Fujitsu Problem

[tennern]

I installed a Fujitsu a 12RQ unit a few months ago for my den. The room is about 325 sq ft. The unit will run until desired temp is reached and cycle off. The unit will then cycle on and off continually about every 4 or 5 minutes. Is the unit oversized or is there a problem with the unit?

[adams?]

when you say it cycles every 4-5 minutes do you mean that it comes on after 5 mins, runs for a minute or so, goes off and then comes on again after another 5 mins. if that it the case it sounds normal. if on the other hand it constantly comes on and goes off within the space of a minute then that could indicate a problem

[The Viking]

Dehum mode???

[a1onetimeagain]

You give very very limited info but.......perhaps the problem may be more due to undersize not oversize.
You say it's in your Den.
A 325sq ft den, containing PC, maybe a lazer printer good lighting and a large south facing window, aga in the kitchen downstairs??????

Freezing up anyone??

More info needed me thinks..

regards

[Makeit go Right]

may be more due to undersize not oversize.

Does the system maintain the desired room temperature easily, with it's frequent/short on periods? ie, If hardly any load, maybe the thing does not need to operate; if it struggles to maintain the room temp - that's the other side of the coin.

[koy]

My be the unit is short circling. Air flow bouncing of something to close, air flow reentering the unit giving false temp, unit thinking it's got the room to its desired temp?

[Gary]

The unit will then cycle on and off continually about every 4 or 5 minutes.

How long is it on?

How long is it off?

[tennern]

How long is it on?

How long is it off?

On for 3 minutes...off for 4 minutes,no matter what temperature setting

[The Viking]

On for 3 minutes...off for 4 minutes,no matter what temperature setting

Sounds like Dehum mode.......

[tennern]

Sounds like Dehum mode.......

not running in dry mode

[Andy]

Hi Guys

if it was a fridge I would say it is either over sized or the control (return air) sensor is picking up on air short cycling straight back to the return air grill form the discharge grill. Is the indoor unit free to circulate the air around the room.

Kind Regards Andy

[tennern]

Hi Guys

if it was a fridge I would say it is either over sized or the control (return air) sensor is picking up on air short cycling straight back to the return air grill form the discharge grill. Is the indoor unit free to circulate the air around the room.

Kind Regards Andy

yes,the indoor unit is free to circulate air

[Andy]

yes,the indoor unit is free to circulate air

Hi

then is it possibly over sized

Kind Regards Andy

[tennern]

Hi

then is it possibly over sized

Kind Regards Andy

with everything else eliminated then oversized must be the case....i guess the unit will short cycle itself to an early grave

[ernestlin]

whether the refrigeratory has the refrigerating duty or it's a empty room? If it's vacancy, there's not a problem.

[tennern]

whether the refrigeratory has the refrigerating duty or it's a empty room? If it's vacancy, there's not a problem.

i don't quite understand your answer...can you please elaborate

[ernestlin]

My speaking is if there's normal refrigeration duty when the compressor unit is working? Just as above mentioned points, if your compressor is over sized? If it is, the pull down time is too short results in the frequent ON-OFF action. But, if your fridge is empty when you run the refrigerated unit, the reason is the insufficient refrigeration duty, not the compressor.

[Si@airconworld]

Sounds to me like the compressor is running fine to start with but then is overheating and the short cycling is being caused by the compressors internal overload - as the compressor cools the overload resets and the compressor runs again until the overload trips again. If this is the case then there is a major problem. Check these:

1. Condensor fan operation
2. Refrigerant charge - abnormal charge will cause abnormally high compressor temps
3. Available air flow to condensor.

Hope this helps

[Brian_UK]

Sounds to me like the compressor is running fine to start with but then is overheating and the short cycling is being caused by the compressors internal overload - as the compressor cools the overload resets and the compressor runs again until the overload trips again. If this is the case then there is a major problem. Check these:

1. Condensor fan operation
2. Refrigerant charge - abnormal charge will cause abnormally high compressor temps
3. Available air flow to condensor.

Hope this helps

I don't think so, this size of compressor would need several hours to reset after an overheat.

[Stuart]

Sounds to me like the unit has reached set point and is cycling on & off normally. Is the fan on automatic this will cause the fan to start & stop.

[wombat]

What is the temperature of the air entering the front grille near the sensor?
Is the sensor in the correct location (not touching a cold coil).
Is the remote operating correctly? Such as changing fan speed, louvres etc.

[scott12]

i had this problem before with fujitsu .take out the return air probe and place it as far away from the unit as you can at ceiling height rejoin the cables by crimping .just use bell wire .and away it should go

[tennern]

This sounds like it might be a good solution. How did you conceal the sensor and wire? I have no attic to run wire thru. Any suggestions?