Samsung HP gen7 minimum compressor frequency limitation

[Michal_S (Misiak)]

Hi all, do you know if it is somehow possible to set minimum compressor frequency via modbus or somehow ? With frequency ratio control I can limit maximum compressor frequency but I would need limit minimum. Can’t believe it’s not possible somehow.

Thing is when my target flow temp is reached and compressor is running at minimum rationale frequency of 20Hz (stable input around 1kW, still acceptable efficiency) then if it can’t hold the target anymore it slows down dramatically to 14Hz for a minute then back to 20Hz all round again. It’s very inefficient and annoying.

I would rather want that compressor stays at 20Hz and don’t drop lower and simply overshoot the target temperature in case target can’t be maintained, I don’t care. Thermostat will turn it off when the target room temp is achieved. This is much more efficient that hold the compressor on for prolonged period of time at such low speed.

Any idea about this ? Thanks!

For reference a chart…

[Topaz]

From modbus you have to configure to write the NASA ID 0x42f1.

I read into one mim modbus adapter the way to do so. And explaining the content of the 42f1 register.

Cheers

[Michal_S (Misiak)]

Are you talking about frequency ration control ? I’m afraid you can’t set minimum with this setting but limit maximum. Maybe I don’t understand correctly, could you elaborate ? Thanks.

[Topaz]

Yeah, clearly, you’re right, you limit the maximum with frequency control, but when the heat demand requires a higher frequency rate than the limit, then the limit is always reached.

Actually, I’m limiting to 50%, which is equivalent to 20Hz on my Gen7 5kW.

I’ll see if I can find something in FSV that could better fit your need to force a minimum running frequency. But for example, asking for a high flow target temperature, with a limited frequency would result in frequency not going lower than a given value, to try to meet the heat request. This is merely a possibility…

Cheers

[Michal_S (Misiak)]

@Topaz

’ll see if I can find something in FSV that could b

I don’t know how exactly it works because I’ve noticed it starts higher. Like 50Hz then decreasing to 22Hz and holds it there. But DHW is heating with 30Hz so not sure how it should behave. Definitely it ramps up slower but I guess it can run above 22Hz if there is a need or not ?

@Topaz

But for example, asking for a high flow target temperature, with a limited frequency would result in frequency not going lower than a given value, to try to meet the heat request.

Yes but it goes down as soon as the target flow temp can’t be maintained anymore at given frequency so it drops to 14Hz usually which is huge step. Doing this the efficiency sucks. At least for me. PID is controlling this erratically but maybe it’s because of my low water volume in the system so thermal inertia is small. I would rather keep it running at 20Hz and simply let it overshoot the target temperature. But seems anything I will do in my system is not ideal. Ideal would be to switch to T22 radiators and add a small buffer but I guess it’s not worth the price. But at least I could add 50L buffer tank to help with thermal inertia so PID shouldn’t react so dramatically. But’s it’s just theory, don’t’ know if it would help.

[JPB (Peter)]

I was told by Samsung tec that the min comp speed is 15Hz on my 8kw gen7?

I’m only a novice! but to actually read the speed (and anything ) is it possible using a MAX485 to connect to the HP then to an ESP32 and read data using a library or am I way off?

Thanks

[SarahH (Sarah Hanson)]

Hi @JPB,

If you are looking for a really simple and low-tech (and low cost) way to monitor your Gen7 compressor speed - and lots of other stuff - you could do worse than to buy an RS485-to-Ethernet adapter (under £50). Just connect this to the F1/F2 terminals on your MIM-E03*N PCB and (via an Ethernet cable) your broadband router. You can use a pair of PLAs in the latter if direct cabling is inconvenient.

Then download the adapter configuration software, a virtual COM port, and SNET-Pro2, onto your laptop/PC. These are all free, and easy to set up and use. I summarised the steps for this process in Monitoring Your Samsung ASHP Controller , but I’ve learned more since, so PM me if you’d like to go down this route and are unsure or would like more details (recommended supplier info etc.).

[JPB (Peter)]

@SarahH

RS485-to-Ethernet adapter

Hi Many thanks for the encouraging explanation…just curious really what mine is really doing and when.
Seems lots of adapters, some slightly different descriptions even on amazon by Waveshare….. RS485 to RJ45 Ethernet Converter Module, Industrial RS485 Serial Server, TCP/IP to Serial Module, Modbus Gateway?

Direct cabling is difficult so it would have to be pair of PLA’s?

[SarahH (Sarah Hanson)]

Hi again @JPB, sounds like I’ve piqued your interest .

SNET-Pro2 offers a really good introduction to monitoring Samsung heat pumps as it requires no programming or electronics skills (even though it contains a few small software flaws), and it works with most (if not all) Samsung heat pump ranges.

If you’re interested in the RS485-to-Ethernet route, I’d recommend the USR-TCP232-306 over the Waveshare alternative. It costs a bit more, but my Waveshare packed up after a few weeks.

The only tricky bit of setup is configuring the adapter, or more specifically setting up the IP address. This particular adapter (the USR) comes with a default IP of 192.168.0.7. If your broadband router has an IP of (say) 192.168.1.nnn you’ll need to change the third octet of the adapter to a “1” to match that of the router (or else change the subnet mask as described near the end of the Monitoring Your Samsung ASHP Controller thread, though this should be unnecessary unless you have tons of devices connected to your router).

In my case I had no device with the address 192.168.1.7, so all I needed to do was change the 3rd octet. Here are my adapter configuration settings:

If you replicate these settings exactly you’re half way there, but make a note of the Local Port address (you can set this to almost any number, but those below 1024 are reserved by some devices and you may get a conflict).

When you come to set up your VCOM, you’ll need to assign its Remote Port to be the same as the adapter Local Port, so that you get a screen like this:

Now all you need to do is download SNET-Pro2 and fire it up. Hit the blue Settings button (top left of screen) make sure you have COM1 selected (or whatever COM number you chose in the VCOM settings), like this…

…and then hit Connect, followed by the Set Layer (F1/F2) button. After a couple of seconds you should see something like this (the heading at the top will vary according to which heat pump model you have):

And now you’re in business. You can see (amongst other data) the compressor frequency half way down the above screenshot (25Hz at the moment I snapped it).

Good luck!

[Bill.Thomson]

@SarahH

but make a note of the Local Port address (you can set this to almost any number, but those below 1024 are reserved

Good advice!
Many ports in that range are reserved by the Operating System as well.

[JPB (Peter)]

Many thanks for all the detailed info….it’s all new to me so very valuable learning and I’m listening

Ordered the recommended USR-TCP232-306 but got other things I must do first so its not going to be immediate. Downloaded the SNet-pro2, didnt realize it was the real stuff. Got a few things connected on wifi but sure we can sort some address out and looking forward to trying it and seeing some numbers..

[Michal_S (Misiak)]

Very nice writing @SarahH Btw, do you know if this SNET can communicate also through F3/F4 modbus ? Via RS485 USB converter? This one connected to Raspberry Pi and to the modbus installed in outside unit. Pi is in my cellar so I would need connect to it with SNet from my PC using some wifi connection and some virtual serial port server. Guess it could work somehow but don’t have a clear knowledge if SNet can communicate with modbus.

[SarahH (Sarah Hanson)]

Hi again @Michal_S.

@Michal_S

do you know if this SNET can communicate also through F3/F4 modbus ? Via RS485 USB converter?

I rather think not. The SNET “manual” (which just looks like 36 presentation slides) anticipates the use of the Samsung MIM-C02N RS485-to-USB adapter, which it appears must be connected to F1/F2 (or R1/R2) - no mention of F3/F4. Of course, you don’t need to use the MIM-C02N - there are much cheaper RS485-to-USB adapters available - but any USB adapter requires a wired connection to your PC which isn’t always practical due to house layout. That’s why I preferred the RS485-to-Ethernet option which allows wireless communication with my laptop via the broadband router, albeit via a pair of PLAs.

@JPB if you need PLAs when the time comes, they don’t need to be expensive high-speed ones. The 9600 baudrate used by the Samsung NASA protocol is pedestrian by modern standards, and the TP-Link TL-PA4010PKIT AV600 Passthrough Powerline Adapter (about £38 per pair on Amazon) easily does the job.

@Michal_S I can’t help with your Modbus query. F1/F2 (the so-called Set Layer) are used to connect the MIM-E03*N to the Outdoor Unit PCB (as well as to SNET, and - according to it’s manual - the MIM-B19N that you use), while F3/F4 (the so-called Control Layer) are just used to connect the Wired Remote Controller. So as far as this layman (laywoman?) is concerned, F1/F2 access the main data highway, though I would defer to experts like @Topaz and @toadhall for guidance on which data are accessible on these two Layers, via Modbus or otherwise.