Tag Archives: duct work

Duct Work and High Ceilings | HVAC Duct Work Systems

Duct Work and High CeilingsDuct Work and High Ceilings - I did not see any reference to my question and would appreciate a response as soon as possible, as due to medical situation, have to make a decision soon. We own an OLD house with 13' ceilings in a large part of the home and 11" ceilings in the LV/DR and BR. We are oscillating on where to place the ducts....Floor or ceiling. It appears to be counterproductive to me to put the duct work in the ceiling since it will have so far to go. We are looking for the most cost effective, not upfront cost but operating cost, solution. In addition, we are considering DF heat pumps. The house will need 2 or 3 to be zoned correctly. Please let me know about the duct placement and thank you for your help?

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Air Conditioning and Heating Sizing | HVAC Technical

Air Conditioning and Heating Sizing - How many tons of air conditioning and heating do I need per square foot?

Air Conditioning and Heating Sizing

Rules of Thumb

It is not uncommon for HVAC estimators or HVAC contractors to use various rudimentary techniques which are generally referred to as rules of thumb. Some will say on the low end you need 1 ton of cooling for every 500 square feet. On the high end you will need 1 ton of cooling for every 700 square feet. These rules of thumb will also generally take into account a basic heat gain calculation for the kitchen and the number of people who will occupy the structure. At best these rules of thumb are educated guesses and may not give you an accurate calculation of what you really need. Unless the contractor used software based on the above mentioned manuals it would be to your advantage to actually do a proper load calculation for the structure based on Manual “J” or Manual “N” whichever is appropriate for your HVAC application.

Air Conditioning and Heating Sizing - Air Conditioner and Heating Ductwork

Manual “D” is used for sizing residential ductwork for the appropriate amount of airflow. For each ton of air conditioning you will need 400 cubic feet per minute (CFM) of airflow. It is imperative that this amount of airflow (400 CFM) be provided to the air conditioner evaporator coil of the air conditioning system. If the ductwork is too small it will restrict the amount of airflow crossing the air conditioner evaporator coil and this will likely cause big problems. If the ductwork is too big the system may have a problem generating enough static pressure to maintain designed airflow across the coil. The proper design and construction of the air conditioning and heating duct work is important for the proper functioning of the system. Using the proper techniques, software, and skilled personal will ensure that the HVAC job is accomplished correctly and will provide many years of reliable and efficient comfort to you. Air Conditioning and Heating Sizing Using good and time tested methods to size air conditioning and heating systems for your home or business is a smart thing to do. Using an HVAC estimator who is going to employ a rule of thumb for something that will be attached to your home and provide you with comfort for 15 to 20 years is not so smart. Use proper HVAC sizing methods and you will be better off and comfortable in the future. For other resources you find them here.   High Performance HVAC

Air Conditioning and Heating Sizing

Outside Air Dampers with Energy Recovery

Outside Air Dampers with Energy RecoveryThe dampers straight across are outside air dampers or make-up air coming from an energy recovery unit. According to the mechanical code commercial buildings require a certain amount of fresh air from the outside to maintain good indoor air quality for the occupants. An energy recovery unit allows the air to be conditioned before being introduced into the building. Other methods include using enthalpy calculations to open economizer dampers and/or CO2 control of the dampers. The dampers at the bottom of the photo are the return air dampers. The return air will mix with the fresh air or outside air and go through the filters where the air is further conditioned based on what the control is calling for based on conditions inside the building, inside the duct work, and outside ambient air temperature. In HVAC using outside air can also be used for free cooling.

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Air Handler Water Coil Freeze Stat – Freezing Protection Control

Air Handler Water Coil Freeze Stat - Freezing Protection ControlThe HVAC Air Handler Freeze Stat is a low temperature limit control and it is used mainly in commercial systems in the duct work on economizers or in air handlers just before any coil especially water coils. It is a safety and protection control to prevent extremely cold air from reaching the hot water or chilled water coils inside the air handler where the air enters from the economizer. Under ideal control set up if the freeze stat trips the economizer dampers close and the blower fan stops. This prevents coils from freezing. A frozen coil can bust open and will need to be replaced if it freezes thus the purpose of the freeze stat in HVAC air handler applications which utilize economizers for free cooling.

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Chilled Water Pipe Vibration Isolators

Chilled Water Pipe Vibration IsolatorsVibration isolators protect the chilled water piping from receiving vibrations transmitted through the piping when the chillers are running. The vibrations can create problems not only for the chilled water piping but also for the buildings structure. The vibration isolators reduce or eliminate the vibrations that can be transmitted by the chillers. Other equipment normally specified with vibration isolators includes air handlers, pumps, condensing units, generators and most types of equipment with motors. Not only are vibration isolators required in the piping but vibration elimination springs or spring isolators are required are required on chillers, pumps, air handlers, and the other types of equipment named above which can produce vibrations when running. Vibration isolators are usually rated according to the static deflection the vibration isolator provides for the equipment. HVAC piping whether it is for hot water or chilled water usually is also specified with springs in the pipe hangers to avoid further issues that can be caused by vibration. Depending on the location vibration isolators will also be rated for seismic activity with further specifications calling for seismic restraints on the equipment and associated piping.

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FRIDAY, APRIL 18, 2014