Unit Heater Mechanical Room Equipment Protection – Mechanical rooms have very important equipment that needs to be protected. Often mechanical rooms are not conditioned and subject to outside temperatures and freezing conditions that can freeze piping inside the mechanical. For that reason mechanical rooms often have unit heaters located there to protect piping and other things that cannot be frozen or subject to freezing conditions. The components and sequence of operation are fairly simple. The main components in a hot water unit heater include a fan, a valve, and of course the piping and coils along with the cabinet. (more…)
Disconnect and Electric Motor Starter is used for turning the power off and on the an electric motor used in HVAC applications. It also has overloads built into the starter so if one of the windings begin to pull too many amps the overloads open the circuit and the motor stops operating. Motor starters can be used for single phase and 3 phase motors and offer a manual way to turn the motor off or disconnect the electricity to the motor to prevent it from starting for maintenance or repair of the motor or peripheral systems. Control wiring can be integrated into the motor starter for automatic control and or monitoring. Monitoring usually occurs with auxiliary contacts or status contacts near the starter. Some solid state motor starters will also detect and stop a motor if it is turning backwards. It is important when troubleshooting motor problems that the technician understand the motor starter and the limitations of the motor starter.
Chiller Barrel Evaporator – A chiller evaporator barrel exchanges heat between one refrigerant and another. Usually the primary refrigerant is R-22, R-134A, or some other blend or alternative HFC. The secondary refrigerant is water. This water is circulated throughout the building where it passes through piping and coils. This is generally in most cases a forced air coil where the heat is removed from the air by a heat exchange process with the water and the coil. The cooler air is then forced through duct work and into the space to be conditioned. (more…)
Boiler Commissioning & Functional Testing – Commissioning (Cx) any type of HVAC equipment is many different procedures from the beginning of the commissioning process to the end of the process. One of the most important procedures during the Cx process is functional testing. The functional testing always precedes the final testing where a test of all the combined equipment is done in an integrated systems testing. Once successful testing is completed and all discrepancies corrected a final commissioning report is generated including all the test data and information collected during the entire process of testing and commissioning. (more…)
Steam to Hot Water Generator HVAC Heating
Steam to Hot Water Generator HVAC Heating – There are some facilities including campus like complexes that use a centralized steam plant as a steam to hot water generator. The steam is generated from a large boiler and piped to various buildings around the campus or whatever facility is used. Typically several buildings utilized the steam for heating and hot water for domestic uses including showers, washing dishes, washing clothes and other domestic uses. The steam is usually high pressure and for this reason it is safer to deliver it to a mechanical room, reduce the pressure, and run the steam through a steam to hot water generator. A steam to hot water generator is nothing more than a big heat exchanger where at one end steam is delivered and at the other end water is delivered. As the steam runs through the exchanger it exchanges heat with the steam heating the water. Thus, producing hot water for domestic use and heating use in the winter.
Steam to Hot Water Generator HVAC Heating (more…)
How VAV Boxes Work? A Variable Air Volume box is typically installed in commercial buildings and provide heating and cooling for occupants. There are different types of Variable Air Volume boxes but how a Variable Air Volume box works is fundamentally the same from one Variable Air Volume box type to another. Essentially a Variable Air Volume system allows a design engineer a way to zone large areas in work spaces such as office buildings and other places where there are large spaces that need heating and cooling or simply just cooling in rare cases. The concept is simple but making it energy efficient and keeping everyone comfortable has taken some time from the inception of Variable Air Volume box.
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 an 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
Glycol Feed System for Chiller Condenser Water Loop
Glycol is like antifreeze and is used in chilled water piping loops to prevent freezing. Everyone knows when the pipes freeze they also break and start leaking. Having antifreeze in a chilled water loop is important to prevent freezing. So, how do you keep antifreeze in the loop when the water/glycol mix goes out to the cooling tower and there is a loss of water/glycol through windage or drift? Meet the glycol make-up unit where it can automatically be added to the loop and prevent freezing. Antifreeze make-up units range from automatic units that will inject the antifreeze right into the loop to manual units that require an operator to control the process of adding antifreeze to the water loop. These make-up units make it easy to add it to the loop without having a shut-down of the chilled water loop it serves so the loop can continue to run while the glycol is injected directly into the loop. The loops are designed to work at low ambient temperatures need the water/glycol mix to prevent freezing especially for critical facilities like data centers that need to remain operation no matter what the outside temperature conditions are. Percent of antifreeze to water depends on the expected operational temperatures outside so the mix is important for expected operating temperatures. An example of this is listed in the following table (follow equipment manufactures instructions for the recommended mix of antifreeze to water for temperatures):. Each loop requires a different ratio of mix based on ambient conditions, flow rates and other factors for determining the proper mix ratios.
Glycol Feed System for Chiller Condenser Water Loop | Antifreeze Protection – Percentage Water to Temperature Ratio
Propylene Glycol% to Water
Actuators for Chilled Water Valve – These chilled water actuators control the flow rate for a chilled water system in a data center. There are various sequence of operations for chilled water systems and the sequence of operation is usually always different from one chiller plant to another chiller plant. It depends on the components in the loop, the application the chilled water system is supplying cold water for, and what the demand of the system requires for the chiller plant. Some chilled water valves control two-way valves while others control three-way valves. A three-way valve can either be a mixing valve or a diverting valve but the actuators controls the flow in either type of application. Other actuators modulate a valve based on demand. The actuator usually receives its command for position for control from the DDC system or another type of control system. In this case these actuators are controlled by DDC. In the sequence of operation the chiller plant will have a valve line-up usually in a valve matrix that was compiled by the original design engineer and this valve matrix shows the default position of the valves which are controlled by the actuators. Some applications in the piping that are controlled by the actuators include:
Outside Air Dampers with Energy Recovery
The 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 IAQ for the occupants. An energy recovery unit allows it 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. (more…)