Fujitsu ARY-A12LATN (problem on auto)

[pen_ster2002]

Hi All,

Sorry for my first post to be a request for help. I am a regular visiter to the site, and have learned alot from here. I mostly do installs so am lacking the knowlege of a service engineer. I got called out to a local hotel that is having problems with a Fujitsu ARY-A12LATN concealed unit. The unit works fine if cooling mode selected, and fine in heating mode. However when Auto function is selected units fan speed drops down (monitor mode). If you increase target temp unit picks up and heats the room. However drop the target temp it falls back in to monitor mode and stays there, even with target temp set to 18c actual temp 26c it does not pick back up. The actual unit is installed in a roof void probably 6m3. The unit is ducted into the room, however the return air is via a grille straight into the roof void (not ducted back to the unit). There is a remote air temp sensor sat behind the return air grill.
I have changed the program on controller to measure room temp from wired remote but still has same fault.
I dont think it's a faulty controller because when target temp set to 18c and room temp being around 25c in auto unit just monitors, change mode to cooling and unit picks up and cools room nicely. Any help would be appreciated.

[nike123]

Is that unit on VRF system or single?
If it is two pipe VRF then it cannot change to other mode if main control is not set to that other mode.

This is from USER MANUAL:

Instructions relating to inverter (❖) are applicable only to “INVERTER
MODEL”.
❖
Operation cannot be done in the following different operating
modes.
If the indoor unit is instructed to do an operating mode
that it cannot perform, will be shown on the remote
controller display and the unit will go into the standby
mode.
Heating mode and cooling mode (or dry mode)
Heating mode and fan mode
❖
The operating mode (heating mode or cooling (dry) mode)
of the outdoor unit will be determined by the operating
mode of the indoor unit that was operated first. If the indoor
unit was started in fan mode, the operating mode of
the outdoor unit will not be determined.
For example, if indoor unit (A) was started in fan mode
and then indoor unit (B) was then operated in heating
mode, indoor unit (A) would temporarily start operation
in fan mode but when indoor unit (B) started operating in
heating mode, will be shown on the remote controller
display and it would go into standby mode. Indoor
unit (B) would continue to operate in heating mode.

[pen_ster2002]

It is a single split system. Forgot to mention Fujitsu told me to ensure switch 5 was to on in the wired controller, still no change. They said they will get back to me (last week).

[paul_h]

When you fitted the remote sensor, are you sure you plugged it into the right plug?
I've seen a few where they were crossed over and plugged into the pipe thermistor plug instead of the air thermistor plug.

[pen_ster2002]

I didn't fit it. Will check, but dont see the point in the remote sensor as you can use the wired controller for measuring room temp. I will remove the remote sensor and make normal connections see if it helps.

[nike123]

Check this, it is how it should behave.

http://farm4.static.flickr.com/3238/3042756169_6a1008389c_b_d.jpg

Check your outdoor air temperature sensor for proper resistance/temperature ratio

http://farm4.static.flickr.com/3060/3042784447_7f42a9f72f_d.jpg

[paul_h]

I didn't fit it. Will check, but dont see the point in the remote sensor as you can use the wired controller for measuring room temp. I will remove the remote sensor and make normal connections see if it helps.I'm just thinking out loud :D
Even when you are using the keypad thermistor for air temp, if the remote sensor is plugged into the pipe sensor plug, the unit is going to be getting weird pipe sensor measurements that could make it unhappy in auto mode.

[pen_ster2002]

Thanks for that nike clears a few things up Tb 25 Ts 18c+2c should cool is monitoring. Will check thermistors values. Thanks again.

[Brian_UK]

Might be a dumb question but how long are you waiting for the system to change over from heating to cooling?

[pen_ster2002]

Sorry I have not replied untill now. Have been back to the hotel. The problem was that the roof void the unit is in is quite cold. Even when you change control so it should be measuring room temp from wired controller it is still taking it from the return in the roof void. As soon as I warmer thermistor on units return it started cooling as it should. I wired the remote air sensor into the room and all is now fine. Strange about the wired controller. Changed the program heard inside unit beep to say it acepted the change, get the little icon on the controller, but warm the thermistor on it nothing happens. Get into roof void warm thermister on the return and it works.