Changing the batteries
Testo 550 uses 4x 1.5 V, AA batteries.To
replace the batteries please follow these few
steps below:
1. Fold out the hook (Pic. 1).
2. Grab the clip and squeeze it together
and remove the cap (Pic. 2).
3. Insert/Change the batteries.
Observe the polarity.
Power ON / OFF
1. Connect probes to the testo 550 prior
to powering it up.
2. Press the power button [ ] to turn testo
550 on.
3. All display segments are lit (2 s.)
4. Measurement view is displayed
5. Press the power button to turn the testo
550 off.
Set the refrigerant
1. Press the [R, Start/Stop] button so you
can choose the required refrigerant
(Pic. 3).
2. Use the arrow keys [pq] to scroll
through the choices.
3. Press the [R, Start/Stop] button to set
the chosen refrigerant.
Set the Units / Altitude / Mode
1. Press the [Set] button once to get to
temperature units menu (Pic. 4).
2. Choose the required units with the
arrow keys [pq].
3. Press the [Set] button for the second
time to be able to chose the pressure
units (Pic. 5).
4. Choose the desired units with the arrow
keys.
5. Press the [Set] button for the third time
so you select absolute or relative
pressure (Pic. 6).
6. Press the [Set] button four times, so
you can set the barometic pressure in
inHg (Pic. 7) .
7. Press the [Set] button ve times to
select the AC/R [ ], heat pump [ ], or
Auto [ ]. (Pic 8). Auto mode senses if
the Low pressure side is 15 psi higher
than the High pressure side, and will
automatically reserve the display of the
High / Low side pressures
8. Press the [Set] button six times to exit
the [Set]-menu.
Backlight
Testo 550 has a backlight to
improve viewing in dark or daylight
conditions. Press the backlight
[k] button to turn the backlight
on. Press it once again to turn the
backlight off.
Pressure zeroing
Please zero the pressure sensors before every use of the
testo 550.
1. Loosen the hose connections
2. Open the valve knobs to conrm no pressure in the
manifold
3. Press the [p=0] button
The sensors are now zeroed and ready for measurement.
Superheat / Subcooling
The testo 550 calculates superheat and subcooling in
real time.
1. Connect the temperature probes to testo 550.
2. Connect testo 550 and the probes to the air condi-
tioning, refrigeration or heat pump system.
3. Switch on testo 550.
4. You will now see the calculated
evaporation and condensation
and temperature (Ev and Co) and system pressures
at the bottom of the display, (Pic. 8).
5. Press the UP-arrow [p] once to see the tempera-
ture difference (D) (Pic. 9).
6. Press the UP-arrow [p] twice to see the real time
superheating and
subcooling (SH and SC) (Pic. 10).
7. Press the UP-arrow [p] for the third time to see the
real time measured temperature (T1 and T2) (Pic.
11).
8. Press the UP-arrow again to get to back to the
calculated evaporation and condensation tempera-
ture.You can also use the DOWN-arrow to switch
between the menus but the order will be reversed.
Leak Test
The temperature compensated leak test is used to indi-
cate leaks in an AC/R or heat pump system.
1. Plug in the temperature probe into the high side of the
instrument.
2. With the instrument off, simultaneously press the Set
and Mode while turning on the 550. This will turn off the
surface compensation to provide an accurate ambient
air temperature. Temperature surface compensation is
turned back on the next time that the 550 is turned on.
3. Zero the pressure sensors.
4. Connect testo 550 to the system.
5. Press the [Mode] button once to get to the leak test
mode (Pic. 12).
6. Now press the [R, Start/Stop] button to start the test.
7. Press arrow keys [p,q] to see the
measured temperature (Pic. 13).
8. The test duration depends on the system size.
9. Press [R, Start/Stop] again to stop the test.
10. The results will be displayed.
11. Press the [Mode] button twice to return to the normal
measurement mode.
Note: rP could be different from starting
and nal test pressure rP as the true rp is
calculated from the gas laws.
Pic. 13
Pic. 12
Pic. 11
Pic. 10
Pic. 9
Pic. 8
Pic. 7Pic. 6
Pic. 5
Pic. 4
Pic. 3
Pic. 2Pic. 1
Pic. 8
