Aircon doesn't work.. need wiring diagram

[bojan]

Hi Guys,
I have old Kelvinator aircon, model R225B with problem (compressor doesn't start).
Would anybody have wiring diagram?
Thanks!

[JA]

Sorry Bojan, No wiring diagram here. Aside from a wire out of place or faulty/corroded etc... one of the most likely causes of non-starting is low refrigerant levels, controlled by a low pressure cut off in the circuit. In the months prior to this, did it seem that the Air Con. had lost its bite? If so then low refrigerant might be the cause of this.

Best
JA

[AndrewJ]

Gday Bojan

Another possibility ( if its one of those big old grunters ) is the capacitor used to get it started may be dead. My Karcher hi pressure sprayer died early this year, and this was the cause. New one from Jaycar and its good as new.


Andrew

[Wavytone]

Bojan, 240VAC stuff is not DIY territory - you must use a licenced repairer or electrician.

The capacitors involved store enough energy to give you a serious shock.

[bojan]

Hi guys,
Thank you for advice... I will check the cap.
The unit came with the house we bought in Ballarat, so I don't know if/when it stopped working and how...
I am not qualified electrician, I am only RF electronics engineer... with license to approve/oversee work like this (but not in Oz) so I will take that risk :P
I already rewired and sort out couple of strange things the previous owner (or tradesman) did..

[Wavytone]

Ditto I'm an electrical engineer and in my younger days both designed and helped wire heaps of stuff for industrial control systems and trains.

But for a domestic installation by law the work has to be done by a licenced electrician.

I could have obtained a licence easily but I never wanted to work as a trade... LOL...

[bojan]

Yes... I have read somewhere that in Vic you are not allowed to even change the faulty bulb.
I am imagining myself as old granddad, on state pension... deliberating whether to have my dinner tonight or to call and pay the electrician to change the bulb for me... and being amateur astronomer, I think the clouds (or lack of them) may decide the outcome :P

[acropolite]

Bojan, if you can get a service manual there may be some diagnostic options. I have a Panasonic ducted system 17 years old now, it's stopped several times, usually the problem is spider webs and dust in the electronics, a spray with contact cleaner and a dust off with a brush always brings it back to life. Also make sure the fan runs, the compressor may not start if the fan isn't operational.

[Boozlefoot]

Fan running? If so, either capacitor on compressor is common, or thermostat not cutting the comp in. If thermostat, consider STC1000 unit at $13 for cost effective repair. I use these in my scope shed to run the fans.

[bojan]

Fan is OK...
This unit is reverse cycle... so I tried heating.
Without thermometer (I forgot it in Melbourne) it is not easy to detect the slight change in temperature, but the heat exchanger felt warmer.. or it was just my imagination? I will try next weekend again.

Now I think it may be the unit needs re-gassing... which means I will have to throw it away because R-22 coolant is apparently not legal any more (at least not for new units).

[bojan]

Progress:
It seems there is no problem with compressor and gas after all... because heating works OK, after pressing "Heat" button and short period of time spend in stand-by mode, compressor started and the temperature of the grill reached 40°C in couple of minutes - so unit seems to be mechanically and electrically sort of OK (last weekend I didn't wait long enough).
However, the control board (thermostat?) may have the problem because compressor definitely doesn't start in cooling mode.
Interestingly, some time ago someone re-made the front panel for some reason as home project, see attached pic (not too bad work though).
I really need wiring diagram now :)

[JA]

Hi Bojan,

If the heating function works well, but the cooling not at all then depending on the design you may have a faulty reversing valve, valve wiring or perhaps there is no voltage to the valve when there should be, i.e: wiring fault to the valve. Typically there should be 24VAC when the valve is energized and nothing when relaxed. One way it sets cooling the other way heating . I dont know if that 24VAC is supplied via a relay to the reversing valve, but if it is then also check the function of the relay. Of course if there is a fault in the temp sensing /thermostat circuitry then that too could cause a non-start on cooling, if the unit thinks it's already cold enough and would also explain it being able to start on heating. (Also check continuity to the in room thermostat / wiring)

EDIT: I just noticed your picture appears to be for an in wall box unit, my comments about the thermostat were more centered around a larger split system, with remote thermostat so YMMV with an all in one, but the principle remains

It goes without saying, that checking such would mean working with live equipment, so , to anyone, irrespective of experience, attempting such, I'd say be careful and do not attempt if in doubt.

Best
JA

[billdan]

Hi Bojan,

Having looked at your photo, I would suggest check for cracked solder joints and also test those small switching diodes with an ohmmeter for fwd/rev bias. Not much can be done for the chips but the cap's and resistors can be tested.

Bill

[bojan]

Hmmm..
Faulty sensor sounds like the most probable culprit.

It is probably a thermistor... encapsulated in the metal tube ø8mm, 20mm long.
Any idea of nominal value in case I found it is open/closed circuit?
It would be worth looking into analogue circuitry around thermal sensor.. There must be OPAMP and comparator feeding signal to processor... If they look OK, I will cut the sensor wires and try open/closed circuit.. If cooling starts to work, this is going to be all I really needed.

[billdan]

Looking at the RS components catalogue the thermistors can vary from 10Ω to 100KΩ.
You would have to find the part number for yours to find an equivalent.

[bojan]

I took out the controller assembly yesterday.
The whole thing doesn't look like original part. I think someone designed both of their own boards, or it was low volume retrofit because the controller was not available any more.
The components look OK, relays look clean, and in the next day or two I will check the general functionality of the unit (hopefully I will be able to do so in absence of some peripherals).
The fact is, compressor works for heating, but it doesn't start for cooling.

However... I started to think that I don't really need such sophisticated controller at all (heating, cooling thermostat, timer... ).

I need this thing to cool only, because I already have gas heater in the room...
If it's a hot day, I will switch the cooling ON.
When it becomes cool or too cold, I will switch it OFF. And I will turn on gas heater in winter.

So I think I will just rewire the whole thing at the end, if it's too time consuming to figure out and repair the controller...
Of course, all depends on the valve condition...

[Boozlefoot]

Bojan,

Try STC1000 in eBay search. These are a great alternative to revamp anything with heating/cooling thermostat problems. 10amp relays for each circuit. I get the dearer option cause they're in Aus and I dont have to wait for OS delivery, and even then they're only $18 delivered. Used last one to drive cooling fans on my astroshed. 1 unit will drive both your heating and cooling circuits.