I wonder if the cycling after the DHW is due to the overshoot being so tight.
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As mentioned, Daikin have a couple of air to water monobloc (all in one) units these days:
EDLA (heating only) or EBLA (heating and cooling) 9/11/14/16 badged models - we believe that the fan speed, maximum electrical input power and compressor max power are all that differ between the models, and therefore all share the same characteristics.
They also do a smaller unit: E(B)LA 4/6/8 model designation.
A number of us have had very poor heat loss surveys to be honest.
If you have the time and the skills, it’s well worth getting to the bottom of what your heat loss actually is.
You can model it using for example the MCS calculator, HeatPunk software, HeatEngineer software and many others.
You can try and measure your heat loss if you have half hourly gas meter readings, known internal temperature and pick a date that was particularly cold but not abnormal (ie you’re after the design temperature). Add up all of your half hourly usage in kWh, remove say 10-15kWh for DWH usage, and divide the rest by 22 hours (to allow ~2hrs for DWH recharge), and then by ~85% to allow for energy lost up the boiler flue.
I think you’ll be surprised how low the figure comes out at.
The other alternative is to try and keep a constant temperature for 24hrs, start tracking the produced space heating heat and also the known internal + outside temperatures, and then working out heat loss from those figures.
Unless you’re seriously out on the heat loss figure in real life, it’s best to focus on understanding how your unit works (best!) and seeing if LWT or Madoka control is best for you and your family.
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I canned our trial on LWT this morning.
While we seem to be able to run at 800 watts for a long time - before 2200 to just before 0400 (last night), our room temps where slightly high - even with the offset over night of -3 degrees we didn’t drop any temp. We gained half a degree instead 
Reviewing the COP (I know it’s not super accurate but it’s all I’ve got) Heat output divided by elec was 4.6…
I’m a bit of a warm blooded person so prefer a steady 18 to 19!
I think having the upper bound set to 40 was too high - so will tweak down 38 instead when we trial on a cooler day.
The bit I’m struggling with is on warmer days it seems to consume more than the previous day. Saturday and Sunday where pretty similar up here. So on a warmer day > 5 degrees it might be better to have a schedule and let the UFH emit the heat during the day, with occasional top up’s.
Our schedule is pretty much most of the day anyhow from 0400 till 0730 at 18.5 the remainder of the day at 18 then an increase in evening to 18.5 till 2200. Our set back temp is 17.5.
Unfortunately, the next couple of cold days are while we are away by the looks of things - this is probably when I’d like to try LWT again!
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Hi @datoon a couple of things:
- 18.5C is a fair bit lower than the MCS standard heat loss calculation will provide for (21C)
This obviously impacts heat loss (much lower), and therefore a high probability of hitting the minimum output/modulation barrier you (and others here) are seeing.
- Without knowing all the figures, it may be that your heat loss is a lower than you thought/were told.
I think it’s a win (for you) that you’re already feeling the curve is too steep!
I only said 40C at top end given you were stating 48C flow at -6C outside originally!
It’s still early days to dial in the weather curve to be fair, and it has been relatively warm - more what you can expect come spring and autumn to be honest.
However, do understand that if you were running minimum output for an extended period of time (it sounds that way!) without the emitters being able to shed heat fast enough, the flow temperature and mean water temperature (MWT) of the emitters will carry on rising until it hits the ~4C overshoot cutoff.
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Thanks for the info, we could run at a higher temp, my wife would love that!
What’s the impact of lowering the deltaT in the above circumstance…
Maybe half the overshoot to 2.
Need the temp to drop before testing again as I think the current setup is ok for these temps.
I’m hopeful Octopus come and put the madoka in so I can assess modulation too.
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I assume you mean higher inside (e.g. living area) temperature? If so yes, it sounds like your system can do it. Remember: when running minimum input electricity (say 900w), it can’t use less, so artificially limiting output won’t always reduce electricity usage. It’s counterintuitive at first.
Is your Tado set to crazy temp say 30C? (To ensure “on” is sent and kept “on”)
Is it doing anything like TPI (which is bad for heat pumps)?
See this post for one of many negative comments on TPI and heat pumps:
Interesting why Octopus 
didn’t install the Madoka as I thought that was standard.
If you’re running at dT of 5C (between flow and return) already, then you’re at the likely optimal configuration. You don’t really want to go lower than this as it’s likely this is most efficient.
What is your maximum flow rate you’re seeing when in heating mode?
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We didn’t have anything limiting output, as we’ve a fully open system with no TRV’s or actuators.
The only thing limiting it would be the thermostat as it is now.
When I started the LWT trial inside temp was already at 19, the main thermostat that I’ve got setup for Tado is in our living room. There is a couple of reasons for this:
- It get’s affected most by the wind and rain when it’s blowing - so has quite a cooling affect.
- When we had the initial problems with the system, the Octopus engineer suggested using the room you wanted the temp as the thermostat.
- This was also the room we had most issues with during the first initial month with the HP.
One downside of having the stat in that room is that bodies obviously affect it, so when we had movie night it increased and never decreased. That being said the rest of the house was nice and toasty - even our poorly insulated bedroom.
Ironically, I’ve still the remaining Tado’s downstairs - wired in, so can switch to use a different stat if I need to.
Yeah, when I turned on the trial I just set Tado to maximum of 25 to keep the (live?) on. I’m not sure what TPI is - I’ll read the other thread.
I believe the issue they find it hard to say get rid of all your Tado’s which cost 100s of pounds and use this. However, it’s something I think they should have done as standard - as everything I’ve read implies not to use 3rd party controls with the Daikin’s.
For the maximum flow rate I presume I would have to open the flow restrictor fully and then set the temp to max. Then monitor for a period of time?
From what I understand (limited) the Daikin appears to modulate the flow as well - once it get’s to a point.
Indeed - any heat pump actually.
I’m not even sure what a flow restrictor is, and I’m scratching my head as to why you’d even want something that restricts flow! Honestly, it sounds like it should always be “disabled” to avoid restricting flow, as the pump (if it can overcome the resistance of a restrictor will naturally consume more power than if there were no resistance/restriction. )
Any way you can photo it or let us know more details?
In theory (famous last words) with you now in LWT mode, actually the thermostat shouldn’t be influencing anything anymore, but I’ve not used this setup with a 3rd party thermostat, so you’ll have to see. Turning the Tado right down to say 12C should have no effect really with the mode (Lwt) you’re in.
This is on the flow to the buffer tank:
Think I need a live from the Tado for LWT to work so turning it down to 12 would cause the HP to stop.
I’m still a little bit unsure of LWT, I noticed on yours today that it did turn off for periods. I’ve not seen this with mine. Maybe it’s my 3rd party controls…
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I’m thinking I need to clean my filters as you suggested the other day… Shame it’s been raining all day.
Getting 30 l/min.
I’ve seen it higher previously.
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Right, this is an Automatic Bypass Valve (ABV)
If anything, it’s doing the opposite of restricting flow, especially (if I’m reading the photo correctly) it looks fairly wide open?!
Basically, the valve will “short circuit” your heating emitters (radiators and UFH) if a certain pressure is detected. And by how “open” that valve looks, your heat pump may be heating water, sending some to the radiators and UFH, and then the ABV is short circuiting the rest straight back to the heat pump.
This is why it’s not a fair test with dT5 - if there is a pressure problem, the ABV will just counter it. Terrible for efficiency however.
But I guess octopus put one on every install in case someone turns off or turns TRVs right down on all radiators in the system. It’ll prevent a “too low water flow rate” error on the Daikin controller, but be basically heating the pipes outside!!
Here is mine (note mine is fully closed).
I know @markocoheat has thoughts on these…
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Sorry, got my piping the wrong way around!
I only had it fully open to show you it, it was about a quarter closed.
I’ll close it fully see difference.
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That’s great you’ve seen it higher.
I was in the same position, I recollected (but had no evidence- monitoring etc) of low 30s l/m, and noticed once I hooked my system up to EmonCMS it wasn’t going beyond 22l/m….got back to 34l/m after cleaning both.
This was one year and only one of the two filters/strainers:
I turn it off manually from the app.
My EDLA11 outputs too much heat at minimum modulation/output in mild weather (four house heat loss).
I just didn’t get on with the Madoka personally (you may however and will be miles better than Tado control!)
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Seem to be getting there now with this setup.
Still a bit up and down during some of the runs in the morning.
Just trying to understand the Pump Limitation setting as my flow rates seem to drop off after the initial run down to 11 l/min. I would have thought this needs to remain around a constant level.
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Hi @datoon,
That’s good to hear things are moving in the right direction and you’re understanding your system.
Going down to about 10-11l/m is consistent with the others on here with the “9” and “11” model designation of the unit you have. And entirely expected.
Flow rate is a big part of the heat output equation.
To illustrate that, below shows the heat output (kW) at 30l/m which you said you’ve seen:
The below shows the flow rate you’re now seeing at “steady state”
You can see that dT between flow and return remains the same, and only flow rate changes.
Unless it’s extremely cold and close to or below design temperature (and even then this is based on your modelled heat loss not actual), you won’t see high flow rates other than initial ramp up or for DWH runs.
With regards to Pump Limitation: this should be set to “only when sampling” and say 60% when sampling:
You do not want to limit pump speed/power all the time, so be careful to select the right parameter and value (“only when sampling”) as this is useful to minimise electricity usage of the pump in between the compressor being on (eg when in LWT mode and the unit is cycling)
My system and others (I believe) use the Pump limitation - 60% pump speed during sampling value
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Hi Stephen,
Is there any setting regarding pump speed that limits the lowest speed that you have seen?
I have my pump at 60% when sampling.
I saw another parameter that was something like pump restriction, I can’t remember exactly waht it is called but I have never touched it.
I would be happier if I could get my flow rate below 10lpm, something like 7lpm I see in the smaller models.
The manufacturer’s spec sheet for Daikin Altherma 3 says you need 20 l/min (if this is the right model)
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Hi @matt-drummer
No, the main pump limitation parameter is documented as limiting the top end (so not a good idea to use)
Pump limitation while sampling is fine and I’d go lower tbh that 60% if possible as that parameter is only in play between compressor turning off and then back on.
Hi @Timbones
Yes, that’s to allow for defrost etc.
If the system at max pump speed cannot handle 20l/m, my understanding is that it errors out and generates a fault.