The UK24LON is a LONMARK®-certified gateway from Belimo Aircontrols.  This gateway is capable of connecting up to eight (8) Belimo MFT actuators as well as eight (8) sensors to a LON network. In the UK24LON, the digital information of the control system and feedback from the field devices are converted to standardized network variables (SNVTs). In this way, the functions of the actuators and sensors can be directly linked to LONWORKS®.

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The Project
Harper Community College is located in Palatine, Illinois. This community college recently added three academic buildings to its campus, each served by a large penthouse air-handling unit.  The controls contracting firm was tasked with designing a cost effective control system for this state-of-the-art college campus.

The Challenge
The air-handling unit for the first building was made up of twenty-eight (28) damper sections, the second had eighteen (18) sections, and the third had nineteen (19) sections.  According to the sequence of operation, each section of the damper bank was to open in stages until the set point was achieved.  In addition, position feedback information was required for each damper section. The control contractors’ challenge is to do this while maintaining the line on cost, simplicity and functionality.

The Options
Based upon the requirements, the controls contractor identified several options to achieve the requirements outlined. The first option would modulate each damper section individually by separate DDC analog outputs.  To do so, twelve (12) controllers dedicated solely to modulating dampers and monitoring feedback would be required.  At a cost of $700 each, the cost impact for this scenario was approximately $8,400, which was not acceptable to the college. The second option involved the use of a signal divider. The signal divider would split a single 0-10VDC analog signal into four (4) staged 0-10VDC analog signals.  This option would reduce the use of controllers from twelve (12) down to two (2) for the first air-handler and one (1) each for the next two air-handling units.  Several issues became apparent, however.  There was a concern regarding how quickly the divider would ramp the control signals up and down, which may result in damper sections being slammed open and closed.  Additionally, there was no cost effective way to monitor individual damper position feedback. The third option was to take advantage of the available LON network and use a third-party device to modulate the dampers.  The controls contractor selected the Belimo UK24LON gateway since it would allow for individual control and monitoring of the damper actuators through integration with the existing LON network. 

[an error occurred while processing this directive] Sensor Connection
One sensor can be connected per MFT actuator. The sensors can be active (0.5-32v) or a switch contact. The analog signal from the sensors can be easily digitized by the Belimo actuator and transferred to LONWORKS® via UK24LON.

LNS Plug-in
Two LNS plug-ins are available for the UK24LON. The actuator plug-in allows the MFT actuators to  be easily commissioned, and the sensor plug-in allows the corresponding sensors to be easily scaled using a LONWORKS® network.

The Solution
Belimo’s UK24LON gateway was found to be the most cost effective solution.  As each UK24LON gateway can support eight (8) AF24-MFT actuators,  ten (10) UK24LON’s were required with a total cost of roughly $2,000.  Likewise, this would free up I/O capacity since the DDC controller used for the air-handler did not have any of damper controls.  There was also a significant savings in wiring costs because the individual damper actuators were daisy chained back to the gateway, instead of requiring individual conductors for each actuator.

The Result
The controls contractor was pleased with Belimo’s UK24LON for several reasons:

• Harper College and the design engineer were pleased to have a solution that met the specification requirements and resulted in a clean installation.

• The UK24LON was easy to program and commission.

• Maintenance is easier due to the use of regular Belimo actuators, which are more readily available. The gateways have now been operating for over a year without a problem.

• Most importantly, the problem was solved with minimum cost to the controls contractor.

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