Nest Thermostats have a "Power info" screen (found under Setup|Equipment) that lists three fields: Vin, Iin, and PS. In this forum, when people ask for help, I constantly see the respondents ask the OP for these values. However, I looked high and low on the Internet for a complete explanation of these fields, and I couldn't find one. The closest I've come is https://support.google.com/googlenest/answer/9241211?hl=en#zippy=%2Cequipment%2Cpower%2Cbase%2Cdispl..., and that is incomplete.
Vin is the only one I think I fully understand (more on that below), but I'm flumoxed by Iin and PS.
Iin confuses me for several reasons: My thermostat it says "385(W)". What are the units, and what does the "(W)" stand for? For the Nest non-learning thermostat, the above web page says "Iin: 200 to 385mA", so I guess the units are milliamps. However, this doesn't make sense because Google's specs for the thermostat says "Power consumption: Less than 1 kWh/month", but if you do the math, 385mA @ 23VAC(RMS) yields ~9W, or a monthly usage of about 6.5kWH. So, is this 385mA a peak value (perhaps when the UI is active) and the thermostat draws a lot less power when it's quiescent? Or is the power consumption specification just plain wrong? Also, all the Internet convos I've seen have people saying their Iin is 385, so is 200 even possible?
PS is even more inscruitable. For my thermostat it says "W-385, WP-17". How do I interpret this (the above web page doesn't even mention it)? Various internet convos show a lot of possibilities for this field, and for the "W-385, WP-x" format, I've seen a lot of different values for x (i.e. 15, 18, 2, etc.). What are all the possibilities and their meanings for this field?
Note on Vin: On my thermostat, Vin is "32.461V" and that's somewhat self-explanatory assuming this is a peak voltage, in which case the RMS voltage would be ~32.5 * .707 = ~23V, which makes sense because I have a 24VAC system. I used the words "somewhat self-explanatory" because stating "24VAC" (or 24V where the system is known to be AC) without any qualifier is traditionally an RMS measurement. So a reasonable presumption is that "32.461V" is VAC(RMS), which immediately becomes confusing when you're expecting 24V. Note that while the above web page says "Vin: 29 to 42V", indicating that my 32.5V measurement is fine, I've seen a lot of Internet convos where people fret over a voltage reading like 36V because they know that their system is a 24V system, and they assume they've miswired it. At least Google could have labelled it VAC-PP. Or perhaps this value represents an internal DC voltage after rectification; if so this should be documented! In any case, IMO, Google really missed the mark in showing peak voltage without any further explanation.
Thanks for your collective attention - I'd really appreciate knowing the details.
