3UV DHW defekt?

[DanieleNeo]

Hi,

while monitoring the operation of the heat pump I noticed that this error is often displayed even though the pump seems to be working correctly and does not show any errors on its monitor. This is the section of code that display it

And this a piece of log

[01:14:41][I][unhandled:146]: can_id<0x10A> data<31 00 FA C0 B4 00 00> [01:14:41][I][unhandled:146]: can_id<0x180> data<22 0A FA C0 B4 00 22> [01:14:42][I][sendGet:146]: Error Code can_id<0x680> command<31 00 FA 13 88 00 00> [01:14:42][E][daikin_rotex_can:313]: 3UV DHW defekt => tvbh: 33.799999, tv: 28.400000, max_spread: 3.000000, bpv: 0.000000, flow_rate: 1424.000000 [01:14:42][I][handle :146]: Error Code<No error|3UV DHW defekt> can_id<0x180> data<D2 00 FA 13 88 00 00> changed<0> [01:14:42][I][sendGet:146]: Operating Mode can_id<0x680> command<31 00 FA 01 12 00 00> [01:14:42][I][handle :146]: Operating Mode<Heating> can_id<0x180> data<D2 00 FA 01 12 03 00> changed<0> [01:14:42][I][sendGet:146]: ES mode can_id<0x680> command<31 00 FA 01 76 00 00> [01:14:42][I][handle :146]: ES mode<> can_id<0x180> data<D2 00 FA 01 76 00 00> changed<0>

what is this error for?

Thanks in advance,
D.

[wrfz]

The air source heat pumps have two 3-way valve switches, which are relatively prone to failure. Usually, they break after 2-4 years. Over time, they calcify and become stiffer, sometimes eventually getting completely stuck. This causes the stepper motor to no longer be able to fully open or close the valve. As a result, the hot water from the hot water tank is quickly diverted to the floor, which is undesirable given the relatively expensive water due to the high flow temperature. The air source heat pump cannot detect this defect. Therefore, we have implemented detection in the ESPHome component, which performs a plausibility check based on the Vorlauf, VorlaufBH, Rücklauf, Durchfluss, and Mixer position or BPV position.

However, in your case, the code is somewhat outdated. There was a bug in the code that incorrectly throws an error, even though the valve may still be functioning correctly.

Please flash the latest version of the ESPHome CAN component! If the error occurs again, please report it again. Then we can check certain values to determine if the valve is actually defective.

[wrfz]

First of all: Please do not mix topics in the future. If you have questions that have nothing to do with the current topic, please start a new discussion. A huge discussion with different topics is not very helpful.

[wrfz]

HPSU Compact (referred to as V4 by Daikin) has at least two known issues related to defrosting:

The HPSU uses hot water from the DHW tank to defrost the evaporator. Ideally, both valves (DHW mixer and bypass) would open, allowing the water from the hot water tank to transfer energy to the refrigerant circuit via the plate heat exchanger. I’m not sure if this was an intentional feature by the developers or a mistake. In any case, the bypass valve closes at that moment, which causes part of the hot water to be pushed into the outdoor unit while simultaneously sending additional "expensive" hot water into the underfloor heating system. In my opinion, this is a flaw.

To address this, I implemented a feature in our CAN component called "Defrost Optimization." When enabled, the operating mode temporarily switches to "Summer" during the defrost phase and reverts to "Heating" afterward. This ensures that the bypass valve remains open during the defrost phase, preventing hot water from being directed into the underfloor heating system. This adjustment should reduce the thermal loss per defrost cycle from approximately 2K to about 0.7K.

(Sorry for a screenshot in German language)

[wrfz]

The second issue with the HPSU Compact control system is that it defrosts too frequently. According to my analysis, in certain situations, it defrosts as often as every 25 minutes, even though the evaporator is only partially iced, with at least 50% of the evaporator surface still ice-free. Statistics show that at the time of the defrost cycle, the dynamically calculated COP does not experience any reduction. Therefore, the defrost process is simply unnecessary in many cases.

There are likely several reasons for this:

• Rotex managed to design a "functional" device with minimal use of sensors (which is quite an achievement in itself).
• The refrigerant routing in the evaporator is probably not optimal (at least some aspects seem unnecessarily complicated to me).
• The detection of a frozen evaporator likely relies on the delta between the outdoor temperature sensor and the evaporator sensor. Since the evaporator doesn’t freeze uniformly (and the evaporator sensor is probably located in an ice-free spot), the defrost cycle is triggered prematurely.

In the Telegram group on the Daikin-Rotex-HPSU-CAN-Serial - Startpage (see at the very bottom), various ideas are being discussed and partially tested:

1. Relocating one of the two sensors to reduce the delta, so that defrosting is triggered less frequently. This idea is already a few years old and has been implemented by various people who successfully reduced the defrost cycles. For others, however, it showed little success.
2. Manipulating the resistance of the evaporator or outdoor temperature sensor via an ESP to intentionally delay the defrost cycle (e.g., only triggering it when the COP value starts to drop significantly). This is a completely new idea and still needs to prove whether it will work effectively.

[wrfz]

Regarding the firmware version: I have repeatedly inquired with Daikin technical support and always received the same response (which I find very hard to believe): There is only one version!

[wrfz]

Regarding control via an adaptive flow temperature, you’ll also find an HA template sensor in the Telegram group, which you can use to control the ESP through HA automation.

Caution: You should ensure that adjustments are made no more than once per hour. Changing any settings in the HPSU (even via ESP) likely results in the settings being persisted. Since the data is most likely stored on an EEPROM, and most EEPROMs typically endure a maximum of about 100,000 write cycles, it’s advisable to avoid making frequent changes to the HPSU settings!

[DanieleNeo]

I tried last version and I can confirm that the error never occurs.

@wrfz @Trunks1982 as I said before I have currently forked the repository and I'm working on my own copy localized in Italian, do you think it could be useful to centralize the textual resources in a dictionary (some are hard coded in the code) and realize a multilingual version German/English/Italian? Because I was thinking about it, if you think it's useful I can spend some time on it, let me know, happy to colaborate.

Thanks,
D.

[wrfz]

I’ll take a look to see if I can implement localization of a dictionary with reasonable effort.

[DanieleNeo]

I'll answer the last one and then I'll answer the others (you're right in saying that maybe it's better to diversify the topics... but should I answer here now?), I could work on the localization, if you think it's useful.