HVAC performance verification
HVAC performance verification
(OP)
Hello all,
Is there a method to verify the actual performance of a packaged unit? I have a 15 ton roof-mount on a metal building (insulated) that doesn't seem to be working as well as it should. Total heat losses for the building, including sun load are calculated to be 38KW.
The unit is new, but it is also a new design. I am looking for a test to find the unit's actual performance vs. what's labeled on the side.
I have at my disposal instruments to measure temp, air flow/volume, humidity, etc.
Thanks.
Is there a method to verify the actual performance of a packaged unit? I have a 15 ton roof-mount on a metal building (insulated) that doesn't seem to be working as well as it should. Total heat losses for the building, including sun load are calculated to be 38KW.
The unit is new, but it is also a new design. I am looking for a test to find the unit's actual performance vs. what's labeled on the side.
I have at my disposal instruments to measure temp, air flow/volume, humidity, etc.
Thanks.





RE: HVAC performance verification
RE: HVAC performance verification
By measuring supply dry and wer bulb, volume flow, it is actually sufficient to calculate enthalpy difference.
Next step is to check reference conditions in manufacturers specs, and eventually find correction factors that correlate to your actual conditions.
RE: HVAC performance verification
RE: HVAC performance verification
RE: HVAC performance verification
Single point measurement of inlet or discharge won't detect that.
RE: HVAC performance verification
Between the several replies, I found way to do this researching your suggestions, not to mention learning something in the process. I'm using psychrometrics initially, then having the supplier evaluate afterwards. The ARI 360 standard also pointed me to ASHRAE Standard 37, which I'm about to purchase.
Appreciate it!
RE: HVAC performance verification
RE: HVAC performance verification
BTUH = CFM * delta h * 4.5 * density/0.075
I agree with measuring entering and leaving dry and wet bulb temperatures. Convert them to enthalpy on a psych chart or online converter. Do the calcs once you know the CFM. It may not be dead on but it should give you a reasonable estimation what the system is delivering in terms of real time capacity.
Also keep in mind that outdoor ambient temperatures affect system capacity. ARI rates most air cooled condensers at 95 degrees dry bulb ambient. Above that the system capacity will derate.