ASHRAE Journal - January 2023 - 6

LETTERS
Analysis of
Refrigerant Use
The article " Analysis of Refrigerant
Use for AC Equipment Maintenance "
by Theresa Pistochini, P.E., Member
ASHRAE; Roger Silveira; Derrick
Ross, Associate Member ASHRAE;
Robert McMurry; and Adarsh
Umarani published in the October
2022 issue does not mention that
Schrader valves are supplied with a
seal cap.
Based on my personal experience,
Schrader valves do not leak if the
seal cap is installed properly no matter
the age of the system.
On most systems I have inspected,
the seal caps were missing.
The amount of refrigerant charged
and invoiced is based on a honor
system and cannot be used in a scientific
article.
I made these statements in a lawsuit,
and the parties quickly settled
out of court.
Reinhold Kittler, P.Eng, Fellow/Life Member ASHRAE,
Virginia Beach, Va.
The Author Responds
The study reported the location
of leaks as identified by the service
technician. We are currently
researching if seal caps are an effective
method to prevent leaks from
Schrader valves.
For refrigerant used, 82% was
accounted for in terms of 30 lb
canisters purchased and used fully
by the facility (this is not an honor
system). The remaining 18% was
based on receipts from third-party
service contractors. The article
clearly states the methodology so
the reader can consider findings in
that context.
Theresa Pistochini, P.E., Member ASHRAE, Davis, Calif.
6
ASHRAE JOURNAL ashrae.o rg
Free Cooling for
Data Centers
Thank you for the column " Which
Free Cooling Technology Should
We Select For Data Centers " by
Mohammad Khurram Saeed,
Associate Member ASHRAE, in the
October 2022 issue. It gives us a good
summary of the different free cooling
options there are from a decade
ago to now. Nevertheless, I would
like to comment on some issues.
The author is referring to MLC/ELC
in regard to ASHRAE Standard 90.4,
but due to free cooling when water
is a big factor (for instance adiabatic
practices he mentions) the so-called
WUE (water usage effectiveness)
must be considered somehow in the
final best selection, e.g., if that water
comes from a wastewater plant or
not, and if water scarcity exists at
the site where the data center will be
located.
In general, the free cooling technology
is mixing the main two free
cooling options, the one from the
air side (air economizers) and the
other from compressor or water free
cooling in chillers. I think it must be
separated since each one has different
scopes, and for the same latitude
and external pollutant conditions
one could be selected and the other
not, and vice versa.
In the case of free cooling with
dual coil DX water-cooled, you
missed that water treatment also is
necessary in the case of dry cooler
supported by an adiabatic system.
For this option, you also missed that
regarding Legionella water treatment
is necessary since water is in cooling
towers.
For the same option above you
say " multiple dry coolers can be
J A N U A RY 2023
avoided by using a common cooling
tower to multiple CRAC units. "
Nevertheless, that common cooling
tower should be provided with
redundancy. Thus, a multiple dry
cooler system with lower size and
capacity could be better in terms
of costs and energy efficiency compared
to 1 + 1 cooling towers, or
even 2 + 1 cooling towers.
In general, you provide a good
review about the main systems
we can take to get a free cooling
technology, but I think the column
missed mentioning the kind of heat
exchangers in the case of indirect
free cooling (with thermal wheel for
instance), which could be decisive
depending on the latitude again.
Last but not least, I think the
source to get the free cooling is
neglecting the natural sources that
were already described in some
interesting articles in the Journal.
These include water for condensing
purposes coming from lakes or
rivers or even from the sea coast,
whereas the free cooling pipework
bypass is giving us a very important
opportunity to select something like
that.
Ignacio Gómez-Cornejo Gilpérez,
Member ASHRAE, Madrid, Spain
The Author Responds
Thanks for your detailed comments
and time. I agree that the
cooling basics have been there for
many years, but the way we apply
them in a particular industry is
ever-changing. For instance, liquid
cooling basics have been there for
decades, but we haven't yet seen it
being applied in a data center in a
meaningful manner, and now we
are actually talking about using it in
the data center industry. Also, the
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