Byte #175 decrypted

[rpannekoek]

I think I figured out what byte 175 represents: this seems to be the position for the Electronic Expansion Valve (EEV).
From what I observed, the value varies between 40 and 120 (when using getIntMinus1), where 120 represents valve max open.
Interestingly, an EEV typically only has something like 8 positions and if you look at the schematics for the WH-MDC05J3E5, only one of 4 EEV poles are actually connected, so the WH-MDC05J3E5 can actually only set 2 positions (whereas the higher power models do have all 4 EEV poles connected, so can set all 8 positions).
From what I observed on a WH-MDC05J3E5, it switches positions around a value of 50. When it switches, you can observe significant changes in Discharge_Temp (and the difference between Main_Inlet_Temp and Inside_Pipe_Temp).
It's a rather technical, internal reading which you probably won't use to control the heat pump, but it may be an interesting value to monitor and better understand the internal working (I was initially rather surprised by above mentioned changes which did not relate to compressor frequency).

[geduxas]

Hi, day 2 ago we have discussed same topic in slack chat :) yes indeed it's looks like as eev control.. also for t-cap models 176 byte looks as bypass valve control.. but it needs more investigation.. first of all what value means what? Why it is in current dataset.. and why there is no other valve records? We have 4 way valve, also 2 way valve.. meanwhile i and @IgorYbema have got value of 128 in byte 175.. so what does it means? Also in different scenarious that value behaves little bit different or it do what it is supposed to do :)

[geduxas]

Here is mine mointoring values for byte 175 (valve1) and 176 (valve2)

you could notice that sometimes bypass temp starts flickering while byte 175 is going down.. EVA temp stays preaty stable.. also byte 176 not always are triggered in defrost cycles..

i am preaty shure 98.999% that byte 175 is responsible for valve control.. but need to work out and understand ..

[geduxas]

Here is another sample

Byte 175 is flickering between 13-31, and flicker bypass temp.. eva temperature stays in almost same position..

[rpannekoek]

Nice to see that there are more people trying to figure out some of the missing sensor/control values.
Indeed, I also noticed that "Bypass_Outlet_Temp" (byte 161) does not seem to behave like a temperature at all on my WH-MDC05J3E5; it actually seems to be something like EEV control with something like 8 discrete values. Also during a defrost it behaves similar to what's documented as EEV behavior during a mode1 deice.
But on another occasion where Discharge_Temp suddenly dropped, only byte 175's sudden value change correlated.

[geduxas]

... an EEV typically only has something like 8 positions and if you look at the schematics for the WH-MDC05J3E5, only one of 4 EEV poles are actually connected, so the WH-MDC05J3E5 can actually only set 2 positions (whereas the higher power models do have all 4 EEV poles connected, so can set all 8 positions). ...

indeed i din't noticed that.. but it maight be error in shematic's.. or maybe it just didnt shown?

Here is one in WH-MDC05J3E5

09-16 kw H series

T-CAP 9-12kw

T-CAP 16KW

as i understand it's simple stepper motor.. so it's need 2 pair of channels to work correctly..

[geduxas]

MDC05J3E5

this model don't have bypass.. only t-cap models have that.. so ithink your's value should be same all time ?

[rpannekoek]

I don;t think it's an error in the schematics; there is a separate schematic for WH-MDC05J3E5 and for the higher power variants (7 KW and 9 KW). I think it partially explains why heat pump variants which are largely the same can perform differently.
It also corresponds with behavior I observe on the WH-MDC05J3E5: it seems to have only two positions for the EEV valve.

Indeed, the WH-MDC05J3E5 doesn't have a bypass at all, but the values of byte 161 do change (with approx. 8 distinct values) and none of the values look like a temperature reading (which makes sense, because it does not have a bypass temperature sensor at all).

[geduxas]

I think it partially explains why heat pump variants which are largely the same can perform differently.

I am not expert.. just learning and trying understand.. what i have found this vide:
https://youtu.be/LqUEIMl6bBM

it explains a lot for valve control.. so i think it should be controlled precisely for heatpump work..
also i think it is possible to calculate same valve behaviour.. and prove 175 byte.

[rpannekoek]

Nice video! It even explains that a heat pump with a "fixed orifice" (single position EV) will work, but doesn't perform very well.
The more positions the EEV has, the better you can regulate the refrigerant flow and the more optimized the heat transfer will be.
I think that (combined with differently sized compressors) is the main difference between the variants, but I digress.

[geduxas]

Nice video! It even explains that a heat pump with a "fixed orifice" (single position EV) will work, but doesn't perform very well. The more positions the EEV has, the better you can regulate the refrigerant flow and the more optimized the heat transfer will be. I think that (combined with differently sized compressors) is the main difference between the variants, but I digress.

For exampe t-cap series, 9kw and 12kW shares exactly same components. Even compressor power is same.. PCB is same.. but in exposed view pcb have different numbers.. so one thing that could be different is either component's on pcb... Or only firmware..

[rpannekoek]

I managed to capture an occasion which illustrates byte 175 as EEV position

When Tdischarge (Discharge_Temp) approaches 110 degrees, EEV (byte 175) increases quite suddenly after which Tdischarge start dropping, whereas Trefr(igerant) (Inside_Pipe_Temp) becomes significantly higher than Tinlet (Main_Inlet_temp) and Phigh (High_Pressure) also drops even though Fcomp (Compressor_Freq) does not change at that time. These are all signs that the refrigerant flow suddenly increased, corresponding with byte 175 values.
As soon as byte 175 value drops below 50 again, Trefr is nearing Tinlet again; a sign of optimal heat transfer caused by a lower refrigerant flow.
For completeness, I also included the value of byte 161 (Bypass_Outlet_Temp), which also changes but does not behave as a temperature at all (nor would I expect that, since the WH-MDC05J3E5 doesn't have a bypass temperature sensor) but at times (especially during defrosts) behaves a lot like EEV control. However, in this case byte 175 correlates much better to EEV position.

[geduxas]

Nice work! So next step is determinate what number means what :) does it represents percentage form, or some open gap.. size.. flow count or what.. also it could mean open close timing as byte 178/179 for mixing valves..

For bypass temp it's interesting why you got values if your pump doesn't have bypass valve at all.. truely it could be that bypass temp is not correct identified or decoded.. maybe anyone has that to compare to cloud? I know that there is no EEV.. but bypass temp i think needs more investigation.

[geduxas]

@rpannekoek do you graph byte 161 as decoded value or what you get from raw?

[rpannekoek]

Byte 161 is shown as raw value (if you would decode it as temperature, you would substract 128, yielding very negative temperatures which jump by tens of degrees).
EEV (byte 175) is shown as "decoded" value, by substracting 1 (as a wild guess for how this should be decoded).
Indeed, the meaning of the values are still quite unclear, other than that higher seems to correspond to valve further open.
The highest value I have observed is 121 (120 "decoded"), which always happens when the compressor stops.
This is remarkable: from what I've read, you want the EEV to fully close (stop refrigerant flow) when the compressor stops.
The step size also increases significantly for the higher values (for lower values, the step size is 1).

[rpannekoek]

As a matter of fact, during a longer run I apparently also got raw value 129 once (spike).
Some other observed raw values (from where step size gets more than 1):

Dec	Hex	Bin
58	3A	00111010
59	3B	00111011
62	3E	00111110
71	47	01000111
82	52	01010010
84	54	01010100
96	60	01100000
121	79	01111001
129	81	10000001