Chilled Water Schematics – How to read hvac engineering drawing diagram

Chilled Water Schematics – How to read hvac engineering drawing diagram

Hey there guys, Paul here from In this video, we’re going to be learning how to read chilled and
condenser water schematics. Now these are engineering drawings that show how the
building’s cooling system is all connected. By the end of this video,
you should be able to read and follow a schematic,
identify the main symbols and know what the components all look like in the real world, understand the purpose of all the main components, and also recognize the different designs. Just before we get started,
I want to take a moment to thank our partner Danfoss
for sponsoring this video. If you’re passionate
about learning all you can about engineering, and
I’m pretty sure you are, then you need to sign up for
these free online courses, available on their online
learning portal, Danfoss Learning. Danfoss Learning have
hundreds of courses available in a variety of languages,
and their e-lessons cover a wide range of topics,
including, of course, chillers. Whether you’re looking to give
yourself a professional edge, or just learning for fun
and self-improvement, there’s something there for you. Getting started is easy, you
just have to click the link in the video description below, and then choose your first lesson. Okay, so firstly, every
schematic you look at will look completely different. The symbols used are always similar, enough to recognize what they are, but they’re always slightly different. However, they will all show how the chilled and condenser
water system is connected and distributed around the building. They will also show the main components, such as the valves and
pressure sensors, et cetera, and they should also show which floor the components are located. Usually they will not display
every air handling unit and fan coil unit that’s
connected to the system. Sometimes they will show the
connection to the main AHUs, and other times they will
refer you to a separate drawing if you want to see this detail. If the building rents
floors out to tenants, and the tenants have full
control over the fit out of that area, then the drawing
will just show the connection from the main risers
over to the tenant space, and anything after that is up to the tenant’s fit out contractors, and they should provide
the landlord with a copy of their own drawings for their area. Additionally, you should
remember that these drawings do not show every bend, or the exact route through the building, they are simply a flat 2D
representation of the system. How to read the drawing. So in the top left and the lower right, you’ll usually find the drawing number, which is a unique ID for
that particular drawing. In the bottom right,
you’ll also find the title of the drawing, for example,
Chilled Water System. You’ll also find the date of production, the revision number,
and other information, such as the client, the
person and/or organization that produced the drawing. And most importantly
on the right-hand side, you should find the legend,
which lists all the symbols used as well as their title. Whenever I’m reading a schematic, I always start by locating
the chillers, the pumps, the risers, the AHUs,
and the cooling towers. This shows you how the system works, how it’s all connected,
what type of system it is, and where each part is located. The schematics can be quite cramped, and you’ll sometimes need to
see through this information to be able to follow the system. Some important things to note
about reading a schematic, the pipes will often have
letters to help you identify which system it is, such as CHW, or CND, for chilled water and condensed water. They would also use F and
R for flow and return. You can see the direction
of the flow in the pipes, just by these little arrows. The diameter of the pipe
is sometimes listed next to the line. Newer designs might show
you the design flow rate, the velocity, the pressure,
and also the pipe diameter. You’ll also see these
letters around the valves, this is just to identify
what type of fitting it is. For example, an IV stands
for isolating valve. The letters NC mean the
valve is normally closed. You’ll also see these little
circles around the drawings, which have numbers and letters inside. This is a unique ID for the fitting. There should be a matching ID tag fixed to the physical fitting. And you can use the number
to find the correct fitting in the system. And also look up details
for it in the log sheet, such as the type and size. Dotted horizontal lines from
one side over to the other on the drawing mean that
there is a floor there. The arrows on the pumps also
indicate the direction of flow. So let’s look around the system
at each of the components to understand how it works. I’ve based this design
off a real world example for an older constant flow
water cooled chiller system, as it’s easy to understand. I’ll show you some real world
examples as we go through, and we can compare these
to some different designs, so that you understand the differences. We’ll first start with the chiller. I’ll just show you some examples of how chillers are
illustrated on the schematics, as it really varies. The two in the top right and
the one in the bottom right are all air-cooled chillers,
and the rest are water-cooled. The components of each system are similar, but as you can see, the design does vary, and not every chiller installed will use the exact same
setup or components. So we’ll start with a
chiller showing the condenser and the evaporator. Then we’ll have a flow and return lines into and out of the chiller. Then we’ll find the isolating valves, which are typically
butterfly or gate valves. These will be used to cut the chiller off from the main system to
carry out maintenance. You’ll also find these valves
and all major components, such as pumps and AHUs. Then we’ll have some temperature sensors, which the chiller or BMS is connected to, and the chiller will read this
and control it’s performance. Then we’ll have a commissioning station to measure the flow rate. This will be used to balance the system to meet the design flow rates, and also analyze the performance. I made another video previously on how to measure the flow rate of a chiller using this exact device. Check it out, link’s in the
video description below. Next we have a bypass
line, and in this example, there’s a double regulating
valve between the two lines, but it’s more common these days to have just an isolating valve here, which is normally closed. Or there isn’t a bypass line at all. These are used to either flush the system and bypass the chiller to stop dirt going into the heat exchanger
during the system clean, or in this case, it’s
used to balance the system as it’s a constant volume system. So this can be used to
simulate the pressure drop of the chiller if the chiller
is isolated for maintenance. Then because we have a bypass line, we’ll also have some
more isolating valves. This allows the chiller to
be cut off from the system, but the bypass line can still be used. In newer systems you will find the motorized control valve here, which is connected to the BMS, and this allows remote control. Then we’ll have some test points, also known as Pete Plugs,
and these allow technicians to plug measuring devices
in to take temperature and pressure measurements. Then we’ll have some temperature gauges to manually take readings. Over time these generally
become less reliable, and the gauges often get stuck. Then we’ll have pressure gauges
to allow manual readings. Again, these can become
less reliable over time, and they can also become stuck. Then we’ll have some flexible connectors. These prevent the vibrations
of the pumps and the chillers from running along the pipes
throughout the building, and they also allow the pipes to expand and contract slightly, which takes the pressure
off the connection. We’ll usually find an
almost identical setup on the condenser sides, so
I’ll just add that in as well. This design is for large
commercial office buildings. There’ll be multiple chillers. All of them will have
identical pipe arrangements, so I’ll just add that in as well. Next, we’ll need some
pumps to push the water through the chiller and
around the building. For this, we’ll usually have
two or more pumps in parallel, typically running in duty and standby. Again, the triangle points
in the direction of flow. Then we’ll need some flexible connectors as the pumps will cause vibrations. Then we’ll want some isolating valves, so that we can cut one or all of the pumps off for maintenance. Then we’ll have some strainers, which capture the particles
and dirt in the water and prevent them from entering
the pump and causing damage. Some pump setups don’t use this, and some will use just one
large strainer elsewhere in the system. Then we’ll have some pressure gauges to allow manual readings. Then we’ll have a non-return valve, which prevents the
pressure in the pipework from forcing the pump to rotate backwards when it’s turned off. Notice that this design doesn’t have a second isolating valve
past the non-return valve. In newer systems, however, like this one, you will usually find there is one. In the real world, it would
look something like this, and this is for a centrifugal pump set. We know the pumps need to push
water through the chiller, so we can connect the pump sets to the chiller’s evaporator inlets. Chilled water is generated
in the evaporator, so we’ll need to connect that back around to the pumps to create a circuit, which will distribute the chilled water. Notice there is a common header here between the flow and return lines. This separates the system into
a primary and secondary loops and allows a constant flow
rate in the primary side, which the chillers prefer as they require a minimum flow rate. It also allows a variable flow
rate in the secondary side, as the cooling load changes. The chilled water is
generated and circulated in the primary side loop. The secondary side loop will
pull the chilled water out of the header to cool the building, and it will then dump it’s
warm return water back into the header. If the flow rate in the
secondary side loop is low, then some of the chilled water will flow into the secondary loop, and
some of it will recirculate back to the chillers. If the flow rate is high
in the secondary side loop, then all the chilled water will
flow into the secondary loop and the return line will flow
straight back to the chillers. Coming off the common
header is another header. This allows the flow to be split, and each will receive equal distribution. On the atlas of the header, you might find a commissioning station, or a double regulating valve. But in newer systems, this is likely to be on the return line. From the header, outlets
will have some more pumps to distribute the chilled
water to different parts of the building. For example, to the east and west side. Some designs won’t have separate pumps for different parts of the building, they will simply have one pump set, which forces the chilled water
around the entire building. These pumps will distribute water off to the AHUs and fan coil units. I explained when this detail
was shown earlier in the video, but I’ll just briefly
give you some examples of air handling unit connections, and also some fan coil units. Pause the video if you
would like to look at these in some more detail. You’ll also find a pressurization unit on the chilled water side,
as this is a closed system. Typically this is connected
to the return line on the main circulating
pumps, as this area is not affected by the pump. This unit just maintains a
certain pressure in the system. Now for the condenser water side. Remember, air cooled
chillers do not require a condenser system. We will need a set of
pumps to push the water through the chiller and around the system, so we can drop these in first. Then we’ll need to connect those pumps to the condenser inlets,
and another line out of the condenser and up
to the cooling towers, which are located up on the roof. So we can then connect the cooling tower to the riser via our header. This connection will need isolating valves and flexible connections. Not all towers will use two
inlets like this example, some will just have one. At the outlet of the cooling tower, we’ll also need another isolating valve and another flexible connector. Then we can connect this back to the pumps to complete the circuit
for the condenser side. As this is a large building
with multiple chillers, we’ll need multiple cooling towers, and in this design, we’ll
pipe them in parallel. Because they are in parallel with a common supply and return, we’ll typically find a balancing line to ensure equal water
levels in the basins, and prevent air from being
sucked into the pipework and reaching the pumps. There might also be a bypass
line with a motorized valve across the cooling towers
flow and return lines. This can have various functions, such as maintaining a minimum flow rate, and also protecting the
chiller from tripping on low and high pressure
due to the temperature of the return condenser water
being out of design limits. For example, during start
up, or a cold winter morning. Another common version for the cooling tower
you might come across will look something like this. It has the flow and return
lines for the condenser water. There is a balancing line
between other cooling towers. They have a make-up line,
which tops up the water if the water was to get too low. And there will also be an
overflow in the drain line. Some will have a flushing line between the flow and return
lines for system cleaning. If you want to know how
cooling towers work, we’ve covered this in a previous video. Link’s are in the video description below. And that pretty much covers
the essentials of the system. So that about wraps things up. Before I go though, I just want to thank Danfoss one last time
for sponsoring this video. Don’t forget to check out
their free chiller e-lessons over at Okay guys, thanks for watching. If you’ve enjoyed this video, please like, subscribe, and share, and
also don’t forget to follow us on Facebook, Instagram,
Google+, and Twitter. And check out our website Once again, thanks for watching.

Dereck Turner

32 thoughts on “Chilled Water Schematics – How to read hvac engineering drawing diagram

  1. Niranjan Kannabathula says:

    Thanks for useful information

  2. Dawain BROWN says:

    Thanks Paul… Very Good explanation ……….What happen to the expansion vessel ?

  3. bule bule says:

    Thank you man! Ill sure be taking notes for this one

  4. Mazin Alrawe says:


  5. Tajamal Turi says:

    beautiful video

  6. Todd Medium Wellington III says:

    I'm going for my associates degree in hvac, and your videos really help me understand different subjects.

  7. Familia Sanchez HVAC says:

    Great video! Thanks for making these videos.

  8. Industrial Refrigeration for you. says:


  9. Marcus Weldon HVAC Director says:

    Great video

  10. Abhishek Mathew says:

    The entrance music to the title should be changed! But good videowork and recording!

  11. SM AJITH KUMAR says:

    Very nice and really i learned more. But one thing tell u pls explain how work in vfd drive.thank you

  12. Mohammed Salman says:

    Could you please add a video about fire pumps and it’s working

  13. The Engineering Mindset says:

    ⚠️ Found this video super useful? Buy Paul a coffee to say thanks: ☕


  14. KleinerC.S says:

    Excelente vídeo, solo falta los subtítulos en español (Y)

  15. Benny Blanco says:

    Can you post a videos on Series Counterflow Chillers? That would be very helpful in the industry.

  16. eracismm says:

    Thanks again Paul… Dan Foss e-learning is a great tool, also. Js

  17. fdggfgdfgd says:

    are u saying water from the cooling tower directly enters the chiller ? should it not have a heat exchanger – to separate these streams?

  18. Technic solution says:

    Thank u very much sir..good to learn

  19. HVAC Azerbaijan says:

    No need any strainer ?

  20. sayed mushtaq says:

    Excellent video very easy to understand bro

  21. ahmed azhri says:

    thanks for your fidio
    i just wandring as opration the secondry pumpe for what and the primre for what kindly Clearview this point for me
    i am electrical engineer
    i work dcp

  22. Toyin Orodare says:

    Thank very much for this video I learn a lot

  23. sintha mathar says:

    Hi i am air engineering in Dubai such a wonderfully video and chapters A to Z fine Thankz for (TEEG MINDSET) LOVE YOU GUYS

  24. Pravakar Khandai says:

    Nice video

  25. The Engineering Mindset says:

    Learn INDUSTRIAL REFRIGERATION basics here ➡️

  26. The Engineering Mindset says:

    Learn PRIMARY and SECONDARY circuits here:

  27. Familia Sanchez HVAC says:

    How does a chilled water system fill up? If you drained the remote evaporator barrel during the winter. Also if you dont want to use a hose to fill it up. I was always told to fill it up with a hose. My question is what is another way to fill it up?

  28. Joseph Sangilan says:

    very informative.. thank you!

  29. Mohammad Bawazeer says:

    Thank you so much.
    but think the strainer is missing from the schematic 07:31

  30. Narendra Negi says:

    Thankes for share with us

  31. omar aribi says:

    Tank you so much for you

  32. Damian says:

    Couple of points on an otherwise excellent presentation.1) If you're using common parallel pumping for primary chilled water and condenser water return, then you need motorised isolation valves and flow commissioning sets on each evaporator and condenser. 2) A common pipe or decoupler is normally used on large primary/secondary CHW systems, not low loss headers. 3) The isolation valve on the outlet of each cooling tower is not needed.

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