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Help! cooling load/efficiency calculations

Help! cooling load/efficiency calculations

Help! cooling load/efficiency calculations

(OP)
I am working for a gas utilities company and our office building is getting a air-conditioning upgrade, here are the details:

old system in use was an inefficient Yazaki chilled water system, with approximately 20 Tons of cooling capacity.  This system was in use basically May to Sept, with a constant load and no scrolling capability 9basically on all the time, not temp control).  We calculated the total power consumption including all parasitic loads to be around 30 H.P.

This system is being replaced by small Sanyo split units, these are more efficient, provide more effective cooling since they are located only in rooms which require cooling (unlike the chilled system which dumped unnecessary cooling into a garage and storage/compressor room area.

these Sanyo units have variable fan speeds, t-stat and on-off timer controls

What I was basically asked to do was to numerically compare the performance improvement of the new system to the yazaki, during the 5 month period the system is in use.  With the Yazaki system, it is easy because that is basically a straight line across as the unit is practically on the entire time, so (30HP)(total running time)and convert that to a KWH and $$$ amount

the problem is I am not too sure how I can approximate the performance of the Sanyo units.  These will not be on constantly obviously, instead these will ramp up gradually as the load increases in the hotter months (from May to July) before slowly falling off until september.

Basically even if these were to run constantly to compare to the yazaki, they would still only use 16HP instead of the 30Hp of the yazaki unit, which is still saving money, but I'd like to show a more accurate depiction.

How should I go about doing this,? I'm thinking I'll need to use cooling degree days and base my approximation around that, but not too sure exactly, so any help/suggestions are appreciated,

RE: Help! cooling load/efficiency calculations

You'd need to model the building using an energy modelling tool. Couple of free ones online, generally you get what you pay for though.

RE: Help! cooling load/efficiency calculations

(OP)
Thanks for your help Chris,
This is mainly going to be an estimate so the figures dont have to be very precise, so a free modeling tool should be enough..

any suggestions/links to a particular one? I'm having a tough time finding this type of software online

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