Fieldpiece SRH2 - Diagnostic Psychrometer - Manual (Page 2)

Air Conditioning Basics
The Evaporator, Condenser, Restrictor
(Throttling valve) and Compressor are the four
basic components of an air conditioner. Following
one pound of refrigerant through the system shows
the function of each component.
Subcooled liquid refrigerant at high pressure
enters the restrictor and is throttled to saturated
refrigerant at a lower pressure. The restrictor can be
of either a fixed or TXV/EXV type. The fixed type
must be charged to a target superheat that varies
with indoor and outdoor conditions. TXV/EXV sys-
tems must be charged to subcooling.
The evaporator capacity varies with the indoor
heat load on a fixed restrictor. The TXV/EXV regu-
lates the size of the restriction to maintain a con-
stant superheat. This essentially adjusts the capac-
ity of the evaporator responding to the indoor heat
load.
After the restrictor, refrigerant enters the evapo-
rator at a low temperature and pressure and boils
(evaporates) into a gas by absorbing heat from the
indoor air. The refrigerant stays at the same tem-
perature and pressure until all the refrigerant evap-
orates into a gas. After the refrigerant becomes a
gas, it will continue to absorb heat and become
superheated at which point its temperature will
change. The Superheat measurement is the best
indication of refrigerant charge level in a fixed
restrictor system. A TXV/EXV system will keep the
superheat constant. There must be superheat pres-
ent to ensure liquid does not flood the compressor.
Superheat measurements are taken on the suc-
tion line between the evaporator and compressor.
The compressor takes this low temperature, low
pressure, slightly superheated refrigerant and com-
presses it to a much higher temperature and pres-
sure.
The highly superheated gas enters the condens-
er and rejects heat into the outside air. The refriger-
ant condenses back into a liquid. Once all of the gas
is condensed into a liquid, additional removal of
heat causes a temperature drop that is known as
subcooling. TXV/EXV systems are charged to sub-
cooling since superheat is controlled by the throttle
valve. Subcooling measurements are taken on the
liquid line between the condenser and TXV/EXV.
Finally, the subcooled liquid enters the restrictor
and the cycle starts again.
Specifications
:
Operating temperature: 0 to 122°F (-18 to 50°C)
at <75%RH
Storage Temperature: -4 to 140°F (-20 to 60°C) 0
to 80%RH with battery removed.
Low battery indication: The is displayed when
the battery drops below the operating level.
Battery Life: Approx. 150 hours (9V alkaline)
Auto Power Off: After 15 minutes of non-usage.
Temperature (K-Type Thermocouple):
Range: -58 to 1832°F (-50 to 1000°C)
Accuracy: ±1°F 50 to 113°F (±0.5°C 10 to 45°C),
when calibrated to NTC at room temperature
±(0.1% rdg+2°F) -58 to 1832°F
±(0.1% rdg+1°C) -50 to 1000°C
Temperature (NTC):
Range: 32 to 140°F (0 to 60°C)
Accuracy:
±1°F 50 to 113°F (±0.5°C 10 to 45°C)
±4°F 32 to 50°F and 113 to 140°F
±2°C 0 to 10°C and 45 to 60°C
Relative Humidity: 0% to 100% RH range
Accuracy: ±2.5% at 77°F (25°C), 10% to 90%RH
±5% at 77°F (25°C) 0 to 10% RH & 90 to 100%RH
Dimensions: 7.9”(20cm) x 2.6”(6.6cm) x
1.4”(3.6cm)
Weight: Approx. 11oz with battery installed
Accessories: (ATA1) K-type dry bulb thermocou-
ple w/ clip, (ATWB1) K-type wet bulb thermo-
couple w/ clip, battery and Operator’s Manual.
Warranty and Service
The product is warranted to the original purchas-
er against defects in material or workmanship for a
period of one (1) year from the date of purchase.
During the warranty period, Fieldpiece Instruments
will, at its option, replace or repair the defective unit.
This warranty does not apply to defects resulting
from abuse, neglect, accident, unauthorized repair,
alteration, or unreasonable use of the instrument.
Any implied warranty arising out of the sale of
Fieldpiece’s products including but not limited to
implied warranties of merchantability and fitness for
purpose are limited to the above. Fieldpiece shall
not be liable for incidental or consequential dam-
ages.
Return any defective SRH2 to Fieldpiece for
warranty service along with proof of purchase.
Contact Fieldpiece for out of warranty repair
charges.
v28
Auto Power Off, to
disable/recactivate,
hold MAX/MIN/HOLD
button while turning on
SRH2
Low battery
indicator
Relative humidity, dew point, wet bulb, or dry
bulb being measured and displayed on upper
display, press the RH/DP/WB/DB to change
Shows which sensor is being used,
Press SENSOR button to choose
Upper display shows
measurements
Lower display shows
calculated Target
Superheat and Target
Evaporator Exit Temp
Press TSH/TEET/NORM
button to change between
Target Superheat, Exit
Temperature and Normal
Psychrometer mode.
Toggle displays MAX MIN,
HOLD or measure in real-time
by pressing the MAX/MIN/H
button
Outdoor Indoor
Direction
A-Coil
Filter
Fan
Dry Bulb and
Wet Bulb T/C
Dry Bulb T/C
Supply Plenum
PRESS FOR 1 SECOND
BATTERY
CHECK
AUTO-OFF
Figure 3
Figure 2
Figure 1
WARNING
If creating a hole in the return or supply
plenum is necessary to take accurate measure-
ments, make sure you do not damage any equip-
ment.
Plug any hole that may have been created in
the supply or return plenum with an air-tight,
long-lasting plug.
! !