re: Preventative Maintenance HVAC programs - ripoff or worth it?

$300 capacitor that you can get on amazon for $20 and do it yourself

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That really depends on the system, available access, and exactly what metrics and desired resolution of the captured data, and how the sensors will be installed. I measure the uF of the capacitors in my system while it's running, I'm not sure how I'd hook up anything to constantly measure that safely in a typical installation.

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I probably would not try measuring capacitance, but rather as I mentioned I would monitor the temp of the capacitor(s) vs ambient, amp draw of the compressor and fan motors, etc. and with high enough resolution to determine startup draw vs running draw and calc startup time.

Maybe it sounds complicated and crazy, but I assure you all this can be done quite easily and cheaply. If I have some time I'll build a prototype and put it on one of my home units this weekend. I'll be back with charts of the data I'm getting. I think that will make it more clear what I'm talking about and what type of alerts we can automate from this data.

Are y'all in the BR area? And if so who do you use? I agree that I'm fine being out $20/month for added peace of mind. I think I'm definitely getting hosed on the price though and added repair costs.

Anyone who wants to clean coils themselves go for some Nu Brite.







Buy a capacitor for the fan on both evap and condenser.

I put together a prototype device this morning. I installed it this afternoon and have begun collecting data. So far I'm measuring amp draw of the whole condenser unit as well as 3 temps (temp in & out of the coil plus ambient). I expect to make a lot of changes to the hardware and software, but this is looking good for a first go.

Here is the BOM:

$6.00 - ESP8266 microcontroller
$6.75 - 3EA temp probes at ~$2.25/ea
$6.75 - 1EA split core clamp on current transformer
$1.00 - breadboard
$1.00 - misc wires and components
$7.00 - micro usb power supply
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$28.50 - total cost

And here is the data I am getting:



This is just a live view of the current data, via Home Assistant.



Historical temp charts. Dark blue is the liquid line right out of the compressor, purple is the liquid line after cooling off through the condenser coil (the quick drop at 2PM was when I put an ice cube on the probe to identify it), and light blue is ambient (the probe is actually inside the panel so a bit warmer than ambient).



Amp draw of the whole unit. You can see the startup spikes at the beginning of each cycle. This is a 5 second RMS value chart. I will probably change the code to produce 1 second RMS values to get a more prominent spike and hopefully a more accurate value for the startup draw.




So this version is running ESPHome on the microcontroller and piping the data via wifi into Home Assistant running on a server in my house. There are many ways to collect and consume this data, including sending it straight to "the cloud" (for example at Amazon AWS) if you don't have or want a local server. There are also numerous ways to process the data and generate alerts for whatever you want.

For example, I will set up rules in HA to send a notification to my phone if there is an anomaly in the amp draw (perhaps if it's more than 8 amps for more than 10 seconds). After I collect more data, I will also set up rules to notify if a certain in/out temp differential is not maintained. This might tell me that my coil needs to be cleaned, or that the unit is not working efficiently for some other reason.


I will likely put a similar device on the air handler / evaporator, and then outfit the other unit in my house as well. Worst case I will be out ~$100 and will have gained some knowledge. Ideally I will be able to detect problems before they turn catastrophic, as well as keep my energy bills down by knowing when things aren't running efficiently. And best case this is my million dollar idea.

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I just call them in April every year to come out and clean the 2 outside units, check everything, coils, refrigerant, blow the drain lines out etc.

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Yea the kicker is they aren't going to tell you if anything looks out of the ordinary or do anything about it until you call them again with a problem and they have to charge you more