Daikin Indoor Unit Addressing

[mchild]

I have a Daikin VRV-S RXYMQ-M installed with four FXSQ-M indoor units in 2008. It has been a great system with sufficient heat to maintain the indoor set point temp with outdoor temps down to about 15*F (-9.5*C) without the need of supplemental heat.

This past summer I had two of the indoor units have fan speed relays on the circuit board fail (low speed relay). I purchased one new board, installed it on one of the air handlers with failed relay, and then had the failed relay on that removed board replaced and used that board to get the second air handler fully functional. Assuming the other two air handlers may also have relay failures, I continued to repair each board removed, repaired, and installed in the next in sequence air handler until all the air handlers had boards with new relays.

The question I have has to do with addressing the indoor units through the binary service mode on the outdoor unit. It has occurred to me that re-addressing was not done after repairs and circuit board swapping in the other air handlers. This past winter, without any other changes, the system could not maintain the indoor temps once the outdoor temps dropped below about 32*F (0*C). Is this failure to maintain indoor temp a possible result of not re-addressing?

Any insight is greatly appreciated.

[frank]

Daikin systems do not require address settings as the outdoor unit is programmed to handshake each connected indoor fancoil and assign an address automatically. Any failure on this part causes an error message. If you don't see any errors then addressing has been successful.
From the binaries, you can check the number of fan coils connected.

[mchild]

Daikin systems do not require address settings as the outdoor unit is programmed to handshake each connected indoor fancoil and assign an address automatically. Any failure on this part causes an error message. If you don't see any errors then addressing has been successful.
From the binaries, you can check the number of fan coils connected.

Thank you for the quick response. No fault codes.

Any thoughts on what may cause the failure to maintain the indoor temps. Over the winter at a time when the outdoor temp was about 20*F (-7*C) the hot pipe temp was 167*F (75*C) so it seems the outdoor unit is creating some meaningful heat. Maybe expansion valve not opening sufficiently?

Thanks again.

[frank]

Here's a link to the service manual.

Have a look at Section 6 which tells you how to carry out a Test run. This should force the system to run and test for any deficiencies which will bring up error codes (if there are any deficiencies).

On page 75, it shows you how to test for the amount of connected indoor fancoils, using the binary settings.

If you have the BRC1D type remote controller, page 95 shows you how to view the indoor sensor readings (this can't be done while in Test mode).

Although you have 75C at the compressor discharge, what temperatures do you have on the large pipe at the fan coils?

Poor performance in cold weather can be related to system charge as well as defective EEV's (control valves).

As VRV systems are quite complex, to really view what is going on, we use a 'Service Checker' tool. Without one, it can be difficult and time consuming to pinpoint the cause of poor performance. They are not really systems that the untrained can diagnose easily.

[mchild]

Thank you for this. I do have the service manaul and BRC1D controller and I'm familiar with how to monitor the sensor readings. I will run the test mode and also look at the temp differences at multiple points of the distribution.

Here in the US we still have limited experience with these systems. When there is an issue I tend to do some research to help my engineer narrow down the possibilities. You have provided some steps we can chase down and hopefully they will help point at where the issue is.

Again thank you.