Hi @Whirly,
Thank you for posting in the community. I understand you want to install your Nest Doorbell (wired, 2nd gen) in your house. It sounds difficult to know if you can install your Nest Doorbell (wired, 2nd gen) with your current system since your chime box has four wires going into it. I'm happy to help.
Are you trying to install your Nest Doorbell (wired, 2nd gen) in addition to the other 2 doorbells you mentioned, making a total of 3 doorbells, or will you keep a total of 2 doorbells?
If you notice that your chime has connectors for two doorbells, you can install your Nest Doorbell (wired, 2nd gen) as shown in the article Upgrade your transformer for Nest Doorbell (wired, 2nd gen). In that article, you'll also notice that the 'T' connector is usually for the transformer, and you'll see that you can have a Nest doorbell and one standard doorbell connected to one chime.
In the article Check Nest doorbell compatibility, you can compare your current transformer with the one required for your Nest Doorbell (wired, 2nd gen). Most importantly, there's a section that says, 'If the chime has two or more wires,' which will advise you to check the wire voltage to determine your doorbell transformer's voltage.
To avoid the risk of shock or electrical injuries, always use caution when working with electricity. Remember, if you're uncomfortable working with electrical wiring, you can have a local pro installer do it for you, especially if you're installing your Nest Doorbell (wired, 2nd gen) as a 3rd doorbell in your house.
Please keep me posted. I'll be waiting for your response.
Regards,
Anders
