geduxas
commented
1 year ago 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 :)
rpannekoek
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.
(NOTE: different line colors used here)
I've highlighted the defrost period (Defrost_State = 1) and within that where I think (based on Panasonic documentation) the 4-way valve is reversed.
Unfortunately, there doesn't seems to be a direct correlation between 4-way valve state and byte 161 and/or 175 values.
But do note how byte 161 behavior looks like EEV position too. As a matter of fact, byte 161 looks maybe even closer to EEV position than byte 175 when comparing to the deice mode 1 diagram as documented by Panasonic (albeit a hard to interpret diagram):
Actually, neither of them exactly match this documentation, but neither does the fan speed, so probably the documentation has to be taken with a grain of salt.
dydek
It has to have 4 connections like a typical step motor has, otherwise it just simply doesn't work. 
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).