Refrigeration Pressure Switches | HVAC Systems

What you will learn from Refrigeration Pressure Switches

  1. A question from one our readers – What are refrigeration pressure switches and how pressure switches protect the refrigeration circuit.
  2. All about high-pressure refrigeration switches
  3. All about low-pressure refrigeration switches
  4. Benefits of refrigeration pressure switches
  5. Lots of related links to help you learn more

Richard – What are pressure switches used for in refrigeration circuits and how do pressure switches protect the system from further damage? (more…)

Water Tower Pumps and Controls | Pumping Systems

Water Tower Pumps and ControlsWater Tower Pumps and Controls | Pumping Systems

Water Tower Pumps and Controls | Pumping Systems – Water towers maintain a ready limited supply of water for communities in the event the water main goes down. Many towers are used for emergency situations for the fire department to have water for fighting fires and for water fire suppression systems to have a supply of water for the emergency if it should arise. (more…)

Hot Water Boiler Components and Controls | Combustion Control

Hot Water Boiler Components and Controls | Combustion Control – This photo shows the boiler cabinet open exposing controls and basic components of the boiler. The module on the left is the ignition control module which controls the sequence of operation for ignition and burner controls of the boiler. When the boiler is enabled to run usually by a thermostat or controls the ignition control module begins the process of firing the burners. The process typically begins by having the ignition module check the safety circuit to ensure all safeties are normal and not in alarm. This includes energizing the inducer or forced draft fan motor and any limit switches and a flow switch to ensure the boiler has water flow. (more…)

DDC Outside Air Economizer System | HVAC Control

DDC Outside Air Economizer System | HVAC Control economizer dampers

DDC Outside Air Economizer System

DDC Outside Air Economizer System  – Outside louvers allow the DDC control system to open dampers and introduce fresh air into the building. Building automation system, or the energy management system as it is sometimes called, monitors outside air temperature and humidity and based on a calculation and opens the outside air dampers when this calculation determines a precise set point. Introducing outside air into the building not only makes common sense it is also required by the Mechanical Code in commercial applications. This is required mainly for health reasons as it rids the building of volatile organic compounds and CO2 which is naturally produced by humans. Large concentrations of CO2 can build-up inside the building and needs to be vented as too much CO2 negatively affects human health. It is therefore, important that along with the intake of outside air into the building there needs to be an exhaust air damper to maintain good building pressure. Negative pressure inside a building is bad as it causes infiltration moisture issues which leads to mold and mildew. Too much pressure also creates its own problems so it is important, with an outside air damper system, to monitor and maintain building pressure. Enthalpy wheels add to the efficiency of a good economizer system. (more…)

Hydronic Pump Cavitation | HVAC Water Problems

Hydronic Pump Cavitation – Pump cavitation can cause severe problems to a pump if not addressed and corrected. To understand the cause of cavitation you need to understand the pressure temperature relationship of the liquid in the loop. Whether it is water or water/glycol mix. As the water passes through the pump it changes pressure from the suction side to the discharge side of the pump. If the waters static pressure drops too much vapor is created causing tiny bubbles in the water or fluid in the loop passing through the pump. These bubbles are unstable and collapse causing severe turbulence inside the bearing assembly and can damage the impeller. (more…)

Boiler Pressure Relief Valve | Boiler Safety

The boiler pressure relief valve is a safety valve designed to relieved an excessive build up of pressure inside the boiler. The is a pressure vessel designed to handle a safe amount of pressure. If the pressure were to build up beyond the safety limitations as set forth by the design specifications the boiler system needs a safe way to vent the pressure to prevent an explosion. The boiler relief valve is this safe way to vent excessive dangerous pressures inside the boiler. (more…)

R-134A Refrigerant Pressure Temperature Chart

R-134A Refrigerant Pressure Temperature Chart – R-134A is an inert gas also known as Tetrafluoroethane and is used in air conditioner systems. R134A is used as a chemical refrigerant in automotive and domestic use air conditioners such as chilled water systems in both commercial markets and industrial markets. You are very familiar with R134A if you are either an automotive mechanic or a chiller mechanic. R-134A uses the names Tetrafluoroethane, Genetron, or Puron among other names depending on the manufacturer. The pressure temperature chart represents the average pressure-temperature relationship of refrigerant R-134A.

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Air Handler Filter Pressure Sensor

Air Handler Filter Pressure Sensor and Low Static PressureAir Handler Filter Pressure Sensor – On the left is a pressure sensor to tell a maintenance technician if the HVAC Furnace Filters and the right control is a low static pressure switch to trip the unit if the mixing box drops below the set point pressure the switch is calibrated to. The low static pressure sensor protects the fan and the duct work including dampers from damage if the economizer damper and the return air damper would fail closed or another possible scenario that would cause the unit to pull negative pressure in the mixing box.

Pressure controls typically either protect the unit from a catastrophic failure or are used to control a fan or dampers. Pressure controls are either switches that trip at a calibrated pressure set point or transmitters that can transmit an analog signal back to the controls systems to control other components that control air flow. On this air handling unit there are four pressure sensors. The pressure sensors shown in the photo (Filter Pressure Sensor and Low Static Pressure) and two additional pressure sensors.

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