HVAC (Heating, Ventilation, Air Conditioning)

2011-10-26T11:46:00.000-07:00

A Class 10 Clean Room designed by Energy Solutions, Architects and Consulting Engineers.

Also, see this animation

2009-04-28T12:16:00.000-07:00

LEED and I: How to prepare for LEED NC Exam

It must have been sometime in the year 2001 when the word "LEED" entered my peripheral vocabulary. My friend Sunil Patel of TMAD Taylor & Gaines was in Oakland to establish a branch office in Northern California. Sunil asked me if I knew what LEED was. I did not know. He passionately explained to me the philosophy behind LEED, and then spread out a number of manuals in front of me. I looked at the material half-heartedly, as I had other things going on in life and was not interested in investing my time in a new green program. Very quickly I forgot everything about LEED I heard from Sunil or gathered from a quick skim of LEED manuals--everything except the fact that LEED wants you to use regional material.
My professional mechanical consulting engineering life went on with LEED existing on the fringes of consciousness. But voices citing LEED were gaining strength, I became aware of the fact that you could take an exam and become a LEED accredited professional. But none of my clients ever asked me if I was a LEED AP. Then last year that is in 2008, I provided my professional services to Applied Materials (AMAT). AMAT was in the process of LEED certification of its existing buildings. My help was sought in earning the Energy and Atmosphere (EA) credits. It was then that I read through the LEED-EB scorecard and became more familiar with the rating system. Then came recession and I found a lot of time at my hand. I decided to earn the LEED accreditation. But I procrastinated, till I found out that the LEED version 2.2 I was somewhat familiar with, would be superseded by a newer version and I needed to register for the 2.2 version exam by the end of March. A lot of people prepare for the LEED exam by first studying the material and then scheduling the exam. That was not going to work for me. I needed a deadline, a goal, a target date. So I registered for LEED NC exam on Monday, March 30, 2009, just one day before the deadline to register for v2.2--I could register only after completing my tax return work. I scheduled to take the exam on Monday, May 4 at 12 Noon at the Prometric office in San Jose. Why Monday? Because my babysitting duties end on Sunday--they start Friday evening. Why 12 Noon? Because it would give me some time to start a relaxed morning and easily reach the exam site without any stress. I now had more than a month to study.
After registering for the exam I started studying, but not right away. I got the LEED NC 2.2 reference guide on Friday, April 10. I quickly realized how long it had been that I had read anything with focus and had retained my attention on the document. I read the chapter on Sustainable Sites lying in bed. I did not take any notes telling myself I only needed to have an overall understanding of the material without getting into the nitty gritty. So, SS prerequisite and credits, along with their intents, requirements, calculations, submittal documentation, and strategies were all reviewed in a couple of hours--that must have been on Saturday, April 11. Then on Monday, April 13, I did similarly justice to IAQ. The chapter on Materials and Resources was read sitting on a bench in the Children Discovery Museum, while the children played. Summary reading of Water Efficiency and Energy & Atmosphere followed. Then I took a sample test and the result felt like a hard kick in the butt. I found out how ill-prepared I was and I was going to be for the exam, with my erstwhile strategy. I decided to make an Excel file of all information I would gather while reading the reference guide. My study took a more serious approach, but then I realized I had already wasted a lot of time. The exam was on May 4, just over two weeks out. I decided I would take two sample exams before April 26 and then take the USGBC Colorado Chapter sample exam on Monday, April 27. If I did not score over 80% in those exams, I would reschedule. So here I am. Today is April 28 and the exam is on May 4. I have scored just over 50% in the sample exams. I must reschedule and do it before the end of tomorrow (Wednesday)--the rescheduling fee is $30. But when should I take the exam? I need to take it before June 30 and I should take it on a Monday or Tuesday. But when? It is not a question to you, it is a question to myself, and I am pretty sure having written all this I would come up with an answer soon.

[Art courtesy of USGBC web site.]

2009-01-12T12:10:00.000-08:00

What should businesses do in recession?
Fill the hole in their pocket.

Businesses spend a fortune on their utility bills, every month. And in many instances they don't realize they can substantially reduce their energy costs. For businesses to waste money in unnecessary electricity and gas costs, especially in these tough economic times, is like trying to be financially astute but with a big hole in the pocket. From lighting to HVAC equipment to office machinery, there are inexpensive yet effective technologies that can save you a lot of money. Just look at your energy statistics and compare them with regional and national values--you will see how much room you have for energy conservation.

[Silicon Valley view, courtesy of Google Earth.]

2008-06-02T17:30:00.000-07:00

Paint Shop compliance

A client of mine recently moved his paint shop from one city to another in the Bay Area. Whereas he was in compliance in his old location he needs to prepare drawings to show compliance to the city he is now operating in. When I visited the site I found a ceiling hung gas-fired heater in the warehouse area he has moved his business to. Section 1503.2.2 of California Fire Code requires open flames to be at least 20 ft. away from flammable liquids and vapors. I am going to have the gas-heater relocate to the top of the office space and blow hot air in the direction of the warehouse. [In high ceiling areas, ceiling hung gas-fired air heaters are not a good way to heat the space—hot air rises up and you need to heat the whole indoor air before benefiting the occupants standing below. It is much better to provide spot radiation heaters. These radiation heaters must be placed directly above the heads of the personnel—here the assumption being that the operators don't move a lot from their workstations. But then, why not do it the old-fashion way? Have operators wear very warm clothes in winter, in such high ceiling areas.]

How much air needs to be exhausted from a Spray Paint Booth?
[Other possible headings:
How to design a spray paint booth?
Exhaust requirement for a paint booth.
Paint shop ventilation design.]

The governing code is CAMC 505.1.2.
“In systems conveying flammable vapors, gases, or mists, the concentration shall not exceed 25 percent of the lower flammability limit (LFL).”

LFL is expressed in % by volume. For example LFL for methane is 5% i.e., if 100 cubic feet of air has 5 cubic feet of methane, then you would be able to throw a burning match in this air mixture and see combustion taking place.
So, how do we go from 25% of LFL to spray paint booth exhaust.
Let's look at an example.
Suppose looking at the MSDS for a particular paint you find its LFL to be 0.7%. Then 25% of this LFL is (0.7/4)%. If you are using a spray gun with a discharge rate of 0.4 Gallons/ second, then you really want to dilute 3.2 CFM (conversion from gallons to cu ft and s to min) of paint to a level of (0.7/4)%. Simple math will tell you, you need 1833 CFM of air to reach that level. And that is what your exhaust fan CFM should be.

2007-10-04T14:11:00.000-07:00

Renewable Energy, my love

I have been trying to find people getting their hands dirty on renewable energy projects. And I am glad I found Mubin Ullah Kotwal. Originally from India Mubin currently lives in Papua, Indonesia. The picture shown above is of a biogas plant he made himself. Mubin meets all his cooking needs using gas from this plant. Kudos to him!

And then came a query. Shahid Zia, my friend and collaborator in Karachi, asked me to write a design brief for a composting plant. Here is what I provided him.

A composting yard will be used to handle solid waste generated by the new Fruit and Vegetable market.

Of the four widely used composting methods for large scale composting (namely turned windrows, static piles, forced-aeration static piles, and in-vessel composting), we plan to use static piling technique at Sangjani, owing to this method’s requirement of low maintenance.

A preliminary calculation shows that for 6000 Kg of organic waste generated daily by the Sangjani Fruit and Vegetable market, a composting yard employing static pile composting method would require an area of 1.5 acres. This composting yard will have controlled access to prevent illegal dumping. Organic waste would be brought to the yard and front-loaders would be used to make piles approximately 10 ft in radius and 8 ft high. For aeration purposes the organic material in piles would be turned over in approximately four weeks. Depending on weather conditions a compost yield would be obtained in 10-16 weeks.

---

And then I generated a news item shown below.

Poor and wasteful, Pakistan does not want to be
A.H. Cemendtaur

For a new Fruit and Vegetable market to be situated in Sangjani, just outside Islamabad, Pakistani government is asking engineering consultants to design a composting plant. The envisioned plant would use waste generated by the produce market--compost produced by the plant would be used by agricultural communities. A composting site situated near a big source of organic waste is a novel idea for Pakistan where waste from city produce markets simply rots on streets. Travel through the developing world and you would see constant themes of poverty and prodigality going hand in hand. In Sangjani Pakistan seems to be breaking that pattern. Let's hope Pakistanis also learn that using gas to produce hot water when sun shines on them for more than 300 days a year is another waste of precious resource they need to break away from.

2007-06-13T00:20:00.000-07:00

Attended a presentation on green certification programs, in San Francisco.
http://www.builditgreen.org/registration/index.cfm?fuseaction=moreinfo

Mark Berman of Davis Energy Group talked about the LEED for Homes program. Bruce Mast explained the GreenPoint rating system for residences.

LEED for homes and GreenPoint are two certification programs for "green" buildings. In a nutshell, if you are building a house and you follow the recommendations of the certification program (either LEED or GreenPoint, or both) on making the house energy efficient, then the program will certify your building. You would not only have the boasting right but you would be given a certificate too. You may say you don't need certification and that you just want to implement the recommendations of the program (because they make sense and save you money). You can certainly do that, but then on selling the property you won’t have anything in your hand to prove to the prospective buyer that you indeed made your house green. The certificate is the diploma your building receives on graduating from the University of Energy.

The success of green certification programs is tied up with the cost of oil and the environmental awareness of the society. With rising oil prices it would make sense to make buildings energy efficient, and the certification programs will gain popularity. The certification programs can gain wider acceptance even with stable oil prices, if the society becomes more conscious of environmental problems caused by burning oil.

Let's protect the environment that nurtures our existence.

2006-09-06T19:14:00.000-07:00

Design Drawings, Shop Drawings, As-built Drawings

Doing design work for a contractor? Make sure the contractor knows the difference between design and shop drawings. Design drawings, often showing single line ductwork and piping, can seldom be used for construction purposes. Design drawings show how engineering-wise things would work. Contractor needs to make shop drawings to make sure things would fit in the field. Contractors develop scaled shop drawings based on design drawings, final equipment submittals, and field conditions. Whereas the design engineer, in general, makes sure specified equipment and accessories would fit, the engineer cannot possibly produce shop drawings at design stage because the information about equipment to be purchased by the contractor is missing. The third set of drawings made in the life of a project is the set of as-built drawings. The as-built drawings are almost like the design drawings except that they show the actual way the equipment and accessories were installed.

2006-08-30T17:19:00.000-07:00

Inline fans

I recently specified belt-driven inline fans on a job. The good thing I found out about Greenheck's BSQ line of fans is that the fans can be rotated in any manner i.e., the motor does not necessarily have to be on top, it can be on either side, it can even be upside down. This is a useful feature because often times you have limited vertical clearance to install these fans. Charles Lauer of Norman S. Wright Company (representing Greenheck) told me fans with motors up to 5 HP can be rotated in any manner.
[Photo courtesy of Greenheck.]

2006-08-21T17:46:00.000-07:00

Building occupancy classifications simplified

Still confused about occupancy classifications? Let me simplify things for you. In Uniform Mechanical Code the building occupancies are designated by letters. Here is my explanation of each occupancy group.

Group A occupancy
A is for assembly
Churches, arenas, stadiums, concert halls, etc.

Group B
Offices and eating and drinking establishments with an occupant load of less than fifty.

Group C
Not used

Group D
Not used

Group E
E is for Education
Sschools and day care for more than 6 persons.

Group F
F is for factory

Group H
H is for hazardous

Group I
I is for institution
Nurseries, Hospitals, Mental hospitals, jails, reformatories, etc.

Group M
M is for merchandise
Shops

Group R
R is for residence
Hotels, apartment houses, dwellings, and lodging houses.

Group S
S is for storage (non-hazardous material)
Storage building, parking garages, aircraft hangers.

Group U
U is for normally unoccupied spaces
Private garages, carports, sheds, and agricultural buildings.

So you live in a house (Group R); in the morning you drop your children at a school or day care (Group E); then you go to your office (Group B); midday you go to eat lunch at a restaurant (Group B); and in the evening you go for grocery shopping (Group M). On Sundays you go to a church (Group A), and if you get sick you go to a hospital (Group I).

2006-08-15T15:56:00.000-07:00

Determining feasibility of a District Cooling and Heating system

A district energy system gets an edge over individual central plans in utilizing the diversity of load on a big campus. Instead of sizing individual units at peak load you size the district energy equipment for the combined peak load of the facility. This lends very well to large facilities where demands vary at different places at different times of the day. College campuses where learning centers are mainly buys during day and residence facilities are mainly occupied at night provide perfect match for district heating and cooling application. Similarly a combination of office and residential buildings in a planned community is also a good candidate for district cooling and heating.

[Places where on-site power generation is being considered a combined power and heating-cooling plant (district cooling) is a logical choice.]

Besides utilizing the diversity of loads the other obvious advantage in centralization of cooling-heating plant is in reduced maintenance costs.

The facilities that are ideal for district cooling applications are where
i) the diversity in load is very high;
ii) the buildings are not too distant from each other (reducing the cost of distribution); and
iii) hiring service and maintenance personnel is very expensive.

All three of the above factors vary greatly with each facility. Thus there is a need to compare the cost of individual units with the cost of centralized plant for each potential district cooling-heating candidate. This seemingly complex task can be simplified by using approximate figures for:
i) cost/ton of cooling equipment,
ii) cost/ft of distribution system, and
iii) annual salary of maintenance personnel.

For cases where the cost differential between individual units and district cooling-heating unit is rather close, a more detailed analysis can be undertaken.

[Photo source: Hiroshima Gas Company]

2006-07-18T22:26:00.000-07:00

Total number of Professional Mechanical Engineers in California

I started looking for this information but did not find it on the web. Tried calling the Board of Professional Engineers but was put on a very long hold. I went about a different way to see how many professional mechanical engineers are there in California. Started looking for individuals with high license numbers. Established that M-60000 does not exist, but M-30000 exists. Did this iteration a couple of times and found out that the latest Mechanical Engineering license number (or presently the highest number) is M-33534. I got my license (M-27808) in 1991. This tells me that the Board has issued a total of 5726 mechanical engineering licenses in the last 15 years; that comes out to be an average annual yield of approximately 380 Professional Mechanical Engineers licensed by California.

2006-07-11T16:59:00.000-07:00

Computer Room HVAC System Design

It works to your advantage when electronic racks in a computer lab are arranged in a fashion where they take air from one end and discharge heated air through the other side--you get a hot aisle cold aisle arrangement. You provide cold (conditioned) air in the cold aisle. The cooling fans of the equipment suck up that air, air gets heated by electrical load dissipated as heat by the equipment, gets discharged from the other end, and ends up in the hot aisle. You should have your return registers in the hot aisle to gather this air and take it back to the air conditioning unit. With this hot aisle cold aisle arrangement you not only resolve the hot-spot issue (hot air does not get mixed with the cold air while traveling back to the air conditioning unit), but you also get better performance out of the air conditioning equipment (as you increase the coil entering air temperature--providing a higher delta T for better heat transfer). A desirable computer room air conditioning system would have bottom supply (through the floor) or top supply (from the ceiling) in the cold aisle, and top return in the hot aisle.

I am currently designing a cooling and ventilation system for a server lab. The lab has six existing Compu-Aire units (CAC-2034). The room has ducted supply but free (non-ducted) return to the units--units have return air grilles in their bottom front panels. Since the owner is interested in having a hot aisle cold aisle arrangement I was thinking of making return air hard connection to each unit. Compu-Aire Engineering folks in Whittier told me the only place to connect return air to those existing units would be in the back of the units (connection to front would block the front control panel, and there is not enough room in the side to take all that return air). They said they can supply accessories needed to convert the free return air units to ducted return units (a solid panel to go in the front, and back panel with filters and flange for return air connection)--the conversion can be done in the field, by the mechanical contractor. The problem is, I don't have room to move the units out of their niches where they are presently butting the wall. So, I am designing for return air ducts that would bring the air from hot aisles and leave it in front of the unit without making a hard connection to the unit. Although this return air scheme would work without a fan, I want to be sure about the air movement through that route and am specifying inline axial fans for these return ducts (my fear being that if there is too much empty space between the racks the air would find the path of least resistance through the cold aisles to come back to the units). Since overhead space is tight I am not combining return air ducts through lateral connections. It would be many return ducts (probably ten) bringing hot air to the units.

Do you have any comments? I would love to hear from you.

2006-07-09T19:29:00.000-07:00

Exposed duct
The designer must not have a choice but to run this long exposed duct on roof. Now milk crates provide support to duct's sagging portion.

2006-07-09T19:23:00.000-07:00

Rectangular supply and return from a Rooftop unit, down through roof

Using long radius elbows at 90-degree turns is a good idea.

2006-07-09T19:14:00.000-07:00

Janitor Friendly Gas Meters
With natural gas prices going up it is a worthwhile exercise to compare the life cycle cost of a Rooftop Gas-Electric unit with that of a heat pump.

2006-07-09T19:08:00.000-07:00

small Gas-Electric Rooftop Unit
You can see the outside air intake, electric disconnect switch, and gas connection.

2006-07-03T17:53:00.000-07:00

Screen around Roof Mechanical Equipment

Look closely and you'll see it: behind the tree on the right hand side of the picture. It is the same departmental store seen from a distance.

2006-07-03T17:49:00.000-07:00

Four way diffuser in the same departmental store

Not a good idea to put the diffuser on top of the duct without providing any volume control damper.

2006-07-03T17:46:00.000-07:00

Exposed ductwork in the same would-be departmental store.

2006-07-03T17:29:00.000-07:00

Supply and Return Air Ducts from a Packaged Rooftop unit
This picture is from a departmental store. Notice the duct smoke detectors mounted on both supply and return air ducts. Duct smoke detector is needed to shut off the AC unit if smoke is detected in the space. One scheme is to have duct smoke detector on main return duct only; if you have smoke in the room, the sensor would sense the smoke and the AC unit would be turned off. But what if a motor burns in the AC unit? You can say that the smoke would go to the conditioned space but as soon as it is drawn in the return air duct, the smoke would be sensed and the unit would be shut off. The latest trend is to not rely on this indirect route and provide duct smoke detector in the supply air duct too.

2006-06-25T14:22:00.000-07:00

A wrong fan for commercial kitchen exhaust
You need an upblast fan for kitchen exhaust. This mushroom roof exhauster was the wrong choice for the kitchen below.

2006-06-25T13:44:00.000-07:00

Commercial Kitchen Exhaust Fan with grease all over the roof
This picture is from a facility that was abandoned a while back. You see grease here on the roof either because the Kitchen hood did not have any grease filters, or the personnel just removed the filters and operated the hood without them. People don't like grease filters because they sometimes catch fire. But they catch fire because you don't periodically wash them and one day when the heat is really high the grease collected on the filters starts burning.
Sometimes grease receptacles are provided at the fan, on the roof. But I am not a big 'fan' of that scheme. Out of sight, out of mind grease receptacle is seldom attended to.
A good kitchen exhaust system consists of grease hood with filters, grease receptacle, and fire suppression system; all this with an upblast fan on the roof. But you still need to periodically empty the grease receptacle, wash the filters, and check the fan on the roof.

2006-06-24T23:07:00.000-07:00

Kitchen Grease Filters and grease receptacle
Commercial kitchens are normally equipped with large hoods housing grease filters. The air exhausted through the hood is made to abruptly change its direction making the accompanying grease deposit on the "filter." The filter assembly is slightly sloped so that grease drains down into a receptacle. See the handles on the grease filters in the picture? The filters should periodically be taken out and washed. Kitchen hoods exhaust large amounts of air. Provision should be made to provide make-up air in the area. Often "compensating" hoods are used that provide make-up air around the periphery of the hood.

2006-06-21T17:24:00.000-07:00

Outside air to a fan coil unit (FCU)
People normally don't forget to bring outside air (fresh air) to an air handling unit (AHU), but generally Fan Coil Units are not treated the same way. May be because Fan Coil Units circulate smaller amounts of air and designers don't see it necessary to bring the very small amount of required fresh air. But when fan coil units are the only source of conditioned air in a habitable space, bringing fresh air to the FCU is imperative. Ducted return is preferable but in this case the FCU had bottom return and the designer supplied fresh air close to the unit.
Once again in this hotel room scenario the fresh air duct runs in a shaft accessible from the corridor.

2006-06-21T17:05:00.000-07:00

Toilet Exhaust
I found this toilet exhaust in a hotel room. For bigger bathrooms it is a good idea to have a separate exhaust over shower/tub too; this way you would avoid moisture spreading in the bathroom and fogging the mirror.
In the case above it was a small toilet and just one air intake served the whole area. See how the exhaust goes to a shaft accessible from the corridor (on the other side). Toilet exhaust is generally designed for 10 air changes per hour (or one air change in every six minutes). To compute the required air flow, calculate the volume of the toilet (lengthXwidthXheight) in cubic foot and then divide that number by 6 minutes, this would give you the required air volume flow rate in cfm (cubic foot per minute). Make up air (the same amount that you are exhausting) must be provided to ensure that you won't create a negative pressure in the toilet and make it difficult to open/close the toilet door. For smaller toilet exhaust cfm's, make up air can come through the undercut of the door (the distance between the bottom of the door and the finished floor). For larger amounts of air you need to have a transfer grill that would bring the required make up air from the adjacent room. For really big toilets you should think of providing some conditioned air. For example if you need an exhaust of 500 cfm, you may think of providing 300 cfm of conditioned air and transfer the rest from the adjacent room, using transfer grill.

2006-05-25T17:27:00.000-07:00

Looking for good mechanical (HVAC) and plumbing details in dwg format?

Thanks to the benevolence of Department of Veterans Affairs, sizable libraries of free, downloadable details are present here:

http://www.va.gov/facmgt/standard/details-hvac.asp

http://www.va.gov/facmgt/standard/details-plumb.asp

2006-05-25T17:16:00.000-07:00

Making HVAC Drawings
(Alternative titles: How to make a HVAC drawing// How to make a mechanical drawing// How Consulting Engineers make their drawings)
I want to write down the process of developing HVAC drawings. HVAC drawings (as well as Electrical, Plumbing, Fire Sprinkler, and Life Safety system drawings) are made according to the constraints defined by architectural drawings. In essence you need architectural drawings to see the layout of the building and the clearances you have to work within. The architectural floor plan becomes the background drawing for HVAC (and other fields). The first thing you need to do is to prepare the architectural plan to be used as your background drawing. To do this you need to clean up the drawing (by turning off layers that have things of mainly architectural interest) and then ‘dimming out’ the drawing. You want to dim out walls, doors, etc in the architectural floor plan so that when you put your mechanical (HVAC) stuff on top of it, your stuff would stand out. As a general rule, entities belonging to a particular field must stand out in comparison to others, in the drawings of that field. [So, in Plumbing drawings, plumbing items must stand out in comparison with elements of architectural, mechanical, and other systems.]

This is how I dim out an architectural drawing to give me a workable background for the HVAC drawings.

Save the Architectural floor plan drawing under a different name. In AutoCADD environment go to Layers using the Layer tool (alternatively, go to the ‘Format’ drop down menu, then click on ‘layer.’) When you see all the layers, highlight one layer; hold the CTRL key, and scroll down to highlight all other layers. Then click on one layer; and change the color to Color 9. This will change the color of all layers.

I believe it is possible to change all the layers of a drawing to any color by using LISP. This feature should come really handy if you have a number of architectural drawings to dim out. If you know how to do it using LISP, please let all of us know. We shall be thankful.

2006-05-24T13:53:00.000-07:00

Internet has been a tremendously valuable source of information for me. It is the first place I turn to whenever I want to find out about anything, literally anything. I have benefited a lot from information people have posted on the Internet, from all over the world. Now it is time to give back. I have been working in the business of HVAC (Heating, Ventilation, Air Conditioning) design for the last seventeen years. I have things I can share with you, with the humble hope that they might be of use to you when you search the Internet for help and reach here.