When Things Don't Work Together: The Impacts of Poor Equipment Interoperability

After about a year since it was installed, my heat pump is finally up and running correctly! Why did it take so long? Controls issues. More specifically, because it is a dual-fuel system (an air source heat pump with a backup oil furnace) all of the components did not communicate properly with each other. The heat pump, furnace, and thermostat are all different brands and their integration was far from seamless.

The system finally worked correctly switching from the primary heat (the heat pump) to the auxiliary heat (the furnace) at the specified temperature when my contractor figured out that they needed to run an outdoor air temperature sensor to my furnace’s control board. So now the system has three outdoor air temperature inputs: one from my thermostat (which uses local weather station data), one from the heat pump’s outdoor unit, and a dedicated sensor for the furnace control board. Not exactly smart, but at least it works now.[1]

I’m an energy nerd, so trying to figure out how to make the heat pump and furnace work together was a fun challenge.[2] But throughout the process, I kept wondering how a technology-phobic older family member would have reacted in the situation. They probably would have given up and only used the furnace in the winter and the heat pump as an air conditioner in the summer, and most of the potential energy and carbon emission savings of the heat pump would have been lost. It got me thinking – how much savings are not realized because of poor interoperability between devices or badly integrated controls?

Examples

There are three broad categories of situations where poor communication or interoperability between equipment could limit savings:

Broken stuff – Often the maximum potential energy savings from controls and equipment is not realized because something is broken or not set up correctly. Our engineers often find instances where facilities staff have lost the ability to update their energy management system or different systems do not communicate with each other. This results in situations where heating and cooling equipment are being run at the same time or pressurization controls in one part of a building are fighting with another part, with one area trying to increase the building’s pressure while the other area is trying to relieve it. Fortunately, retro-commissioning studies can identify these issues, and their solutions are often relatively inexpensive.

Complexity – New technology offers many savings or load flexibility opportunities that were not previously possible. However, they can be complex and need educated installers and users to maximize their benefits. A great example is networked lighting controls. Now that the lighting market is essentially transformed to LEDs, energy efficiency programs are looking for new opportunities to replace those savings and networked lighting controls are a potential candidate. The energy savings factor of networked lighting controls with luminaire level lighting controls (LLLCs) is more than twice that of traditional occupancy sensors (61% vs. 24%, per the Illinois TRM).[3] The value of better lighting controls decreases as the fixtures they control become more efficient (i.e., LEDs), but LLLCs offer additional energy (and non-energy) benefits. LLLCs can integrate with other systems to support other control strategies, like HVAC room temperature and plug load control, and other analytics, such as occupancy data. Thinking beyond energy savings, it is easy to imagine information from LLLCs used to help facilities and utilities with flexible load management, where lighting levels and heating or cooling are reduced imperceptibly to help the grid during peak periods.

This all sounds amazing, but few installers have the experience to implement these solutions perfectly and it may be a hard sell for facilities to spend extra money on new technology that, in their mind, may not bring all of the promised energy and non-energy benefits.

Walled Gardens – Customers’ energy and equipment use data are valuable and companies typically want to monetize that. This can lead to “walled gardens” in which users are tied into a certain manufacturer’s ecosystem with costly barriers to leave (with their data). Relevant (non-Apple) examples of this are Tesla restricting the ability of its Powerwall batteries to interact with third party virtual power plants in some states and countries or some electric vehicle manufacturers not providing accurate data to third party telematics companies. Decisions like this limit the savings and load management potential of equipment that don’t belong to a single brand.

How Evaluations Can Help

Evaluations can help programs understand the cases when savings are limited due to poor interoperability. First, impact evaluations can determine the actual energy use or savings that occur instead of what is estimated using assumed values. Second, process evaluations can explore the factors driving the difference between the anticipated and actual impacts. Finally, because technology markets are always changing, these findings will not be static. Lighting contractors, for example, will eventually become trained and more experienced with networked controls and the difference between the real-life impacts and theoretical impacts will shrink over time. Evaluations will need to be updated regularly to reflect the changing industry standard practices.

[1] Now that the heat pump and aux heat are working properly, I have been able to test what crossover temperature is best. So far, the outdoor air temperature has only gotten into the mid-20s but the heat pump seems to work great at that temperature. Hopefully I can get the switchover temp down to 15 or 20ºF, which would mean that I can use the heat pump exclusively for the vast majority of the winter in Massachusetts.

[2] It also helped that I had the backup furnace so I was never in danger of freezing while we figured out the issue.

[3] But note that the savings from lighting controls decreases in value as the fixtures they control become more efficient (i.e., LEDs).