Techinical advice on Fujitsu AOT30RMAL?

[Taaz1275]

Please could someone advice on a situation that I cant figure out..on the given model unit, my compressor cant run....control comes from indoor unit to a relay that energizes and therefore closes contact from main power supply to a soft starter which I believe according to the wiring diagram should then brings in the compressor. "Off" the soft starter it goes to the compressor which has a start capacitor & a run capacitor. I have tested the capacitors which were okay , even ohms tested the compressor windings which were not reading to earth.....Could someone please advice other reasons that might be causing the compressor to run..I have changed the soft starter but still compressor wont run.....condenser fan runs but not compressor ...condenser fan does not branch off the soft starter ...
Please advice....

[nike123]

Did you checked resistance between C-R and C-S.
If there is infinite, internal overload is active and you should check again after compressor cools down after 2-3 hour.

[Taaz1275]

Thanks for your response Nike123, ...actually my problem is my compressor cant seem to run coz no power supply is going thru from the soft starter if Im correct,...just to quickly describe the soft starter: it has 6 terminals .....Terminal 1: is the feed from the main supply (L) on the NO contact of the relay( relay is controlled by the indoor unit when call for cooling)..im reading voltage on 1 when cooling is called for by the relay,..Terminal 2 links to the C of Compressor..TerminaL 3 Links to S and to Run capacitor,
Terminal 4 links to Start capacitor, ...Terminal 5 links to Run capacitor and to R of compressor..Terminal 6 links back to Neutral....
When relay coil energises (power comes thru as a signal for call for cooling from indoor unit) ...the NO contact closes and power goes to Terminal 1....that then should start and run compressor, but compressor never runs .....and doing my volt readings ...voltage only shows at 1 but not on any other terminal on the soft starter.....
..but anyway I will check for ohms reading on CS & CR & SR....I think I did at first and the readings were okay ...as it adds up to the third ohms reading....

[paul_h]

Soft starter should put out voltage on terminal 2, if it doesn't, maybe it's cutting power due to compressor fault.
Megger compressor, check amps when it's trying to start, or bypass the soft starter all together and see if you can the the compressor running.
You can't leave the soft start bypassed as the relay isn't big enough to handle normal start current though.

[coolhandlew]

Hi, Do you have a wiring diagram for the soft starter. I would have thought it should have had an unswitched live direct from the supply and a switched live from your relay/contactor.

[nike123]

Thanks for your response Nike123, ...actually my problem is my compressor cant seem to run coz no power supply is going thru from the soft starter if Im correct,...just to quickly describe the soft starter: it has 6 terminals .....Terminal 1: is the feed from the main supply (L) on the NO contact of the relay( relay is controlled by the indoor unit when call for cooling)..im reading voltage on 1 when cooling is called for by the relay,..Terminal 2 links to the C of Compressor..TerminaL 3 Links to S and to Run capacitor,
Terminal 4 links to Start capacitor, ...Terminal 5 links to Run capacitor and to R of compressor..Terminal 6 links back to Neutral....
When relay coil energises (power comes thru as a signal for call for cooling from indoor unit) ...the NO contact closes and power goes to Terminal 1....that then should start and run compressor, but compressor never runs .....and doing my volt readings ...voltage only shows at 1 but not on any other terminal on the soft starter.....
..but anyway I will check for ohms reading on CS & CR & SR....I think I did at first and the readings were okay ...as it adds up to the third ohms reading....

Yep, you are right, soft starter is faulty if no other than terminal 1 have voltage. You should have 220 (240)V between terminals 2-5 and 2-3 when running, and aditionaly 2-4 when starting and running.

[nike123]

Hi, Do you have a wiring diagram for the soft starter. I would have thought it should have had an unswitched live direct from the supply and a switched live from your relay/contactor.

.....................

[Taaz1275]

HI nike123,

Thats the correct wiring diagram, I havent found time to attend back to that job but will soon and will update you and the rest of the guys out there when thats done, but it's really great to be getting all ideas as to how I can tackle this fault....oh ,yeah I have changed the soft starter as well but the problem still exists, ...I will try to megger the windings and see how it goes from there....thanx, I gotta run now....

[Taaz1275]

Hi Guys ; nike123,paul h,coolhandlew,:
Thanks a lot for the contribution into helping solve my problem.
I have megger tested the windings to earth, ...and it shows that the windings has leakage ...used the MegaOhms Range (500V)...and for each winding it read 10.2 MegaOhms and then slowly rises in value till it reaches 90.3MegaOhms ...., I have ordered a new replacement compressor and surely feel that it should solve the problem.
Please if any of you think otherwise then do advice.

Anyway, once again, thanks very much guys!!!!!

[paul_h]

Anything above 10Mohm is usually OK, it's only when you get down to 2Mohm and below are things likely to give trouble.
As I said, the soft starter MAY be cutting power because there's a problem with the compressor.
Have you tried bypassing the soft start and running the compressor DOL and measuring the amps, seeing if it starts OK and draws the right current, pumps OK etc?

[nike123]

That insulation value should not produce any trouble and you could cancel order of new compressor for that reason.
http://www.flukecommunity.com/forums...tachmentid=581

[Si@airconworld]

Replace the soft start with a contactor, they suck

[Curnow]

G'Day Gang,

I've just come across a similar problem.
My question is when substituting the soft starter with a contactor is it ok for the start winding to be permanently connected? I am not sure if the soft starter drops the start winding off after the compressor starts.

Cheers
Dennis

[paul_h]

The start winding is permanently connected on these compressors (nearly all a/c compressors) as they are PSC.
Soft start relays only create circuit for the extra capacitor.
Hope you're not just fitting any cheap undersized contactor, and are using one rated for more than just FLA.
The right sized contactor costs about the the same as a soft starter, and you get your house lighting dimming every time the compressor cycles on.
I normally do away with soft starters on smaller units, but not the 30k BTU ones.

[Curnow]

Thanks Paul,
I mainly want to make sure the compressor is ok then decide which way to go. Replace soft starter or fit a contactor.

Cheers
Dennis

[paul_h]

Remove cable at #1 terminal, fit to #2 terminal (so 2 black cables there). remove cable at #5 terminal, fit to #6 terminal (so grey and white cables together there). Disconnect #3 and #4 and the (95uF?) capacitor they go to. Disconnect that (95uF?) capacitor from the 45uF capacitor.
Start unit with a clamp meter measuring current from compressor common. If amps high or compressor stalled, soft start is probably good, but the 45uF capacitor or the compressor is bad.
So before playing around with the soft starter, better to check the compressor windings (take electrical cover off and inspect the spade terminals for burning/melting and check winding resistances), and test the 45uF capacitor first anyway.