Posts Tagged ‘johnson controls’
If you have portable or modular classrooms you know how hard it is to implement energy saving temperature control strategies. Johnson Controls has the answer with the Johnson Controls T600 family of thermostat controllers.
To understand the elegance of the solution Johnson Controls provides with the T600 series of thermostat controllers, you must first understand the problem that portable classrooms provide from a control strategy perspective.
MIke Glenn from Johnson Controls walks us through the Johnson T600 family of thermostats in Part 2 of a two part series on how to control and save energy in portable classrooms.
Stromquist & Company would like you to join us in a new series of tutorials that focus on the Johnson Controls DX-9100 controller. As one of the all time leading legacy controllers, the Johnson Controls DX-9100 lives on as reliable central plant controller. Stromquist & Company will gear these effective training clips towards servicing and reprogramming the Johnson Controls DX-9100. Please continue to check back for new videos here at www.ControlTrends.com
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One of the really cool things about direct coupled actuators like those made by companies like Belimo, Honeywell, Johnson, Siemens, and Invensys TAC is that they can be usually be inter changed. Meaning if you have a 35 inch pound Belimo direct mount actuator, but there is not a Belimo 35 inch-pound direct mount actuator to be found in your city, you should be able to replace it with a Honeywell 35 inch pound direct mount actuator, or a Johnson 35 inch-pound direct mount actuator. Although each brand of actuator has it’s pros and cons they all for the most part close in quality and value. So if you have a job that has all Belimo and you need a replacement Belimo actuator but your local distributor does not have one on the shelf and you cannot wait for a Belimo actuator to be shipped then most likely you can find a Read More
One of the biggest problems our school board friends face is how to control energy in the portable classrooms. These classrooms are used to handle excess students, and like regular classrooms, they need to have proper lighting and temperature control. Getting the right lighting and HVAC systems is not a problem, but controlling them in an energy efficient manner is more of a challenge.
With these systems unless the HVAC units and lights are turned off when the space is unoccupied, we are wasting very expensive energy. Most schools have a building automation sytem to perform these functions in the main buildings. However, this is not usually a viable way to control the portable classrooms since they are detached from the main building and the high cost of running the building automation system control wire between buildings makes this a very expensive option. We have provided “ wireless” solutions that work well, but the expense is still too high for most budgets, especially in these tough economic times.
Many schools have been provided with programmable thermostats so they can schedule times when the space will be occupied. The challenge with this approach is that holidays and schedule changes are not accounted for, so someone must go to all the portable classrooms and manually override the system or the units will be running with no one in the room.
Stromquist has a solution. If you took a programmable thermostat, added an occupancy sensor and an auxiliary output relay to control your lighting, what would you have? A low cost way to control energy and provide excellent temperature control in your portable classrooms.
If you are a Stromquist customer or are located in Georgia or Florida call 800.241.9471 and ask for Steven or Cera. If you are not a Stromquist customer please contact one of our affiliates at CGNA.
First, to understand these types of control you must have the elements of control. The elements of control are the sensor (senses the medium being controlled), the controller (device either preset or programmed to react to the sensor), and the final controlled device such as a damper or a control valve (receives input signals from controller to affect change in controlled medium). These elements are considered the control loop.
On/Off control is the basic type of control in a control loop. With On/Off control, the sensor senses the controlled medium and sends a signal back to the controller, which processes the signal. For ease of understanding, our example will be a heating application. The set point (the desired control point) in this case is 68 degrees with a temperature differential of 2 degrees for the controller. When the sensor’s signal to the controller reports a temperature of less than the controller’s set point, the controller sends a signal to the final control device (hot water valve) to position to fully open until set point is achieved. When the controller receives a signal from the sensor that the set point has been achieved, the controller then sends a signal to the valve to position to fully closed. The problem with On/Off control is over-shoot temperature of the desired system set point because of reaction time between sensor, controller, and final control device. Review: With On/Off, the controller asks “Is there an error?” The controller compares the actual value of the controlled medium to the set point through the sensor. As the controlled medium deviates from set point, the controller’s output cycles the final controlled device on, and when the set point is reached the controller’s output cycles the final control device off.
Floating control is a variation of On/Off control that requires a fast responding sensor and a slow-moving actuator connected to the final controlled device (valve or damper). Using the same example as the On/Off example above, when the sensed temperature drops below the set point of 68 degrees by the controlled medium’s sensor, the controller sends a signal to activate the actuator on the final control device. The actuator starts to slowly drive open the hot water valve, increasing the heat in the controlled medium. When set point is reached the actuator stops opening the final control device (hot water valve) and tries to hold at set point. If set point starts to be over-shot, the controller sends a signal to the actuator to start to drive close the valve. Review: Set point control is achieved when the sensor signal (from the controlled medium) starts to deviate from the controller set point. The controller sends a signal to the actuator of the final control device (valve or damper) to slowly drive open. As the set point is approached the controller sends a signal to the actuator, then the actuator stops and tries to maintain set point. If set point is passed the controller sends signal to the actuator to drive the final control device to a closed position.
Modulating/Proportional represents the higher end of control positioning. In modulating/proportional control the output varies continuously and is not limited to being fully open or fully closed. Proportional means that the size of the output is related to the size of the error detected by the controller. The key phrase for modulating/proportional control is “Continuous Control Action.” The sensor, controller, and final control device act as one unit to maintain constant precise control over the controlled medium. Continuing with the previous example, when a modulating system senses a deviation from the set point of 68 degrees, the controller calculates the amount of the error (1 degree less than set point) and sends a signal to the actuator, which will drive open the final control device (valve or damper) by a certain percentage of the controlled medium’s set point deviation (1/2 degree) to maintain set point without over-shoot. The controller calculates how much the final control device needs to open without over-shoot and will start reversing the actuator to close the final control device to a percentage of the closed position to maintain set point.
Popular modulating control signals include 4-20 ma and 0-10 volts. If you were to look into a control panel like a Hoffman Enclosure you might see controls like a Honeywell UDC3200 that could be taking a 4-20 ma signal from a device like a Hawkeye 908 current transmitter and based on the control input signal from the Hawkeye 908 ( which would most likely be a 4-20 ma signal) the UDC 3200 controller would respond with a 4-20 ma output signal to a device like a Honeywell Variable Frequency Drive which would control either a fan or a pump. This is an example of how a proportional signal like a 4-20ma signal is used in modern HVAC controls.
If you are in Georgia or Florida,the control pros at Stromquist & Company can answer your control questions.
2-way valves are pretty simple and straight-forward. A 2-way valve is any type of valve with two ports: an inlet and an outlet port, typically labeled “A” and “AB” respectively. 2-way valves are used in many applications, from basic on/off to more complex variable flow applications with pumps and VFDs. The type of valve you need for an application depends on the amount of flow, the degree of control, shut-off, and pressure drops over the valve.
3-way valves have, yes, three ports, labeled “A”, “B”, and “AB”. Port “AB” is common to the “A” or “B” port. 3-way valves are commonly found in constant flow/volume pumping systems and can be either mixing or diverting valves. 3-way valves can be piped in the supply or return. If in the supply, then a diverting valve is used. If piped in the return, a mixing valve is used. Ball valves can be piped to be mixing or diverting, but globe valves require different bodies for mixing or diverting.
Mixing applications have the 3-way valve configured with two inputs from the supply piping and one output to the return piping, thus mixing together two inputs before sending it out. Mixing valves are most commonly used with modulating control but can be on/off.
Diverting applications have the 3-way valve configured with one input from the supply side and two outputs to the return piping. In general, diverting valves are more expensive than mixing valves.
There are many different types of valves for different applications, so how do you know which is the best to use for your application? We’ll start by looking at globe valves and ball valves. The main difference between these two types is the way they close. A globe valve uses a plug (stem) that closes against the flow, and a ball valve has a gate (ball) that closes across the flow. Globe valves are good for regulating flow, whereas ball valves are better for on/off control without pressure drop.
For many decades globe valves were considered the industry standard in control valves. They are designed with a stem that moves up and down inside the valve to control flow. They are commonly used on hot and chill water coils, and larger models are often used to control flow to chillers. One of the main limitations of globe valves is that their close-off rating can be lower than other valves, especially in the larger sizes.
Ball valves are designed with a ball inside the valve. The ball has a hole through the middle so that when the hole is in line with both ends of the valve, flow will occur. When the valve is closed by turning the ball 90 degrees, the hole is perpendicular to the ends of the valve, and therefore flow is blocked. Ball valves are very durable and usually have excellent shutoff even after years of use. They are generally preferred over globe valves in shutoff applications. The main limitation for ball valves is proportional control because of the large amount of flow that the ball allows.
Check back soon for more valve comparisons. Up next, 2-way vs. 3-way valves. Until then, I hope everyone has a Happy New Year!
Check out Sophia Bellos as she shows us why Honeywell’s direct coupled actuators are a great choice. Sophia demonstrates unique features that save time and money on valve and damper installations including Honeywell’s new Zelix Actuator.
Stromquist & Companykeeps a large inventory of these products in our Atlanta and Florida locations so if you are a Stromquist customer or are located in Georgia or Florida call today for a free catalog. Others can contact one of our affiliates at Controls Group North America.
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