Welcome to the second in my series of ‘Myth Buster’ blog posts shedding light on the inner workings of the Ecosmart control solution, Nuaire’s proprietary fan controller. In my previous blog post, I discussed the basics of Ecosmart and using our various user controls and sensors to control our fans as stand-alone items of plant. In this post, I will be discussing the various ways Ecosmart can be controlled by external controllers such as Building Management Systems (BMS).
Trend Systems and BACnet
Some Nuaire products, such as the award winning XBC range, can be supplied with a fully integrated Trend IQ3 Excite internal controller as an alternative to the basic Ecosmart1 controls. These Ecosmart2 devices can be fully incorporated into a Trend or BACnet over IP BMS and offer a full range of features. I will discuss the Trend and BACnet control devices available on Nuaire products in a later post in this series, this edition however details the basic BMS functions native to every Ecosmart1 fan controller when combined with the ES-CI (control interface).
Fan Status Monitoring - Run and Fail indicators
One of the most basic requirements when connecting to a BMS is to monitor the fan status. Ecosmart makes this basic requirement very simple to implement by providing Volt Free Relay Contacts to indicate each condition. These contacts operate like switches: the ‘Run’ contacts are closed when the fan is running, and the ‘Fault’ contacts are closed when there is no fault (to indicate a status OK). In the event of a fault occurring in the system the ‘Fault’ contact will go open circuit. These switched contacts can be connected to any BMS or control panel to monitor the fan system and in general are rated at 5A resistive, 0.5A inductive, but contractors are advised to check the appropriate I&M manual before switching loads with these connections.
The Ecosmart Control Interface (ES-CI)
The ‘ES-CI’ connection device can be added to any fan by simply connecting it to the ‘NET’ link socket on-board the Ecosmart device and it provides a whole host of terminals available to a BMS to control the fan. This device can be placed at the fan, or brought remotely (up to 300 meters) to the control panel or interface outstation by simply extending the 4-core SELV link wire (available from Nuaire).
The Fan Terminal – Enable/Disable
This is a simple volt-free contact which, when closed by a switch or relay, will turn on the fan; the speed at which the fan runs at when enabled is governed by the following terminals.
Min / Max - Speed Control (Trickle and Boost)
The most basic form of speed control is obviously trickle and boost. The ES-CI makes trickle and boost control via the BMS simple. Once min and max speed positions have been set on the commissioning dials (details of this process can be found in part1 of this Blog Post), these speeds can be selected by connecting the ‘select’ terminal to either min or max. When ‘select’ is connected to ‘min’ the fan will run at its trickle speed (set by the ‘min’ dial) and conversely at its boost speed (set by the max dial) when ‘select’ is connected to ‘max’. Obviously the fan needs to be enabled by closing the ‘fan’ contact. In this way a simple three position speed controller can be achieved with off, trickle and boost being easily selectable.
0v-10v – Variable Speed Control
If a variable control of speed is required then you should use the 0v-10v interface terminal instead, leaving the select terminal unconnected.
As discussed in my previous blog post once the fan has been commissioned by setting the min and max dials, Ecosmart creates 10 intervals of speed between the min and max positions as shown here.
These 10 speeds can be selected by applying the required voltage to the 0v-10v terminal of the ES-CI, the following look-up table provides the voltage ranges required to achieve each speed setting. You will notice that the first voltage band 0v-0.375v has a special property, called ‘auto’. This is a very useful function of the ES-CI system, as you can instruct the fan to respond to local sensors for its speed control. If, for example, there is a carbon dioxide sensor also connected to the fan (via ‘NET’ link terminals) then, when in the ‘auto’ position, the fan speed will be governed by the sensor. Multiple sensors can be added for various metrics such as humidity, temperature, or carbon dioxide on a ‘highest takes precedence’ basis. Driving up the voltage present at the 0v-10v terminal will override the sensors and force the desired fan speed. This can allow controls engineers to create powerful, cost effective control strategies combining local sensors with BMS authority at very little extra cost.
The Heat and Cool Terminals
Some Nuaire Ecosmart devices can contain heating and cooling components, such as Ecosmart Boxer AHU’s and XBC, the ‘heat’ and ‘cool’ terminals can be opened and closed to control these functions. The target air-off temperature for these modes of operation is set by the control thermostat on the Ecosmart control board. Take for example the XBC with an internal LPHW coil, the air-off temperature is set internally to 19oC – When the ES-CI ‘heat’ terminal is closed the system will automatically regulate the flow of water through the coil to reach 19oC, first taking account of any free heating available by way of the heat recovery system. If the target is being met the valve will close and regulate the supply air temperature accordingly. Selecting cooling mode will achieve a similar effect when cooling devices such as coils are connected.
Putting It All Together…
By combining ES-CI with the standard Ecosmart controller, most basic BMS functions can be achieved in a simple and cost effective way. Using sensors and local settings to automate some functions is a great way to control energy without the expense of a fully integrated BMS solution. I will discuss deeper BMS integration using Trend and BACnet enabled devices in a later blog post.