Daikin Defrost: a conscious choice ?

Daikin Defrost: a conscious choice ?

As you already know I am trying to understand my heat pumpt daikin defrost cycles by few winters. And I am trying to optimize the configuration to minimize consumption and maximize comfort.

I am trying to escape from defrost cycles by few winters.

Current winter I actually realized that something is not working as expected. Daikin Italy cheered me up writing me that based on the data collected onto my system everything is working as it should.

Unfortunately it was not explained why I should be calm. Something does not come back to me. So I am not calm.

The beginnings

I reccomend the following preliminary readings (unfortunately in Italian only at the moment) to understand how I reached my conclusions:

Riscaldamento invernale e pompa di calore aria-acqua- attenzione agli sbrinamenti

Rotex HPSU Compact: come funziona lo sbrinamento ?

This behaviour was already clear past winter.

Starting point is a ticket (200344216) opened to Daikin Italy on 27th December 2016.

On 8th January 2017, without any answers to explain my problem, I wrote a summary email to  infotecno@daikin.it (as suggested on Daikin Italy website in case of “Hai dubbi di natura tecnica o desideri semplicemente approfondire degli argomenti tecnici? Se nessuno dei canali di contatto sopra elencati è adeguato alla tua richiesta”).

The “phenomenon”

My system, as many other people frequenting italian technical forum cercaenergia, has realtime electric power monitoring of my Daikin HPSU Compact: different heat pump behaviours are clearly highlight.

A data example of 8th January 2017 (but any of the previous winters would be the same):

Daikin Defrost

Heat pump defrost cycles can be easily identified thanks to electric power realtime monitoring. Zooming into 8th January 2017 you can recognize univocally Daikin defrost cycles:

Daikin Defrost

My Daikin HPSU Compact evidences, and of many other HPSU Compact users of cercaenergia forum and also of Dutch customer that found this article in italian, are the following:

  • defrost cycles, when starting, have almost always a 25 minutes frequency independently of outdoor temperature or outdoor humidity
  • so frequent defrost cycles lead to a fast hot water tank exhaustion with resulting very frequent DHW cycles
  • the only action apparently improving the heat pump behaviour is a huge increase in external unit thermal power generation

This Daikin HPSU Compact behaviour is bad for the following reason:

  • very frequent DHW cycles increase greatly electric consumption
  • the two three way valves are very noisy very frequently => it is annoying and I imagine that components will have really shorter life
  • not continuous heating, especially when required thermal power is limited

The turn

Daikin Defrost

My reasonable certainty started at the Christmas vacation end when I found, thanks to my Google search black belt, Daikin Altherma Service Manuals (Daikin Group hungarian company – you can find them in blog documents section).

Unexpected I discovered that Altherma external unit (ERLQ04-08CAV3) is identical to the one used by the Daikin HPSU Compact current version (now called also Daikin Altherma integrated solar unit).

I reasonable believe that the manual perfectly applies also to my HSPU Compact external unit (RRLQ006CAV3). This assumption backfired me and made me really restless.

The Daikin Altherma manual perfectly describes (finally !!!) external unit Daikin defrost algorithm:

Daikin Defrost Daikin Defrost Daikin Defrost

The manual would explain that my Daikin HPSU Compact (also of all other users complaining with ERLQ04-08CAV3) when Daikin defrost cycles start, never exits, as designed, from “Defrost Requesting Area” because defrosts frequency is almost always a cycle every 25 minutes.

As explained above, greatly increasing thermal power (raising flow temperature setpoint) the frequency reduces slightly but never closer to the 2 hours documented in the manual.

This behaviour is found also by other customers complaining and it seems wrong: increasing thermal power is expected defrost frequency increase in order to prevent increased frost risk.

We made also some stats on the forum about users having Daiking HPSU Compact real time monitored:

  • 4 kW model => 1 user, no issues
  • 6 kW model => 2 users affected by the problem (including myself)
  • 8 kW model => 2 users affected by the problem
  • 11 kW model => 2 users, no issues

With our stats: 4 users out of 7 are affected by the “apparent” problem (60%).

The escalation

Daikin Defrost

Strengthened by Altherma manual and without any answers from Daikin Italy, I boldly tried an escalation. On 12th January 2017 I opened a formal complaint through Daikin Group website.

Incredibly the following day I was contacted by Daikin Italy Technical Support manager who assured me that technician of Genova Centre of Excellence would come to my home ! Simply AMAZING !

Anyway quite hard to be listened.

Here comes the cavalry

Daikin Defrost

Defrost battle royal day was 17th January 2017: 2 Daikin Italy technicians travelling from Genova + local Technical Support Centre owner worked on my heat pump most of the day.

Really very kind and expert. I was declared to be first case to be analyzed in order to collect data and hopefully solve frequent defrost problem. They answered to any of my question (with a simple language).

They performed following activities:

  1. internal unit verification
  2. external unit behaviour analysis with PC data collection – 2 x 25 minutes defrosts observed
  3. refrigerant gas quantity verification: found 1.330 grams instead of 1.600 grams (nominal quantity for 6 kW external unit)
  4. internal unit factory reset to clean any “noise” due to any strange configuration performed by the customer (myself)
  5. internal tank addition of 20 liters water (not an issue, latest check was done 12 months ago)
  6. refrigerant circuit emptying to remove any humidity
  7. new refrigerant gas load (1.600 grams nominal quantity)
  8. system restart and monitor with PC data collection
  9. 2 x 25 minutes defrosts observed just after restart – no defrosts in following minutes
  10. external unit sounds becamed regular as per Genova’s technician
  11. evaporator temperature increased of few degrees after gas addition (no actual data provided)
  12. consider that outdoor temperature increased in the meantime of all operations
  13. reccomended seasonly external heat exchanger cleaning

We agreed to be in touch in order to:

  • observe system behaviour
  • collect feedback on external unit collected data analysis (performed by Daikin Italy and Daikin Europe N.V.)
  • define if noisy three way valves replacement is required

The “un-questionable” results

Few hours after technician left my home, joint to outdoor temperature fall, were enough to understand that things were not significantly changed.

Never ring bells too early.

I decided to free my numbers passion monitoring in a microscopic way defrost cycles for the following 7 days in order to produce indisputable statistics:

  • 174 defrost cycles in 7 days => 25 defrosts / day on average
  • average interval between defrost cycles is 44 minutes
  • defrost cycles are NEVER more distant than 1 hour and 10 minutes
  • defrost interval seems to increase slightly with outdoor temperature decrease

Daikin DefrostDaikin DefrostDaikin Defrost

Unfortunately comparing these data with product documentation (Daikin Altherma Service Manual) I can only conclude that my Daikin HPSU Compact is not working as per product specification (defrost frequency).

I sent this analysis back to Daikin Italy on 24th January 2017.

Here you can find all the data defrost_daikin.

The answer

Daikin Defrost

Given the data collected your sistem is working properly, we sent information and data recorded to parent company, we are waiting for a further confirmation that we’ll happily share with You. For your information the documentation about Daikin defrost operations included in the Manual You retrieved does not appy to GBS units (like your RRLQ006CAV3).

One row answer, non fact based but self-declaration based, to justify everything I explaind above.

Daikin Defrost

Something still does not come back to me. And I am really restless.

Now I’ll explain why in more detail.

Frequent DHW cycles increase electric consumption

As usual, let’s start from electric consumption data:

  • my Daikin HPSU Compact used 198 kWh (electric) in 7 days
  • 174 defrosts in 7 days
  • 44 minutes average defrost interval
  • on average one DHW cycle is required every 6 defrosts
  • one DHW cycle requires 2,0 kWh (electric)

Now few assumtions to make estimates:

  • a perfect behaviour would require, when necessary, one defrost cycle every 2 hours => 64 defrosts in 7 days => 11 additional DHW cycles in 7 days
  • an average behaviour would require, when necessary, one defrost cycle every 80 minuts => 96 defrosts in 7 days => 16 additional DHW cycles in 7 days
  • actual behaviour of 174 defrosts in 7 days => 29 additional DHW cycles in 7 days


  • with a perfect behaviour I’d saved 18 (29-11) additional DHW cycles in 7 days => 36 kWh (electric) saving
  • with an average behaviour I’d saved 13 (29-16) additional DHW cycles in 7 days => 26 kWh (electric) saving

Electric consumption summary:

  • actual behaviour => 198 kWh (electric)
  • average behaviour => 172 kWh (electric) => 13% less than actual
  • perfect behaviour => 162 kWh (electric) => 18% less than actual

Conclusion: due to too frequent defrosts electric consumption could be increased of about13% / 18%.

Keep in mind this is best case scenario because I don’t have data on COP reduction due to continuous on/off of the system !

Three way valves noise (and reduced life ?)

Daikin Defrost

I’ll let you listen to this video recorded close to my Daikin HPSU Compact internal unit while one defrost cycle was operated (please do not increase the volume)

Daikin Italy technician during the visit confirmed me this noise is regular. Confirmed also by email.

Imagine your internal unit placed inside your wardrobe in your bedroom as suggested in a Rotex brochure. Or in the living room:

Daikin Defrost

But the best option to handle defrosts (stress relief) is the following:

Daikin Defrost

Choose the best option for you.

Not continuous heating

Now let me underline another behaviour caused by 25 min defrosts bursts:Daikin Defrost

The joint effect of Daikin defrost and long delay of compressor restart heavily reduces heating operation time: the actual thermal energy is reduced even with an higher thermal power available.

Again we can put figures considering the example interval 17:31 (first de-frost) -> 21:05 (fifth defrost):

  • total time: 3 hours 34 minutes
  • active heating time: 1 hour 32 minutes => 43% of total time

So, in this example, thermal power/energy was 57% cut vs power/energy available.

So no heat curve can fit for all outdoor temperatures and it is required to increase flow temperature (reducing COP).

Keep in mind this is best case scenario because I don’t have data on COP reduction due to continuous on/off of the system !

Daikin defrost findings

Daikin Defrost

This journey made me really tired as customer / consumer. First for the complexity to access and to be listened by a big international company. At the end, reading the answer, because not considered at all.

I found extremly interesting the opportunity provided by internet to share intelligence and knwledge of many people (social intelligence).

Which findings for people owning an heat pump or evaluating to buy a new one ?

Anyway it is a very good option. The choice should be based on what best fit for us and to select a company who provide the best technical support. And then for the costs.

Unfortunately winter defrosts are not a neglible factor and can lead to unpleasant surprises. If the choice is not conscious.

Based on multiple cases collcted into fourm, not all Daikin HPSU Compact are affected by the issue I explained in this article. But I wasn’t able to find any 6 / 8 kW model not affected by the “Daikin defrost precox” problem.

Users of other brands / models tell of neglible defrost frequency compared to mine (in some case different order of magnitude).

When you choose an heat pump please make a conscious choice (ask and don’t accept not fact based answers) also about defrosts. In winter time they are unavoidable and healthy. But when you overdo it …

Would I buy again Daikin ? I’ll let you choose !


  • every number or analysis of this article is based on data public available on my monitoring system
  • no “Daikin defrost precox” was damaged to write this article
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