- Preface for the NFPA 90A requirements for duct detectors in air conditioning and heating equipment.
- The question: Where do you install duct detectors in duct work?
- detailed answer to satisfy requirements
- exclusions and exceptions to the requirement
- references for further information about HVAC equipment and fire safety
- Finally, additional related information about fire and smoke dampers regarding HVAC
Evaporator Coil for Heat Pumps & Air Conditioners
Evaporator Coil for Heat Pumps & Air Conditioners – the evaporator is responsible for absorbing heat into the coils and the refrigerant. The evaporator is an essential component of vapor compression refrigeration. This is usually done as result of passing air or water over the evaporator coil where a heat exchange process takes place. Heat leaves the air or water (whatever medium is used) and is absorbed into the coil and the liquid refrigerant. As more and more heat is absorbed by the evaporator coil and the refrigerant again changes state from a liquid to a refrigerant vapor. By the time the refrigerant leaves the evaporator coil the refrigerant should be all vapor and ready to be received again by the refrigeration compressor. (more…)
Fixing a Refrigerant Leak – You had the new air conditioner or heat pump system installed some years ago and suddenly it stopped heating or cooling properly so you call the HVAC contractor to check it out. The HVAC technician arrives and spends about thirty minutes HVAC troubleshooting and then he comes to you with the news. The unit needs a charge of refrigerant. It is low on refrigerant (R-22) or R-410A. You ask the HVAC technician if it is normal for this to occur and he informs that, no, it is not normal for the HVAC system to lose refrigerant that you have a refrigerant leak. (more…)
Variable Speed ECM Blower Motors – Variable speed blower motors have become increasingly popular in residential air conditioning and heating systems and for good reason; these motors increase efficiency of the systems and offer a whole range of other benefits that help the system and the consumer.
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Variable Speed ECM Blower Motors
Variable Speed Blower Motors first offer a higher efficiency for air conditioning systems based on the manufacturers set up of the control with the ECM Variable Speed Motor. Each manufacturer calls it a different thing such as Trane calling it the Comfort R and Carrier calling it Infinity Control. Despite what the manufacturer calls it helps efficiency with air conditioning by starting the blower slowly and letting it run at a 50% speed for the first few minutes (up to 7 minutes) to remove more humidity. This increases comfort and efficiency by removing more moisture from the air. The lower the humidity in the cooler you will feel so the variable speed blower with this type of control will enhance comfort.
Running New Thermostat Wire – It is possible that you may have to run a new thermostat wire from the air handler or furnace to the location where the existing thermostat is located. Running new thermostat wire can challenging even for professionals. If you must then following these instructions and helpful hints will hopefully help you in this endeavor. Pulling new wire should only be done as a last resort. The purpose of running new thermostat wire is necessary for certain reasons such as: (more…)
Duct Work and High Ceilings | HVAC Duct Work Systems
Duct 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? (more…)
Variable Air Volume Box with Hot Water Reheat
Variable Air Volume Box with Hot Water Reheat – The variable air volume box or VAV box is a commercial solution to adding multiple zones to large buildings. VAV boxes offer zoning solutions so that separate zoning demands or temperature selections can be maintained in different areas of the building. If the president of the company wants the temperature in their office to be 70 degrees Fahrenheit but the vice president wants their office to be 74 degrees Fahrenheit then it is possible with the VAV zoning system as long as their VAV boxes are on different zones.
Variable Air Volume Box with Hot Water Reheat
This particular VAV box in the picture is not fan powered. It relies on the main VAV air handling unit to provide all the air. Generally, when a fan powered VAV box is calling for heat the damper inside the VAV box closes down so that minimal CFM’s are coming through the primary duct from the air handler. The fan turns on and pulls air from the plenum space above the ceiling. This plenum air is normally warmer than the air inside the occupied space. The heating system kicks in and adds heat to the air until a set point is attained. The heat for a VAV box can typically be a hot water coil or electric heat strips. The VAV box in the picture has hot water reheat and is controlled by a building automation system or DDC. Building automation systems are capable of being linked to the internet for remote control and monitoring which adds many beneficial factors for managers and technicians of commercial property. A single building can have several hundred VAV boxes and with a DDC system managers can quickly see where problem areas are or change control set points with a few clicks.
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Variable Air Volume Box with Hot Water Reheat
Air Handler Equipment DDC Controllers | HVAC Control
Air Handler Equipment DDC Controllers – These controllers will control an air handler once the wiring is completed. The panel is freshly mounted and waiting for the technician to run the piping and pull the wire from the control points. Other points, such as outside air, temperature sensors in piping or duct work, flow meters, actuators, or other control points can be terminated to these controllers and the data collected from those input points can be networked over the entire building automation system through the communication trunks. Included in this panel are: a terminal strip connection point for line voltage and control voltage, a transformer to step-down line voltage to the required control voltage of 24 volts which powers the controllers and a surge arrestor which is a requirement on many government jobs.
How DDC Status Works – DDC and Status – Is the Device On or Off
The basics of DDC include learning about the status of a fan or a compressor or pump. How does a DDC controller read the status of the device it is monitoring? There are several ways to prove a device is running and some pros and cons of each type of device used to monitor on or off status. This is a basic DDC guide or reference to help a person understand the basics of DDC status and how it works. When one learns how DDC status works they can improve their troubleshooting skills. Too many maintenance technicians and others including HVAC technicians don’t understand DDC systems or building automation systems and are therefore crippled when it comes to troubleshooting DDC systems. High Performance HVAC hopes to change that and help HVAC techs and HVAC maintenance staff learn the basics of DDC systems including how DDC status works. Once someone understands the basics about DDC a light will turn on and they will see that DDC is not really rocket science.
HVAC Control and Direct Digital Controls – The (Field) Technical Aspects of Direct Digital Control
A HVAC technician who knows nothing about HVAC control systems would wonder how these hvac control systems work. To understand hvac controls, one must understand basic electricity and circuits. Starting with a large commercial VAV air handling unit with three stages of DX cooling and add all the necessary hvac ddc control points. We have variable frequency drives (VFD’s) on the return and supply blower fans. There is a mixed air damper which closes off the return and opens up to outside air for economizing and CO2 control. Static pressure control will be achieved with a duct pressure transducer and the HVAC control program through the frequency drives and blower motors. Direct Digital Control needs to monitor supply air temperature, mixed air temperature, and return air temperature along with outside air and outside humidity. We will also monitor the duct smoke detectors and a freezestat for safety reasons. This is the set-up and we need to make it work. We need to get a point count and set-up our inputs and outputs.