Well spotted, I must start reading the instructions. 🙄
Edit.
So there must be other parameters which limit the starting and stopping of the heat pump in fixed and WC mode.
To save me having to 'read' the instructions, has anyone noticed anything of interest. 😀
lol. And I did allude to that earlier - if those settings only apply in AA mode, why oh why don't/can't they apply in other modes (are Mitsubishi trying to entice users towards AA mode..?). If the other modes are configurable by other parameters, I've yet to find them. I'm also interested if anyone has noticed them buried somewhere, or understanding if they are not configurable at all.
As it states it is a 'thermo diff', that is measured with relation to the calculated LWT, so as the calculated LWT goes up and down, the limits will do the same.
In AA mode the 'calculated LWT' is based upon both the outside temperature and the indoor temperature, so will frequently differ from that calculated by WC alone.
When the heat pump reaches the limits of its operating envelope, and can no longer vary the speed of the compressor and/or water pump, there needs to be limits to both stop and restart the heat pump, whilst limiting short cycling.
Yup that's clear enough. It's got me wondering what the upper and lower value actually does? It's not deviation from the set WC values because when on AA mine goes way more than 5 degrees over.
In terms of the thermo diff adjust, it does appear to do what it says on the tin from my testing, I've not seen it go way over or under the Upper/Lower limit values. Attached is a test from a couple of weeks ago, also look at DaveW chart from a few posts earlier as another example, it does look to be working as advertised.
I now want to add in the Minimum Temp setting in to the mix given the description noted against the Minimum temp function (below) does appear(?) to be for addressing the cycling in higher ambient temps issue we've been discussing. I'm hoping a higher minimum limit keeps my system out of the danger zone (I feel the need to try and see).
"Minimum Temp: To minimize the loss by frequent ON and OFF in mild outdoor ambient temperature seasons."
In fact.. I'm wondering.. in a system that will happily deliver low LWT in milder ambient temps without cycling too often, whether the opposite needs to happen i.e. reduce the Minimum Temp setting from the default of 30 to say 25.
It is difficult for me to provide definitive answers, since I don't have an Ecodan with which to 'play', so I must rely on the very useful data provided by yourself and others on the forum.
From the point of view of the minimum temperature setting, I would say that it should not be higher than that set in the WC curve or in any other operating mode. To be quite honest setting the minimum temperature limit at 20C would be of little consequence, whereas setting it at 30C may limit the operating range of the heat pump. If short cycling should occur in milder weather conditions, then increasing the temperature setting on the warmer end of the WC curve should have the same affect as setting the minimum operating temperature.
From my understanding, there are two main operating parameters which control the quantity of heat energy produced by a heat pump, one is the speed of the compressor which regulates the LWT, with the second being the speed of the water pump which varies the water flow rate. If one or other is limited from reducing to its lowest operating speed, then I would assume that this would also limit the minimum output capacity of the heat pump.
This I suspect could lead to premature short cycling (PSC), not a desireable ailment. 😒 Which could even be worse than CathodeRay's syndrome. 🙃
It would be interesting to see the effect of increasing the 'Time Interval' from 10 minutes to 60 minutes.
I tried 60 mins for a couple of day's in AA mode - no change that I could see.
Do you have any graphs or data? One of the problems is that you cannot compare like for like, since the weather will insist upon changing. The other factor is that changes can be quite slow, so may not initially be noticed. A further factor is that changes may not be possible in the present operating conditions.
It would be interesting to see the effect of increasing the 'Time Interval' from 10 minutes to 60 minutes.
I tried 60 mins for a couple of day's in AA mode - no change that I could see.
Do you have any graphs or data? One of the problems is that you cannot compare like for like, since the weather will insist upon changing. The other factor is that changes can be quite slow, so may not initially be noticed. A further factor is that changes may not be possible in the present operating conditions.
Just remind me what changes were you expecting?
You suggested it as something to try to see if it had any positive improvement on the cycling at mild ambient temps I've been observing. I do have the attached chart taken about a day after setting 60 min interval. To be honest I wasn't expecting any change but thought worth testing out (the cycling was made no better or worse). The Interval as I understand it is the sampling interval; for rads where the reaction time is faster a shorter sample time is required, for UFH with slow reaction times a longer sample period is required. In either case from my observations if LWT hits target+'thermo diff adjust-upper' it's not waiting for the next sample interval to check/validate, it just stops the cycle. I therefore think for rads a shorter sampling interval is needed as it needs frequent feedback as to where the internal and external temps are at, it can then adjust as necessary. My thoughts based on what I've observed.
Today I changed my heating mode from AA to WC. At the same time I changed my pump speed from 5-3-2-1. Each change has had no effect on the flow rate (FR). Before I made any changes the FR was 17/18 l/m and at each increment change it remained at 17/18 l/m. Id there any obvious reasoning for this?
Yup that's clear enough. It's got me wondering what the upper and lower value actually does? It's not deviation from the set WC values because when on AA mine goes way more than 5 degrees over.
In terms of the thermo diff adjust, it does appear to do what it says on the tin from my testing, I've not seen it go way over or under the Upper/Lower limit values. Attached is a test from a couple of weeks ago, also look at DaveW chart from a few posts earlier as another example, it does look to be working as advertised.
I now want to add in the Minimum Temp setting in to the mix given the description noted against the Minimum temp function (below) does appear(?) to be for addressing the cycling in higher ambient temps issue we've been discussing. I'm hoping a higher minimum limit keeps my system out of the danger zone (I feel the need to try and see).
"Minimum Temp: To minimize the loss by frequent ON and OFF in mild outdoor ambient temperature seasons."
In fact.. I'm wondering.. in a system that will happily deliver low LWT in milder ambient temps without cycling too often, whether the opposite needs to happen i.e. reduce the Minimum Temp setting from the default of 30 to say 25.
Hmm, when I first tried AA, it put the flow up to 53 right away and the WC maximum is 43. I've since limited it to 48 (which definitely works). If you have a well tuned (to your house) WC curve, then isn't the lowest value on that likely to be the minimum flow temp?
It's hard to know which way to go without knowing how AA actually works. But it seems right that increasing the minimum flow temp will allow the ASHP to run longer.
I have noticed that AA doesn't cycle at ambients where pure WC does. In fact it hasn't got warm enough for any cycling with AA for me yet in the 2 weeks it's been running.
Hmm, when I first tried AA, it put the flow up to 53 right away and the WC maximum is 43. I've since limited it to 48 (which definitely works). If you have a well tuned (to your house) WC curve, then isn't the lowest value on that likely to be the minimum flow temp?
It's hard to know which way to go without knowing how AA actually works. But it seems right that increasing the minimum flow temp will allow the ASHP to run longer.
I have noticed that AA doesn't cycle at ambients where pure WC does. In fact it hasn't got warm enough for any cycling with AA for me yet in the 2 weeks it's been running.
Yeah, 43 + 5 (default thermo diff upper limit value) does not = 53. I'm equally confused why it's chosen that initial value - did it not settle at lower values as it learnt over the following days?
Just as an aside; it looks(?) to me that if any config changes are made in the Heat Operation settings, or switching back to say WC mode then back to AA mode, that AA mode 'forgets' all it's previous learning and starts again (i.e. to get a true reflection of what it is doing it has to be left alone for a few days to settle, then not touched thereafter). Does this ring true with you?
In regards to minimum flow temp, I wonder what takes priority; the lower WC curve values or the default value of 30 set under the Heat Operation settings. My guess is the latter takes priority else it would not do anything useful.
I'll report back findings in a couple of days on how my new AA settings are going (allowing time for them to settle and adapt).
It had me confused at first. But in the FTC6 manual it quite clearly states all those settings are for room temp mode only. Also in all my tests it's had no impact when running in fixed or curve.
It says the same in the FTC5 manual, but it did seem to have an impact in my testing of Auto-Adapt mode. Lengthening the interval seemed to reduce the over-aggressive raising of flow temperature. So, I wonder whether the settings influence AA mode as well as room temp mode, but maybe they're not adhered to as strictly, just like AA mode seems to take the curve as an input but not gospel. Sadly, we're only guessing until and unless Mitsubishi release the source code for AA mode.
I don't think those settings are used at all by fixed or curve modes, as you found.
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