Let Diversity Dictate HVAC Use

I'll hire people of every color, sex, orientation thereto, nationality, religion, age, ability, disability, beauty, tallness, initiative, and character. Wouldn't want a bunch of clones; that would be boring.

Comfort condition is a relative term. Often a single parameter called effective temperature is used as an index of comfort. Based on ET concept many comfort charts have been developed like Fanger's chart. To maintain the comfort conditions in the room it is necessary to supply the air at appropriate condition. Supply air condition lies on the room sensible heat line on the psychrometric chart. Thermodynamically there is a wide choice available for supply air condition. For each supply air condition there is a supply air rate. By pass factor of the conditioning apparatus and variable flow are few concepts used in HVAC system to conserve energy when the rooms are not occupied especially in central plant system. Usually when there is frequent change in the occupancy such as hotels fan coil unit along with individual control s are provided .

Diversity is built into modern ddc control equipment and firmware. The limiting factor's are 1. lack of supervision by owners during construction, you can't hire a contractor and expect him to place details of construction above profit. 2. Owners by nature look to first cost and appearance rather than health, comfort and operating cost. 3. Human nature, we all tend to develope tunnel vision when we look to our tasks and normally lose sight of the laeger picture (ie, the lastest changes to 90-1, 5'f diferential will cause discomfort and the irratic changes of setpoints by occupants as well as the wasted energy to recover what was lost or gained during deadband.

Proportional control with a tight throttling range and demand based ventilation with attention to i/o enthalpy calculation and application is not new but often disregarded because of human nature. We need to tune the 'hunting' out of the design and developement process as well as the actual equipment and controls. When the 1% of code enforcement plan reviewers and inspectors that are competent demand strict compliance we hear complaints and disparaging comments and complaints. I prefer them because they eliminate "grey areas" and create a more objective standard.

agree with you but would go further Owners when the conceive the project do not bothers about the type of occupancy in commercial buildings,assumption plays vital role ,in todays design no body believes if its a commercial Building we need to be sure the kind of activity that the building is going to be used like banking/trading activity or call center or software development activity its assumed 100-120 Sq feet /person and HVAC designed most of the time you find HVAC operating around 40-50% of designed and installed capacity,the main reason is the ego of architects,project management team who decides and Miss lead owners to increase the project cost for an extra pound of flesh.

crm

Sometimes it is very difficult to make the architects and structural engineers to make them understand the concept of HVAC requirements. It needs continuous follow up and design stage to avoid many complication during execution and handing over stage of a project.

What you say is very good. To implement and verify this is the issue. The commissioning agency (third party hired by Owner) is responsible for the verification sequence. Many of them rely on the commissioning agent (HVAC Contractor) and control contractors (sub to HVAC contractor). If they are buddy buddy you don't know what you are getting for the final operating sequence. Don't forget the balancing team. They can make or break the operation of the system from room to room. All in all it takes more time than any contractor has allotted to do the job correctly. As a result things don't get completed with the best interest of the owner in mind. Don't forget LEED. We can and will build great efficient buildings without LEED. We are going thru the LEED phase of building. God only knows how long it will last.

There are many great engineers, technicians, installation contractors, and commissioning teams that take pride in their work. Keep up the good work.

Diversity in HVAC design has has been in use for decades. The latest technology in equipment and controls has allowed the industry to fine tune this strategy to a gnat's fanny avoiding installing oversized machinery instead of "let's play it safe and have enough horses in the systems." Highly accurate load calculations allow us to provide the building owner with greater comfort, ie, better humidity control, longer equipment life, fewer breakdowns, and lower energy bills. Not a bad bundle of benefits.

My latest adventure started last week. Contractor wants controls for current project. Specifications call for vav's some fan powered, all cooling only, plenum return. My thoughts, why the fans with a plenum return. Spec's call for Carrier rtu's with 3" external available static, setpoint 2". Contractor made submission for York with maximum static of .45 ts. My thoughts, ???. Specifications call for available protocols of bacnet mstp, lon, modbus rtu, n-2, ccn and a few others. My thoughts,???. Engineer wants duct smoke detectors to activate through the ddc. My thoughts, who needs to follow any codes. The plans locate the control panels in the electrical closets. My thoughts, why not the MC is pulling all the wire. The MC asks about the purpose of the fans on the boxes and why he needs to pull a 24v wire to the boxes when the are supposed to have transformers installed from the factory. He's pulling the wire and making terminations because the owner, a small hotel chain, is very cost consious. You have an engineer that draws a lousy zone system with average $2200 Titus boxes, half fan powered on a non-rated plenum return ceiling with no thought to fire or smoke division that could be done with $100 motorized dampers, no perimeter heat consideration with glass exterior(ssb) and a contractor and engineer who don't appear to have any experience with this type of project or any basis in controls and the owner wants to save money. The engineer also specified demand based ventilation with factory installed dual enthalpy economizers. 2 Hours to program and 2 days for tuning and working with the balancer. There was a time when I would not want my name or controls associated with a pile like this but this is the real business today, not all but the majority. The only people that are going to be happy with this are the ones that sold the equipment.