citi multi question

[kklobas]

hi, just starting to work at hotel with 20 outdoor citi multi units. i was wandering if it's worth finding an inverter checker (in usa) or will i be ok checking for balanced voltage output at inverter board?

[kklobas]

we have maintaince tool on laptop. what is cms-mng converter?

[Koopy]

the maintenance tool and converter is the bomb.

The converter allows your computer to talk to the citi multi network and the software

[Thermatech]

The Mnet monitor can giva an indication of inverter dc voltage & compressor run amps with data update every 60 seconds.

But typically if there is a problem with the inverter circuit or compressor locked / ground fault then the outdoor unit stops on a fault within a few seconds of comp start up & so you wont catch it on the 60 second update snapshot.

So to some extent you are better off setting SW1 on outdoor unit to monitor comp amps on the outdoor unit display which then gives you constant live data & start the compressor. Then you can also monitor the inverter output supply with a clamp meter.


With compressor inverter problems the acid test is always to mega the comp windings & measure the inverter for ballanced supply ( stand alone disconnected from the comp ) & the Mnet monitor does not do that for you.

So whatever data you see remotely on the Mnet monitor you will still have to test the compressor & inverter with appropriate instuments to confirm exactly what the problem is.
The lazy way is to use an inverter checker type tool which will give an indication of the inverter output ok or not ok.
But measuring the output with a meter gives you the real voltage data.

When you are commissioing to test the outdoor unit 3ph power supply do you use a 3ph power supply check tool & record on the commissioing sheets a pass / fail for power supply as indicated by your power supply check tool ?
or
Do you use a multi meter & record on the commissioing sheets the actual voltage on each phase ?

If you are competent to measure the incoming power supply to the outdoor unit & make judgement that it is ok or not ok then I would suspect you also should be able to measure the inverter output & make judgement ok or not ok.

The real skill is in being able to test all the inverter circuit components & identify which components have failed & then rebuild the inverter with new parts & get the system running again.

[kklobas]

i noticed in the service manual it says not to use a digital multi meter to measure voltage of inverter circuit but that you must use an analog meter? i'm not new to hvac or testing with multi meters etc.. but have not worked with the citi multi before. planning on takeing mittsubishi service course in october. any other advise would be welcome. thanks

[Thermatech]

The old type analog meter is best for testing the inverter circuit components like TRM's , IPM's , Diode stack bridge rectifiers after they have been removed from the circuit.

But digital multi meter is ok for measuring final 3ph power output from the inverter to ensure ballanced supply to compressor.

[kklobas]

thanks for all replys.