Power Monitoring – Harness the Power!


Update!! The ENG-ETH Ethernet Communication Module for endicator is now available. It reads data from the endicator™ main processor, formats the data, and transmits it over Ethernet using BACnet IP, Ethernet IP, and Modbus TCP protocols. The module also hosts a website where meter status can be viewed using any browser that supports Adobe Flash.



For 30 years Kele has been the building automation industry distribution leader, providing parts, solutions, and world class personal customer service. Kele works hard to stay ahead of the curve when it comes to industry changes while always focusing on maintaining the highest level of customer service.  Our power monitoring offering is no exception. Kele has been offering a wide variety of power monitoring brands and products since 1983 and building power monitors since 1993.

Power monitoring is not new to the building automation and energy management industries. Those that have been around building automation and energy management systems can, almost jokingly, say “We were green before green was a thing.” However power monitoring has changed. With the growing focus on saving energy and resource management, power monitoring has been thrust to the forefront of building automation and energy management.  Enter endicator™. Kele’s new power monitor.


Kele’s endicator™ power monitor, introduced earlier this year, is the cutting edge of power monitoring devices. Designed with future upgradability in mind, the endicator™ power monitor gives user the ability to make changes and perform upgrades in the field. Firmware, communication capabilities, and other features can be upgraded according to changes in your customer’s needs. This kind of forward thinking sets endicator™ apart from the others. Think of it as “future proof”.

Here are just a few of the many features of the endicator™ power monitor:

  • NEMA 4 enclosure standard
  • KWH Accuracy class 0.5% ANSI C12.20 For meter alone with unmatched CTs.
  • 0.5% system accuracy with factory calibrated matched CTs.
  • Data port for setup and trend retrieval
  • Measure voltages up to 32,000 VAC (voltages over 600 VAC require the use of a potential transformer, not included)
  • Supports 0.333V safe CTs and 5A CTs (must use optional 5A adapter board)
  • BACnet MSTP, LonWorks, N2 and Modbus RTU available
  • Password protected configuration
  • Powered by separate 24 VAC supply
  • On-board data logging
  • Auto configuration
  • Upgradable firmware through data port
  • Bidirectional power measurement
  • CSI (California Solar Initiative) approved

Kele doesn’t stop there. We also offer power monitoring units from Honeywell, Veris, and WattNode.

Honeywell H-Series The Honeywell H-Series 500 submeters, available from Kele, feature a direct-read 8-diget LCD display of cumulative kWh. The H-Series 500 also is UL Listed and meets or exceeds ANSI C12 national accuracy standards. Communication options include Modbus RTU or TCP/IP, BACnet IP or MSTP, and LonWorks.
Veris’ E50 Series power meters, also available from Kele, provide a solution for measuring energy data with a single device. The E50 series is conveniently mounted on DIN rail, has password protection capability, and works with popular 0 to .333V or 0 to 1V current transformers. Veris E50
 WattNode The WattNode NC series AC power meters can communicate over 50 values via BACnet and over 27 values via LonWorks. WNC series meters have diagnostic LEDs that provide per-phase indication of power to help with installation and troubleshooting.

These are just a few of the many power monitoring devices that are available from Kele. We also have current transformers, current transducers, voltage potential transformers, and more – all with Kele Inventory, Kele Service, and Kele Technical Support. Check out our complete power monitoring line at Kele – Your Source For power monitoring.

AC to DC – Linear Versus Switch-Mode Power Supplies

For years, Kele has provided dependable, quality 24 VDC power supplies like the DCP-1.5-W, DCPA-1.2, DCP-250, PW2, and the SLS Series. All of these DC power supplies are “linear” power supplies. Another type of DC power supply gaining popularity with building automation and temperature control contractors is called a “switch-mode” power supply (PS6R Series). While both linear and switch-mode power supplies ultimately perform the same task, it is the design technique used to convert AC voltage to DC and the resulting advantages that differentiate the two types.

How they work

To convert AC voltage to 24 VDC, a linear power supply first uses a relatively big, heavy transformer to step down the AC line voltage to a lower voltage around 30 VAC. The transformer also provides electrical isolation by separating the AC line neutral or ground from the power supply’s output. The reduced AC voltage is rectified into a pulsating DC voltage using one (half-wave) or two/four (full-wave) diodes. The pulsating DC voltage is then filtered or smoothed using a large value electrolytic capacitor. Finally, the filtered DC voltage is controlled by a linear regulator to output a constant voltage, even with variations of the input line voltage, the output load, and temperature. The regulator also helps to suppress any output ripple voltage.

Switch-mode power supplies use a different method to convert AC to DC. First, the 60 Hz AC line voltage is rectified and filtered using diodes and capacitors resulting in DC high voltage. Power transistors, typically switching at a preset frequency anywhere from 20 kHz to 500 kHz, convert the high voltage to a higher frequency AC. The high frequency AC is then reduced to a lower voltage using a relatively small, lightweight transformer. Finally, the voltage is converted into the desired DC output voltage by another set of diodes, inductors, and capacitors. Corrections to the output voltage due to load or input changes are achieved by adjusting the pulse width of the high frequency waveform.

Advantages and drawbacks

Size and weight

Linear power supplies operating at 60 Hz require relatively large and heavy transformers. Because switch-mode supplies operate at high frequencies, much smaller transformers are used, making switchers substantially lighter and more compact. For example, a 7.2A output linear supply weighs 14 pounds, mostly due to the large transformer required. However, a 10A output switch-mode supply weighs only 4.4 pounds. The small size and light weight of switch-mode supplies make them well suited for DIN rail mounting in control panels.

Linear supplies that are available with a single voltage input transformer must be ordered for a particular application. Some linears have multi-tap input transformers allowing some application flexibility but they still must be manually tapped for the correct input voltage in the field. Most switch-mode supplies will operate with any voltage from 85 to 264 VAC connected directly to their input, without manual configuration.


After filtering and regulating, some small amount of undesirable AC voltage will still remain superimposed on the DC output of a power supply. Linear power supplies are quite effective at minimizing noise. A typical specification for noise on the output of a linear power supply is 3 mV peak-to-peak or 0.0125% of a 24 VDC output. Switch-mode power supplies are noisier with a typical maximum specification of 2% of the output voltage or 480 mV on a 24 VDC supply. While some applications like audio equipment or very delicate test equipment may be sensitive to noise on the output of a switch-mode supply, most BAS/HVAC control applications will not be adversely affected.


The efficiency of a power supply is the ratio of its total output power to its total input power. Linear power supplies operate with only 40% to 60% efficiency due to energy lost in the form of heat dissipated through large heat sinks. Switch-mode power supplies are much more efficient, operating around 80% to 90%.


Linear power supplies have been proven to be reliable but operate somewhat inefficiently. They are relatively noise-free but are generally heavy and bulky because they require large transformers.

In contrast, switch-mode power supplies are small, lightweight, and highly efficient. Although they produce more noise on their output than linear supplies, that is not a factor for most BAS applications.

Whether you need linear or switch-mode, count on Kele to make it easy for you to find the best power supply for your application.

Does Your Building Own its Energy Destiny?

Those of you who have read some of my past blogs have probably gathered by now that I’m fascinated by the intersection of building automation, energy and the coming Internet of Things (IoT) revolution. What captivates me most about this collision of previously tangentially related and/or non-existent industries? The monumental shift of perception I believe we are witnessing of the relationship between buildings and energy.

Historically, buildings have been viewed simply as high intensity energy users and rightfully so. Today, commercial buildings alone account for upwards of 40% of all electricity usage in the US at a cost of roughly $160 billion annually. Building automation arose decades ago to serve the need of not only assuring environmental comfort and safety but also helping lower a building’s energy load and the corresponding energy expenses borne by owners/occupants. There has been amazing progress in building automation and energy efficiency (e.g., better materials, mechanical and electrical systems controls advancements) and grid technology (e.g., smart meters, interval pricing, demand response capabilities) since those first days, but buildings are still simplistically viewed as merely a consumer of energy. Increasingly, however, owners are beginning to rethink their building’s relationship with energy and envision value they can derive from these capital-intensive, physical footprints far beyond a place to simply conduct business that only consumes (no matter how efficiently) energy. People are starting to talk about buildings both as tangible, competitive advantages and sources of new revenue streams and energy is the common denominator.

I read an article today that does an excellent job of highlighting this shift in mindset. The article’s author, Erich Gunther of IEEE (Institute of Electrical and Electronic Engineers), uses the term Smart Buildings 1.0 for the first integration interval of building automation and grid technology where the initial focus has fittingly been on increasing the bottom line via energy efficiency, demand response opportunities and automation technology advancements. The next phase, which he logically calls Smart Buildings 2.0, is, “less about efficiencies and more about corporate energy destinies”. This iteration implies greater control over where, how and when energy is both generated and consumed by a building. Some call this next step in energy control the ability to “island” or go “net-zero”.

So when and why might this ability to control ones “energy destiny” be important? That’s a bit of a rhetorical question, as most folks understand that a business’ productivity level is still very much tied to its access to reliable energy. During major power outage events resulting from natural disaster or grid failure, which have doubled (it’s important to note) over the period 2001-2008 according to Energy Information Administration (IEA), a business’ operations can grind to a halt without a holistic energy strategy/contingency plan while its competitor, located on the other side of the country (or world for that matter) and unaffected by the event, quickly picks up where they left off taking the customer relationship with them.  Control of ones “energy destiny” quickly begins to look like a vital piece of a proactive, forward thinking organization’s Business Continuity Plan.

Under Smart Buildings 2.0, business continuity, viewed through the lens of energy independence, will focus more on renewable, onsite sources of energy generation that allow a building or campus to continue business-as-usual during momentary grid outages and keep mission critical, customer facing functions up and running even in the event an outage that lasts for weeks. Although Gunther only touches on this lightly, I believe the building automation system will be the key enabler of an organization’s ability to ramp up or down power generation and/or consumption and dictate the hierarchy of where onsite generated energy is delivered. I believe that orchestrating both supply (i.e., power generation) and load (i.e., power consumption) side actions will be a critical function of tomorrow’s intelligent building automation/management systems. As buildings become more “energy autonomous” in the future, building automation systems will evolve dramatically to empower this complex level of inter-dependency with the grid and some level of self-sufficiency.

What role(s) do you see building automation systems playing in enabling an organization to own its energy destiny? I’d love to hear your thoughts on this or other energy related news affecting our industry.