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# Commercial AHU cooling coil saving cost2

## Commercial AHU cooling coil saving cost

(OP)
I am interested in gaining some additional information on how I can calculate the savings possible from modulating a valve back for a commercial AHU cooling coil. I am trying to show for a project how an estimated saving can be achieved, by calibrating the Discharge Air sensor on multiple Air Handlers that are reading too low; which will result in the cooling coil to back off. Which will save the facility money, I was thinking about using this equation from the AHU data (BTU/H= GPM X (detaT) X 500); Then convert that into TONS
(TON= (BTU/H)/12000). After I find the tons, I was thinking about calculating how much those tons would be saved from the chiller for that instant.

Please let me know if I need to use a different equation, or approach to find the saving cost for AHU cooling coil.

Thanks for any and all assistance!

### RE: Commercial AHU cooling coil saving cost

You hit the nail on the head with "that instant." How are you going to track and totalize this over time? A BTU meter that measures flow and Delta-T can accomplish this for you.

So what happens now? The coil control valves do not modulate and you just over-cool or reheat to maintain space temp?

### RE: Commercial AHU cooling coil saving cost

Bron:
I believe that the valves will still modulate as he mentions that he will calibrate the discharge air sensor, not eliminate it...

JT, you might also want to calculate the energy savings in the chilled water pumps, as you will not need to move so much chilled water and the condenser water pumps as well, due to the reduced chiller demand.

### RE: Commercial AHU cooling coil saving cost

(OP)
We have a BAS (Building Automation System) on the site, which stores the trends for the DA-T. For the flow, I want to give the facility reason to invest in devices that tracks the BTU/GPM/FLOW so we can find exact savings through calculations.

The valve for the example of a DA-T that is reading too low, will case like you stated; the cooling valve to over-cool or the re-heat to needlessly use heat.

I will look into also the savings for the chilled water pumps.

Thanks for responding, I really appreciate it.

I may respond again, if I run into another problem that I may need additional assistance with.

Thanks!

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