USE OM - JANUARY 2017
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5.5.3.1
ASHRAE Standard 37 Section 7.8 outlines a method for calculating the latent capacity
based on the mass flow rate of the cooling condensate draining from the indoor coil for equipment with
a rated capacity of 135,000 Btu/h or higher that use an indirect method for determining airflow rate.
This appendix shall apply the same methodology to equipment with a rated capacity of 65,000 Btu/h
or less with a direct measurement of airflow rate.
5.5.3.2
The required setup for running the latent capacity test is to connect tubing between
the condensate drain on the indoor coil and a secondary reservoir. A drain trap shall be used in the
tubing between the outlet of the condensate pan and the secondary reservoir. The drain trap shall be
installed per the manufacturer’s installation instructions. The secondary reservoir shall be placed upon
a scale capable of measuring weight to the nearest 0.01 lb or in a container capable of measuring
volume to the nearest 0.1 oz.
5.5.4
Running the Test Procedure
.
5.5.4.1
The Tests required in Sections 5.1 through 5.3 of this appendix shall be performed
prior to the latent capacity testing.
5.5.4.2
The blower fan speed shall be set to the lowest airflow setting.
5.5.4.3
The system shall be run at the A or A
2
condition for at least five (5) consecutive A tests
during the cooling Tests of the Full System Psychrometric Round Robin Testing (see Section 5.4).
5.5.4.4
The condensate mass flow rate draining off of the indoor coil shall be measured during
each of the five (5) consecutive A or A
2
Tests.
5.5.4.4.1
At a minimum, measure the weight or volume at the beginning and at the
end of each individual A or A
2
Test. Calculate the difference and divide it by the total
time (0.5 h in this case) to obtain the condensate mass flow rate.
5.5.4.4.2
A preferred method i
s to connect the scale to the lab’s data acquisition
system to log the data for the entire A or A
2
Test. The reservoir should be emptied as
needed between tests to avoid overflowing.
5.5.4.4.3
If the condensate mass flow rates from the last three (3) A or A
2
Tests
meet the requirements of Section 5.5.6.3, then the Latent Capacity Measurement
testing is complete. If the requirements are not met, then either a) adjustment to or re-
calibration of the Laboratory Facility equipment shall be performed, or b) consecutive
A or A
2
Tests shall be continued until the requirement is met, with a maximum of 10
consecutive Tests. Any and all tests required by this Standard that may potentially
have been affected by adjustments or re-calibration shall be re-run.
5.5.5
Minimum Data Collection Requirements
5.5.5.1
All of the data from Section 5.4.5 and the following additional data shall be recorded:
w
c
= condensate mass flow rate, lbm/h
B
LC
= latent capacity energy balance, %
