VAV versus PIU, have you ever had to try and figure out the difference?

 

VAV versus PIU, .... WTF (Where's the Fan)?

 

 

 

In many commercial Air Conditioning Air Distribution systems, there is a strange phenomenon.  That is, what is a VAV and what is a PIU and why do many people call all of these one or the other?

 

Great questions indeed.Unlike your home, commercial and/or industrial duct systems work at substantially higher internal duct air pressure, this is called static pressure.  Static pressure allows the air to flow (move really) from a higher pressure within the duct system to a lower pressure area within the duct system.  This creates the air flow that we all love to feel when we are hot.

 

In the common fan unit, it can be called an Air Handling Unit (AHU) in many instances, but could located within a Roof Top Packaged Unit (RTU) or a built up air handler, this is where many components are assembled in the field to make an AHU, usually on rather large equipment, there is a fan of some variety that produces static pressure.  This fan(s) could be a typical fan as you would have in your furnace (Forward curve), a backward incline a fan axial, etc... Many types, all trying to do one thing, produce static pressure within the duct to allow the Air Distribution System to deliver air flow.

 

The Air Distribution System is made up of the fan, as we discussed above, the duct system as well as incorporates all Terminal Units.  These terminal units are the VAV's and PIU's that brought us here to begin with.

 

                          VAV = Variable Air Volume     PIU - Powered Induction Unit

 

Both of the devices incorporate a damper than automatically adjust the air flow when the building controls (#Tridium as an example) ask for cool air to be delivered into the space that particular VAV is serving.  These areas being served are referred to as Zones.  In most modern layouts and engineered buildings, the VAV's serve the interior parts of the building, the areas that typically do not require heat.  The heat in these areas is provided by lights, people, solar warmth, etc...

 

The PIU is an assembly that takes the same concept as the VAV, but once the controls tell the damper to close due to the space set point being satisfied, the PIU will in fact completely close the medium pressure air from the duct system then start a small internal fan that will recirculate return and/or plenum air to begin to temper the space if the temperature still continues to fall, once the fan moving this non-cooled air cannot suffice, the PIU can start to heat, many times this is a single or multi-stage electric heating element or possibly steam or heating water.  These PIU devices are typically located within the exterior zones of a building where heat is required to keep the occupants and or goods at a comfortable temperature.

 

Knowing a bit more about what is lurking above the ceiling tile may never wind up helping you in your day to day, but at least you will have a good idea of whom to call if things were to get hot and sticky in the office.

 

For more on HVAC for Office Buildings, Data Centers and any Mission Critical Environment, please visit or The Tech Corner @ http://www.airtight.co/the-tech-corner/

 

 

DISCLAIMER:  Verbiage within our wacky Mechanical Industry can vary greatly, I have tried within the post to capture the general essence of what "most" people call "most" of the devices.  We try to get along, this is what happens when things go wrong!

 

 

 

 

 

 





Someone just said, "The SWUD Unit is down". What does that even mean & why is it making the building HOT?

SWUD:  More than just an acronym

Back in the 1990's, the Trane Company, now part of Ingersoll-Rand, introduced a line of Environmental Unit's designed to condition low & mid-rise buildings.  These units model numbers began with four letters ... You guessed it , SWUDU9042**BC360095BB101, as you can see if you do not have a Trane operations & maintenance book handy, the short cut to defining what this unit is would be simply to call it a SWUD unit.  These systems have gained in their sophistication and the markets served and now are commonly used in high-rise building applications.

The design of these systems are very compact and deliver a great punch for the limited foot-print that they consume in regards to floor space.  SWUD-style units have a complete mechanical system built within them to allow for the total conditioning of an office environment with the exception of the heat rejection component.  Either a cooling tower or a remote condenser. 

Just like in any home or office, laboratory or data center air conditioner, there a four required components to provide "cooling".  The Compressor(s), Condenser, refrigerant Metering Device, commonly refereed to as a TXV or a TEV and lastly the Evaporator, this is the section where the heat from the air stream jumps into the refrigerant in order to produce the cooling effect that we all need this time of year.

The basics of refrigeration are not all that basic, if you would like, please let me know via @gregcrumpton on Twitter and I will dive deeper into the particulars on the vapor compression cycle (refrigeration) itself.

The gist of this note is to allow you to understand that a SWUD unit, usually resides in the mechanical room of your building, is connected to a medium pressure duct (air distribution) system, works in conjunction with the buildings temperature controls and 9 times out of 10 is connected to a common cooling tower that serves as the final point of heat rejection from the building into the atmosphere.

This is a real simple explanation, but knowing the acronym may allow you to know whom to call if indeed you are hot and sticky at work.



Air Filters for Dummies: The Guide to Changing Your Air Filter

Air Filters for Dummies

Have you ever wondered when, why and if to change your air filter(s) at home or in the office?  Sometimes your thermostat tells you ... How does it know when?  Sometimes you happen to think about it when you see those ugly blue filters in the grocery store.  And then, you really think about it when the A/C stops working and the technician shows up and the culprit is ... You guessed it, Dirty Air Filters.

Back to basics:

Air filters are designed to catch fairly large, it is all relative, particulate out of the air stream.  Most filters are great at catching dust, per hair, etc...  The "ugly blue" air filters are really great for catching pigeons, children and other items of that size, not so good at removing the proper sized particulate from the air stream though.

To really help with dust control, pet dander, and pollen, we suggest using a pleated air filter, it has more surface area, due to the folded pleats designed into it and does a much better job than old blue.


Why are air filters really designed into an HVAC system?:

Air filters are designed into the total HVAC system for only one reason:  It isn't to control the dust on the end-table ... The main purpose of these filters is to prevent the dust and debris from collecting on the face of the coil (heat exchanger) of the air conditioning portion of the system.  The refrigerant (trade name Freon) in the system requires that heat be transferred from the air stream into the refrigerant circuit, it can only do this efficiently when the entire coil surface is clean and available for this exchange.  The natural by-product of air conditioning (cooling) is dehumidification, hence when dehumidifying, the evaporator (indoor coil) is wet with condensation, this would really gum-up with dust and grime if the filter was not there to PROTECT the coil surface.  That is the entire purpose for the filter, all of the other benefits we enjoy are just icing on the cake.


The BIG question ... How often to Replace the Filter(s):

As i said above, sometimes your thermostat will tell you to do it ... It is simply guessing.  It uses a hypothesis to say to do it based upon hours of operation, not "dirtiness" or pressure drop or anything scientific.  This is really a convenience feature that is there to simply serve as a reminder to do it.  We suggest changing the air filters in your home and office environment quarterly, four times per year.  Most residential systems only have one or a few filters, many office buildings have a much larger count and therefore will need to be considered in the budgeting process.  Your HVAC service contractor can help with the value to add in for that replacement program. 

The other thing to consider:

Ina commercial office building, there are systems that allow you to induce outside air into the space as the primary cooling source.  This is called an air-side economizer, there are water-side economizers as well, but that is for a different day, these will require a little more monitoring of the air filter condition due to the high percentage of ambient air that is being puled through the filters.  The economizers are a great money saving tool and even though the filter replacement cost will increase with use, your overall power consumption will be reduced so far, there will be a "No Brainer" conversation to be had.  For more on Economizer Use Read about it in a past Newsletter @:  www.airtight.co/newsletters/AirTight_Newsletter-April_2012.pdf

Wonderng where these terms came from?

 

Common Questions Regarding HVAC Terminology & Applications

 

Over the years, many people have had similar questions to common thoughts. During my 30 plus years, I have catalogued many of these. Seems to be a great time to start eking them out, summer is here and the mighty HVAC industry roars!

Ø Why is it that I hear people talking about how many “Tons” their HVAC unit is? Is it that heavy, does a 3 ton system really weigh 6,000 lbs?

ü A ton of refrigeration is approximately equal to the cooling power of one ton (2,000 lbs.) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts.

The original design utilized a big block of ice, roughly a ton of it, then a fan, either electrically powered or otherwise driven would blow air over the ice, the air would surrender its heat to the ice, thus melting it, then the now cooler air would be delivered to the place people had gathered, typically in places of worship or community gathering sites. These values were established long ago before the mass use of centralized systems. There are many variations, designs and styles of units and complete systems. Large, small, water-based, refrigerant-based, etc… For more information and further details, visit: http://www.airtight.co/the-tech-corner/technical-glossaryand/or https://en.wikipedia.org/wiki/Air_conditioning

Ø What is the part of the A/C system that sits on the roof and/or behind my house in the shrubbery?

ü It is the Condensing Unit with the Condenser Coil within the cabinet. A condenser coil is one means of heat rejection commonly used in an air conditioning system. It is typically located on an outdoor pad or on a rooftop and looks like an automobile radiator in a cabinet. It is usually hot to the touch (120°F / 49°C) during normal use. Its function is to transfer heat energy from the refrigerant to the cooler surrounding (usually outdoor) environment. Yes, even when it is 100 degrees outside, it is still cooler than the refrigerant that is circulating with the tubing. The more commercially related Dry Cooler or Fluid Cooler serves the same purpose of heat rejection and physically appears similar, with the difference that the condenser coil uses hot refrigerant which changes from a gas to liquid as it move through the coil, whereas the Fluid Cooler uses hot liquid such as water or a water-glycol mix.

http://www.youtube.com/watch?feature=player_embedded&v=IF5WORhyXj4

These coils typically require an annual cleaning with water and/or a solution, determined by the particular manufacturer. This cleaning will keep the heat exchange rate within normal limits, thus saving energy consumption, therefore power and keep the system cooling at optimum levels. This cleaning should always a part of your Preventive Maintenance program.

The Difficulty and the Enjoyment of Finding the Next Technician to Hire

The wonderful world of HVAC is where I spend much of my life.  Many of the hours spent are with our people who are or become core members of the tribe, we call them AirTightans.  We search high and low for the right type of person to join our tribe.  No they are not tribe members day one, but if we search out the right kind of folks, they can blend into our tribe and as they learn the AirTight culture, eventually (10,000 hours or so) they morph into AirTightans.

Yes, we do all of the "must do's" to ensure we are vetting out and getting the people to interview who at least have the best chance to stick around long-term.  35% of our small and young company have been with us 5 years or longer.  We are 14 years old and have 35 employees on the pay-roll.  We also have the first ever employee, Denny Baumgart and our first customer, Childress Klein Properties.

As you know if have ever tried to hire anyone, let alone a skilled craftsman, it is a laborious effort.  As you are interviewing, multiple times with multiple different people within your tribe, real life keeps going.  So after three rounds and three different groups of us interviewing, we narrow down or list, as that list gets narrowed, we ouch into the relationship with a ride along session with team leaders, work with our production team, etc...

If all of that goes well, then we get to make an offer and see if we can come to terms on finances and benefits.  We are not a unionized shop, so we actually get to negate the person skills value, versus there positional pay, way better in my mind .... Kind of like our customers do us!

Well, this past Friday we came to an agreement with such a gentleman, we are excited by the prospects of him coming, his opportunities to understand us, our ways and most importantly, how strongly we feel that Excellent Customer Service and Care are the cornerstone of AirTight.

Wish us well in our new relationship, we will be learning each other, coaching, mentoring, guiding and everything humanly possible to allow this to flow as it should.

Next up .... Start looking and being open to the next great soul that comes along and wants to take the ride with us.

Is that you?

Lunch as part of Success Series of Interviews / "Bob Smith" – A World Class I.T. Industry Leader



The lunch interview was one more installment of the “Success Interview Series”.  “Bob Smith”, the successful CEO of a local, Charlotte, NC, Co-Location & Managed Hosting Company was my willing guest.  Bob has been a friend of AirTight for many years, we have been fortunate to be able to assist their growth within the infrastructure of their companies multiple data centers scattered throughout the region.  I asked him if he would break bread and allow me to better understand what it took to become successful, at  least from my view-point, as you know, most successful people are slightly reserved when it comes to anointing themselves as successful.

After settling in, he was kind enough to really open up, we discussed how he got to where he was, the real road map, complete with pot holes, steep grades and even some dirt roads.  It was really amazing to me to be able to get a glimpse into the world that normally we only imagine.  Most often, I find anyway, that when I think about success and the people who fit under that banner, it seems pretty glamorous, then to find out about the pot holes and the slippery slopes of inclement weather, it allows a deeper appreciation.

This interview was certainly not the exception to that rule.  The exception was how much this gentleman told me and how goofy I must have looked as he told me some of the happenings.  We talked for over an hour, towards the end, he settled on just a few examples of what had “Made Him Successful”.

Being Forgiving:  This was the dominant thought.  Bob relayed how forgiveness allowed him to move from one business relationship that didn’t end so well, but the forgiveness he allowed to enter his heart, really put him on his current course.  I didn’t take this at all lightly, in fact it made me recount a time or two that I should have been / wished I would have been more forgiving.  It certainly would have allowed for quicker wound healing.  The second and most spoken about publicly part? … Having people around you that you can trust and have candid conversations with without the raw words spilling out.  Just good, simple and clear communications to put all on the same page.  The final thought was about your investors: …  Be it capital, emotions or just confidence:  Work to have a great rapport with the team, they can allow you to really roll, but they have to believe in the mission, they cannot do that if they do not believe in you.

This session, like all of them thus far have been, are about just a handful of things.  You do not have to complicate things, just concentrate on the basics.  (Jim Rohn was/is famous for this line / www.jimrohn.com)  Honesty, being fair and do not put your reputation at risk.

These are the exact things that Bob has done.

Warren Buffet's 10 Rules to Success

I like to follow Warren Buffet.  He is a quirky, funny and great guy.  While he operates in an entirely different stratosphere than our company does, these rules seem to work for many different sized enterprises.  They are a good read and good things are bound to happen when you implement as many of them as you can.  He appears to have a great time in life and hangs out with some "fairly" successful folks as well.

So here they are, as he presents them:

1. Reinvest Your Profits. This makes sense not only in the stock market, but in a small business as well. Entrepreneurs who bleed all the profits out of a business find that they may struggle to grow the business into something larger and more valuable.

2. Be Willing to be Different. Buffet didn’t make his fortune by following the crowd. Instead, he invested when everyone else was panicked, and sold off when everyone else was buying. That strategy always beats the market. Doing what everybody else is doing - the same way they are doing it - is the recipe for becoming average. Nobody pays extra for “average”.

3. Never Suck Your Thumb. After you gather the information you need, make a decision. To Buffet, any time wasted to get to a decision is just “thumb sucking”. Success comes from immediately grabbing every opportunity that you can recognize.

4. Spell out the Deal In Advance. Your bargaining position is never stronger than before you are committed. So, advantage of that opportunity to spell out the details and specifics of any deal before you start. This is especially true when working with friends or family.

5. Watch Small Expenses. In the investment world, this translates into watching not just the returns offered by investment funds, but also the fees charged by the fund managers. This is so true in every aspect of small business and personal finance, as well.

6. Limit What You Borrow. Buffet claims to never have borrowed a significant amount of money. His advice is to remain debt-free, and then save and invest money. This is a very counter-cultural (see #2) contrast to those who preach getting rich using Other People’s Money.

7. Be Persistent. This is an advantage that the small entrepreneur has over larger, more established competitors. Persistence and ingenuity can, and often does win against large odds. If you’ve done your research, taken care of the details, watched your expenses and stayed out of debt, your success through persistence may only be a matter of time.

8. Know When to Quit. Don’t throw good money after bad. Resist the temptation to salvage a bad deal with a last-minute home run.

9. Assess the Risk. Buffet recommends thinking through both the best-case and the worst-case scenarios. This helps clarify the risks and rewards for any venture, which is critical to the decision making process.

10. Know What Success Means. Buffet doesn’t measure success in terms of dollars. As he says, “When you get to my age, you’ll measure your success in life by how many of the people you want to have love you actually do love you.” Here is wisdom.