Hello, we have a 10 years old TRANE air conditioner for our 8-story
building. Lately the electricity bill is out of control. One A/C
technician told us that this model of TRANE was actually designed to
serve 16-story buildings.

We are trying to cut down the cost of running this thing. Of course
the first thing we tried was to set the temperature higher, but then
some tenants complainted. But with the current temperature setting,
the building is so cold that some of us have to put on sweater.

We are looking for a way to run this TRANE air conditioner that would
cut down cost and still keep our tenants happy. I guess the key is
that since our building is half the size of the machine was intended
for, we were wondering if there's anything we can do from a air
conditioner configuration/setting standpoint. Thank you.

Although I can't answer your question I can tell you that my family
has been in htg/ac for many years and have always understood that if
you buy a bigger unit than you need it will actually cost you less
because it won't have to run as much to cool the residence. Have you
had your thermostat checked?

It is likely the unit is less efficient than when it was new. A commom
cause is less than the optimum amount of freon. It is also possible
someone added an excessive amount of freon.  Cleaning the inside and
outside heat exchangers and fan blades will help some.
For tenents who think the room is too cold, partially block some of
their vents and/or aim them so they don't blow on the people. Then set
the therostat about one degree warmer. When people complain they are
hot, clean their ducts and check that all the vents are fully open. It
might even be cost effective to add another vent for tenents who think
it is too hot, or a supplimental duct if their is a floor or section
that most tenents think is too hot.   Neil

I question your technician's comment on the oversized unit.  If this
were the case your duct work would be way undersized, (ducted for a
8ton), resulting in evaporator freeze ups and pre-mature motor
failures not to mention a noise factor.  If humidity isn't a problem
in your region then sizing it to meet the BTU demand would be cost
effective.
One thing people are overlooking when it comes to their electric bill
lately is the cost per kilowatt.  Call your local electric company and
ask how many KW were used last year along with last years cooling days
and cost per KW.
Good Luck,
Jim.