This apartment building located in Toronto, Canada had a reciprocating water-chiller original to the building – 1968! We conducted an energy audit to determine its performance and confirm the actual capacity of 80 tons. In addition to saving electricity and securing incentives from the local electric utility, Toronto Hydro, this article will focus on how this unique chiller retrofit saved natural gas and secured incentives from the local gas company- Enbridge!
Most chiller retrofits are intended to improve efficiency and save electricity. How can this chiller installation save natural gas as well? While most chillers reject their condenser heat outdoors through a cooling tower, this chiller diverts waste heat and uses it for domestic hot water instead. That means the chiller can cool the building during summer months and deliver free hot water at the same time! As part of the energy audit, we measured the domestic hot water flow rate and temperatures. This gave an accurate depiction of the actual hot water use in the building. In most high-rise residential buildings, the chiller can develop more than enough heat for the domestic hot water load. In this case, it was determined that 2 ModulAIR chiller modules should be installed: one 25 ton heat recovery module and one 55 ton standard module. This meets the total required cooling capacity of 80 tons while the heat recovery module delivers 240,000 btu/hr of heat at 160 F.
Looking closer at the two modules, you can see the far chiller (25 ton) has an additional heat exchanger (condenser) and circulator pump. The chiller is piped to the boiler loop just like any other boiler. When there is a call for heat, the pump kicks on and moves boiler water through this secondary condenser. The cooling tower water that circulates through the primary condenser is cut off and the chiller begins rejecting heat to the boiler loop.
The new ModulAIR chiller records and sends data so anyone can view it remotely. Below is a graph showing the heat recovery operation for a given day. As you can see, the chiller cycles in and out of heat recovery mode to maintain the domestic hot water temperature at night. During the day, the chiller spends most of its time in full heat recovery mode.
The chiller at this apartment building runs from June through mid September. During this 14 week time, the heat recovery module had an average demand of 82% and saved over $5,400 in natural gas! Enbridge offered an additional $1,500 incentive. The incremental cost of the heat recovery feature was more than paid for in the first summer of operation.
For more information about this system, visit the ModulAIR page or Contact AIR. We can conduct the audit to determine feasibility, help with the piping layout and confirm energy savings with actual data!