Energy savings from existing air handlers

Energy savings from existing air handlers

Today’s Fun Fact Friday is on an HVACR retrofit opportunity for existing single speed air handling units. How do we get energy savings from existing equipment?

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Those of you who have sat in the window seat on an airplane have likely looked down at those “big box” retail stores and seen roofs scattered with air handlers. For those older buildings, often the air handlers are equally old.

Outdated equipment means lower efficiency, especially in the HVACR world. While replacing the entire AHU (Air Handling Unit) RTU (Roof Top Unit) is preferred from a kW consumption viewpoint, budgets do get in the way.

A much lower cost solution to consider adding a variable speed drive (VSD) to that previously constant flow fan.

Now we can’t go in all ad hoc and put VSDs on fans and slow them down a bunch and walk away. There are application considerations, as slowing down the fan too much can result in a frozen coil (cooling mode) or unit tripping on overheat (heating mode) because there isn’t enough air moving through the unit.

Thus care must be taken and the solution implemented by a knowledgeable technician; however, even a 10% speed reduction will result in a ~25% energy saving on the fan.

There are a variety of control systems for these older constant flow RTUs. An example may be a RTU that has high cool, low cool, high heat, low heat, and ventilation modes – each of these commands coming from a single unique contact from a thermostat.

The fact there is no dedicated “start” command and 5 independent t'stat commands, will be a challenge to many HVACR VSDs. Those VSDs can’t take 5 separate commands independently while treating each input as its own speed reference and run command. 

But the ABB ACH580 is optimized to integrate into those types of existing control systems. (For the techy folks, that means the ACH580 can have its run command virtually connected to each separate constant frequency command, and there is no need to use the 011 type logic to create your multiple constant frequencies.)

Slowing down the fan speed in the low heat and low cool modes results in the energy savings.

The ACH580 can take 24 VDC or 24 VAC control commands as standard, and has an option card to allow 120 VAC inputs, offering flexibility to integrate into different existing controls.

Check out the technical note for more application considerations and on how to integrate to the ACH580. Reach out to your local ABB HVACR VSD guru if you may have an opportunity for energy savings.

ACH580 drives family
ACH580 drives family
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