Samsung SH24TA8X

[airflo]

Arrived at a job today and found the isolator had been turned off by the customer, after turning it on the indoor unit started working so i went outside and after a few minutes the outdoor fan started shortly after i heard a crackle and a bad electrical burning smell i quickly turned the unit off at the circuit breaker & isolator, i then proceeded to open up the unit to find that a coil had been fried inside leaving alot of soot inside. Having never worked with these units i don't exactly know what that coil does, but it has 2 wires going to the pcb and the others are the A +N. The N looks pretty burned and so does that whole half of the coil.

The compressor, soft starter & start cap had been replaced 1 1/2 years prior to my visit and the unit had been working fine untill now.

Didn't have a megger on me but i tested resistence of the compressor windings with a multimeter and got 4, 1 & 5 Ohm which seems normal.

I'm guessing this coil has something to do with the compressor as the burning smell happened as soon as the compressor was supposed to kick in.

Is it worth finding a replacement coil or is it best to replace all coils and the PCB as well?

Anyone have any ideas?

[airflo]

anyone got any ideas? :confused:

[nike123]

Is this coil in outdoor unit? If coil is related to soft starter, then fit some MCB, rated slightly above FLA of unit and disconect compressor. Also remove soft starter and rewire it to direct online start. Than check current with ammeter while compressor is disconnected and if that looks OK then when connected. If then you have high amperage reading or MCB is acted you have faulty compressor and best is to chang whole set.

[paul_h]

What is this coil? I'm guessing resistor or the small add on relay?

I know a lot about these samsungs, but can't think what this coil is. I've never looked inside one and called something a 'coil' so I don't know what part you are refering too

Do you have the type that has a small PCB on the side with two resistors, one capacitor and one relay? These had an upgrade kit with a tiny PCB/relay added that plugs into the PCB and an extra capacitor cable tied onto the existing run capacitor. If it was all replaced 1.5 years ago, odds are they fitted the upgrade kit with a small add on relay, cap and NTC connectors in line from the capacitor. Attached picture is the type of PCB that has a small relay added in the upgrade kit.

Or the other type of SH24 has a big plastic chassis with two large omron relays, larger PCBS, one PCB with 5 resistors and factory fitted with two capacitors.

[airflo]

Hello,

Nope it has a PCB with 4 large white resistors on it though.

The coil is positioned right next that pcb, it is rectangular shape and has 6 wires or so going into it 2 Actives, 2 Neutrals and 2white wires which go to another PCB (not the one mentioned above.).

Oh yes the coil is in the outdoor unit.

Attached is a quick sketch of what the outdoor unit looks like with the top taken off.

Thanks in advance for your help.

Cheers,
airflo

[nike123]

Hello,

Nope it has a PCB with 4 large white resistors on it though.

The coil is positioned right next that pcb, it is rectangular shape and has 6 wires or so going into it 2 Actives, 2 Neutrals and 2white wires which go to another PCB (not the one mentioned above.).

Oh yes the coil is in the outdoor unit.

Attached is a quick sketch of what the outdoor unit looks like with the top taken off.

Thanks in advance for your help.

Cheers,
airflo

That is power relay! Check compressor windings for short circuit and check insulation with insulation tester. Check compressor capacitors.

[paul_h]

Well besides that single small PCB, the other SH24 looks like this.
Ahh, with your drawing I see the part you must be talking about now, I'll look it up.

[airflo]

thats the one in the bottom left of the picture.

[airflo]

As in my first post i check the resistence of the compressor and all seemed fine, although i don't own a megger (im a install mechanic) so i couldn't test it.

Ok when it comes to testing capacitors im a little confused, do i just take my megga and charge it up to see that it holds charge?

Sorry if i sound stupid but i have never been shown this stuff as i have done installs my whole career.

[paul_h]

You can charge the cap up somehow and then use an analogue multimeter to see if there's voltage in it (doesn't work with a digital meter though)
Your best bet is to go into Jaycar (It's an electronics shop like D_ick smith or tandy is, but they have better range). Jaycar have proper digital capacitor testers for only $70.

Here's the diagram for the unit, I can't see anything in it that's not a relay besides the PCBs and capacitors.

[airflo]

cool i will grab a cap tester tomorrow along with a megga.

It seems as if the burnt out part im talking about is a relay coil CN-1 as i described it has the white cables. Am i correct in say that CN-1 is the relay for the Run winding?

Where do i go from here? test compressor and caps??

BTW the thanks for you rhelp it is much appreciated.

[paul_h]

Yeah well you may have a dead capacitor, they cause other things to crap themselves like relays, NTCs and soft starters when the capacitor goes.
Or you may have a seized compressor, or just have got wiring that worked itself loose. Any of this things could burn out components.

Test capacitors, megger test compressor (at actual terminals on compressor not the end of the leads, so you get a visual check on whether the terminals under the compressor cover are loose or burnt).

If that's all OK, I usually rewire the system to run the compressor straight of the mains (with capacitor in circuit obviously). Active to common, run and start to capacitor, neutral to run side of capacitor. Everything else disconnected and then I switch on the isolator
If the compressor runs at normal amps and pumps OK, then I just replace all the broken stuff in the control circuit and call it a day. edit: Or replace the whole soft start kit with a contactor and an australian made hyperstart 2000.

If compressor draws high amps or doesn't run, time for a new air conditioner.
It's a PITA to get samsung parts, and a compressor change is about $900+ anyway

[airflo]

Ok will do the test in the next day or 2thanks for the help.......

Don't really know what you mean by neutral to run side of capacitor though.

I know the wires connecting to the compressor look ok and have a nice firm connection.

I would be interested to know how to replace the soft starter kit with a contactor and hyperstart i'm guessing it couldn't be to hard but i'm just not quite sure what to do.

[airflo]

now that i think of it i probably know how to wire in the contactor and hyperstart.

control wire goes from pcb to contactor.
Supply is given to the contactor and then goes from the contactor to the hyperstart return lead.
Start coming off the hyperstart is wired to the start capacitor.
Run coming off the hyperstart is wired to the run capacitor.
Supply goes directly to the run winding???

I could be way off but at least i tried.............any help would again be appreciated.

[nike123]

now that i think of it i probably know how to wire in the contactor and hyperstart.

control wire goes from pcb to contactor.
Supply is given to the contactor and then goes from the contactor to the hyperstart return lead.
Start coming off the hyperstart is wired to the start capacitor.
Run coming off the hyperstart is wired to the run capacitor.
Supply goes directly to the run winding???

I could be way off but at least i tried.............any help would again be appreciated.

Logicaly it would be that supply goes to contactor and return to C of compresor!

[paul_h]

Don't worry about wiring up a hyperstart or any other type of soft start unit you actually need too. You might just have a burnt out relay, besides hyperstarts come with wiring diagrams and instructions.

What you need to be able to do, is look at the proprioety system, and work out how to disconnect it and end up with a basic compressor circuit.
That is, compressor, active, neutral and capacitor. Thats the set up and components that all small a/cs have when they don't have soft starters and outdoor circuit boards at all. So go look at a wiring diagram for small cheap units.
Or even the wiring diagram for the misubishi MS-18NV that's in my thread that brian_UK posted a link to a service manual.

Once you can strip a system down like that for direct mains running, it's easy to add a relay/contactor and soft start to the circuit, no matter what spaghetti filled, PCB controlled outdoor unit configuration you started off with.

[nicdan]

Hi Paul, some time ago you were talking about a problem with a Samsung SH24TA8X, which i have a job i am looking at and you posted a pic of the main board and there is a green dotted line showing the part i am after (RY2 - on the wiring dia). What is the part called and do you know the part no. Hope you can help.

[paul_h]

They just use omron G7L-2A-T relays available from rs components or farnell, and any major electrical shop.

http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0329991