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PMRefrigeration Tool page |
'Q & A' style application examples
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| A
real-life situation - someone recently supplied this partial
set of data on an HVAC system. I ran it through PM Refrigeration
Tool , as below. Notice the analysis report. The
person working on the system found that the piston was missing from the
system entirely, from the factory, on this 1 year old system. Follow the below screens in order and see what
this program had to say about it. It correctly identified the
possible problem as 'metering device open', and warned of compressor damage !!! |
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data available, even if not complete, and run the 'Full Report'. |
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the report ( some pages of extra detail not shown here ) |
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the analysis, correctly diagnosing the problem, even from partial data
as above. |
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Given a VAV system that is currently moving 55,000 CFM SA,
including 25 % OA, on a summer day, what is the load created by the OA
? What is the mixed air point ? What is the total system load
against a desired supply air condition of 55 degrees F, 90 % RH at the VAV
boxes ?
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First, use the Percent OA calculator to obtain the CFM of the RA
and OA, and enter them into States 1 & 2 with your RA and OA numbers,
then run the Mix process.
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You see that your OA is adding 99 tons of
load to your system ( compared to the RA ), 68 tons of which is latent
load.
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| Now, leaving
your mixed air point in state # 3 alone, enter your SA data in State # 1
and calculate that point, then run the Deltas report. You see that
your total load is 330 tons, 212 tons of which is latent load.
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What is the effect of adding xxx BUTH or KWH of heat to
a system ? There 2 ways to do it in the program - the
'short form' ( temperature rise method ) and the full psychrometric
method ( which requires a few more pieces of input data ) |
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| In the 'short form',
often called 'temperature rise method', you choose 'Temp rise - heating'
from the psychrometric calcs list, and input CFM plus any other factor (
in this example, 10 KW of strip heat added to a 3 ton system) |
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the ' full psychrometric' method', you first enter and calculate an
entering state point, then specify your heat in BTUH or KWH, and you may
optionally run ' Deltas' also, if you require that information.
Full state points are calculated. |
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