HVAC (Heating, Ventilation, Air Conditioning)

Tuesday, May 10, 2016

Duct Smoke Detectors. Install in return, supply, or both return and supply air ducts?






Duct Smoke Detectors.
Install in return, supply, or both return and supply air ducts of an air handling unit?

Let’s first establish the goal of this exercise.  Why do we need duct smoke detectors?  The goal is not to fan the fire.  In case there is a fire, all air movement should be stopped so that the fire is not aided by the air provided by an air handling unit, a rooftop unit, a forced-air furnace, a supply air fan, or any other HVAC equipment.  A duct smoke detector is installed to sense smoke (a byproduct of fire), and in case there is a fire send a signal to an alarm panel so that the respective HVAC unit is shut down.

Now let’s imagine an HVAC system comprised of a rooftop unit. [The logic presented below applies to other HVAC systems comprising of supply and return air ducts.]

Scenario 1:  Duct smoke detector in the supply air duct.  Rooftop unit WITHOUT an economizer.

A)  If there is a fire in the space, the smoke will go in the return air duct, and ultimately end up in the supply air duct.  Once the duct smoke detector installed in the supply air duct senses the smoke, the signal will be sent to an alarm panel that will work towards shutting down the rooftop unit.
B)  If there is a fire in the rooftop unit, the duct smoke detector installed in the supply air duct will sense the smoke and other processes will follow to shut down the unit.

Conclusion: For units without an economizer a single duct smoke detector installed in the supply air duct will work fine.


Scenario 2:  Duct smoke detector in the return air duct.  Rooftop unit WITHOUT an economizer.

A)  If there is a fire in the space, the smoke will go in the return air duct where the detector will sense the smoke, the signal will be sent to an alarm panel that will work towards shutting down the rooftop unit.
B)  If there is a fire in the rooftop unit, the supply air will first go to the space, and eventually come back to the return air duct where the installed smoke detector will sense the smoke and other process will follow to shut down the unit.
Conclusion: For units without an economizer a single duct smoke detector installed in the return air duct will work fine too, but will expose the people to smoke in case there is a fire in the unit.

Scenario 3:  Duct smoke detector in the supply air duct.  Rooftop unit WITH an economizer.

A)  If there is a fire in the space, the smoke will go in the return air duct; if the unit is not running in the economizer mode it will ultimately end up in the supply air duct.  Once the duct smoke detector installed in the supply air duct senses the smoke, the signal will be sent to an alarm panel that will work towards shutting down of the rooftop unit.  BUT if the unit is running in the economizer mode, all return air will be exhausted, and the duct smoke detector will not have a knowledge of the smoke in the space.
B)  If there is a fire in the rooftop unit, the duct smoke detector installed in the supply air duct will sense the smoke and other process will follow to shut down the unit.

Conclusion: For units with an economizer a single duct smoke detector installed in the supply air duct will NOT work.



Scenario 4:  Duct smoke detector in the return air duct.  Rooftop unit WITH an economizer.

A)  If there is a fire in the space, the smoke will go in the return air duct where the detector will sense the smoke, the signal will be sent to an alarm panel that will work towards shutting down the rooftop unit.
B)  If there is a fire in the rooftop unit, the supply air will first go to the space, and eventually come back to the return air duct where the installed smoke detector will sense the smoke and other process will follow to shut down the unit.  But before this happens, people in the air conditioned space will be exposed to a lot of smoke.
Conclusion: For units with an economizer a single duct smoke detector installed in the return air duct will work, but it is better to have detectors in both supply and return air ducts to avoid exposing people to smoke.



 Photo courtesy: System Sensor

Friday, March 11, 2016

Revit vs AutoCAD

Revit is a powerful design tool. Revit begins where AutoCAD reaches in its stretches to reach in the 3-D domain.
In Revit you work in 3-D, right from the get go.

Collaborative Effort of the Design Team
In a design team, everybody works on their own Revit file.
For example, if you want to design electrical system for a building for which an architectural Revit file already exists, you will start from a new electrical template Revit file and then ‘link’ (pretty much like xref in AutoCAD) the arch Revit file.  You can then start working on your electrical design viewing the arch setup.
Revit families are like AutoCAD symbols, and Revit has extensive families.  Suppose you are working with the floor plan and say you want to show a transformer on your drawing, you will find transformers of different ratings in the transformer family. You drag and drop the transformer of your choice. As soon as you drop the transformer at a particular place in your drawing, the software
will ask you for the 'offset'--the third dimension (height) that you are currently not looking at in the floor plan.  In essence, all objects are placed in three dimensions and all views are coordinated.

Coordinated Views
If you are looking at an elevation view and change the place of a certain object, all views (floor plan, elevations, etc.) will automatically be upgraded to show the new location of the object you have moved.

Seeing Sections is a breeze in Revit
Revit makes it super easy to see sections.  In Revit, you DON'T make sections--they are already there, you have already drawn things in 3-D.
All you have to do is to drop the section line to see what a section across a space or object will look like.




Revit makes it easy to make schedules of material

If you are an architect
Every time you put a door on the drawing, Revit takes it into account.  When you opt for the door schedule all the information about doors you have used is automatically populated in the door schedule.

If you are an electrical engineer
Every time you put a transformer or distribution panel on the drawing, Revit takes it into account.  When you opt for the transformer or panel schedule all the information about the equipment you have used is automatically populated in the schedule.
The program even warns if you if a distribution panel is overloaded.

If you are a mechanical engineer
Every time you put an air device or a VAV box on the drawing, Revit takes it into account.  When you opt for the air devices or VAV box schedule all the information about the equipment you have used is automatically populated in the schedule.

The program even sums up the air flows, making you see if the sum of all air provided in a zone equals the air coming out of an air handling unit/FCU/VAV box serving that zone.


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Tuesday, October 06, 2015

Out of sight, out of mind


Out of sight, out of mind

This exhaust fan serves a busy restaurant kitchen.
I sometimes wonder if there should be cameras focused on out-of-sight rooftop mechanical equipment.  If property managers will see this equipment more often, they will know its condition, and will be more inclined towards spending money for the upgrade work.

Wednesday, September 16, 2015

A roof full of rusted mechanical equipment


This site was close to the beach.  HVAC equipment appeared rusty before reaching its normal useful life.

Tuesday, February 10, 2015

Make shift arrangements


It is good to come up with innovative designs, but it is often more efficient and economical to buy products best suited for the application.

Wednesday, September 18, 2013

Variable speed fans in Packaged Units over 10 tons


Variable speed fans in Packaged Units over 10 tons

On a recent job I specified two 10-ton rooftop units.  The application was a Class 1000 Clean Room. I wanted constant volume rooftop AC units—initially, air handling units were discussed but because of budget constraints we had to settle for packaged units.  Later, when I reviewed the submittal that came from the contractor I did see the wording ‘Multi speed fan’ but did not get alarmed as many manufacturers provide units with low, medium, and high speed fan settings that is just a one-time adjustment at the start-up.  It turned out that because of the latest Title 24 mandates, all AC units over 10 tons now need to have varying speed fans.  The fan speed is varied based on the staging of the compressors.  In the old days, a ten ton unit will supply, say, 4000 CFM all the time, and the supply air temperature will be changing based on the staging compressors, but now the supply CFM will vary based on the staging of the compressors and the supply air temperature will remain almost constant.
This Department of Energy documents describes the changes meant to increase the efficiency of rooftop units:

In short, the AC units we received had variable speed fan motors.  Now the challenge was to change the fan to constant speed.  The first set of instructions from the manufacturer on changing the fan speed to constant did not work.  These were the instructions.

>>Unplug the J9 off the RTRM then unplug the J8 pins 6&7.  Reset power to unit and adjust the R136 to the desired fan speed.
The contractor kept talking to the engineering department of the manufacturer.  The second set of instructions did work.  Here is what worked:
>>For standard ID Fan operation, ensure RTRM 3J9, RTDM 5J12, and RTOM 5J8 Pins 6-7 are open (no connections).
I wish AC unit manufacturers will say it very clearly on their brochures: The supply fan speed is automatically varied based on the cooling requirements.  This is the default unit that will be shipped to you unless you specifically ask for a ‘Constant Speed Fan’ option.

Sunday, July 21, 2013

Brake horsepower vs horsepower

Brake horsepower vs horsepower



Horsepower of a motor is what the motor is capable of delivering (the work it can do).  Brake horsepower is what you are actually making it deliver.  Using belt driven motors you have the option of increasing the load on a motor.  You should really not load the motor more than its listed horsepower.  But can you get more brake horsepower out from a motor than its listed horse power?  Yes, you can—although you should not.  It can be done because there is a safety factor built in.  It is called the Service Factor.  A motor listed as 10 HP is normally capable of delivering 11 HP (assuming a 1.1 or 10% Service Factor).  If you are using this motor in a belt-driven configuration you can load the motor beyond its listed 10 HP rating.  As you increase the brake horsepower of a motor beyond its listed HP, more current will be drawn by the motor and the motor will start to heat up.  If you have thermal protection on the motor you can safely venture into the service factor zone.  It is not recommended to increase the brake horsepower of a motor above its listed horsepower, but it can be done.  Obviously, this overloading cannot be done on direct drive motors--a fan (or a pump) with a direct drive motor will only operate at the motor rpm.

 Photo: Courtesy of http://www.rtftechnologies.org


Tags: brake horsepower exceeds motor horsepower; brake horsepower exceeding motor horsepower; brake horsepower more than motor horsepower; Can brake power exceed listed motor horse power?; Making your motor work harder; thermal overload protection; Service Factor of a motor; heating up a motor; direct drive motors; belt-driven motors

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Monday, July 01, 2013



E
quipment in a crowded commercial kitchen

Saturday, June 01, 2013



Exposed ductwork on roof.  What you see is the external cladding--the insulated duct is inside.

Wednesday, May 01, 2013



Large kitchen exhaust hood with grease filters, sprinklers, and make up air outlets.

Monday, April 01, 2013




Supply and return air ducts penetrating roof.

Friday, March 01, 2013



A small kitchen exhaust hood.

Tuesday, February 26, 2013

How to visually tell an ODP motor from a TEFC motor?





How to visually tell an ODP motor from a TEFC motor?

ODP stands for an Open Drip Proof motor.  Here drip proof part of the abbreviation is not important for our discussion—it just means that any nothing can drip out of the motor enclosure.  ‘Open’ is the main characteristic of this type of motor.  Here ‘open’ refers to the motor winding—open as in open to air stream.  In this type of motor, winding is cooled down by air freely entering the enclosure where the winding is.  If the air can freely get in the winding space, so can all air borne dust, and in extreme conditions even water can get in.
ODP is a less expensive motor in comparison to TEFC and can be used indoors where dust or water is not a concern.

TEFC is an abbreviation for totally-enclosed-fan-cooled motor.  In fact the real name of this type of motor should be TEFC-DP, or totally enclosed fan cooled drip proof motor, as this motor too is drip proof.  But the main difference between this type of motor and the open type--or the ODP motor--is that here the motor winding is totally enclosed in a chamber—air cannot get into the chamber.  So how do you cool the motor when it is totally sealed?  Easy!  The metal enclosure housing the winding gets hot--you put fins on the motor enclosure and blow air over it using a fan.  So, in fact you are not directly cooling down the winding (as you do in ODP), but you are cooling the motor enclosure.

How can you visually tell a TEFC from an ODP?  Look for the fins on the motor enclosure.  If the enclosure has fins, it definitely has a fan too that is blowing air over the fins—it is a TEFC motor.  You don’t see any fins—it is an ODP.


ODP motor image courtesy of http://www.fastenal.com
TEFC motor image courtesy of http://www.wegelectricalmotors.com

Friday, February 01, 2013



Supply and Return air ducts in ceiling space.

Tuesday, January 01, 2013

Commercial Air Compressor



An air compressor blocked by storage.

Saturday, December 01, 2012

Kitchen Exhaust System


A kitchen ready for some renovation work.

Thursday, November 15, 2012

Roof Equipment



New boilers replaced old ones.

Thursday, November 01, 2012

Mechanical Equipment on Roof




An air handling unit and two boilers.

Monday, October 15, 2012

Underground Storage Tank (UST) Removal- EPA



This video shows the procedure to safely remove an underground fiberglass diesel storage tank following EPA guidelines.
ESMEP.com
Energy Solutions, Consulting Engineers

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Monday, October 01, 2012

Small industrial exhaust system needed




A motorcycle shop in desperate need of a ventilation system.

Saturday, September 01, 2012

Environmental Chamber



Addition of an environmental chamber to an existing facility.  These chambers typically require the following services: chilled water lines (CHWS&R), city water line, CDA, Vacuum, Nitrogen, and drain.

Wednesday, March 21, 2012




Look at this sketch. Does the toilet exhaust steel duct penetrating the fire-rated shaft on the second floor but having no opening in the space require a combination fire-smoke damper? Yes, it does. Here is the code reference.


California Building Code 2010
Chapter 7: Fire and Smoke Protection Features

Section 716: Ducts and transfer openings

716.5.3 Shaft enclosures.
Shaft enclosures that are permitted to be penetrated by ducts and air transfer openings shall be produced with approved fire and smoke dampers installed in accordance with their listing.

Exceptions:
1. Fire dampers are not required at penetrations of shafts where:
1.1 Steel exhaust subducts are extended at least 22 inches (559 mm) vertically in exhaust shafts provided there is a continuous airflow upward to the outside; or
1.2 Penetrations are tested in accordance with ASTM E 119 or UL 263 as part of the fire-resistance-rated assembly; or
1.3 Ducts are used as part of an approved smoke control system designed and installed in accordance with Section 909 and where the fire damper will interfere with the operation of the smoke control system; or
1.4 The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less that 2-hour fire-resistance-rated construction.
2. In Group B and R occupancies throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, smoke dampers are not required at penetrations of shafts where:
2.1. Kitchen, clothes dryer, bathroom and toilet room exhaust openings are installed with steel exhaust subducts, having a minimum wall thickness of 0.0187-inch (0.4712 mm) (No. 26 gage);
2.2. The subducts are extended at least 22 inches (559 mm) vertically; and
2.3 An exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with the provisions of Section 909.11, so as to maintain a continuous upward airflow to the outside.

3. Smoke dampers are not required at penetration of exhaust or supply shafts in parking garages that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction.
4. Smoke dampers are not required at penetrations of shafts where ducts are used as part of an approved smoke control system designed and installed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system.
5. Fire dampers and combination fire/smoke dampers are not required in kitchen and clothes dryer exhaust system when installed in accordance with the California Mechanical Code.




Note that for fire damper requirements the installation shown in the sketch meets none of the exceptions under 716.5.3.1, and for smoke damper requirements the installation does not meet any of the exceptions under 716.5.3.2, 716.5.3.3, or 716.5.3.4.

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Tags:
When are fire dampers required?
Which code specifies required fire and smoke dampers?
Why fire dampers?
Fire dampers in ducts, when?
When do you need fire dampers?
At what places fire dampers are required?
Do I need a fire damper?
Duct penetrations requiring fire and smoke dampers.
Do steel ducts require fire dampers?
Do steel ducts have 1-hour fire rating?
I don’t need fire damper if the steel duct does not have any openings in the space?
Steel ducts can stop fire?
Steel ducts can stop smoke?
How do steel ducts behave in case of fire?
Can fire transfer through a steel duct?
If a duct penetrates a fire-rated shaft but does not have any openings in the space, does it need a fire damper?
Do fire dampers really work?
Why combination fire/smoke-dampers?
Do buildings with automatic fire sprinkler systems need fire dampers?

Wednesday, October 26, 2011











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


Also, see this animation

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Tuesday, April 28, 2009




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.]

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Monday, January 12, 2009



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.]

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Monday, June 02, 2008



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.

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Thursday, October 04, 2007



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.

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Wednesday, June 13, 2007









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.

Wednesday, September 06, 2006

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.

Wednesday, August 30, 2006






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.]

Monday, August 21, 2006


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).