More and more, we are hearing about the Smart Grid and the use of Smart Meters. Illinois has announced that they want the entire state to be on Smart Meters and have started replacing older meters with the new Smart Meters and this is already occurring in other states as well. In the long run, it should be a good thing.

This post is intended to provide some information on the effects Smart Meters can have on any control board operation and fault codes used in HVAC equipment. This could be in a furnace, air handler, heat pump, air conditioner, or anything using a control board.

As a portion of the much larger “Smart Grid” project, Smart Meters are increasingly being installed on consumer’s homes. Currently the primary use of Smart Meters is to make it easier for the power companies to get more detailed information about power usage on their system which can be used for a multitude of things.

Automatic meter reading (AMR) is one of the primary benefits of Smart Meters.  There are currently three methods of AMR. There is Short Range RF transmission (ERT), Long Range RF transmission, and Power Line Carrier (PLC).

It is the Power Line Carrier technology that is causing issues with equipment. Power Line Carrier involves using the existing power line infrastructure as a method of transmitting and receiving digital signals. The power company embeds a signal onto the 60HZ power signal that requests information from the meter. The Smart Meter then embeds a signal into the 60HZ to communicate back to the power company. This is a simple example, but in reality, this is still a complicated system due to all the transmission levels, transformers, and sub-stations the power company uses for power distribution.

Simply put, the power company is adding a signal onto the power which many devices see as “noise”. In reality, noise on power lines is quite common and can come from loose grounding wires at pole transformers or radio signals leaking into transmission wires.

The unfortunate issue with power line noise is it is extremely difficult to predict how it will react. The transmission grid itself is a very large, very complicated entity with all sorts of absorption, reflection, and amplification going on. Each individual home is a random assortment of inductive or capacitive loads and wire lengths that can snub, reflect or amplify noise. Often they can add noise and waveform distortion. An example would be fluorescent lights that are on the same circuit as the furnace has been known to cause different issues with furnaces which can range from invalid flash codes to no operation.

Like many devices, several HVAC controls utilize the 60HZ signal as a timing mechanism. Noise can trick the control into thinking that fewer or greater cycles than expected have occurred which can cause different issues depending on how bad the signal looks to the control. These controls also use the incoming voltage to verify the power has been wired in phase. Noise can fool the control into thinking that there is a voltage potential when there shouldn’t be, which roughly is how polarity is determined. The potential for problems exists with nearly all controls anytime there is added noise to the incoming power. Our industry is not the only one affected as any devices using similar technology will also see issues.

Although the vast majority products will never see a problem, the biggest concern is with equipment that is “on the edge” of not working. These will only exhibit issues at certain times, usually right after the technician leaves the job  :>). Most often these issues are caused by some type of change in loading such as the freezer coming on, turning on fluorescent lights, or your neighbor’s old inefficient AC starting up. These types of issues may incorrectly be attributed to our devices rather than to a dirty power signal.

What can we do about this?

  • First, check the wiring. Bad wiring throughout the home may make it such that any filtration being provided by the power company is not working. Incorrect wiring at the unit may also be the culprit. 
  • Next, change the load on the circuit containing the malfunctioning unit. This can be done by adding a RF filter choke (like we recommend for ECM Motors) which may give a small enough change in load and enough filtration to fix the issue. It may be necessary to re-wire certain devices or outlets to change the load to individual circuits. Check with a local electrician before making any changes.
  •  Lastly, Please Complain To The Power Company. Their systems should be designed such that the PLC signals are small enough to not cause issues. If they are causing issues, there is a chance that something is not correct in their power grid system.

Currently, manufacturers  are working with the control board suppliers pursuing incoming power filtration options. The protection provided by power filtration and shielding the controls is limited. There is no way to predict the noise levels that PLC can apply to the controls. There will always be some amount of noise above what can be shielded at which point the controls will fail or at least seem to have failed. With more than eleven million Smart Meters in service today— noise can be a real issue.

Keep this in mind on jobs that seem to have “random nuisance” problems.  Find out if the home has a new “Smart Meter”. Find out if the problems seems to start when , or just after, the meter was installed — even a month or so later. If it does, now you have to see if this is causing the problems and do some of the checks above.

(Special thanks to our Residential Controls Engineering department for the information provided in this post.)


About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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  1. Here’s a link to your September 2011 post. https://yorkcentraltechtalk.wordpress.com/2011/09/26/pf-choke-for-ecm-motors/

    In my area the local power company has been using Smart Meters for years. They use a Power Line Carrier (PLC) communication technique as does the older “Radio Shack” X10 light and receptacle AC control modules.

    The X10 system offers additional plug in and wire in choke modules to eliminate interference that might block their signals. An intermittent failure to communicate within the X10 system is a common complaint but does not cause board or module failures. Often computers and some flat screen TVs that use “switching power supplies” (i.e. “wall warts” and “bricks” that provide DC to the computer) create significant interference to the X10 modules which is then eliminated by installing a plug in X10 choke on the computer’s power source. Obviously critical equipment should be and often is designed with inductive and capacitive chokes to protect their electronics from power line noise. It is interesting that most older laptops have a choke in their DC leads immediately before the DC plug. The manufacturers knew their low cost brick power supplies created interference and therefore provided a choke to clean up the DC before it arrived to the more expensive and warranted laptop.

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