Heat Pumps: anyone have one/thought about it?

6°c overnight here as well, maximum our flow temperature got up to was 32°c, heat pump seems to run about 600w.


200sols said:
Get a tumble dryer.
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That's been one downside of the heat pump, we used to air dry the washing in the utility room, which was always nice and toasty, now it doesn't get overly warm, so the tumble dryer gets used when it can't go out, which is a lot this time of year.
 
First properly cold week so I was looking too when I woke this morning. 4C OAT and 30C in app. I'll check again tomorrow in the MMI for a more accurate figure. Temp was very slowly creeping up so must be quite closely matched to the heat loss. Small, well insulated house with all rads changed to the biggest that would fit.
 
It dropped to 3.6C here with a gale force wind blowing at the front of the house aswell, so it was certainly a good test. I run on LWT only with no thermostat involvement and have found the new curve I set is spot on when its not too windy, but I have to put in a positive offset if its very windy. Last night it was running at 34-35C flow but with the wind it needed a +3 offset to get the coldest rooms up. Weirdly it doesn't affect power use too much. AT 34-35C LWT it was using about 400-500w and at 38C it was still only around 600w. COP is still 4.5-ish even at that. It's much quieter now that its running with a delta T of 10C. By all accounts, it should be much less efficient, but I've found on my microbore system that it increased efficiency by almost a third over the fancoil setting with its delta T of 5C.

The radiator still isn't big enough in the living room though. Octopus said it would be fine on their survey but I knew from previously with the gas boiler that it would be a struggle to bring it up in there and it has proven so. It's 19.8C at the moment in there with all other rooms in the house between 21 and 22C. That is the radiator I purchased myself and asked Octopus to fit for me at the time. I can only imagine if we'd kept the smaller one!
 
reef said:
It dropped to 3.6C here with a gale force wind blowing at the front of the house aswell, so it was certainly a good test. I run on LWT only with no thermostat involvement and have found the new curve I set is spot on when its not too windy, but I have to put in a positive offset if its very windy. Last night it was running at 34-35C flow but with the wind it needed a +3 offset to get the coldest rooms up. Weirdly it doesn't affect power use too much. AT 34-35C LWT it was using about 400-500w and at 38C it was still only around 600w. COP is still 4.5-ish even at that. It's much quieter now that its running with a delta T of 10C. By all accounts, it should be much less efficient, but I've found on my microbore system that it increased efficiency by almost a third over the fancoil setting with its delta T of 5C.

The radiator still isn't big enough in the living room though. Octopus said it would be fine on their survey but I knew from previously with the gas boiler that it would be a struggle to bring it up in there and it has proven so. It's 19.8C at the moment in there with all other rooms in the house between 21 and 22C. That is the radiator I purchased myself and asked Octopus to fit for me at the time. I can only imagine if we'd kept the smaller one!
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Imagine if the WDC was set to the Octopus design of 50C LWT! Currently set to 33C @ -5C. We'll see if Grok was right this week.

When I used Grok (AI) with a full description of my setup the fan coil setting was suggested as a cause of pump surging and excessive pump speed. Reported multiple times on the Daikin support forums. There appears to be firmware limitations of 25C to 55C in operation due to the heat output characteristics of actual fan coil heat emitters. I found that when setting the warm LWT to 24C the heat pump would not switch back on after a heat cycle. As soon as you added +1 in the app/Madoka it would start working again. I went back to rads but changed the Delta-T manually to a lower setting.
 
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bimbleuk said:
Imagine if the WDC was set to the Octopus design of 50C LWT! Currently set to 33C @ -5C. We'll see if Grok was right this week.

When I used Grok (AI) with a full description of my setup the fan coil setting was suggested as a cause of pump surging and excessive pump speed. Reported multiple times on the Daikin support forums. There appeared to be firmware limitations of 25C to 55C in operation due to the heat output characteristics of actual fan coil heat emitters. I found that when setting the warm LWT to 24C the heat pump would not switch back on after a heat cycle. As soon as you added +1 in the app/Madoka it would start working again. I went back to rads but changed the Delta-T manually to a lower setting.
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Pump surging and excessive speed is exactly what I was seeing when set to fan coil. On my 10mm microbore it runs very stable on the radiator setting and a delta T of 10 with the lower pump speeds. As far as Im aware the Daikins will turn off at below 25C leaving water temp and don't really like going under 30C. Ive set 30C for the minimum LWT on my weather curve and it can maintain that using its minimum power draw.

Octopus appear to be very conservative with their settings. I suppose it makes sense as it ensures a warm house for those who don't want to tweak stuff. I cant fault them to be honest, the install is very good.
 
The temperature down here in the south east has dropped overnight to a chilly 1c and we've had our first long heat pump run, not sure how long, it started at 22:09 and its still going.

Todays COP so far 5.9 (no hot water yet), yesterday was 5.86 overall.

 
Ron-ski said:
The temperature down here in the south east has dropped overnight to a chilly 1c and we've had our first long heat pump run, not sure how long, it started at 22:09 and its still going.

Todays COP so far 5.9 (no hot water yet), yesterday was 5.86 overall.
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So at a glance you have two water heating events and the HP cycles during the day, though not very often, because you have a thermostat enabled. COP is very good and the overall power draw is also very reasonable. Appears to have run continuously overnight because of the lower OAT. Low flow temps and Delta-T so WC also very closely matched.

I think you posted a 21C flat temperature so the HP was very closely matched to heat loss overnight hence no cycling.
 
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Last night was the coldest so far and was 1C from late evening all the way to 6AM. First test for the Grok (xAI) recommended settings. When I woke the HP had been running all night despite a small LWT setback from midnight to 4AM. This had stopped the HP running previously with warmer outside temps. OAT was 1C, LWT was 31C and the house was sat at 19.7C with no deviation. Checking the MMI the LWT was 31C with 28C return matching my target Delta-T of 3C. Flow rate was 7.9 l/m actually lower then that which Grok had calculated. Power draw was a steady 500W.

I fed the data back to Grok which did a "quick" calculation of 1.65KW heat loss at 1C OAT from my previous uploads. Everything seems to be as calculated though I don't need the temp to be much above 19C overnight so I dropped the WDC at -5C from 33 to 32C to see what happens tonight.
 
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I’m the opposite, I ramped the flow temp up to 45c and went ham overnight :cry:

It needed 3 defrosts (about 1 per hour) by the looks of it and it cycled once at the end of the hot water cycle.
 
bimbleuk said:
So at a glance you have two water heating events and the HP cycles during the day, though not very often, because you have a thermostat enabled
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Thank you for the detailed reply.

On the Vaillant system there is three options for what they refer to as the room temperature mod.

Extended: acts like a traditional thermostat.
Active: WC with subtle adjustments based on indoor temperature.
Inactive: Pure weather compensation ignoring indoor temperature.

My installer had it set to extended, I've changed it to active, they also had the WC set at 0.8. I've been gradually dropping the WC, when I got to 0.4 some rooms were losing temperature, so upped it back to 0.45, which gives a flow temperature of 36°c at zero OAT.

I have my Valiant SesoHome controller in the hall on a window sill, seems to hold a pretty stable temperature all day, and works well for the rest of the house. It is set for 20.5°c 24/7, no set back.
 
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Ron-ski said:
Active: WC with subtle adjustments based on indoor temperature.
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This sounds like Load Compensation which a lot of the entry level heat pumps like my Daikin Altherma 3M lack. Main difference is the indoor temp sensor is still dominant but outside conditions which change the fixed WDC are compensated for by monitoring the indoor temp changes.

On my setup with no internal temp sensor currently, a windy or damp day would change the WDC so the inside temp will vary. I can make +/- LWT changes to compensate but of course its an ad hoc process.
 
The Daikin can do load compensation, the setting is called ‘modulation’ and will automatically vary the LWT by up to +/- 10c based on the internal temperature sensor.

That said it’s recommended you set the range to be as low as possible as it can reduce efficiency as the heat pump has a habit of ramping up if you are below target, overshooting and then ramping down. It’s handy if you run 24/7 and get a lot of solar gain though.
 
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b0rn2sk8 said:
The Daikin can do load compensation, the setting is called ‘modulation’ and will automatically vary the LWT by up to +/- 10c based on the internal temperature sensor.

That said it’s recommended you set the range to be as low as possible as it can reduce efficiency as the heat pump has a habit of ramping up if you are below target, overshooting and then ramping down. It’s handy if you run 24/7 and get a lot of solar gain though.
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So that's what that setting does as Heat Geek mentioned it in the vid that recommended the fan coil setting which doesn't appear to be that great Afterall. As I switched to LWT I didn't ask Grok about it. I had lowered it when I was still using WDC + Temp.

Asked Grok and as WDC is already close and working well it may not be needed but could offset overshoot due to solar gain (like you wrote) on warmer days. Might add the final polish to the system and recommend not to go over 3C for my setup at least. Easy to switch modes as the WDC is retained just some of the pump settings might differ (from sample to demand). Something to play with.
 
Can anyone else set the Delta-T below 10C on a Daikin Altherma 3M when the emitter type is set to radiator? Mine appears to be locked to 10C or above when using WDC + Thermostat. Grok suggests this is due to old firmware or an installer lock set deeper in the MMI settings. Not sure I want to play with the field settings/codes.
 
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Mines stuck at 10C when on radiator i believe.

Today was a good test of the weather curve as we dropped to -1C this morning and was below 5C most of the day. I actually saw my first three defrost cycles overnight. At -1C the LWT was around 41-42C and the house was a little warm if anything, so I can perhaps drop that a bit still. The heat pump has stopped pulsing and being so noisy after changing the emitter type to radiators so it runs well now. Even at -1C it was using about 1.1kW of power, so not too bad.

It has also been a good guide on how our battery will last. The heat pump used 19.6kWh yesterday and the battery lasted, but it was a sunny day. Today it has used 17.6kWh so far but it has been cloudy so the battery is at 25% and might not quite make it.
 
Mines used 17 kWh today, only 8.52 kWh solar, no export, and battery at the current rate has 3 hours and 12 minutes remaining, which means it will last to 23:30.

Think I had one defrost today, just after 12:00, not entirely sure though OAT was 5.5c

 
I only did 5.5kwh today and the heat pump just knocked off for the day until midnight per my timed settings. 33% (~4kwh) battery remaining so I'll even do a bit of exporting later.
 
bimbleuk said:
Can anyone else set the Delta-T below 10C on a Daikin Altherma 3M when the emitter type is set to radiator? Mine appears to be locked to 10C or above when using WDC + Thermostat. Grok suggests this is due to old firmware or an installer lock set deeper in the MMI settings. Not sure I want to play with the field settings/codes.
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Not an issue as there doesn't appear to be any downside to using the UFH setting to select Delta-T of 3C. My well insulated house with relatively large radiators loses heat very slowly. Even a 1C setback takes ages to to retrigger a heat cycle.

First heat cycle after making the changes was a bit erratic with spikes to 1.3kw then a pause which repeated a couple of times. Once the temp had reached the thermostat setpoint the modulation backed it down. Only stopped after midnight until 4AM and then did a single ~25 minute cold ramp up and down to 400W idle once the temp had dropped.

Daikin specific but the "Pump Limitation in Sample XX%" setting also limits the pump speed using Request mode (default for WDC + T). In my house anything above 15 l/m (60%) can be heard up one wall and over the ceiling where the feed and return pipes run. This does not limit the heat generation just the HP measuring the system water temp in between heating events. Below 4C OAT this can be almost continuous.
 
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Today is not far off as extreme as it gets weather-wise around here. Since midday it has been around 1C with a 20-30mph wind blowing straight at the front of house. Peak LWT has been around 40-42C and its still pushing close to a COP of 4 at this temp. The house is mostly 21C, but the living room is proving a real issue. It's barely 19C in there as we have a log burner and wall vents meaning there's just too much airflow.

So far it has used 16.1kWh today so I think it'll end up higher than yesterday's 20.9kWh. The battery is quite likely to run out later, but I need to do a large car charge tonight, so that might save me if I get an earlier cheap slot.
 
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