LG UB36NGB boring problem...

[cool#9]

Hi everyone
Have to repair LG UB36NGB+UU37UEB : non inverter split ducted type r410a, 2 years old.

1st: the 2 small fuse blown; one on outdoor pcb (3.15amp) and another one from R phase (5amps) suppling the indoor unit from the outdoor side, change them, everything's alright for 1 hour then fired again !!!
2nd: I've check indoor/outdoor fans, relays, compressors one by one, check the whole control-circuit, etc...
3rd : change the fuse again, wait for 1 hour and leave...the customer called me 2 hours later " Mr ***** my LG doesn't work anymore, are you sure you're relevant enough ?!!"
4th: i decide to order new pcb but i'm afraid it will be the same.
In addition let's say indoor pcb fuse and outdoor neutral fuse from N terminal never failed. See attachment.
When the problem occurs the circuit breaker goes down as a short circuit fault but not the RCD breaker.
Strange !!!
Awaiting for advices, hope HENDRAG will read and help, thanks
cool#9

[monkey spanners]

Hi cool#9
From looking at the diagram the fault has got to be on the outdoor unit either the fans, reversing valve, the things labled TP in comp A and B or the wiring to them. why not compare the resistances of the thing you have two of.failing that, you could wire in an inline fuse to each and see which one blows, not very technical.

Jon

[cool#9]

Hi monkey spanners
I'm afraid this trouble will lead me to your solution...
Got to choose lower amps fuse to do it as well...
Hope someone on the forum had the same problem and found.
If not i'll maybe modify the machine and explain to my customer it appens only on LG outdoor unit ?!
thanks so much
cool#9

[Contactor]

Can't get my head round this one at all. I think M. Spanners is heading in the right direction with the outdoor unit. Is T/B1 a timeclock alternating the motors after an hour during low loads? However if you have checked all the motors could this be overcurrent on the R phase itself? How is the RCD wired?

[momo]

Probably far fetched, but...
1. fault on Signal line [3]
2. Check S, T and N lines if R for some reason has a higher resistance (e.g. faulty contact in circuit breaker) the current imbalance will run through the fuses into other parts and blow the fuses.
Corrosion, loose screws, irregular vibration, wire loose, shorting winding on compressor could also lead to this irritating irregular trrouble.

[coolments]

Hi Cool 9


Not familiar with this kit but heres my thoughts, I am tending to lean in other directions after reading this, the black and white wires after CM comp conection on the PCB i assume are the run signals for the compressors that pass through the compressor thermal trip (normally closed) then through the secondary protective device / timer (Not sure what that is but is also normally closed) and finally onto the coil of the contactor (a1) to energise it and bring on the compressors. I would expect a fuse to blow instantly on compressor demand if there was problem with these as they dont draw much current and an electrical short circuit would be needed to blow fuses.
The condenser fans how ever draw current from this fuse so i am leaning towards them, i would look at the capacitors to see they are ok as if they are tired you may be getting intermitent starting or high current draw on there start up. also one of the fans may have a dry bearing so run ok when cold but after a while over heat and swell up making it harder for the fan to spin also causing excessive run current. Maybe indepent fuses on each fan maybe a good idea.
One other thing to consider, has the unit got a condensate pump fitted and wired off the indoor isolator, if so this could also have a short circuit thats causing fuses to blow as the short tracks back through the electrics.
After looking at the above and also what others have mentioned i would also be ordering a new PCB.

Intermitent faults..........dont you just love'em.........Not..!!!!!!!!. good look with it cool9.

[monkey spanners]

Just thought of a problem i had with a 3ph fan motor. the thermistor in the windings (wired into control circuit) shorted out to one of the phases suppling the motor, this blew the control circuit fuse as it was on a different phase (415 across control circuit) is the thing labeled "TP" in the compressor? Short could also be in the wiring.

Jon

[cool#9]

Hi thanks everyone for suggestions.
Coolments: there's no pump indoor as it's an option for UB 36 unit. I'll check outdoor fan capacitor also.
Jon: i'll check the wiring of control circuit that follow power circuit, maybe an insulation problem with the power cords of the compressor or something like that...
Momo and Contactor: i'll follow advices, the RCD is above the airconditionner circuit breaker.

I forgot to tell you the system run non stop and rarely cut by thermostat off due to poor installation capacity so i think it maybe link with a compressor overload and/or overheat...
ok, i'll go back to this problem before i get a new pcb and try electrical test with the actual pcb, helped by your advices ive a new motivation to go ahead !!!
rgds
cool#9

[Jase]

Are the contactors for compressors in good condition?
Possible arcing?
Check contactors when operating by carrying out mV test across contactor. All readings should be within reasonable balance of one another.

Regards
Jase

[hendrag]

Hi the problem is with the indoor unit or the 4 way valve or the outdoor fan motors. Assuming both fans are running and the beast is in cooling it wont energise the 4 way valve (heating) but if its switching over this could be the problem. On the indoor there is not much to go wrong the pump runs all the time the compressor is running in cooling but doesnt run in heating and the fan is on most of the time. Its a wierd one this if you get this in time call me tomorrow on 08708720791 option 4 we will sort you out.

Hope we can help

regards

hendrag

[cool#9]

Hi Hendrag and glad to meet you on the forum again !

The system runs only in cooling mode and there's no additionnal pump in the UB36NGB (as it is optional).
I remind you the indoor fuse never blown...
Next days i'll test again the whole parts and of course i will tell what i found (i hope so).
Thanks for your calling invitation but before i've to be sure it's not a simple eletrical part failure...
rgds
cool#9

[philjd26]

hi,

to me it looks like an indoor thing,transformer maybe..however why not try dry running everything for an hour i.e...disconnecting compressors,fans,4 way valves and just have the control work and maybe put an amp meter round the cable see what been pulled through that cable...

[Contactor]

Hendrag - what is T/B1? Is there a guide available for LG wiring diagram abbreviations?

Thanks

[Mac1]

Hi, the problem sounds like it is almost certainly to do with the Outdoor Unit control side wiring.
Check the Control wiring from CN_Comp to the Compressor. In the past I've seen abrassion on these wiring looms where they rub against the discharge pipework and intermittently short out.

Rgds.
Mac1

[hendrag]

its a shot in the dark but intermittant faults are the hardest to fix. if the compressor power leads rubs against the hot pipework the insulation wears through and the unit shorts against the pipework . its a bugger to find unless there is visible damage to the insulation/ pipework. Check all the wiring to the compressors to see if this has happened.

keep us posted on what you find

regards

hendrag

[cool#9]

Hendrag - what is T/B1? Is there a guide available for LG wiring diagram abbreviations?

Thanks

In my opinion that mean Terminal Block 1 for commun neutral wires, but what's exactly above with EOCR-A and EOCR-B ?

[cool#9]

its a shot in the dark but intermittant faults are the hardest to fix. if the compressor power leads rubs against the hot pipework the insulation wears through and the unit shorts against the pipework . its a bugger to find unless there is visible damage to the insulation/ pipework. Check all the wiring to the compressors to see if this has happened.

keep us posted on what you find

regards

hendrag

Hendrag, and everyone
I've find today insulation problem of the "A" compressor leads (white insulation tape ) against the low pressure copper tube ! It also created a small hole in the pipe and then refrigerant leak, never had it before on supposed cold surface pipework !
I'll try to put pictures on line next days.
The system runs well now but an expensive work for the customer...
Kind regards
cool#9

[Brian_UK]

Hey Cool, thanks for the update.

Cables shorting (arcing) on pipes are not unique to LG, I've had it on several makes before. It is often the power supply cabling that has been run in the wrong place and trapped when the covers go back on.

[cool#9]

Hey Cool, thanks for the update.

Cables shorting (arcing) on pipes are not unique to LG, I've had it on several makes before. It is often the power supply cabling that has been run in the wrong place and trapped when the covers go back on.

Thanks but can't accept it appens on the cold gas pipe...
See the pictures
rgds
cool#9

[expat]

Hi COOL#9, that looks nasty!
Careful with "admettre" because I think you meant accept, but "admit" here means avouer (I hope my spelling is correct)
Maybe after an hours running the humidity from the condensation on the cold pipe was creating the short to the wire.
Where abouts are you btw I'm near Marseille.

[cool#9]

Hi COOL#9, that looks nasty!
Careful with "admettre" because I think you meant accept, but "admit" here means avouer (I hope my spelling is correct)
Maybe after an hours running the humidity from the condensation on the cold pipe was creating the short to the wire.
Where abouts are you btw I'm near Marseille.

Hi expat
So glad to meet a new french on RE forum ! Now we are two !!!
Thanks for the word correction, i'll take english lessons in next september.
I live near Monaco, what's your job, do you enjoy the forum ?
Kind regards
cool#9

[expat]

Hi expat
So glad to meet a new french on RE forum ! Now we are two !!!
Thanks for the word correction, i'll take english lessons in next september.
I live near Monaco, what's your job, do you enjoy the forum ?
Kind regards

Yes, I think the forum is great and very helpful. Sorry to dissapoint though but I am actually an English expat.
I was working on boats here in La Ciotat and you can see some of work in this thread
http://www.refrigeration-engineer.co...e+wine+coolers
now however I am an artisan. And you?
Salutations.

[cool#9]

now however I am an artisan. And you?
Salutations.

Salut.
I've my own (small) company doing after sales service, commissioning, maintenance contract...
I work on VRF,VRV , split, multi ,packaged, chillers sometimes...
See the pictures, some of my crazy situations !!
rgds
cool#9

[Sledge]

When I have ain intermittent fuse blowing situation, I take a real farmers approach to fault finding...I put in th ebiggest fuse that I can fit, without causing a hazard to people...My thinking is that the cost of having me return 20 times, will be a lot more than quickly overloading and burning out the failing component.
I know this is not a real high tech approach, but after running in and out for uncountable intermittent faults, I force myself to slow down, and create a situation that will finally identify the fault, once and for all.