Slope weather curve and questions

ninjaef

Octopus installed my Daikin EDLA04E2V3 4kw air heat  pump in April 2024..

I live in a 1940 bungalow , 98m2 floor space, 2 beds, lounge, bathroom, open plan kitchen diner extension.

They replaced all rads to correct sizes and spec as designed.

Heating schedule is 19C between 6am and 9om , 17C all other times, every day. 

All TRVs fully open.

Questions...
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It's 1degC today and leaving water temp is 41C.....

1. MMI unit using weather curve type slope -offset. Offset zero, slope 26. What do these mean?

2. In MMI unit, the Emitter type is set to Fancoil. Octopus engineer on phone  said this is normal. Why should it not be dry too Radiators 

3. House takes 3 hrs from 6am, to heat house from 17C to 19C. Is this a long time? 

thankyou

smallblueplanet

Struggling to get the hang of a new Octopus Daikin myself.

1. Don't know, but there's lots of Youtube vids about weather curves. On FaceBook there's a Daikin group and an unofficial Octopus group.

2. The Emitter (ours too) is set to Fancoil rather than Rads as its to do with the DeltaT being better. But I don't really understand it.

3. Probably not, but might be better not to let it get so cool?

ninjaef

Thanks. Joined the group. Thanks for that. 

I've changed my emitter back to Fancoil !

What do you mean, too cold? Referring to 17C? That's a bit warm for me at night tbh but it takes 3 hrs already so left it at that. If that's what you mean...I could not sleep at 18C. jeez 🥹

Is 41C ok ? only I read every degree above 37C reduces efficiency by 2.5% so I'm running at 10% less and using more energy? If they were 37 I doubt the house would get to 16C never mind 19.

Exiled_Tyke

ninjaef said:

Is 41C ok ? only I read every degree above 37C reduces efficiency by 2.5% so I'm running at 10% less and using more energy? If they were 37 I doubt the house would get to 16C never mind 19.

Isn't that the point though?  The system monitors the outside air temperature and sets the flow temperature to the lowest it thinks it can get away with to maintain the house temperature.  So the cold spells make the system far less effecient but when it's warmer outside the system chooses a lower flow temperature.  If it's getting it wrong (too warm or too cold) for the outside temperature the WD curve can be altered. 

Three hours sounds about right to me.  Mine is set to start warming for when I get home from work, from 2pm onwards. 

stripling

ninjaef said:

Octopus installed my Daikin EDLA04E2V3 4kw air heat  pump in April 2024..

I live in a 1940 bungalow , 98m2 floor space, 2 beds, lounge, bathroom, open plan kitchen diner extension.

They replaced all rads to correct sizes and spec as designed.

Heating schedule is 19C between 6am and 9om , 17C all other times, every day. 

All TRVs fully open.

Questions...
----------------
It's 1degC today and leaving water temp is 41C.....

1. MMI unit using weather curve type slope -offset. Offset zero, slope 26. What do these mean?

2. In MMI unit, the Emitter type is set to Fancoil. Octopus engineer on phone  said this is normal. Why should it not be dry too Radiators 

3. House takes 3 hrs from 6am, to heat house from 17C to 19C. Is this a long time? 

thankyou

1. You'd need to detail all the points for an answer - X1 Y1 X2 Y2 - but they are basically the leaving water temp at different outside air temperatures. Offset means the amount it can deviate from the rule. Your best bet is to join the very helpful Octopus (unofficial) Heat pump FB group and include screenshots of your curve. There's 2 videos on the Heat Geek YouTube channel on using the Daikin MMI too.  If you are not happy with how your system is running you can tweak these but keep a record of settings before you change things and do it gradually - watch and feel for 24/48 hours before any further tweaking. There's a useful diagram in the otherwise un-useful Daikin manual but also watch vids and ask in the 🐙 Heat pump FBook group. 

2. Fancoil gives a Delta T of 5º - the difference between leaving and returning water temperatures. Radiator gives 8º - it just means the relationship between the water temperature, room temperature and pump speed. 

3. Every set-up is unique to the location - if you find your compressor/pump is firing up hard and eating lots of juice then you might want a more gradual set-back at night [18º?] but generally no, 3 hours is fine - low and slow is good for a heat pump.  Maybe start it at 5 instead of 6? 

I'd freeze to death @ 19º in the winter - mine is 21º for early day going to 22º then even 23º in the evening if necessary. 🥶😁

matt_drummer

stripling said:

2. Fancoil gives a Delta T of 5º - the difference between leaving and returning water temperatures. Radiator gives 8º - it just means the relationship between the water temperature, room temperature and pump speed. 

No.

In fan coils and ufh the delta t is adjustable.

In radiators the delta t is set at 10c on the 4/6/8 kW models and 8c on the larger 9/11/14/16kW models.

The set delta t is just the difference between the flow and return temperatures and is controlled by the circulation pump speed.

The room temperature is irrelevant.

ninjaef

matt_drummer said:

stripling said:

2. Fancoil gives a Delta T of 5º - the difference between leaving and returning water temperatures. Radiator gives 8º - it just means the relationship between the water temperature, room temperature and pump speed. 

No.

In fan coils and ufh the delta t is adjustable.

In radiators the delta t is set at 10c on the 4/6/8 kW models and 8c on the larger 9/11/14/16kW models.

The set delta t is just the difference between the flow and return temperatures and is controlled by the circulation pump speed.

The room temperature is irrelevant.

Octopus came yesterday, I asked why Fancoil not Radiator. He said all installations Octopus do, he's seen only Fancoil. My t is 5 and Fancoil. I have the 4kw monoblock Daikin Athena. Should I change it and why?

matt_drummer

They set them to all to fan coils as this then allows them to adjust the dT, it is not adjustable using the radiator settings.

It makes little difference using fan coils as the heat pump has no idea what it is connected to, it just heats water.

The different profiles allow for the differing response times in different types of heating, ufh is slow to respond whereas fan coils and radiators respond faster.

Unless you have some reliable, detailed and accurate way of monitoring the affects of any changes you make I would advise you to leave it as set.

A dT of 5c with radiators is considered to a decent setting for heat pumps.

ninjaef

It's changeable  the MMI, if set to Emitter=Radiator dT van be set to 3, 5, 7, 10, 12. But you sound knowledgeable and I shall leave it as it is. I've got rads and no mechanism  to measure response times and what to do with those measurements anyway 
Appreciate you kind help. 

matt_drummer

ninjaef said:

It's changeable  the MMI, if set to Emitter=Radiator dT van be set to 3, 5, 7, 10, 12. But you sound knowledgeable and I shall leave it as it is. I've got rads and no mechanism  to measure response times and what to do with those measurements anyway 
Appreciate you kind help. 

Every one of these Daikin heat pumps I know about the dT in radiators is fixed, the 4/6/8 are fixed at 10c and the larger 9/11/14/16 are fixed at 8c.

The dT is only adjustable in fan coils and ufh.


But maybe you have a newer firmware and they have changed something.

The response times I talked about is just how the heat pump behaves in response to heat demand.

That is, if your house is cold and you turn the heating on, in radiators/fan coils the heat pump knows that the house will heat up much faster than it would do with ufh. Under floor heating is very slow to respond to changes in heating demands, radiators and fan coils (radiators with fans) respond very quickly to changes in heat demand.

Therefore, if you have radiators, the heat pump will behave accordingly and give best performance for most people set at dT 5c in either fan coils or radiators if the adjustment is now there.

ninjaef

Oops. You're correct. It cannot be changed  -  I just had a look. One can change the emitter type and the dT is modified automatically but it can't be changed. Radiator=10c, Fancoil is 5c. I bet that's why it's set to Fancoil because 10C isn't appropriate or best, but  why that would be I've no idea. What's the impact of a 5c Vs 10c dT
(I got those numbers in my previous post, from the manual)