Who can help me with wiring an Eufy E340 doorbell?
I installed a transformer in the meter cupboard, but the doorbell won’t charge (the transformer is powerful enough). I understand this may be because the original chime interrupts the power supply, and that two wires therefore need to be connected together.
The connections on my chime are as follows:
What would be the best way to wire this?
I would go about it like this, on the rear of the eufy doorbell see what colored wire is connected to it. Orange or red, as for the black wire, I would disconnect one of them from the chime box, then press your regular doorbell button to see if the chime works. If it doesn’t then you know that is the black wire that goes to your regular doorbell and the wire that is still connected to the chime box goes to the eufy doorbell..
Then just connect the two eufy doorbell wires together with a wire nut.
Thanks for your comment and tip.
Both cables on the back of the doorbell are black.
You do have two doorbells, correct?
The Eufy and a regular push button doorbell.
Don’t know of an easier way to figure out the wiring, it’ll be trial and error.
In the chime box remove one wire from either terminal 3 or 2, then press the push button on your regular doorbell, if the chime sounds then you know that the wire that still connected to 3 or 2 is the one for that regular doorbell, if it doesn’t chime then the wire you removed goes to that regular doorbell.
From there you’ll now know if the orange or red wire is connected to the eufy doorbell. Reconnect the wire back to the terminal.
You’ll need to do the same for the two black wires removing them one at a time and pushing the doorbell button to find out which one of them goes to which doorbell.
It sounds a bit confusing and I tried to word it as easily as I could.
We managed to get the doorbell charging!
We borrowed a multimeter from someone, and that helped us figure out where the problem was. 
Make sure that your color wires are connected correctly and if you use a different on the chime blocks or button if the time of your doorbell is wired differently contact eufy security technical support and let them know