Daikin FBQ71 / RZQ71 poor cooling

Hello everyone,
I'm new to this forum.

I have a Daikin Ducted Heat Pump: Indoor unit FBQ71B8V3B Outdoor unit RZQ71B9V3B from 2006.
The indoor unit is installed in the antic between the roof (not insulated) and the ceiling (insulated) therefore hot in summer and cold in winter but the HP duct boxes are surounded with rockwool.

During last summer in southern France, the cooling was really insufficient with air outflow (ceiling outlets) at around 30 celsius while the outside temp was over 35 or 40 celsius.
However, during winter (now), heating works well.
For the avoidance of doubt, the Air filter is clean (there is none in the indoor unit but one at the inflow inlet in the corridor.

Question 1: I suspect that the refrigerant liquid (R410A) should be refilled as it has never been refilled for 14 years. Although heating work well currently I would like not to wait if the efficiency is poor and hence it would cost me more electricity for the same heating. Did one of you face a similar situation ?

Question 2: when I look at the indoor unit, on the left of the PCB cover panel, there is a one inch hole with a quarter turn locking and I have not found on various service manuals what is it for. Could it be used for maintenance like for cleaning something ?

Thanks ahead for your replies.
Apicats

Answer 2.

There is an access hole provided to allow for the adding of water to test the condensate drain pump.

The link below is for an installation manual, check figure 10 which shows the method of adding water and page 4 which explains the process.


https://www.google.com/url?sa=t&sour...MgCEhzHxfxdq0g

Answer 1. In theory the refrigerant should remain in the circuit. It does not decay over time.

However, there is always the possibility of leakage and to establish that would require monitoring the temperatures of the refrigerant around the system. To leak check the system would require more work such as recovering the refrigerant charge, pressure/leak testing, and repairs necessary and recharging the system.

Is the return air inlet on the fan coil open to the space in the loft area or is it ducted to the room/'s you are trying to condition?

If it is what we call 'free back return' then your problem will be due to the fan coil having to deal with the excess temperatures in summer and winter, rather than just the air from the room.

Thanks Brian_UK and Frank for your feedbacks.

Well noted Brian, the one inch hole in the indoor unit is for water drain checking. Thank you also for the service manual.

In answer to Frank's question: the double fans of the indoor unit (FBQ71B8V3B) are flowing air through the ducts with a duct damper controlled by a thermostat in each room (other than in the corridor); there is no fan coil dedicated to each room. Could there be another issue ?

I understand from Brian's answer 1 that refrigerant does not necessarily decay over years, therefore I would appreciate some other support to test if the heat pump works properly before seeking external assistance, for instance through reading a few codes in the 40-50 range. Some measures: currently, outside temp is around 15 celsius, the heat pump works well with 21 celsius as target on the BRC1D52, I read 21 in the remote controller sensor (code 41-0), 17 at the return thermistor (code 41-1), 19 in the exchanger (code 41-2). For info I changed code 50-4 to 01 instead of 00 to use the controller sensor instead of the return air sensor.
Last winter at lower outside temp, the unit did deliver the required heat and the exchanger temp was much higher than 19; the problem is/was cooling during summer and therefore I suspect a defect that could lower the efficiency of the system hence draining more power than it should.

Another request: If someone could send me the table of the daikin code up to 50 or more if applicable it would be much appreciated as so far I did my own recap from tips collected on various forums.

Thanks ahead for your advice.
Apicats

Have you run the unit through a self test cycle?

Frank, sorry for my late reply.
I did press the test button on the BRC1D52 once to read the last error code which was U0 for insufficient refrigerant quantity which might be a leakage or a valve malfunction but this might be a very old problem (before I bought my house).
So I did press the on/off button for a few seconds to reset the error code and put the heat pump in forced mode (test button pressed 4 times) which pulled out hot air. After a while (few minutes and even a few hours after being back in normal mode), the error code remains with 00 as it was just after the reset (same for the "wrench" indicator or the blinking "eye" indicator which are also visible which mean "inspection required").
Question 1: what is the process to run a "self test cycle" as suggested by Frank earlier ?
Question 2: does this self test cycle clear up the "inspection required" (wrench and bling eye indicators) or is there another way to start some test and clear these indicators ?
Thanks

Hello everyone,
Could someone help me ? My questions raised on 20 October (just above) are:
Question 1: what are the steps on the BRC1D52 to run a "self test cycle" ?
Question 2: does this self test cycle clear up the "inspection required" (wrench and bling eye indicators on the bottom left of the remote control display) or is there another way to start some test and clear these indicators ?
Thanks ahead for your reply.

On the BRC controllers, any error (current) shows up as a 'spanner' icon and a flashing 'eye' accompanied by a 2 digit error code. The operation lamp (red or green depending on which model of BRC) also flashes. While the error code is flashing, the error is current and requires fixing.

When the error has been fixed, the display returns to normal and the operation lamp is 'steady'. If you press the bottom left hand 'Engineer' buttom once (on the BRC 1D), the last error code is displayed. When this last 'fixed' error code is showing, it can be cleared by pressing and holding the operation button for 5 seconds,

Using the '40' level codes, you can see the last 10 error codes - these cannot be cleared from memory.

By pressing the 'engineer' button 4 times, the system can be put into 'Test' operation, where the system self tests for approximately 20 minutes and compares readings, (temps, resistances, pressures, current draw etc.,) to factory data within memory and anything outside of 'normal' results in an error code. If all is good, then the system returns to normal operation after the test function and no error codes are reported.

Many thanks Frank for the advice and sorry for the late reply, I couldn't access my account before.
I did run the test cycle by switching ON the BRC1D52 before pressing 4 times the test/'engineer' button and the test ran for maybe 30 minutes. A the end the remote control went back in normal mode.
When I press the test button once, I get in the bottom left corner the little spanner icon and the 'eye' blinking icon and the mention 'unit NO. 0' and below '00'.
When I go in the 40 level codes, I read 'UNIT NO. 0' and below'1-UO'
when I press the 'clock' button once more, I get 'UNIT NO. 0' and below'2-00'
and the same happens for all numbers up to 'UNIT NO. 0' and below'9-00'.
I see the '1-UO' means 'Insufficient refrigerant quantity'
but does it mean that it was the last error code before I ran the test?
or is it the result of the current test although the test button when pressed once shows 'unit NO. 0' and below '00' ?
or is it the very first error code while all tests run since are good and show 'UNIT NO. 0' and below'2-00', same with '3-00' etc up to '9-00' ?
If this '1-U0' is the result of the current test, then is my understanding that R410A pipes shall be refilled, correct so I can get someone to do it ?
Another side question: is there a battery inside the BRC1D52 remote control since I got an electricity outage for 10 minutes and the clock was reset where it is supposed to keep data memory for one hour ?
Many thanks ahead for your replies.

Many thanks Frank for the advice and sorry for the late reply, I couldn't access my account before.
I did run the test cycle by switching ON the BRC1D52 before pressing 4 times the test/'engineer' button and the test ran for maybe 30 minutes. A the end the remote control went back in normal mode. Therefore no current errors

When I press the test button once, I get in the bottom left corner the little spanner icon and the 'eye' blinking icon and the mention 'unit NO. 0' and below '00'. Indoor address and no Group address - normal on a split system

When I go in the 40 level codes, I read 'UNIT NO. 0' and below'1-UO' Last recorded error

when I press the 'clock' button once more, I get 'UNIT NO. 0' and below'2-00'
and the same happens for all numbers up to 'UNIT NO. 0' and below'9-00'.No other errors recorded

I see the '1-UO' means 'Insufficient refrigerant quantity' but does it mean that it was the last error code before I ran the test? Last recorded error on the system - if the fault does not re-occur when you run the Test operation then it is an old error

or is it the result of the current test although the test button when pressed once shows 'unit NO. 0' and below '00' ?
or is it the very first error code while all tests run since are good and show 'UNIT NO. 0' and below'2-00', same with '3-00' etc up to '9-00' ? Using the '40' level codes, you can see the last 10 error codes - these cannot be cleared from memory.

If this '1-U0' is the result of the current test, then is my understanding that R410A pipes shall be refilled, correct so I can get someone to do it ? By pressing the 'engineer' button 4 times, the system can be put into 'Test' operation, where the system self tests for approximately 20 minutes. If all is good, then the system returns to normal operation after the test function and no error codes are reported.

Another side question: is there a battery inside the BRC1D52 remote control since I got an electricity outage for 10 minutes and the clock was reset where it is supposed to keep data memory for one hour ? No batteries inside the BRC controllers, memory is maintained by a capacitor.

Thanks Frank for the clear answers.
So in heating mode, my Heat Pump seems to work properly.
I will check again during summer time using the same procedure when in cooling mode to make sure the 'test' cycle runs properly without error.
Before I can conclude this thread, it would be great if you could provide me with:
- a table of the 50 codes (I got some of them in various forums but miss a synthetic table) and
- the P/N of the special PCB to (in heating mode) stop fair flowing through the system every 7 mn for approx. 1 mn despite the target temperature is reached, , creating fresh air feeling while the room temperature is already correct. If special settings (in the 40/50 codes) can make the same without a PCB, it would be even better.
Many thanks and Merry Xmas to all

Level 50 settings are for Daikin techs only as they can brick your system if not applied correctly.
Level 40 settings are for monitoring

There are field settings for all other fine tuning readily available on the net for your particular system. Do a Google for Daikin field settings.

In heating mode, the indoor unit allows a small amount of hot gas pass through on a vrv system to prevent oil logging but the only adjustments you can do on a split system is to set fan off when at 'thermostat off' condition via the field settings.

Many people think that the unit is blowing cold when in heating mode as the fan ramps up on thermostat on due to the fan starting to circulate the air as the coil reaches 34C, but it's just air movement they can feel. This feeling disappears as the air off temp increases.

Hello Everyone and Frank "Moderator" in particular.
We are now in summer time and outside temp is pretty high those days in the South of France (35 Celsius) so I can check the cooling mode following Frank's recommendations.
Cooling is still insufficient apparently since the temp at the outflow holes in the ceiling is around 25 deg.
The temp shown in the 41 codes of the BRC1D52 are:
26 in the remote ctl (code 41-0)
31 in the inflow area (code 41-1)
19 in the exchanger (code 41-2)
Q: Is it normal to have only 19 deg in the exchanger knowing it is located in the attic with no insulation under the roof (only btwn the attic and the ceiling below) therefore while it is 35 deg outside it is probably 40 or more in the attic ?
The Self-Test mode does not show any error after 30' run.
Q: If the self-test is OK, especially because it does not show the U0 code (insufficient refrigerant), it means that there is no need to do a recharge of R410A gas. Is this correct and could it be that my system is under-sized?
Thanks ahead for your reply.

Does the ducted unit have return air ducts from the room connected to the back of the fancoil where the filters are?

On full cooling I would expect the evaporator coil temp to be between 2C and 8C.
19C is way too high.
Is your outdoor coil clean?
What size (diameter) and how many ducts do you have connected to the outlet of the fancoil

Thanks for the quick reply, Frank.
The return duct (diam around 250 cm) is located on 1st floor.
There are 7 ducts (diam around 150 cm) connected to 3 bedrooms on 1st floor and on ground floor: 1 bedroom, 1 kitchen and 2 in the corridor (the 2 latter have no on/off thermo-switch).
The outdoor coil is clean.
The room temperature is too high on 1st floor: 25C on the outlet hole is not not enough to cool down a room on the 1st floor where temp is above 32C without a/c.
Thx

The FBQ71 has a nominal airflow rate of 18m3/m or 0.3m3/s on high speed fan.
With a 250mm dia return air duct the velocity onto the coil is in excess of 6m/s. The ideal coil face velocity is 2 to 2.5m/'s. This allows the air sufficient dwell time for heat transfer to take place. With a low dwell time, less heat exchange takes place.

You need to install either a larger return air duct or additional return air ducts.

With 7 outlet ducts serving multiple areas, and assuming zero external static, it is difficult to ensure that each room has a balanced airflow to match the room heat gain, i. e. small room small airflow, large room, large airflow. With 7 outlets, each outlet will only get 0.3/7 = 0.042m3/s if they were balanced and in my opinion, this is way too low to achieve individual room cooling.

For a room measuring 4x3x2.4m (28.8m2) you will only get 5.3 air changes/hour.

In reality, your flexible ductwork will add a great amount of external static resistance which will reduce the airflow volume to below the published figures thereby reducing your cooling capacity further.

The liquid line temp (40-2) at 19C does not look right. Are you able to access the fridge lines where they connect to the fancoil and take a temperature of the small pipe adjacent to the brass nut with the unit on full cooling?

Can you try a 'test cooling' with all the flexi ducts disconnected and monitor the 41 code temp's?

Thanks Frank. I was able today to check the installation iaw your recommendations.
There are actually 2 return ducts (250mm dia) but one is shared (using a Y) with another a/c system (Hitachi RAD-35NH7A) which was installed later (probably because the installation was undersized) and it reused some of the existing ducts.
I disconnected the Y to perform the test so that 2 (250mm dia) return ducts are fully available.
I closed all outlet ducts except one.
On the exchanger box in the attic, I opened the little plate where the water pump is and cleaned the exchanger radiator (which was clean anyway).
I cleaned the water receiving little black bucket.
I put a standard thermometer on the radiator and switched the system on.
After 30' operation I got 26C on this thermometer.
In the attic where the exchanger is located: 44C
41-0 27C
41-1 32C
41-2 18C

The brass pipe entering the exchanger area is pretty cold but not frozen (I can keep my fingers on the brass pipe near the nut for a long time) but I don't know how to measure exactly the temperature. What I can say is that I see water condensing on the exchanger and pouring slowly in the receiving bucket.
Maybe this refrigerant is not cold enough.
Q: could it be on the outdoor unit which is not cooling down enough the refrigerant ? Which tests I could perform on this outddor unit ?
Thanks ahead for new advice.

Thanks Frank. I was able today to check the installation iaw your recommendations.
There are actually 2 return ducts (250mm dia) but one is shared (using a Y) with another a/c system (Hitachi 3.5kW RAD-35NH7A) which was installed later (probably because the installation was undersized) and it reused some of the existing ducts.
I disconnected the Y to perform the test so that 2 (250mm dia) return ducts are fully available.
I closed all outlet ducts except one.
On the exchanger box in the attic, I opened the little plate where the water pump is and cleaned the exchanger radiator (which was clean anyway).
I cleaned the water receiving little black bucket.
I put a standard thermometer on the radiator and switched the system on.
After 30' operation I got 26C on this thermometer.
In the attic where the exchanger is located: 44C
41-0 27C
41-1 32C
41-2 18C

The brass pipe entering the exchanger area is pretty cold but not frozen (I can keep my fingers on the brass pipe near the nut for a long time) but I don't know how to measure exactly the temperature. What I can say is that I see water condensing on the exchanger and pouring slowly in the receiving bucket. But compared to the Hitachi 3.5kW RAD-35NH7A system water out pipe, it is pouring much less.
Maybe this refrigerant is not cold enough.
Q: could it be on the outdoor unit which is not cooling down enough the refrigerant ? Which tests I could perform on this outdoor unit ?
Or maybe the system is simply undersized (for the cooling mode at least) as it is delivering 9 kW for 4 bedrooms, a kitchen and a corridor and as its exchanger is located in the attic and not not inside the home where the temperature is cooled down ?
Thanks ahead for new advice.

With a liquid line temp of 18C on full cooling, it sounds like there may be a problem with the refrigerant circuit, could be a thermister out of calibration, problem with the EEV or even a refrigerant overcharge - a refrigerant shortage would be indicated by frosting on the liquid line/evaporator.

I think at this stage, you need help from a local A/C technician who has the necessary tools and knowledge to find the cause.

Before calling an A/C technician, I did a few tests:
- I checked the 2 electromagnetic valves "Y1S" and "Y2S" using 230V power and they open/close correctly (at least I can hear the little part inside moving in/out).
- I removed the "YE" EEV solenoid, cleaned the cylinder, but couldn't check the proper functioning as it is powered by 6 wires probably using low voltage. Maybe is there a way to check it ?
- I will check the thermistors if I could be told which thermistors and where they are located. For info, there is no faulty LED blinking on the outdoor unit PCB (nor on the BRC1D52 Remote Control).
One thing I forgot to mention: the temperatures displayed at 41-0 41-1 and 41-2 codes of the remote control are more or less the same whether I choose the cooling mode or the deshumifier mode. Is it giving some indication of the faulty area ?

As you say the system heats OK in winter but fails to cool OK, I'm leaning toward the system being overcharged, given the high liquid line temp. However, you need specialist tools and knowledge to determine this, hence my suggestion that you should engage a local tech. One of the first things in a system when the operation is not as it should be is to make sure that the charge is correct.
If it is, then you start to look for other issues.

To check the thermistor resistances, do an internet search for a service manual for your model which will list the resistances at varying temperatures or download the Daikin app from the Apple store or Android store