Mitsi inverter puhz p125 trips power

[gwm121]

Mitsi puhz p125 vhaz 12.5kw s/phase inv R410 twin fan has been running on 20 amp breaker 5 years but this month tripping out after 20 mins running consistantly.

With clampmeter, compressor start 7 amps, 3 mins later revs up 14.3 amps 2 min later revs up 19.7amps, 3 min later revs up 25.6A then circ breaker trips.

Suction starts static 200 (after running 10 mins ago) , down to 140 at start run (7 amps) then settles later at 110/1120psi

discharge 190/200psi AT 3 WAY VALVE not compressor output.

Suction 3 way valve sweating, ambient 20 degrees, fans on low speed most of the time, coil warm to the touch. Air off hot, 36 degrees

OBVIOUSLY.. the fuse and wiring will be changed to 32 amp, but so I know what may happen later, can anyone advise me if a 12.5kw mitsi cassette dealing with a reasonable load (top floor office flat roof) would be expected to ramp up to 26 amps. The machine spec shows 17.3 run 28a max. (what exactly is "max") ...Idont like it when something that worked for 5 years albeit on wrong circuit breaker, suddenly behaves differently.

[paddyaircon]

I would check the mains connection terminals on outdoor unit- possibly loose or arcing ?? and also check your isolator for water ingress, sounds more like power supply fault- btw where are you measuring your current?

[install monkey]

is it a motor rated breaker? megger just the compressor to test the insulation,the inverter circuit will protect from overcurrent but not earth leakage.check the supply cable isnt rubbing on the casing

[gwm121]

In essence starts at 6 amps, then every few mins the compressor ramps up (can hear it easily) till after 20 mins 24 amps...... so is 25 amps normalfor this type of kit? no rubbing cable breaker is going at 24 amps what i want to understand is is this current normal.

When compressors fail can they draw high current but still show 110 suction and 200 discharge at 3 way valve high side?

I asssume this wouldnt be low gas with these pressures.... I know its difficult to check now without reweighing as inverters try and compensate.

No loose arcing wires wont be water in isolator as can hear inverter spinning up and thats why current going up.

spec for this 12.5kw unit 17.3 amps 28kw max ....with the Fujitsus i usually use they allways run around the running current, never anywhere near their max, so uncertain here with mitsi.

[install monkey]

its not a server room in battersea with a condenser in an underground carpark?

[install monkey]

are u clamping on the compressor leads or the terminals on the supply cable/fuseboard

[gwm121]

Clamping on terminal leads to outdoor unit, measuring total curent taken by system, current goes up progressively with the "operating whine" from the compressor from 6 amps start to 25 amps... id loke to know if 25 amps is normal or not normal if anyone knows for this unit

[install monkey]

you can restrict the compressor by adjusting the dipswitches on the outdoor unit to set the max frequency to 75% or less.could be compressor siezing.
would u like me to forward a manual if so please advise on training credentials,swimming certificates,and other relevent experience! haha

[gwm121]

Hi Instal monkey,
Thank you for reply re dip switches, that is useful, I can get manual from mitsi tech. usual quals and 16 yrs experience, but mostly on Fujitsu which is what we fit.

What should happen and will, is the circuit breaker is changed for the correct one and diagnisis continues. however I cant stop thinking about this, and would feel happier if i knew that in 20 degrees ambient for a largish top floor offec 8 people modern computors and FLAT ROOF, indoor temp 26 degrees, system set point 21 degrees, would it be normal or not normal for this mitsi 12.5kw system to ramp progressively up finally end up the compressor running hard and drawing 25 amps. Spec is 17.3 amps run 28 amps max. on a Fujitsu we would never expect to see the running current exced by much. on Mitsi i have no idea if max is max running current or max it can take before a problem.

If comp is starting to sieize wouldnt this show as a faiirly immediate rise in current. (its taking 15/20 mins)
If it was an earthing fault also tripping should be fairly immediate
If it was a gas fault dont think would get 110 /120 suction .. though appreciate have to weigh charge to be sure.

so really want understand what is a normal current this unit under load.
Reducing max fequancy as you suggest sounds a good short term solutiion afterr breaker changed.

[install monkey]

u have mail!

[polarpodge]

if its in 6 years has the indoor coil been cleaned in dat time its seems like a progressive problem rather than something that happened overnight, only way to find out is clean both coils pull the charge and work from there

[a/c.king]

Hi gwm121
If you have unit with spacified max currnt drow of 28Amp you should have 4mm calble for power supply and 32Amp breaker.
If you ave 32Amp breaker installed but unit still triping.then you need to sheck the inverter compresso if it is nosy more then usual and vibrating this means you have mechanical fult on the inverter compressor.
If you have the 32Amp breaker installed and the inverter compresor exceed the 28Amp it should not trip the breaker instead the CT should detact the over currnt in it should indecate i fult code on the controller or on the indoor or out doorPCE LED'S

GOOD LUK
a/c king

[polarpodge]

forgot to mention to check the invertor power board make sure it delivering voltage to the compressor equally through each phase. u can test this with an invertor checker