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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8511
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Regards to a daikin RZQ160KV4A air conditioner
, The

Customer Question

Customer: ***** *****, regards ***** ***** daikin RZQ160KV4A air conditioner
JA: Thanks. Can you give me any more details about your issue?
Customer: The unit seems to perform under capacity. never used to behave like this. it strugges to cool 50m2 down when its hot outside.
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Customer: Yes
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Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
The system has had its refrigeration recovered.. and recovered 3.6Kg. matching the 3.7Kg factory charge so no leaks. The unit had then been vacuumed to 500 microns and fresh R410A added. the system was run and 3.8Kg refrigeration added. The suction line is showing about 110 psi and the discharge is showing 220 psi which seems a bit low, but being an inverter no idea how the controls are performing or ramping of the inverter. No leaking air ducts, and all zone motors operational. new filters and filters have always been maintained on this unit.
Expert:  Phil replied 1 year ago.

Hello, your views on the topic are right on.

Wait until it warms up outside, to 80C+ then set the thermostat down to 60F, that should ramp the compressor up to a fully loaded condition. Get me the suction and head pressures along with the exact indoor and outdoor temperatures at the time.

I suspect so far that the system is working well, without defects, these tests however will prove it, if that is the case.

we can go from here without a time limit.


Customer: replied 1 year ago.
Hi Phil,Today was 34C (93F) Outdoors and the indoor temperature was 24C (84F), thermostat on 16C (60F)
Ran the unit and after 20 minutes the gauges was checked. The Suction Side showed 105PSI and teh discharge 210PSI
The Outdoor coil off temp was about 38C (100F) which i expected to be a bit more like 45C (113F).
The diagnosic temp readings on the indoor controller showed the return at 25C(77F) and the coil off temp at the FCU side at (12C) (54F)Puzzled as to why coil off temp indoors looks good yet system not performing.
Pleany of air and all ductwork in the ceiling space has no leaks.
Expert:  Phil replied 1 year ago.


Both suction and head pressure are 25% or so low for those conditions. With what seems to be a good job charging the system, the compressor not running at maximum speed would seem to be the culprit.

You have not said where the thermostat was set... if you had set it at 80F for instance with the room at 84F the compressor would run at about 1/4 of its full capacity.

With that in mind, set the thermostat to 68F in cooling mode, then check the compressor motor amperage draw... if the amperage draw is not within 10% of full load amps when it is over 90F outside, and the room is over 80F, then the problem is with the inverter controls, that regulate the compressor speed.

You need a clamp around amp meter to do that test. $50 at a big box store usually.

Let me know how that goes.

Customer: replied 1 year ago.
Hi Phil,As it rained all last week i couldn't test it. Today is a warm day here so i gave it another goI set the thermostat to 16C (61F) in cooling modeIndoor return temperature at the time of testing was 34C (93F), outdoor temperature was 40C (104F)The compressor was drawing 17.2 Amps. There is no running amps on the spec plate but did have the locked rotor amps at 23.4AI ran the unit in monitor mode and it said the inverter was "Overall Current Stepping Down" mode.Pressures today was Suction valle 115 PSI and Discharge was 220 PSI. I even confirmed this with a second set of different branded manifold set.This unit runs on R410AIt took the unit nearly 4 hours to bring the room down to 22C (72F)Although ive never noticed it on other units before the liquid line on the valve does feel cool to touch and sort of feels like there are bubbles in it from the minor pipe vibration if you know what i mean?Non inverters from the past experience the liquid line is usually warmThanks for reviewing
Expert:  Phil replied 1 year ago.

Hello again, thanks for the data, its going to take a Daikin dealer computer analysis to sort that one out. A qualified Daikin dealer will have a lap top they can plug into your systems analysis port, that they can then send directly to Daikin for an analysis

So far however it sounds like it is about 30% undercharged, I do not consider that an answer however, there is no need for you rate my effort here.

I will respond if if you have questions about what your local Daikin dealer tells you, meantime I will opt out,

Customer: replied 1 year ago.
Hi Phil,It seems to be Ramping down possibly due to outdoor air temperature sensor misreporting the temperatures, or mechanical failure or near failure of the compressor. according to thier engineering department causing the "overall current stepping down" mode, however this cant be confirmed without one of thier analysers as mentioned.I Have orderd the Daikin D Checker for my laptop but they are taking their good time on getting it to me.The unit has been a bit intermittent but behaving nornally most days now on the past 3 weeks, which is a change from the past year. i have checked all the plugs and connections. We had a 44C (110F) day here and the unit cooled all zones open to 18C (65F) within an hour.Im a little unsure on this website and the star rating? you dont get paid until i provide a rating? as ive had to pay the full amount to the site before asking the question.Thanks.Michael
Expert:  Phil replied 1 year ago.

Hello, the integrated circuits (chips) are atomic scale in size, wires are 8 to 10 atoms of gold wide, invisible without a microscope... all sorts of things can happen in the manufacture that can lead to intermittent failures later.

There are similar issues with the printed circuit cards the chips are mounted on, namely cold (delaminated) solder joints and cracks in the printed circuit 'wires'. As the printed circuit card warms and cools, these cracks open and close the circuits..... electrical arcs often form and will 'heal' such a crack for a while... then it will fail later.

These can be difficult or impossible to trouble shoot, as the voltage from the meter used for the test can cause an open circuit to arc and heal temporarily. Lets wait for the analyser software you ordered and see what comes up.

There can be similar problems with oxidized wire connections... all of this is is inexcusably complex in my book, but it is the world we are living in.

Regarding your payment, you paid Just Answer... but I only get paid from that amount from Just Answer IF I provide a an answer that you rate positively.

Stay in touch, let me know what you can discover, we can go from there without a time limit.

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