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GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy (ACRA) in Edenvale.
He holds a Bachelor of Business Administration and an associate degree in educational administration. He
has a National Technical Diploma and completed an apprenticeship with Transnet. He has dual-trades status:
refrigeration and electrical. He has been involved with SAIRAC for 17 years and has been a Johannesburg
committee member for the past eight (chairman in 2011 and 2012). Currently he is the treasurer
(Johannesburg council) as well as president (national council).
GUIDE TO
FLAMMABLE REFRIGERANTS
By Grant Laidlaw
Many people ask for assistance in the understanding of theoretical and
practical aspects of the industry. I will endeavour to enlighten.
Chris asks: Grant,we are beginning to see a lot of R290 in
the commercial refrigeration space and in particular the cold
drink type fridges. We were wondering, what changes to
tooling and basic procedures do we need to make as this is a
problem for us. Any advice would be appreciated. Also, are
we allowed to transport these new flammable refrigerants
in our vehicles? Again, what additional procedures do we
need to implement a professional driving permit (PDP)?
As equipment may only use 150g of hydrocarbons is this
really viable for air conditioning systems or only for larger
refrigeration systems?
C
hris, I addressed the first part of your question in the previous
issue, let us look at the types of equipment that can utilise
R290 as the refrigerant. Again, I am using international standards
as South Africa is in the process of developing and amending the
applicable standards.
When we look at the maximum flammable gas charge size,
we find that the amount of flammable refrigerant which can be
used in systems is restricted and depends on various factors:
• Location of equipment, e.g. below or above ground level;
• Occupancy of area being cooled, e.g. unrestricted access by
the public, or authorised access only;
• Type of system, e.g. direct expansion or secondary /
refrigeration or air conditioning.
The limits are different for comfort cooling / heating and non-
comfort cooling / heating applications. Systems with less than
500g flammable refrigerant charge can be located anywhere,
though it should be noted that the potentially flammable zone
should still be assessed.
60
RACA Journal I March 2020
COMFORT COOLING / HEATING APPLICATIONS
For comfort cooling / heating applications the maximum
charge is based on the Lower Flammability Limit or LFL of the
refrigerant, the floor area and the height of the indoor unit:
NON COMFORT COOLING / HEATING
APPLICATIONS
There are practical limits. Chris, as I have said previously, South
Africa is in the process of updating the relevant standards.
Looking at the European standard EN378-1 specifies practical
limits for all the refrigerants covered. I am reasonably sure our
standards will be very similar.
To determine the maximum charge imposed by the practical
limit (PL), the room volume is multiplied by PL. Examples of
maximum charge determined by PL:
• Cold room size 4m x 5m x 2.5m high, cooled by a direct
expansion system using R290.
• Cold room volume = 8m x 5m x 2.5m = 100m 3 .
R290 PL = 0.008kg/m 3 .
• Max charge = 100 x 0.008kg = 0.8kg.
Then, as above, but using R1234yf:
• Cold room volume = 8m x 5m x 2.5m = 100m3. R1234yf
PL = 0.06kg/m 3 .
• Max charge = 100 x 0.06kg = 6kg.
The practical limit can be exceeded in machine rooms, but if this
is the case, the design of the machine room must comply with
EN378 and it will be designated a special machine room.
In addition to the limits above, EN378 also specifies overall
maximum charges – whichever is lowest applies.
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