If you have ever worked with an energy efficiency consultant to study your building, you may know how deceptively simple the advice can be. In many ways energy efficiency is just common sense – turn that thing off when you don’t need it, fix that other broken thing – but actually achieving those energy reductions is a messy business.
For example, your consultant might tell you that your economizer is broken and fixing it will generate thousands of dollars of savings per year. An economizer that is stuck open can cause an air conditioning unit to use much more energy than if it didn’t have an economizer at all. Great! So how do you fix it? Economizers are relatively simple mechanical devices consisting of a set of dampers that controls how much outside air to bring in to the building depending on temperature conditions. When they work properly they can dramatically reduce the amount of mechanical cooling that a building uses. However field studies have found more than 30% of economizers surveyed to be broken.
So why doesn’t everyone fix their economizers? Great question. To paraphrase Tolstoy, working economizers are all alike; every broken economizer is broken in its own way. Let me take you on the journey of some of my favorite broken economizers that I have had to fix over the course of my career at Carbon Lighthouse and you might understand why.
The “Out of Sight, Out of Mind” Economizer
How often do you crawl into your ceiling ducts and look around? Not that often, right? Unfortunately, that is where a lot of air handlers, and therefore economizers, are located. One of the buildings I worked in had the dampers on their economizers literally rusted shut and crumbling like an old ship left to rot in the harbor. The service team had just never bothered to check them because they were difficult to access. By the time we got to them, the only thing to do was cut them out in pieces and replace them with brand new dampers.
The Broken Economizer that Wasn’t
Why would an economizer not be working even if all the components are? In test mode, the dampers actuate and everything looks good, but when we observe the building over time, the outside air ratio never changes. What is going on? It often is actually the exhaust fan that is the culprit.
For example, I was working with carrier package units in a building near LA. Everything worked fine in test mode, but the economizers weren’t actuating in real life. The contractor we were working with told me it was completely fine twice, but I kept insisting that the data showed that it still wasn’t working. Finally, I found a clue in the exhaust fan – it never ran even though the fans on the surrounding units ran a lot. It turned out that there was a short in the relay for the exhaust fan that was causing it to trip off, and therefore disable the economizer as a safety (economizers regulate the volume of outside air coming into a building, so they need to work closely with the exhaust fan to maintain building pressure). We replaced the fan controller and the economizer started working great again.
I ran into a similar problem in San Francisco. We discovered that the building operator had disabled the economizer on purpose because of building pressure issues. This had happened more than two years before we got to the building, so that whole time they weren’t taking advantage of free cooling. The building had Carrier package units, and it turns out that they are shipped with the pressure sensor intended for inside the building temporarily stored where the condenser fans are. When the unit is installed, the pressure sensor should be landed inside the building, but it turns out that this one never was. The unit was 15 years old, so for that whole 15 years the exhaust fan had been controlled off of a pressure sensor that wasn’t measuring inside the building. No wonder they had pressure problems! Putting the pressure sensor where it belonged completely solved the problem.
Dear Municipal Transportation Agency, will you please fix my economizer?
I never thought that when I started as an energy efficiency engineer at Carbon Lighthouse that I would end up sitting in a San Francisco Municipal Transportation Agency (SFMTA) public hearing in order to fix an economizer, but that is in fact what happened. One of the hardest to fix economizers I ever worked on wasn’t broken at all.
The outside air intake for this particular air handling unit was located at street level. Unfortunately, there was a commercial loading zone immediately outside the building right where that fan pulled in fresh air. The problem wasn’t actually the commercial vehicles – they tended to shut off their engines when they parked to make a delivery – it was the cars that used those open spots to stop for a minute and idle their car while they made a quick call or looked up directions. The fumes from those idling cars caused major tenant complaints, which lead to the service contractor closing the outside air dampers to 0%, meaning the bottom two floors were getting zero fresh air (which happens to be a major code violation).
So that brings me to the SFMTA hearing. As part of this solution, I successfully petitioned the city to move the commercial loading zone further up the block, a process that required 3 months of waiting and representing the building at a public hearing, all at no extra cost to the client. A lot of work for an economizer, but hey, if we promise to get something done, we do it – that’s why we can guarantee our returns.
What about all the other measures?
These are examples from just one type of measure that would be a line item in your consultant report. Implementing comprehensive solutions that can save 20% of your building’s energy with guaranteed returns takes dozens of these types of fixes, each with their own complications. Getting all of those right is our job – we do it both to guarantee your financial returns and our impact on the planet.