RETROFIT TEAM
MECHANICAL CONTRACTOR: Eclipse Inc.
HVAC DESIGN SUPPORT AND MANUFACTURER: Mitsubishi Electric Trane HVAC US
THE RETROFIT
Minnesota Power is a regional utility company, serving 145,000 customers in northeastern Minnesota. Staff members pride themselves on promoting energy-efficient technologies and saving customers money. Like many of its customers, Minnesota Power faces efficiency challenges within existing and aging facilities. This led leadership to pursue a high-performance HVAC retrofit in its 5,000-square-foot Cloquet office, which houses the utility’s customer service and linemen.
After seven years of failing compressors, humidity issues and frigid winters, a defective HVAC system needed replacement. “For four summers in a row, we didn’t have air conditioning. We went through winters with only baseboard heat and hot summers with fans running constantly,” expresses Craig Kedrowski, business service advisor, Minnesota Power. “The HVAC units seemed to be ‘fighting’ one another and the vendor was not responsive in helping us with our system’s issues. It prompted us to seek out another solution.”
Local mechanical contractor Zach Wehr from Eclipse Inc., who had worked with Minnesota Power’s conservation program, invited Jake Sajevic, account manager, Trane, to tour the office. Their goal: determine the issues with the existing system and offer a solution. Ultimately, Wehr and Sajevic chose
CITY MULTI from Mitsubishi Electric Trane HVAC US as the solution. The pair invited Mark Totino, commercial area sales manager, METUS, to visit the property and consult on the system’s design.
The design includes an R2-Series Heat Recovery System with Hyper-Heating INVERTER (H2i) technology, as well as two PKFY Wall-Mounted Indoor Units, 10 PEFY Horizontal-Ducted Indoor Units and three Lossnay Energy Recovery Ventilators to bring in fresh, outside air. Twelve Smart MEs and one AE-200A Centralized Controller were specified for system management. Each tie into Minnesota’s Power’s building automa- tion system at the Duluth headquarters, streamlining efficiency and comfort control.
Another benefit: the VRF system doubles as a display of energy-efficient performance for the company’s current and future customers. “Because we recommend this equipment in our conservation program, we were interested in having a showcase where we present simultaneous heating and cooling,” Kedrowski says. “Beneficial electrification is something that’s really coming along.”
In the Cloquet office’s conference room, two indoor units each connect to an individual thermostat that lights up blue or red for cooling or heating, respectively. “Side-by-side, they’ll be able to show and explain the concept of heat recovery. This building is a testament to their support of electrification,” Totino notes.
However, Minnesota winters pose a big challenge with electrification: extreme cold. “There are some unique hurdles the farther north you go,” Sajevic adds. “Our design’s low-ambient temperature is -20 F and it can get even colder. I’ve talked with engineers all over the region and they think VRF is a great technology but only a few are comfortable specifying it because of the low-ambient conditions we face.” For Sajevic, combining supplemental heat with VRF technology is a win-win; customers get clean, energy-efficient energy with back-up heating for freezing winters.
“For many developers and engineers, their gut reaction is to explain why electric heat is super expensive
to run. What I explain to them is that when paired with Mitsubishi Electric’s H2i units, the auxiliary heat will almost never run,” Sajevic says. “For this project, we’re going to continue to submeter the electric heat going into next winter and we’ve interlocked the controls system with our CN-24 accessory, which enables supplemental heat sources. We’ll be able to verify how often the supplemental heat actually runs and under what outdoor conditions it is enabled.”
Wehr agrees, especially as a commercial engineer in the region.“First and foremost, the technology has come a long way, especially in terms of payback, life expectancy, rate of return on investment and performance, though I can understand the apprehension of some based on past technology. That said, the system we installed at Minnesota Power will kick off at -25 F and switch to supplemental heat. I have the highest confidence in the equipment. I’ve had it in my building since 2008 with no issues.”
Since installation, the system has only received positive feedback, especially in regard to the simultaneous heating and cooling. “I’m glad we finally got this rectified,” Kedrowski says. “Our coworkers are loving it. We have some people that want their room 80 F even in the summer and then some want it 65 F. The Mitsubishi Electric system allows them to do that.”