil that has :46? copper tu#es. The return air enters the coil at $++7 8. The air is thencooled to =+7 8. 8or this particular coil the maximum allowa#le face !elocit" across the coolingcoil is (:+ fpmThe sensi#le heat ratio for this coil was gi!en as +.6).

/hat is the total cooling load on the cooling coil0

%olution5ine this pro#lem has no dehumidification or humidification we can sol!e the pro#lem using thesensi#le heat ratio %5H1'.

The sensi#le heat ratio is the percentage of sensi#le heat di!ided #" the total heat load.

8rom what the pro#lem tells us3 we can get the sensi#le load3 which is the cooling load across thecoil3

http://www.peexamquestions.com/hvac-4/http://www.peexamquestions.com/hvac-4/


8/15

8irst we need to find the !olumetric flow rate %cfm'

/ith the !olumetric flow rate know we can sol!e for the sensi#le load

The sensi#le load is (==3:=+ #tuh

ow we can use the 5H1 and the sensi#le load to determine the total heat load

The total load seen #" the coil is :*= ,BT-H

Problem (Chiller G& has the lowest C P with $$.). /hereas chiller G$ has a C P of $$.;. Chiller $ is the

#etter chiller.5olution for HVAC uestion G:

Calculating the Coe)cient o* Per*ormance *or a Chiller

Problemou ha!e #een asked to e!aluate two chillers using the coefficient of performance. Both chillers

are a#out the same tonnage and "our client would like to use the more efficient chiller.

Chiller #1

• "lo rate o* ((+ ,P-

• Entering $emperature (./ "



9/15

• 0ea ing 2ater $emperature '(/ "

• Compressor input !( $ons

Chiller #!

• "lo rate o* (++ ,P-

• Entering $emperature (./ "

• 0ea ing 2ater $emperature ''/ "

• Compressor input !( $ons

%olutionTo sol!e this pro#lem we need to calculate the theoretical coefficient of performance %C P' for

each chiller.

8irst we need to find out how much heat is a#sor#ed3 #" using the following e9uation

The pro#lem does gi!e the work in3 ust in tons instead of #tuh3 so we use the next e9uation tocon!ert e!er"thing to the same units

Chiller G$

Chiller G&


10/15

Chiller G& has the greater flow rate which gi!es the lowest C P with $$.). /hereas chiller G$greater range of temperature #ut onl" has a C P of $$.;. Chiller G$ is the #est choice

Problem #3The pressure near the inlet fan is 2).: inches of water 5olution for HVAC uestion G=

4sing Bernoulli5s E6uation to "ind Pressure

ProblemAn air handler has $:3+++ cfm of air passing through the coiling coil. The !elocit" across theface of the cooling coil has a maximum !elocit" of :++ fpm. The air then passes through the faninlet section of the air handling unit and then passes into a $6? diameter plug fan. If a pressuresensor records a pressure of 2*.+ inches immediatel" downstream of the cooling coil3 what is the

pressure when the air enters the plug fan0

%olutionIn order to sol!e this pro#lem we need to look at BernoulliJs E9uation

! K Velocit"

p K Pressure

g K @ra!it"

M K 5pecific /eight K densit" D gra!it"

5ince the air is tra!eling at the same height N $ K N&

P$ is gi!en in the pro#lem statement as 2* inches

! $ is gi!en as :++ fpm



11/15

! & is not gi!en3 #ut can #e calculated #" finding the !olumetric flow rate.

Velocit" K 6(6) fpm

ext we sol!e for P &. /hen working this pro#lem it is helpful to write out the units. The !elocit"is in minutes3 while gra!it" is in seconds. ne will need to #e con!erted. In this pro#lem we aregoing to con!ert e!er"thing to seconds.

ast item left to deal with is the specific weight. The pro#lem is asking for the answer in inchesof water3 #ut we ha!e #een using air in the pro#lem. The con!erting is done #" di!iding #" thedensit" of air then multipl"ing #" the densit" of water. Then di!ide #" $& inches per foot.

Here is what the pro#lem looks like when it is completel" laid out

The pressure near the inlet fan is 2).: inches of water

Problem #7The !entilation load is $*(36&+ #tu per hour or a#out $$.* tons5olution for HVAC uestion G)

4sing Enthalp8 to Calculate Ventilation 0oad

ProblemThe design conditions for a dining room at a pu#lic school are ):7 8 dr" #ul# and =&.:7 8 wet

#ul#. -sing A5H1AE =&.( to calculate the outdoor air re9uirement3 it was calculated that the!entilation re9uirement for the dining room would #e $3(++ cfm. The temperature outside has a



12/15

maximum range of ;:7 8 dr" #ul# and 6$7 8 wet #ul#. /hat is the !entilation load the coolingcoil will see from the outside air0

%olutionThis pro#lem can #e sol!ed #" using enthalp". The !entilation load can #e calculated #" #"

using the difference #etween the enthalp" of the lea!ing air and enthalp" of the entering airs.

ou will also need to con!ert the entering air speed from feet per minute to feet per hour. This isdone #" multipl"ing the air speed #" =+

h& is the enthalp" of the outside air3 which is ((.: #tu4l#h$ is the enthalp" of the air lea!ing the cooling coil3 which is &*.$ #tu4l#V is $(++ cfm

O is the a!erage densit" is +.+): l#m4ft*

The !entilation load is $*(36&+ #tu per hour or a#out $$.* tons

Problem #.The gpm per pump is :&6 or $:6( gpm for all pumps5olution for HVAC uestion G6

Pumping 9et "uel

ProblemA fuel depot at the airport has %*' ): horsepower pumps that can each deli!er :++ gpm of et fuelto the holding tanks. All three pumps operate at =:< efficienc". The total d"namic head neededfor each pump is (++ feetThe fuel depot is getting read" to #e retrofitted. our #oss wants to know what is the maximumthroughput "ou can attain with the current pumps.

%olutionsThis 9uestion will re9uire & different e9uations to sol!e. The first e9uation is to find out theactual horsepower3 the horsepower listed in the pro#lem is for a nominal motor. The seconde9uation is one of the pump laws which will gi!e the maximum flow rate.



13/15

The head loss is (++ feet

The specific gra!it" of et fuel is +.6&

The motor efficienc" is +.=:

The flow rate is :++ gpm

The actual horsepower the motor is using is =*.)

The next siLe up motor would #e a ): hp motor

ow using the pump affinit" laws3 we can see there is a relation to the flow rate and the speed atwhich the impeller turns

Also using the pump law we can see that there is a relation to the flow rate of a pump and the power re9uired for the pump.

Inputting the data that was calculated form the earlier e9uations

5ol!ing for $ gi!es us a flow rate of :&6 gpm of et fuel per pump

-sing the * exisiting pumps "ou will #e pumping et fuel at a com#ined rate of $:6( gpm whichis a#out :&6 gpm per pump


14/15

Problem #The total amount of heat lost per "ear on the wall is ;.&$=3+++ #tu per "ear 5olution for HVAC uestion G;

Heating Degree Da8s

ProblemAn architect has asked "ou to get an estimate of the fuel that would #e needed to heat an exteriorwall per "ear. The wall has an area of $:+ s9uare feet. The thermal conducti!it" of the wall is+.+6 BT-4%ft>& D h D8 '. uring the heating season this wall will see a#out *&++ degree da"s.

/hat is the total amount of heat lost in a "ear

%olutionHeating degree da"s are used to get an estimate of the fuel that will #e needed for an area for a"ear. Heating degree da"s are determined #" taking the a!erage of the lowest and highesttemperature for a da". If the a!erage is lower than =: degrees 8ahrenheit it is considered to #e aheating degree da". If the temperature is higher than =: degrees 8ahrenheit then it is a coolingdegree da".

A is the area in 9uestion

- is the thermal conducti!it"

The total amount of heat lost per "ear on the wall is ;&$3=++ #tu per "ear

Problem #1+EE1 1ating K 65olution for HVAC uestion G$+

http://www.peexamquestions.com/hvac-9/http://www.peexamquestions.com/hvac-10/http://www.peexamquestions.com/hvac-9/http://www.peexamquestions.com/hvac-10/


15/15

Calculating EE ating

ProblemA &+ ton air conditioning unit has an a!erage electrical load of *+ Fw. /hat is the EE1 rating0

%olutionThe Energ" Efficienc" 1atio %EE1' is a standard measure of air conditioning efficienc" during a

normalQ annual cooling hour

EE1 K BT- of Cooling 4 /att Hours of Electric Energ" Input

$ Ton K $&3+++ BT-H

EE1 1ating K 6

practice pe exam hvac breadth and depth

Documents