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My newly installed Ring Doorbell Pro 2 wasn't functioning properly due to low voltage and Ring sent me a new transformer (specific product here here). When I went to remove the doorbell chime from the wall I saw that the transformer wasn't located behind the chime. I believe I was able to track the wire to the circuit breaker and identify the existed doorbell transformer (see attached photo below).

existing configuration of doorbell transformer that is to be replaced

I ended up not proceeding with the installation because (1) I wasn't 100% sure if what I had identified was the appropriate transformer and (2) the existing transformer only had 2 wires coming out of it while the new transformer had an additional ground wire.

I am seeking guidance on how to complete this installation. Specifically, I am looking for additional confidence that I identified the appropriate transformer to replace and I trying to understand how to account for the "extra" wire in the new transformer. I'm under the impression white would go to white and black would go to black I just don't know how I'd handle the green wire from the new transformer. I'd also like to know if electrical tape is required given the videos I've seen only use the wire caps.

I've looked into other threads I wasn't satisfied with the responses, so I decided to post an independent thread.

AndrewC
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2 Answers2

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The new transformer shows a black, white, and a green wire. The colour green(or bare) is only allowed to be used for ground.

Having a green wire is only there for your safety. It does not change how the device works.

It is not recommended, but not using/connecting the green wire to ground will not affect how the device works.

Do turn off the breaker/s providing power to that box and check there is no power in the box before sticking your fingers in it. There might be a second breaker for that box, that you do not want to find out the hard way.

crip659
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    If it is a typical box-mountable transformer (like the old one, except the old one isn't mounted properly) then transformer case to metal box takes care of the ground whether the wire is connected or not. It doesn't look like there is a practical way to mount the transformer on the top or side or bottom because of the limited clearance. But should be able to use a cover [like this one](https://www.homedepot.com/p/RACO-4-11-16-in-W-Galv-Steel-Gray-Flat-Square-Cover-with-1-2-in-KO-in-Center-1-Pack-833/100013239) - just check the size of the box and the transformer knockout size requirement. – manassehkatz-Moving 2 Codidact Aug 01 '23 at 18:13
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    @manassehkatz-Moving2Codidact According to the installation, you just use a screw to mount it to a box. It looks like they use the same screw holes as what is used to hold that cover onto the box. – crip659 Aug 01 '23 at 18:35
  • @manassehkatz-Moving2Codidact thank you for the responses! Bit confused by the verbiage since the picture I provided is the "current" installation. I haven't changed anything yet. I took the picture when I removed the cover - it looks like the one you linked to. Based on the way it's currently installed the transformer is hanging on a nail in one of the screw holes - I can't tell if the metal is actually touching the box. When I install the new one should I mount it anywhere specifically? Or change how it's currently positioned? – AndrewC Aug 01 '23 at 19:05
  • @manassehkatz-Moving2Codidact apologies I re-read your comment. Indeed the old one appears to be incorrectly installed. If I wanted to install the new one properly how would you recommend I make a proper connection from the metal transformer to the metal electrical box without proper clearance? Additionally, I read somewhere I may need to install the ground wire to a neutral bar. Any guidance there? – AndrewC Aug 01 '23 at 19:25
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    There is not enough clearance to screw the new trnsformer to the hole the wires are going through right now. But you could get a short 90 deg bend fitting that would connect to that hole and allow the transformer wires to go through that hole. This would make a mouse proof installation. If you would get new cover with a knockout in the center, then you would need to get a pug or cap to cover the original hole. This is in order to make the installation mouse proof. Of course the original installation is not mouse proof. Ideally you want to prevent any mice getting to the wires. – Jim Stewart Aug 01 '23 at 20:00
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    The old one is **improperly** installed hanging out of a hole on top of the box. It needs to be attached to one of the knockouts. There are usually knockouts in top (in use, no space), bottom (in use, no space), sides (not enough clearance) and back (not accessible). So that leaves the front. Since the box is only a junction box (the same type of box can be used for switches, receptacles, etc.) instead of using a plain cover, use a cover *with a knockout* and attach the new transformer to that knockout. Ground is automatic metal to metal. "Ground to neutral bar" refers to a panel, not a box. – manassehkatz-Moving 2 Codidact Aug 01 '23 at 20:00
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    @AndrewC According to the installation instructions, you can use a knockout hole in the box or cover, or the transformer has a tab with a screw to mount the transformer to one of the screw holes in the box corners. – crip659 Aug 01 '23 at 20:05
  • OK this is making a lot more sense now. Thanks all. I do have a few (hopefully final) follow-ups. If I were to do a 90 deg bend fitting instead of a knockout do you have an example of what that looks like / an amazon listing for me to purchase? Also, how do I deal with the spare green ground wire? Do I just cap it? If the metal to metal is serving as the ground. Lastly, I noticed the wires with the white cap aren't installed to the transformer. I assume I can safely ignore those? – AndrewC Aug 01 '23 at 20:23
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    Something like this ( )https://www.amazon.com/Sigma-Electric-ProConnex-44047-90-Degree/dp/B00C3YC23Y/ref=pd_lpo_sccl_2/130-5757339-6087811?pd_rd_w=AEJL8&content-id=amzn1.sym.116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_p=116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_r=J74JGDFV24GZBXGCZ8DZ&pd_rd_wg=1yT1B&pd_rd_r=67b96b9a-13b0-41c2-b5ee-ad695255349b&pd_rd_i=B00C3YC23Y&psc=1 not sure if this is exactly it Probably better to get a cover with a kockout and put a plug in the old hole. – Jim Stewart Aug 01 '23 at 20:36
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    90% of the time you connect the wires to the new device(light/switch/outlet/transformer) exactly the same as the old device. Pictures are very good for this. The other 10% it was a mess to begin with and might be hard to make right. You should be in the 90%. – crip659 Aug 01 '23 at 21:01
  • I'm leaning towards just screwing the transformer onto the corner. Thanks for the all the help. Any thoughts on how to deal with the spare green ground wire? Do I just cap that? Once I have that answered I think I should be good to close this thread. Thanks again for the help. – AndrewC Aug 01 '23 at 21:48
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    I would connect it to the other ground wires in the box or to the box. Most boxes have a threaded screw hole for grounds. More ground connections never hurts, but capping it if using a screw/metal hole connection should not hurt either. Quite often a ground wire is provided in case you are using a plastic box. – crip659 Aug 01 '23 at 22:12
  • Thank you crip659. I know it's a rough sketch, but would something along the lines below make sense? Basically just using the corner of the transformer to screw it into the box since there's not enough room inside the box and then capping the ground https://imgur.com/a/CMrwx4D – AndrewC Aug 02 '23 at 00:02
  • Hi Crip659 apologies for the double tap. Would you be willing to review my rough sketch above and provide any input based on the conversation thus far? Thank you again - will close out this thread afterwards. – AndrewC Aug 03 '23 at 15:10
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A way to test the transformer to see if it is the doorbell transformer rather than the HVAC transformer (before disconnecting anything) is to clip or touch the leads of a multimeter (in a/c voltage mode) to the output terminals of the transformer.

You will read a constant a/c voltage of about 20 V. Then have someone ring the doorbell while you observe the a/c voltage reading. If the voltage dips momentarily, then this transformer is powering the doorbell. Mine momentarily dropped from 20 V to 14 V when the doorbell was rung.

I believe that it is unlikely that the same transformer powers both the doorbell and the HVAC low voltage thermostat wire. But to test this, disconnect one wire from the low voltage side of the transformer, and confirm that the doorbell no longer rings when the button is pressed but the HVAC continues to cycle off and on in response to the thermostat.

If there is only one set of wires connected to the low voltage side (~20 V screws), then this would indicate that the transformer is only powering one system, but you could confirm that when you have the transformer disconnected (either one wire or both wires) the HVAC thermostat is controlling the HVAC system. This is assumming you have a central HVAC.

Jim Stewart
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  • Thank you for the detailed response! Few quick follow-up questions if possible (1) should the power be on when I perform the multimeter test? (2) I don't have an HVAC system it's a boiler / thermostat / baseboard heating. I believe our thermostat is battery powered (3) for the second test do I need to perform if I don't have HVAC? If yes, do I do that test with power to the breaker on or off? – AndrewC Aug 01 '23 at 19:01
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    Yes the power must be on when you perform the multimeter test. You are testing the doorbell under operating conditions. Since you do not have a central HVAC, you do not have to perform further tests. If you do not want to mess with a voltage measurement just disconnect one of the low voltage wires from the transformer without letting it contact anything else. Bend the wire away so it is not in contact with anythinng. Now press the doorbell button (with the power on). If the doorbell fails to ring, then you know this is the transformer for the doorbell. – Jim Stewart Aug 01 '23 at 19:13
  • Thanks Jim! I am going to order a multimeter and a tester from Amazon just so I have the proper tooling for the installation. Would you happen to know how I can perform the multimeter test? Does it matter which color I put to which terminal (red / black) of the tester? – AndrewC Aug 01 '23 at 19:20
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    The green ground wire is supposed to be connected to the metal box. Did your metal box have a cover on it or is it just open? One easy way to connect the ground to the box is with a little clip that hold s the ground and slips over the edge of the metal box. If you have a cover, you could just hang the bare end of ground over the edge of the box and screw the top down on it. – Jim Stewart Aug 01 '23 at 19:21
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    Andrew, a multi meter is a good thing to have, but you don't need one to do this installation. If you are going to get one, get a decent one like a Fluke brand. What you do need to be safe is a non-contact voltage tester to verify that power is off when you think you have turned it off. – Jim Stewart Aug 01 '23 at 19:24
  • It had a cover. I removed the cover and then re-installed the cover after taking the picture. The current installation (as shown in the picture) did not have a ground wire and the transformer doesn't appear to be mounted to the metal box. Do you recommend I use the ground wire to the metal box and don't both trying to attach the new transformer to the metal box? – AndrewC Aug 01 '23 at 19:35
  • would you be able to review this sketch? Basically just using the corner of the transformer to screw it into the box since there's not enough room inside the box and then capping the ground https://imgur.com/a/CMrwx4D – AndrewC Aug 07 '23 at 14:20
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    That connection should work. – Jim Stewart Aug 08 '23 at 15:59