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Saturday 30 January 2021

AC unit replacement.

Looks like AC has failed in shack so neither cools or heats now.

Right now operating without any heat in shack is a tad uncomfortable after a while.

The AC unit is an old eIQ-12WMINV the original gas was replaced with a new refrigerant a while back. Anyway the comms from the inner and outer have failed so time to get a new one. Done that but now it seems that the local AC guys that installed the previous one will not install this one as they didn't supply it, and as not prepared to pay a 150% mark up for the same unit just because they order it so a bit stuck or am I?

This is <7KG of R290 so doesn't actually need you to use an AC company. Not sure that is the wisest option but it looks like the locals have given me have no option but to commission this myself.

Why would I even think of doing this?

After recharging my dad's car AC and knowing all the kit still exists and having worked with gas lines, pumps and gauges and CFC's when I did my PhD for years I thought why should I not try and DIY this?

I got lots of hints and suggestions from others with similar units and this is what this post is about.

I have this kind of manifold gauge.

So worked out this much...In summary, inside unit is charged with nitrogen. Outside with refrigerant. So let the nitrogen out, connect the pipes. Then vacuum the whole lot inside and connect the outside.

These units are all supplied with refrigerant contained in the outdoor unit, so as long as don't open that it stays there.


You need to purge the other pipework of all the air. I have a vacuum pump to do this first down to about -30 PSI. Once done and connected up, and tested there are no leaks in the pipework, will do this two ways, one see that the unit holds the vacuum for a while and second to pressurise it with N2 as well and monitor the pressure levels on both occasions, open the outside unit gas line (containing the condenser), with the AC unit turned on and set to cool that will then draw/fill the gas lines with refrigerant and the AC unit will then work as planned.

I was told that without a pump and specialist A/C kit as this is new it is still possible to connect things up but you can risk losing too much refrigerant. If you do that you will probably need an A/C engineer to refill your unit properly. Think lots of costs.

However, it is not impossible, definitely not recommended but if no other options and if you are prepared to risk this the steps might be these. With the inner unit set to run cool then once you have tightened up all the joints fully on the gas lines then use a 1 second fill from the liquid valve with refrigerant, that is open the valve, having first got ready with leak spray or soapy water and a brush. You need to test all your joints several times with spray and listen and look for a serious leak. You might need to repeat a few times if you do find a leak but when satisfied with all of the joints you need to work out carefully the path of the refrigerant from the outdoor unit, through the indoor unit and back to the outdoor unit . The end of this is the T shaped valve on the outdoor unit. Take off the plastic cap on the T to reveal the schrader valve. Open the liquid valve for an other 3 seconds (you must hear the system filling up for 3 seconds) Close it and leak test the joints again.

Then with both valves closed, press in the schrader valve to expel air and refrigerant for 5 seconds. You will possibly see some oil deposits and aget a cold blast. The pipework is now full of refrigerant in gaseous form. Now open both valves fully and replace the purge cap. The system should now work.

However, this is a warning.......not using an Fgas engineer will invalidate the long term warranty of the unit and if it all goes wrong you will have to call one in anyway.....not cheap if they will even look at DIY units with R290 refrigerant (which is basically refined Propane so very flammable!). There is a very very real chance this could all go badly wrong with R290 as this ia a refined version of the same stuff you will find in camping gas and the AC unit has aboiut the same as two of those small cans so the result could be very bad. This is perhaps why the non technically minded, those without any tools should probably not even attempt this and go with an FGas engineer.

Anyway waiting for a period of drier weather and will go through the process.

(and I guess any comments to pick up if I had missed anything)

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