Mitsubishi settings for DHW and Home Heating

[ReedRichards]

On 09/11/2023 at 16:23, JohnMo said:

So start the slope at 15 deg OAT and finish at say -5.

 

Start flow temp say 28 deg, end flow temp say 35 or 40.

 

It can be a bit more scientific than that.  If your heat pump was sized for a maximum flow temperature at some particular outside temperature then that gives you the finish parameters.  For example, my heat pump (a retrofit with new radiators) was sized for 50 C output at -3.8 C so my finish outside temperature is -4 C and my finish flow temperature is 50 C.  I then made a spreadsheet about how radiator output varies with flow temperature and used a fit to this to get a start temperature and flow.     

[JohnMo]

1 hour ago, ReedRichards said:

 

It can be a bit more scientific than that.  If your heat pump was sized for a maximum flow temperature at some particular outside temperature then that gives you the finish parameters.  For example, my heat pump (a retrofit with new radiators) was sized for 50 C output at -3.8 C so my finish outside temperature is -4 C and my finish flow temperature is 50 C.  I then made a spreadsheet about how radiator output varies with flow temperature and used a fit to this to get a start temperature and flow.     

It certainly can be more scientific, but many would run a mile, instead of doing what you and I, have done. My predicted curve at around zero is about 0.3 degrees out; because I didn't forecast in defrosts cycles. Mainly as I had no idea, when they would occur, how long the defrost cycle was etc.

 

So I gave a simple intuitive means of getting the same result. Even with the spreadsheet there is still some manual adjustments, or you just over compensate (most installers do that so they don't get call backs) run slightly hotter, than you need and use TRV's to keep you right.

[ReedRichards]

I don't disagree @JohnMo but every installation will have its own WC curve and so its own right answer.  I would be shivering in a cold house if I used your suggested values.  And for heat pumps to become mass-market items there needs to be a way of setting up Weather Compensation quickly and fairly accurately, not using the play-safe values a typical installer will program at present.  Perhaps a bit of software that will tell the installer what values to use?

[sharpener]

8 hours ago, ReedRichards said:

And for heat pumps to become mass-market items there needs to be a way of setting up Weather Compensation quickly and fairly accurately, not using the play-safe values a typical installer will program at present.

 

Depressing comment on  the Heating Design FB group  "I’ve given up fitting weather comp to my customers boilers, causes too many problems, people just cannot get their head round a simple thing of moving a dial to set it." Not sure which dial he means, my WC curve is set by a preset pot behind a dummy knob, not exactly a user adjustment!

 

And several others saying e.g. ppl don't like it because the rads don't get hot and they cannot dry their smalls on them. WC never enabled on new build housing bc there are too many callbacks (I thought it was now mandatory).

 

So not a specific problem with heat pumps, however WC clearly needs some kind of Auto-tune sw before it will achieve much greater market penetration.

 

Edited November 16, 2023 by sharpener

[ReedRichards]

Plus people need to learn that in milder weather a tepid radiator can provide as much heat as you need.  

[sliderule]

Hi Roadrunner, on the WC LHS view screen, if you keep pressing the F4 (right hand) arrow, you will eventually walk down the slope and can see the WC temperature target for every outside temperature. It's not for editing.

Re the FTC mounted on the Hydrobox ( I don't have one), I would expect this to be warmer than ambient, and of no use in controlling the heating.

I have been trying out the Advanced Auto Adaptation, extending the cable from the little FTC box and moving it into the living room. With our setup (all UFH in concrete floors), it's great, low power and no cycling. The only con is I need to keep the existing living room thermostat a little higher than the FTC "Room Temperature", as if I don't, my thermostat may switch the UFH manifold pump off, the flow temperature would go up quickly and the FTC will switch the HP off for a while, as the connection from my existing thermostats to the FTC is removed on AAA. I am now going to order a Mitsubishi wireless controller and receiver (£167 at heatpumps.com), and make it permanent.

[Beelbeebub]

On 16/11/2023 at 21:50, sharpener said:

 

Depressing comment on  the Heating Design FB group  "I’ve given up fitting weather comp to my customers boilers, causes too many problems, people just cannot get their head round a simple thing of moving a dial to set it." Not sure which dial he means, my WC curve is set by a preset pot behind a dummy knob, not exactly a user adjustment!

 

And several others saying e.g. ppl don't like it because the rads don't get hot and they cannot dry their smalls on them. WC never enabled on new build housing bc there are too many callbacks (I thought it was now mandatory).

 

So not a specific problem with heat pumps, however WC clearly needs some kind of Auto-tune sw before it will achieve much greater market penetration.

 

need a simple learning algorithm where the occupant can press "I'm too hot" or "I'm too cold" 

 

Over time the system tweaks the curve up if "too cold" is pressed too often, and down if "too hot" is pressed too often.

 

Could also do clever things like start to notice patterns and dynamically adjust the curve for different parts of day/week.  So if it notices "too cold" is prodded a lot on weekend mornings, tweak the curve up a bit on weekend mornings.  "too hot" in late afternoons, tweak it down a bit etc.  If it also had some extra external sensors like solar radiation monitor or wind speed (or it could pull them off the cloud) it could start to correlate that info as well.

 

Machine Learning is supposed to be able to do all manner of clever things,  surely working out how to heat a house is a trivial task!

[sharpener]

Seems things are moving in the right direction. Went this morning to a seminar by Paul Williams of Homely https://www.homelyenergy.com/.

 

Uses wireless temp sensor plus UV sensor and online weather data to optimise HP settings, with a 14 day initial learning period. Claim it currently interworks over ModBus with Samsung, Midea/Riello, LG, Ebac, Airwell, Clivet. User interface is a simple phone app with intentionally limited settings.

 

Integration with Vaillant & Mitsi in development but needs them to produce proprietary interface boards. Integration with EV and PV also in the works.

 

In comparison with normal weather compensation they claim 3% improvement in CoP and 6% energy saving.

 

Cost ~£200 plus £25/yr optional subscription for smart service to accomodate variable electricity tariffs.

 

 

[billt]

Homely's been mentioned before on this forum. Unfortunately it seems to rely on an internet connection, which rules it out from my POV.

 

It's probably a good idea for installers / customers who don't want to fiddle / don't understand how to set a system up.

[Beelbeebub]

47 minutes ago, billt said:

Homely's been mentioned before on this forum. Unfortunately it seems to rely on an internet connection, which rules it out from my POV.

 

It's probably a good idea for installers / customers who don't want to fiddle / don't understand how to set a system up.

I am very wary of "smart home" and "smart" systems that require a subscription or cloud connection.

 

There is a pretty long history of these items just stopping working because the company has gone bust, decided to stop support or even just decided to change the terms to remove functionality.

 

There's a popular garage door opener in the US that has just stopped working with Google and alexa because the company has decided to change their business contracts.

 

Don't want that to happen to your heating, or have to pay extra for different weekend timings or if you want to have night setback just because some silicon valley exec decides to boost their earnings.

[sharpener]

2 hours ago, Beelbeebub said:

If it also had some extra external sensors like solar radiation monitor or wind speed (or it could pull them off the cloud) it could start to correlate that info as well.

 

18 minutes ago, Beelbeebub said:

Don't want that to happen to your heating, or have to pay extra for different weekend timings or if you want to have night setback just because some silicon valley exec decides to boost their earnings.

 

You seem to want to run with the hare and hunt with the hounds on this one @Beelbeebub!!!

 

I am sceptical too but I think this direction of travel is more or less inevitable. I fashioned my own internet controls in 2009 and my son has been using his Tado for many years now and moved house with it.

 

I think you have to consider the fallback options available. If it optimises the HP settings in the light of its experience and after that makes only small adjustments, a temporary outage is not a big deal. And if all else fails £200 written off is not a big sum compared with the possible improvements in energy saving or comfort.

[JohnMo]

Think the ideal is something with the functionality of homely, but is just a temporary install. Wireless inside and outside temperature sensors and UV sensor on the southern side of the house. Almost the installer sets up a weather compensation curve, from design data.  The homely type tool, is loaded with the same curve. It monitors over a week to a month time period and logs how the house responds and suggests delta to upper and ends of the curve. Installer removes the temporary equipment, and moves on.

[Beelbeebub]

53 minutes ago, sharpener said:

You seem to want to run with the hare and hunt with the hounds on this one @Beelbeebub!!!

To some extent yes! 😁

 

I'm not implacably against cloud data. I have a homebrew bit of kit that uses open weather data.

 

But if that source were to go dark for whatever reason (failure at my end, API changes or just stopping) the system just rolls on without it. The cloud data is "gravy" - nice but not essential.

 

Any WC system will require tuning from time to time. Changes to the house fabric (say new windows) or occupancy levels (kids arrive or leave home),  external factors (hedge grows up and shades windows) will change the curve,.so we need a system that can adapt.

 

This is why some sort of "too hot/cold" button would be useful (and maybe an internal sensor).  It could feed back when to adjust the curve.

 

 

 

 

[Beelbeebub]

Following on,

 

If you had a setpoint dial (as now) and internal temp monitor you could see the actual internal temp Vs the desired.

 

If you were spending alot of time away from that temp the system could realise something isn't right. 

 

It could monitor the response times to external fluctuations, especially at night when there is no solar gain issue.

 

This would allow it to tweak the flow temps higher than one might normally set it if the response times were too sluggish. Likewise, lots of overshoots might indicate turning the flow down to slow the response.

 

Like I said, with machine learning it should be possible to work out the optimum flow temps given the external, internal and desired internal temps over time.

[Gary68]

I trialed Homely on our Ecodan a few years ago, it was ok, but limited due to the integration with the Ecodan it could only use the smart grid connections to boost the room temp by 2 degrees in cheap periods it couldn't modulate flow temp, so great in theory not so much in practice and the temp nodes kept losing connection to the hub which was an issue.  Now that it can modulate flow temp its probably a much better offering but at £200 and a subscription to get the best out of it, i'm not sure its going to get much traction.  As @JohnMo suggested as an installer tool I can see the value in that in setting an initial curve for a customer rather than setting too high so you don't get a call back.

[HughF]

Homely is also complete turd when it comes to packaging and end user interface. The damn thing is micro usb powered and only has an app as the front end. What’s actually needed is an opentherm to modbus converter that will read the load compensation calculated flow temp from a proper smart thermostat, and convert that to a weather comp curve adjustment value.

 

The vaillant sensocomfort will modify the curve up and down as required to reach the target room temp, automatically (as far as I can tell).