E-stop on low voltage negative

[Mb2658]

I am finishing up the wiring on the control panel for my Brewtroller based EHerms. I have the Oscsys E-Stop module which pauses the Brewtroller and opens two relays when the E-Stop button is pushed. I intend to use the two E-Stop relays to control the high voltage and low voltage sides of my panel. I have the quad relay board to control my pumps and other 110v accessories which will be controlled by the low voltage side of the panel. I designed my control panel with 3 way switches (Auto/Off/On) for the elements, pumps and accessories. Auto will allow for the Brewtroller to control the items and on will connect the control side of the relay directly to the low voltage transformer to close the relay and allow the switch to be operated manually. Is there any problem with wiring the E-Stop relay on the negative side of the low voltage circuit? That way the E-Stop relay will function regardless of whether the switch is set to on or manual. I know that switching the neutral on 110v is against code and potentially dangerous but this is low voltage. The E-Stop will disconnect the low voltage negative lead and will effectively open the relays. Is my thinking correct?

 

[Yuri_Rage]

That will work and should give the desired effect, but why not wire the e-stop to the source hot lead? That way it's a guaranteed failsafe, even with relay/contactor failure.

 

[Mb2658]

I want the Brewtroller to keep power in the event that the E-Stop is pushed so that the program can be resumed once the problem is corrected. As it stands right now, I plan on running two positive lv wires to the switches. One will come out of the Brewtroller and the other will come from the lv positive bus bar. The lv power supply has two positive and two negative connections, The Brewtroller will connect directly to the lv transformer via one of the connections and the positive bus bar will connect on the other. The Brewtroller will provide power to the circuits that it is controlling, The manual on will connect directly to the power supply. So I will be running the two positives to the switches which will then connect via one positive to the relays. I don't see a way to switch the 8 hots with one relay where as I can switch the common negative with one relay. I have a keyed switch the controls the main contactor providing power to the panel that could be switched off in the event of a relay failure.

 

[Facinerous]

With control circuits "switching" the negative wire is common. If you look up holding contact circuits in google and click images you will see quite a few circuits with something similar to what you are doing. Using a on, off, auto configuration. Plus its your equipment, NEC code really applies to electrical work being provided for people who don't know anything about electricity. As far as the safety side of things are concerned, what you are doing is safe. Its just a switch.

 

[Mb2658]

Thanks for the input Gents, I appreciate it.