Carrier 30XA 0502 HIGH PRESSURE

[Palkoper]

Hi Guys I am so unhappy because really dont know what is a reason to high pressure on Carrier XA 30 R134A refrigerant .

Circuit A work perfect no problems at all but circuit B high pressure its slightly higher 11 - 13 Bar .

1 - Condenser is clean as brand new .
2 - All fans running perfect no inverter driven ...
3 - Suction pressure 2,3 bar
4 - Superheat 8 K


So any suggestions what cold be a reason ???

It happen one time within 20 days

[install monkey]

short cycling of rejected cond airflow?- can you enable circuit b only (disable circuit a) and see if that cures it
compare td's accross liq drier
degass and comfirm the charge.
test hp switch trips at stated pressure

[Palkoper]

Thanks a lot BTW it cant be one of solenoid on compressor because 12 bar it was holding on 30 percent ... How to check if those two solenoids working properly ( magnet ? ) ?? On screw compressor those solenoids controls discharge pressure I am right or not ?


Thanks anyway it helps a lot !!!

[install monkey]

http://www.mediafire.com/view/?53o7z3oyyoib6y0
operation manual- few notes below

Head Pressure Control —
The Main Base Board
(MBB) controls the condenser fans to maintain the lowest
condensing temperature possible, and thus, the highest unit efficiency.
The MBB uses the saturated condensing temperature
input from the discharge pressure transducer to control the
fans. Head pressure control is maintained through a calculated
set point which is automatically adjusted based on actual
saturated condensing and saturated suction temperatures so that
the compressor(s) is (are) always operating within the manufacturer’s
specified envelope (see Fig. 31). Each time a fan is
added, the calculated head pressure set point will be raised
25° F (13.9° C) for 35 seconds to allow the system to stabilize.
The control will automatically reduce the unit capacity as the
saturated condensing temperature approaches an upper limit.
See capacity overrides #16-18. The control will indicate
through an operating mode that high ambient unloading is in
effect. If the saturated condensing temperature in a circuit exceeds
the calculated maximum, the circuit will be stopped. For
these reasons, there are no head pressure control methods or set
points to enter. The control will turn off a fan stage when the
condensing temperature is below the minimum head pressure
requirement for the compressor. Fan sequences are shown in
Fig. 31. See Table 38 for compressor nominal capacity.


The 30XA units utilize
screw compressors with a modulating slide valve which varies
capacity from 30% to 100% of compressor capacity for each
circuit. See Fig. 49 for a view of a typical 06T compressor.
The slide valve position is varied by opening and closing the
2 solenoid valves located on the compressor. To unload the
compressor, both solenoids are deenergized. To increase in
capacity both solenoid valves are energized together which
will cause the slide valve to slide towards the fully loaded
position. To stop the loading process solenoid 2 is energized
and solenoid 1 is deenergized. This will cause the slide valve to
maintain its current position. There is no feedback for the position
of the slide valve. The control utilizes compressor current

as an indicator of the slide valve position. Once the calculated
position of the slide valve reaches 100% circuit capacity, the
control will try to increase capacity again if the compressor
current continues to increase. The control will continue to load
the compressor until the compressor current no longer
increases. At that time the control will energize both solenoids
and the circuit will be considered fully loaded.

[THE DUDE]

Verify the Discharge Transducer are reading correct. Check The Discharge Transducer and Temp sensor with external Gauges and Thermometers. Ive had a few bad Discharge transducers lately

[serviceman]

has electric valve in the discharge? verifies that the two valves open,

[kumaraudhesh]

Plz. maintain the suction super heat 0 to 6 digree