Hitachi VRF Set Free - Cassette RCI

[Rafael Brazil]

Dears,

I have faced a problem on a Hitachi VRF Set Free FS5. In fact, the problem is just one cassette RCI model (RCI015A3F - RCI0409).

That cassette is not working well when the outside temperature is high (around 32° / 34°C). Even if the operating temperature has been set to 19°C, the temperature inside the room does not reach even 24° / 25°C. The situation becomes worse if the we switch on the following cassettes from the same refrigerant line. It seems that the cassette`s performance has been disturbed by some unknown reason.

When the outside temperature is not so high, no matter how many cassettes form that refrigerant line are working at the same time, the temperature inside the room reachs the desired value.

The refrigerant`s pressures were check and both are OK.

What may causes disturbs on cassette`s performance?

What may causes problems similar that?

What should I check or test?

I thank in advance for any help.

Cheers,
Rafael

[bigor_2]

This indoor unit has the largest length of pipe or not?
One reason may be the exceeding of the total capacity of the indoor units.
Eg 120-130% of outdoor unit capacity

[The Viking]

Well the first thing to check is the airflow around the outdoor unit…
Is it obstructed?
Has the outdoor coil been properly cleaned lately?
When the ambient is at 30-34ºC, what is the temperatures behind and in front of the outdoor unit?
What is the temperature going in to and leaving the indoor unit?
How many cassettes and what models is connected to which model outdoor unit?
.
.
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[install monkey]

your not supposed to run only 1 indoor on a vrf as the inverter pot will chug at say 20htz and performance will be poor- u need to run all units in test heat or cool and moniter the outdoor performance- old hitatchi's have a lcd display on the outdoor pcb which will show p errors- low output,running current out of range etc
used to have dip switches to enable test heat or cool

[RusBuka]

Whats the length of liquid pipe to that indoor unit?
SC temperature and temperature before and after subcooler?

[Rafael Brazil]

This is the second indoor unit. There is not a long length of pipe. There are more 5 units ahead, at the same pipe line.

[Rafael Brazil]

OK. Thanks. I have seen those dip switches. I will run test heat and cool and take a look at the display.

[Rafael Brazil]

The pipe length is not too long. This is the second unit at that pipe line.
I have to check the temperatures.

[Rafael Brazil]

The airflow around the outdoor unit is not obstructed.
I was cleaned one week ago.
I have to check the temperatures around the outdoor unit.
I have to check the temperatures going into and leaving the indoor unit.
There are 9 cassettes RCI models connected to a RAS24FS5 outdoor unit.

[frank]

Has the cassette been able to meet the temperature set point in the past when the ambient temperatures are high?

Have you done a heat load calculation for the room?

Is the cassette sized to handle the heat load?

As it meets the temperature set point when ambient temperature is lower (lower heat gain) then the cassette may not be sized correctly