Here is some actual data we can discuss (link to data):
Hypothesis: does reducing the flow rate on a DHW cycle increase the dT, allowing more time for heat transfer to occur (please correct me if I have this wrong)
The test conditions:
- Heat the water to a set temp (46c) - Occurs at the same time of day 12:00 - Tried to find very similar OAT and heat output figures for comparison
I've added another date in (5th) which has a closer average OAT and still: Basically, there is nothing in it! The only real difference between the two tests was the OAT being 1.5c apart.
This post was modified 4 weeks ago 2 times by stuartornum
Hypothesis: does reducing the flow rate on a DHW cycle increase the dT, allowing more time for heat transfer to occur (please correct me if I have this wrong)
Very interesting.....yes the thermistor was not pushed in fully and bent over so not quite picking up temp properly but only minor issue.
Most interesting part was his thoughts on the hot water heating. Very adamant that having set point of about 48 and low of 40 and to run it on constant. Was clear that putting it on for 2 hours in middle of day would be less efficient. But, as we've got such a big tank, we'd have to use loads of water for us to not have hot water....seems a bit redundant to keep it at hottest temp all the time when we only really want hot water from 5 - 8 pm....but heat pump logic seems the opposite of what all us normal people would expect.
He also told me that if I want to run it cheaper just lower the wc...
Averaging about 45kwh per day for last 2 weeks. It's a little higher than I'd like but not horrendous. 10kw system,5 bed semi detached, minimal radiator upgrades....I would assume this would have quite a big impact going forward.
How many cycles should I be looking for in 24 hours? I'm definitely going to leave it alone for a but now and just try to let the system find it's best way of running.
Sounds like they want you to run the DHW like you would a combi boiler, also remember that when the HP is doing DHW, its not heating the house.
I would go with your gut and have two slots to heat DHW and go from there.
With regards your CH and changing the WC. It's a good option as most Installers / manufacturers set them higher to save call backs complaining its too cold. If you go this route just make small changes 1° at a time and leave 24hrs. I find having a simple thermometer in the main room so you can see the temp, rather than just thinking it's warm / cold.
Note - most systems have two WC settings, one for DHW, one for CH. With yours I am not sure this is the case as I could find any notes on the advance settings. If there is only one WC then it must be set for DHW. Otherwise each can be set separately.
Cycling is hard to nail down and there are a number of reasons why it happens. If you only get it say every 60mins then small changes needed, if it happens every 5 mins then more work required.
First you need to find out when it takes place in CH, DHW or both. If in CH then you can lower WC or push more to the radiators. If in DHW, reduce the time to 90mins, then 60mins etc
No problem about taking your time, only do things when your happy and if you need help, then come back
Mostly (but not completely) I agree with @uk_pete_2000
I would say
I would go with your gut and have two slots to heat DHW and go from there.
With regards your CH and changing the WC. It's a good option as most Installers / manufacturers set them higher to save call backs complaining its too cold. If you go this route just make small changes 1° at a time and leave 24hrs. I find having a simple thermometer in the main room so you can see the temp, rather than just thinking it's warm / cold. Whilst you are doing it have all thermostats and TRVs turned to max so the only control is the WC. Turn down the target flow temperature at the cold OAT end until either the house is just right or just too cold. In the latter case turn it up half or one degree. The aim is to get it as low as possible consistent with heating your house.
Note - most systems have WC a flow temperature setting for DHW, and two WC curves, one for cooling and one for heating - lets leave the one for cooling for now and concentrate on the WC setting for heating
No problem about taking your time, only do things when your happy and if you need help, then come back
Cycling is hard to nail down and there are a number of reasons why it happens. If you only get it say every 60mins then small changes needed dont worry about it, if it happens every 5 mins then more work required. Once we get the WC right we can worry about cycling if we need to, at present mine is cycling due to defrost and there is not much you can do about that!
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
Turn down the target flow temperature at the cold OAT end until either the house is just right or just too cold. In the latter case turn it up half or one degree.
No idea what this means. The ideal doesn't seem to be able to target flow temp just adjust the wc to get required flow temp for relevant outside temp.
Note - most systems have WC a flow temperature setting for DHW, and two WC curves, one for cooling and one for heating
Not sure my one does. Only target dhw temperature. So I can put setpoint temp at say 46 for hot water and it will sort itself out.
I have decided on testing out pure wc. Want to maximise efficiency and tweak from there. So no room influence with the halo air just using as a thermostat for now. Target temps will be 22 and setback 20 but assuming without the room influence this is purely academic at this point....unless the halo air trumps the logic hp. If that is the case I can always change target temps.
Not particularly. Middle of day gives best efficiency, middle of night less efficient but a time when you are happy to have the house cool a bit. If you have a ToU tarrif during the cheap period otherwise to suit your lifestyle. DHW is inherently less efficient than space heating so give it priority for cheaper periods/periods when the OAT is higher
No idea what this means. The ideal doesn't seem to be able to target flow temp just adjust the wc to get required flow temp for relevant outside temp.
Sorry I forgot that the Ideal has the (better IMHO) one parameter WC user interface. You turn it down by reducing the curve value from 1 to 0.9 to 0.8 etc. Dont worry about the labels ('standard radiator' etc) on the right hand axis, just get it as low as possible!
I have decided on testing out pure wc. Want to maximise efficiency and tweak from there. So no room influence with the halo air just using as a thermostat for now. Target temps will be 22 and setback 20 but assuming without the room influence this is purely academic at this point....unless the halo air trumps the logic hp. If that is the case I can always change target temps.
Good plan!
There is some ambiguity in the manual but I think the following should help (The way Ideal do WC curves seems to be the same as Vaillant and, once you get your head around it, MUCH better than the '4 point' adjustment that others do, so Im also leaning on my knowledge of Vaillant whilst reading the ideal manual).:
Installer parameter 750 (Room Influence Heating Zone 1) can be adjusted and should be set to 1 (I think) to disable any room effect (almost) completely, thus running on pure WC. Its quite possible that the room effect driven by the Halo does trump/amend the WC setting unless you do this. Because of the way the heating curves work, the setback will (I think - but am not absolutely certain) still operate even if you do this.
This post was modified 4 weeks ago 3 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
These appear both confusing (and you need to know what a weather compensation curve is to make any sense of that chart) and restrictive because these are actually fixed curves that you select by dialling in a number. Midea already does this (curves 1-8) and then adds the flexibility of custom curve 9 where you do have the option of setting the end points.
The basics of weather compensation are covered in the ABC guide here.
Weather compensation for DHW? That's a new one on me. Still, always willing to learn!
Midea 14kW (for now...) ASHP heating both building and DHW
These appear both confusing (and you need to know what a weather compensation curve is to make any sense of that chart) and restrictive because these are actually fixed curves that you select by dialling in a number. Midea already does this (curves 1-8) and then adds the flexibility of custom curve 9 where you do have the option of setting the end points.
The basics of weather compensation are covered in the ABC guide here.
Weather compensation for DHW? That's a new one on me. Still, always willing to learn!
They are confusing at first if you are used to the 4 point interface, but actually its a better system IMHO. Vaillant has the same and from what you say it appears Midea have a variant.
The curves aren't restrictive in practice because (on Vaillant anyway) there are intermediate curves between the ones shown on the diagram. Unlike the 4 parameter system there is only one number to change, which is simpler, you just dial it up or down to get it in the right place.
The killer feature though is the 'parallel displacement' feature. This means that, once its set up, the user can change a 'target room temperature' on the UI, and what it actually does is shift the WC curve. So it presents to the user (eg my wife) a familiar interface (target indoor temperature) whilst, under the hood, actually modifying the WC curve. Note that this is NOT dependent on room influence being enabled, and it works with time programs. Im not absolutely clear from the Ideal manual whether this works in the 'Ideal' case if you also disable 'room influence'. Unfortunately they have conflated the two in the description.
This is possibly better explained by Vaillant than by Ideal: Id be interested to heat if Midea has the 'parallel displacement' feature.
This post was modified 4 weeks ago 2 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
there is only one number to change, which is simpler, you just dial it up or down to get it in the right place.
Yes, I can see an advantage in that. But it does come at a cost of understanding, which of course isn't essential, who of us understands how our cars actually work these days? Yet we still use them to get from A to B.
I'm pretty sure Midea units as supplied out of the box don't have a parallel universe displacement feature. If they do, I have never seen it. There is just one custom weather compensation curve where you get to set the end points. Presumably third party add-ons like Homely do implement this feature, or something very similar, and my auto-adapt script is in effect a 'parallel displacement feature' with the added advantage that it can also be a non-parallel displacement feature ie I can also change the gradient.
That said, I can also see the advantage of thinking in terms of a target room temperature rather than 'I need to move my weather compensation curve up a bit'.
I have to say that second Valliant 3D chart does take a bit of understanding. I'm not even sure you need the third dimension why not just displace the line in two dimensions? Or maybe the thing is that it is the angle of the third dimension (axis) that determines the amount of the shift.
Midea 14kW (for now...) ASHP heating both building and DHW
I have to say that second Valliant 3D chart does take a bit of understanding. I'm not even sure you need the third dimension why not just displace the line in two dimensions? Or maybe the thing is that it is the angle of the third dimension (axis) that determines the amount of the shift.
Agree. It took me a while to work out but once it clicked it is definitely a better approach than the 'four point' approach. I think the 'third dimension' is there to indicate the size of the shift in response to a change in target temperature, but its definitely confusing until you get your head around it.
The other interesting feature of this approach is that, if the installer sets up the wrong WC curve, you can just chage the target room temperature to get it 'right'. This may of course make the display look 'odd' in that the actual room temperature may be say (21), but this achieved when the target is set to (say) 17. There is almost an argument here for removing the calibration on the 'target' so the user just turns it up or down until its just right.
I suspect Vaillant in particular, who are of course German (whether WC has been compulsory on boilers for ~two decades ) have spent some time thinking about the UI to WC and what they have done is their best attempt. I dont know if outer EU boiler manufacturers do similar for the same reason; I wouldnt be surprised. I still dont think its quite right although if you remove the explanations and calibrations and just tell the user 'turn this know until its right' perhaps it is!
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
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