Just need to check myself on wiring 24vac

[Dan-Ark]

Installing a used Air Logic triple foam panel located some distance from my main control boxes. It has its own 120v input and its own 24v transformer which powers its programmable control relay and switches the 24v from the main control transformers to the solenoids for each bay and possibly directly powers the solenoids used to switch the colors. It is a 3 bay wash. I want to make sure I don't need to run 3 separate commons across the room to the air logic unit (one from each transformer) or if I can just run one from one transformer, in which case I am thinking I would need to tie all 3 neutrals together in the main control cabinets if they are not already. I don't think I can use the neutral from the transformer in the tri foam unit (can I?) The cable I am using has 5 conductors so not enough for 3 bays if I need to send separate neutrals... I know in 120vac wiring, you only tie Neutral to ground at the first breaker box after the meter, but I dont remember the specific reason for that and not sure if that applies here.

 

[MEP001]

The 24V "common" side of the bays' transformers will need to be tied together at some point to run a single common to the triple foam panel. If it's not already, you can tie them at the transformer or terminal strip and run only one common to the Air Logic system. Before you tie them together though, make sure the phases are in line. You should be able to take a voltage reading between bay 1 "hot" and bay 2 "hot" and it should read zero volts; same between bay 2 and 3. The common side needs to read the same, especially if they are not already jumpered together. The neutral in the trifoam probably won't work because it's a neutral to ground and the "common" from the bays is usually one side of a pair of 12V AC legs which together make the 24V AC. If your bays' transformers are 120V to 24V AC, you can use the neutral at the triple foam panel.

 

[Dan-Ark]

Makes sense. thanks. didn't want to just try it and "see what happens". sometimes bad things happen doing that LOL.

 

[mjwalsh]

Ever since my electronic electrical engineer nephew (former part time help when he was 15 years old (pre certified-safety control engineer at that time) ..... over 12 years ago during a moonlighting episode ... steered us into making sure that one side of transformers are tied in with both the ground & each other ... we seem to have fewer issues. He explained to us that having 12 VAC & not 24 VAC between the created hot leg & ground opens the door to "floating voltage problems".

To be fair ... I suppose there could be an exception somewhere somehow???

 

[MEP001]

Ever since my electronic electrical engineer nephew (former part time help when he was 15 years old (pre certified-safety control engineer at that time) ..... over 12 years ago during a moonlighting episode ... steered us into making sure that one side of transformers are tied in with both the ground & each other ... we seem to have fewer issues.

You can only do that if the transformers are 120V AC and one side of the 24V is neutral.

He explained to us that having 12 VAC & not 24 VAC between the created hot leg & ground opens the door to "floating voltage problems".

It is never a problem if the phases are in line.

I have yet to meet any professional certified electrician who can fully understand the low-voltage side of a car wash.

What are these "fewer issues" that you have?

 

[mjwalsh]

I will try to get back to you on that. If I remember right ... it was not just related to car wash equipment but other parts of our facility. I wish I was able to be more specific at this time but I believe the issues were related to "electrical noise". Of course there can be other causes for "electrical noise". I won't argue about the competency of many electricians when it comes to low voltage car wash operation. I would think that there are some good ones who tend to specialize in HVAC because that field uses a lot of 24VAC ... possibly more than 24VDC.