By Dana Lilly, Technical Sales Support Specialist for U.S. Boiler Company
A Power Quality Primer for Service Technicians Part 1 was a brief discussion of the most damaging and most common power quality issue, the voltage transient or spike. At the risk of oversimplification, part 2 will lump together all the other potential power quality issues.
Why should you bother considering power quality issues?
The reality is that modern residential boilers, in the name of both safety and efficiency, employ electronic controls that are far more sensitive to power quality than in years past. So, as a tech working on critical equipment (the heating system) that depends on sensitive electronic controls (any modern boiler), should at least be aware of how power quality can affect your work.
This is not a deep dive discussion of power quality, but rather some basic information pertaining to where these issues come from and possible solutions you can recommend to your customers before there are problems. The following will discuss only those issues that are likely to impact boiler operation.
What is “Everything Else”?
I’ve chosen to combine the remaining power quality issues for two reasons – 1.) They tend to be infrequent problems in light commercial and residential settings. 2.) In these types of settings, with respect to the boiler power circuit, the way we deal with them is the same.
Voltage Sags and Surges
Generally defined as an under or over voltage of more than 10% and lasting for a brief period. Most boiler equipment in the United States has been tested to ensure that it will continue to operate well in excess of the 10% threshold. However, frequent or sustained operation at these levels can eventually cause damage and shorten a boiler’s life expectancy. Voltage sags and surges can be caused by heavy loads being cycled on and off (such as an A/C condenser) coupled with improperly sized wire or electrical service. Heavy loads on utility grids at peak times or seasons can also cause sags and surges.
Momentary Power Interruptions
These interruptions, though brief, can cause equipment to shut down. If they occur due to improper wiring connections that either overheat or intermittently interrupt current flow, the frequent on/off cycles could substantially shorten the life of heating system components, especially motors or circulators. When caused by utility failure, momentary power interruptions can result in significant transient surges.
This is a type of sine wave distortion that can be caused by several things including radio frequency interference, electromagnetic interference, or improper grounding and/or wiring methods. Though not usually destructive, it can cause operational errors in electronic circuits. For a boiler, this could create a lockout condition.
This is another type of sine wave distortion that can be caused by significant electronic loads, such as computers, printers, motor speed drives, and some types of lighting. Though not a common issue in residential settings, harmonic distortion could manifest itself in commercial establishments that may use these types of electric loads extensively. Harmonics can cause increased heating in motors and reduced torque output, leading to premature failure. Significant harmonic distortion can cause misoperation and failure in some types of electronic control circuits.
Portable and Standby Generators
Another potential power quality issue can be caused by portable and standby generators. Many generators fall short in terms of power quality. In many instances, a boiler’s control will lock out or even fail due to “dirty power” supplied from a generator. If it is necessary to power a modern boiler from a generator, consider using a good quality inverter generator.
Solutions for “Everything Else”
As mentioned, there is a single solution to deal with all the above potential problems. This is with an uninterruptible power supply (UPS). These were developed primarily as a temporary backup power source for computers and servers in the event of a power outage that would allow an orderly shutdown without loss of data.
UPS Type, Size, and Maintenance
When properly connected, a UPS can electrically isolate a boiler’s power from either the grid or generator power, thus protecting it from surges, spikes, sags and even brown out conditions. As to type, a continuous or online UPS that provides a true sine wave output would be the best choice. Depending on which power quality issue you are trying to alleviate, you may find that a standby or offline UPS type is suitable for less cost. For instance, harmonics may be mitigated by an online UPS, but they would not be with an offline type. As to size, a 1000VA to 1500VA unit would likely be sufficient for most hydronic heating systems, but this should be confirmed based upon the components it is required to power. If a system includes several pumps, they need to be added into the calculations along with a minimum 50% “cushion” to allow for motor starting currents.
A good quality UPS can in some ways make up for the shortcomings of an inferior generator by smoothing an unstable frequency or voltage when these happen on a brief and temporary basis. However, be aware that the UPS may reject the power the generator is providing if it is too far out of tolerance for too long a period. If this happens, the UPS can only provide power to the boiler for as long as its battery contains enough charge, which by design may only be for ten minutes or so. The time will vary depending on your system and the size UPS you are using.
A UPS does require occasional checks and maintenance in accordance with the manufacturer’s recommendations. The internal battery has a service life of approximately 3 to 5 years on average, but this may vary depending on conditions of use. They are typically affordable and easy to replace.
While a modern UPS will often incorporate a surge suppressor, this should be considered as a secondary protection measure. A good quality primary surge protective device or transient voltage surge suppressor (TVSS) as discussed in part 1 should always be installed at the main panel.
Eliminate Issues Before they Become Problems
So again, why should you even think about power quality issues if they are not likely to be a problem? Well, consider this scenario: Imagine the angry finger pointing when the boiler you installed fails to operate from that expensive stand-by generator after the big storm. Few people would blame the generator when all their lights work just fine! Of course, they fail to consider the high safety standard that boiler controls are required to maintain and how that effects their operation.
It would be wise to educate your customers and make them aware of potential power issues and solutions before they become real problems! If these problems exist and are ignored, the result is (at the least) erratic or unreliable heating system operation due to lockout errors or (at the worst) failed components due to excessive wear or overheating.