Energy savings from cooling load reduction

[cme]

I am trying to calculate the cooling energy savings freehand via psych chart and a formula. I have a formula for heating and am looking for one for cooling. My psych chart tells me I'm reducing the load by 52 tons by going to a return air system. The system will then have 95.5 tons for a hospital lab area ..... 20,000 cfm. The client wants to see what the payback is by going return air instead of 100% OSA which it is now and so the calculated reduction in cooling load. The project is close to Newark, NJ.

Anybody have something in archive?

 

[ChrisConley]

Hi fastuser,

I'd recommend, if you already haven't, starting a new thread with a descriptive title. When a new idea happens in a large thread it usually gets missed.

Secondly, you would have to model the house to get an idea of the proposed energy savings - too many factors to consider.

You could model a few dozen 'standard' houses and then develop an average for marketing, but no rule of thumb exists.

 

[tombmech]

Looks like lilliput1 calculated the actual OpCost savings. I was going to suggest the Bin Method if you wanted to do it manually. The key, as several mentioned, is that there is a peak energy difference, but that energy difference varies throughout the year depending on the load difference from that peak. So, the total energy savings must be calculated accumulatively with the loads that occur over the span of a year.

All that being said, I am more interested in SAK9's question: Who said the OA could be reduced from 100% anyway? Obviously, the premise was vetted long ago when the system was first installed. If a laboratory area is completely converted for non-laboratory use, return air may be justified. Yet, a system designed to condition 100% OA may be a poor choice to apply to a converted area that uses return air. The coil ratios, air change rates, etc., are all wrong.

Besides, what about the exhaust fans?