I’ve been monitoring my heat pump system for some time not but I’m not so sure it is being calculated correctly. My water heater circuits look to be calculating correctly. The heating elements are about 4.5 KW and that’s what is being calculated for them.
The issue is with my heat pump outside circuit. It’s showing 1.44 KW with 12.5 Amps, 240Volts and .944 power factor. A manual calculation gives me 240 x 12.5 x .944 = 2.832 KW. It’s like it is not doubling the power like it should. I definitely have the “Double” check box selected as you can see below. My configuration for my heat pump input is exactly the same as for a water heater input. Using the same AcuCT-H040-50 CTs for both circuits and they are both 240 VAC.
I can only think that I’ve configured something incorrectly for this input but cannot imagine what it could be. Does anyone have any suggestions?
You have it setup correctly. This is the second report on this problem, which I have just discovered was introduced with version 02_06_00. The amps are overstated. They are actually half what is showing there.
The good news is that the recorded data is correct. It’s the script interpreter converting VA to Amps that is not recognizing that volts are doubled. It will be fixed in the next release.
That’s interesting. Golly you’re right. Looking more closely at one of my water heater circuits its Amps is also not correct. Here I was thinking that it was the Watts being reported incorrectly for inductive (non-unity power factor) loads.
Here’s what a water heater circuit looks like in the graph. I re-scaled the Y-axis to make it easier to see.
A 240V, 4500W water heater certainly would not draw 38A on a 30A circuit. I’m surprised I had not caught this earlier. I was only looking at Watts. The issue only became apparent to me in my heat pump circuit.
Any idea when the fix will become available and downloaded by our IoTaWatt devices? I need Amps to report correctly in the graph because I’ve been having trouble with my heat pump and need that data for the tech.
Not sure I can explain this simply. Vmult is a relatively new attribute and not directly settable in the config program. It is used primarily for modifying a reference voltage as part of derived three-phase functionality, where both the phase and amplitude of a reference signal are synthesized from a physical signal. Double is an older attribute intended for what you are using it for. They both modify the voltage used in the power and VA calculations.
One problem that you might have with using vmult is that the config program is a little possessive about it and might remove it if the input isn’t using a derived three-phase reference.
Neither. The metrics stored in the datalog are Watts and VA. The voltage reference is not stored as an attribute of the power channel. It is maintained in the separate voltage voltage as it’s true value.
Both vmult and double are applied to the calculated Watts and VA. Subsequently, if you extract Amps from the datalog, it divides VA by the reference voltage. The bug is that the double (and vmult) must be applied to that reference before the division.
version 02_06_00 introduced a reimplemented script interpreter, and that step got lost in translation. It’s been there for a few months now, but in the last week I’ve also had another user pick up on it.
The data in the datalog is fine, it’s just being reported incorrectly.
I’ve had some time to look further into this. Experimenting with vmult vs double, the new script works correctly with vmult but ignores double, so I have looked at the config app and it does not appear that making those changes would be undone by any of the derived three-phase logic. I experimented with that change and it does work and appears to be unaffected by config. So if you want to do that, (set double = false and vmult=2.0) that should resolve your issue and also be fairly benign when I release a fix.
With release 02_06_00, you can no longer directly upload config.txt. It is protected. You would need to download it, make your changes, then upload as config+1.txt. IoIaWatt will vet the new config and if it passes, will rename your old config to config-1.txt and install the new config as config.txt, deleting config+1.txt. This new protocol add a lot of integrity to the update process.
I have modified the development source to fix this issue and will include in the next release.
For anyone reading this cold, the problem is that inputs using “double” for 240V split-phase circuits will report doubled Amps. The datalog is correct. It’s a problem with the script system that, when corrected, will report both real-time and historical amps correctly again.
I made that change in the config file to all of my 240V circuits and everything seems good right now. I’m now seeing the correct Amp draw by the water heaters. The heat pump Amps agrees with the KW calculation so it must be correct too. I almost cannot believe how few Amps and how little power my heat pump actually uses. I’m going to have to take my handheld clamp meter to the heat pump circuit to convince myself .
I am not currently exporting anything to anywhere. At this point I was just expecting to wait for the next update or to learn about using a database on a local Raspberry Pi and graphing from that with Graphana.
For the monitoring I do the internal graphing of IoTaWatt itself has been sufficient. I’ve used it mainly to analyze what size generator or solar system we might want/need. I also use it to analyze the performance of our heat pump system as we have been having trouble with it.
Thank you, thank you, thank you.
Have a great holiday weekend.
P.S.
BTW to let you know too my temperature implementation has been working great and very accurate. It agrees with the weather service within a couple tenths of a degF. I don’t know if you remember me coming up with a way to use a 4-20mA temperature transducer to display temperature as amps on the graph.
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