All Heat Pumps / Daikin Altherma 3 and SOLAR GAIN

[HeatStig (Daikin Althema 3 8kW)]

SOLAR GAIN!

Here we are again with lovely sunny almost spring weather in the South of England.

The way our house faces gives it a huge solar gain!

The Daikin external temp sensor is mounted on the north face recessed, gets no heat and currently reads 3 C.

Without the sun (pretty much thus far during the winter) that would give about 35 C LWT.

House temp is up to 22+ C and will climb and climb if I do nothing.

At the moment I have manually reduced the offset in the Onecta app by -7 C to compensate.

The concumption is right down, house nice and warm but not too warm.. Heatpump running on fan only pretty much.

Would be great to automate this somehow or would moving the single temp sensor and trialing different positions be an idea?

My experiences of the Madoka last year (Winter into spring) were all bad, on/off no real modulation! Hence going LWT.

The existing temp sensor works fine for little to no sun days and of course nights.

I would like to integrate a 2nd temperature sensor, could be external or room, that would give some average / common sense control this.

I’ve come across Daikin’s KRCS01-1 that looks like it might fit the bill!

It is for rooms but perhaps could work undercover or in a garge if suitably configured?

Installing in a house room will be much more hassle.

The installation manual shows where to connect it. Then it’s configured in the controller.

Has anyone done such a thing? Does it work as desired?

The other option would be to use another same as existing external temp sensor and somehow aggregate the two to give a sensible reading for what the house is really seeing - techy..

[Begall (Ben)]

Here’s my setup:

• Heat Pump linked to HA via ESPAltherma for data
• Hear Pump linked to HA via ONECTA API for control
• Network of 8 Zigbee temperature sensors spread through the house, linked to HA and keeping track of the overall average internal temp

With this kind of setup, you can set whatever logic you like to control the pump as per any internal temp or pump data parameters. For example, you can automatically bring flow temps up or down based on internal average temp or set a cut off internal temp based on a single room if you wish.

The key component is having HA to manage all of it

[dMb (davidMbrooke)]

I’m with Ben; if you’re comfortable with using something like Home Assistant you could automate the adjustment of the offset in Onecta, using HA’s Onecta integration.

Do you have / could you add a data source that’s a good proxy for the amount of passive solar gain you’re getting - e.g. solar PV where the power output is (roughly) proportional to the solar gain? That would respond quicker than relying on a response from indoor temperature sensors.

Personally I think you’ll struggle to find an alternative location for a single external sensor that will achieve the balance you want between reading the ‘true’ outside temperature (which is what your existing external sensor seems to be doing very well) and reflecting the effect of solar gain.

I have the same “problem” with passive solar gain which has taken my house 1C above its set-point this morning (and one south-facing room is 5C above set-point). My NIBE system uses its indoor temperature sensor to reduce the target flow temperature as the house warms so the heat pump hasn’t run since 08:30 and probably won’t come back on until tomorrow. While that works without any manual intervention (and is built-in to the NIBE controller) it relies on the indoor sensor responding to the temperature rise - and I have a lot of thermal mass so there’s an annoying ‘lag’ in the response. I sometimes think I should try to use a forecast of sunny weather to dial-down the heating in the expectation of future solar gain.

[HeatStig (Daikin Althema 3 8kW)]

Great ideas and interesting to see you reckon it could be done.

Unfortunately not got the time and or the energy right now to get into home assistant.

Agree entirely on the not finding a good single place for the external temp sensor attached to the house / outbuildings.

These systems really need more flexibility and to be easier to configure.

In about 10 years time heat pumps will be adaptable and user friendly (maybe).

I might try something like the Weather station housing.

These are designed to give a true ambient temperature regardless of sun and shade.

Bolting the sensor to a cold north facing recessed outside brick wall, as the installers did, can’t be right..

[HeatStig (Daikin Althema 3 8kW)]

Here’s a mini one that’s turnkey and cheap. Might not be big enough though

Netatmo - Functional protective housing for the smart weather station,...

Aliexpress have very cheap ones..

[Robert.Wall]

Maybe of interest: Stevenson screen - Wikipedia

[HeatStig (Daikin Althema 3 8kW)]

Yes exactly.

[HeatStig (Daikin Althema 3 8kW)]

I had an hour today and went out and measured the temp at the current sensor position. Full shade, cold sheltered corner outside wall / cold garage. Never gets any sun. Always well behind ambient temp.. 6 to 7°C!

Ambient temperature 10°C

Under the rear / shady side of our thick soffit woodwork at the front in full sun the temperature is 10°C.

Essentially this is acting as a weather measurement shelter.

I going to monitor at different times.

I moved the sensor to a spot where it is 9°C. Took 5 mins. Half an hour later this spot is 10°C. Weather curve is throttling nicely!

I have no worry that the temperature will fall with the ambient in the new spot.

It’s being more intune to full sun that’s required.

See how it goes, may move to the front position, if monitoring looks good.

[chrisg (Chris Geary)]

The Madoka is just not fit for purpose for several reasons. I’ve also tried various strategies but I’ve settled on the addition of a Heatmiser Neo Air and set the Altherma for external thermostat control. Using Home Assistant and a couple of Switchbot thermometers, HA provides slight offset corrections to the LWT to maintain a ground floor temp of about 20-20.5c. If the solar gain is too much, the Heatmiser stat (set for 21c) shuts off the heat pump. At 20.5c, it’ll restart the heat pump.

It’s now set and forget, doesn’t rely too heavily on the cloud and uses the weather compensation curve to keep the house just right no matter what the outside temperature is but if there is solar gain, the Heatmiser prevents the heat pump carrying on when the internal temp is good (and usually rising the sun’s heat).

[HeatStig (Daikin Althema 3 8kW)]

This sounds like a great solution.

I will study it

[maximundo (Max Frimond)]

This is awesome. Would you share your automations for this?

[chrisg (Chris Geary)]

Sure! Below is the YAML for the automation that adjusts the LWT offset based off of one or more temperature sensor entities.

Heating Automation YAML

alias: "Heating - Ext Thermostat "
description: >-
Control Heat Pump, maintain GF average 20c.

Works around the Madoka’s 2c hysteresis, sun hitting it etc by using switchbot
thermostats for offseting lwt. Heat pump off and on controlled by Heatmiser
stat
triggers:

• entity_id:
  • sensor.ground_floor_avg_temp
    for:
    hours: 0
    minutes: 5
    seconds: 0
    above: 20.7
    id: Above 0.2c
    enabled: true
    trigger: numeric_state
• entity_id:
  • sensor.ground_floor_avg_temp
    for:
    hours: 0
    minutes: 5
    seconds: 0
    below: 20.7
    enabled: true
    trigger: numeric_state
    id: Below 0.2c
• entity_id:
  • sensor.ground_floor_avg_temp
    for:
    hours: 0
    minutes: 5
    seconds: 0
    above: 20.3
    id: Above -0.2c
    enabled: true
    trigger: numeric_state
• entity_id:
  • sensor.ground_floor_avg_temp
    for:
    hours: 0
    minutes: 5
    seconds: 0
    id: Below -0.2c
    enabled: true
    below: 20.3
    trigger: numeric_state
    conditions:
    actions:
• alias: House too warm, reduce flow temperature
  continue_on_error: true
  if:
  • condition: trigger
    id:
    • Above 0.2c
      then:
  • alias: Lower offset to -3c
    action: climate.set_temperature
    metadata: {}
    data:
    temperature: >-
    {{
    state_attr(‘climate.heating_leaving_water_offset’,‘target_temp’)|float(0)
    -3 }}
    target:
    entity_id: climate.heating_leaving_water_offset
• alias: House just right, set normal flow temperature
  continue_on_error: true
  if:
  • condition: trigger
    id:
    • Below 0.2c
    • Above -0.2c
      then:
  • action: climate.set_temperature
    metadata: {}
    data:
    temperature: 0
    target:
    entity_id: climate.heating_leaving_water_offset
    alias: Reset offset back to 0c
• alias: House too cool, raise flow temperature
  continue_on_error: true
  if:
  • condition: trigger
    id:
    • Below -0.2c
      then:
  • alias: Raise offset to 3c
    action: climate.set_temperature
    target:
    entity_id: climate.heating_leaving_water_offset
    data:
    temperature: 3
    mode: single

Notes

• Assumes you have installed the Onecta Home Assistant integration and have the various cloud-based entities present.
• Assumes you are running LWT or Ext. Thermostat modes which both permit the use of the offset sensor: climate.heating_leaving_water_offset
• sensor.ground_floor_avg_temp - this can be anything you like. For me, this is a template sensor averaging two other Switchbot sensors. There’s no reason why this couldn’t be the entity created by the Onecta integration for the Madoka’s room sensor.

[maximundo (Max Frimond)]

Thank you!

[HeatStig (Daikin Althema 3 8kW)]

For completeness I’ve posted this here too..

I’ve moved our external temperature sensor from a very sheltered north facing spot (I was in a cold sheltered spot with brick and tiled roof on 3 faces around it), to under a thick wooden soffit on the south / sunny side.

The sensor is never in direct sunlight though.

Now instead of the temp sensor being about 4 to 5°C lower than ambient and it entirely missing the amount of solar gain the house gets when sunny, it actual tracks what’s going on much better!

It’s still in the shade as it were, but it feels what the house feels.

When there’s no sun, it’s also showing the correct cooler temperature.

The sensors are a two-bit part.

Simply a two wire thermocouple / 4 screw connection block to the cable.

The cover just pops off. One central screw secures the base.

Really easy to replace / move.

[JamesH]

I have the issue of solar gain problems too. Maybe I also should move the external temp sensor locations. For me, with a vaillant, it’s a shame their active compensation mode isn’t strong enough to correct temp spikes. I’ve had to drop the heat curve by 0.1 from 0.7 to 0.6 to try reduce the issue recently. Actually and interestingly the issue is more at night time, because the huge stone walls store so much solar heat, the requirement for heat at night when temp falls to 1C is a lot lower.

[HeatStig (Daikin Althema 3 8kW)]

Yes, with a high heat retaining property unless you put the temp sensor in a place where it can feel the warmth of the stone, it will be reading cold outside while the house is still warm.

That’s where a proper 2 sensor set up would be great.

Some logic added - time of day, month of year, previous average temperatures outdoor and indoor etc, to better calculate what the weather and the house are doing. It’s a combined environment, should be measurement and controlled thus.

Have you tried the average temp sensor settings?

It’s 12 hour avg on the Daikin. Could be something there to sustain a longer warm reading to reflect your heat retention?

Try putting the sensor so when it is sunny it gets more of that higher daytime temperature to balance up the average?

When there’s no sun and no solar gain all day it will still transmit colder conditions to the heatpump controller.

The current heatpump sensor solutions are very poor IMO.

Installers give zero thought to the single temp sensor placement. Just fit it to the north wall, they are told.

They don’t know the house aspect, heat retention etc etc.