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Looking for a ground wire

2112
Explorer II
Explorer II
I'm installing an external LED light strip under my awning. Man, these things are BRIGHT. I'm trying to install a dimmer controller but can't find a ground. The controller requires both 12V and ground input. The below image is what I'm dealing with.



Is there a ground wire accessible from here and I'm just not finding it?

The AC thermostat has ground going to it. The 16' light strip pulls 2A. Would it be unwise of me to tap off of that ground? Would I be creating noise issues by the PWM controller affecting the thermostat if I did? The controller PWM frequency is 2kHz.

Thanks
Dave
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857
18 REPLIES 18

DrewE
Explorer
Explorer
mr_andyj wrote:

AC wires will be grounded to the frame the same as the DC wires. As you say, probably not at the same connection point or in the same box, but AC Neutral is connected to the DC ground, and AC ground on the frame. This should not be a concern at al


Actually, in an RV, the AC neutral should not be connected to the chassis ground in any way. Connecting neutral to ground (bonding neutral) is only done at the main service entry point, and an RV when plugged into shore power is not a main service entry point--it's basically treated as a subpanel.

If there's a built-in generator, neutral and ground are bonded at the generator, and the neutral is switched along with the hot(s) through whatever means there is for power transfer--usually an automatic transfer switch or a separate socket the shore power cord gets plugged into.

If neutral and ground are connected together in an RV, that creates a ground fault, and supplying the RV power via a GFCI socket will rightly trip the GFCI. While most campgrounds don't have GFCIs for their RV outlets, there have been moves afoot to start requiring them sometime in new versions of the NEC--and personally I think that's not a bad idea at all.

mr_andyj
Explorer
Explorer
Gdetrailer wrote:
larry cad wrote:
Gdetrailer wrote:
mr_andyj wrote:
Ground is ground. 2 amps is not a concern, but higher amperage might burn out the little tiny thermostat wire, not a concern here. Ground is ground, so if ground is issue with your pwm then any ground will be an issue. The steel camper frame is ground also, the entire frame of the camper is ground, all the ground wires are ground, they are all connected to the frame and to the negative post on the battery, ground is common to everything.
The only concern, as stated, is how much amperage will be flowing through your chosen ground wire.
I dont think there would be concern with your thermo wire, but try it, if it works then it works, job done.


Ground WIRE is not always "ground".

Yes it is!

That would be a blatant disregard of proper electrical wiring and a violation on NEC rules.

Can you please list the specific "NEC rule" that would be violated?

120V ground wires must terminate in the 120V breaker box on the ground buss. Yes, the ground buss must be bonded to to trailer frame but the 120V wiring has the potential for 120V currents which can cause voltage potentials on any of the ground wires that can cause issues like GFCIs false tripping or even higher voltage potential than 12V on your 12V system.

Gibberish! Voltage and Potential are the exact same thing. Voltage is potential.

The remainder of your comment makes no sense.


120V systems ground WIRE and 12V systems ground WIRE should never be exchanged or substituted or mixed.

We are back to "ground IS ground"

I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.

Wrong

Since there is no real 12V ground available OP will need to get creative on pulling an extra wire for the ground. If the location is close to wall trim you might be able to remove the trim carefully and carve out or drill a hole to thread the wire through the wall stud. Check at floor level to see if you can fish a wire from the floor up. Often you can drill holes just large enough to thread the wire but not too big to cause major damage that can't be hidden with some trim.

This is the closest you came to a sensible comment



Playing dumb is not an excuse.

NEC and "Common Sense" (yes, I realize Common Sense is dead but he was much smarter than anyone else on this planet) requires "separation" between "low voltage" items and "High voltage" items.

12V is considered and recognized as "low voltage" by NEC.

120V is considered and recognized as "high voltage" by NEC.

NEC requires "low voltage" and "high voltage" wiring to not be in the same space. You can plainly see this if you open up the breaker and fuse panel. All 120V wiring is in a separated compartment from the 12V wiring.

There is no DIRECT connection of the 120V wiring to the 12V wiring inside the breaker and fuse panel.

all 12V DC negative ground wiring is typically done outside of the breaker and fuse panel, all of the 12V negative ground wires will be found bunched together outside the panel under one huge wire nut. Under that wire nut one of the grounds is run to the trailer frame..

The 120V side, all grounds must terminate on a fully isolated ground buss bar, one of those wires will then run on its' own run separate from the 12V ground to the trailer frame.

While you might be "technically correct" that a 120V ground wire is at battery negative potential, it isn't what it was designed for or how it should be used.

The reality is the 120V ground wire is a safety ground for your 120V items, as such it has the potential to be carrying 120V voltages and currents under a fault situation.

The potential for 120V currents on the 120V safety ground is the reason in new builds that 240V items are no longer allowed to be wired as 2 HOT and only a safety ground and now are required to provide a Neutral wire.. In the old 3 wire scheme, things like driers would use the safety ground as a neutral for the motor and timer..


You might be right depending how the thermostat is wired in that the thermostat could break the connection to ground, but that seems unlikely. The ground should not go through circuitry, only the 12+, but without seeing the wiring exactly nobody knows... Technically the thermostat wires are not either positive or ground, they are just out-and-back and can be reversed as all that is happening is that the circuit is connected or not, nothing more, thermostats are an on/off switch, nothing more.

You might be wrong about ground not being ground.

We are talking about 12v DC current, not AC current. Do not connect DC items to an AC wire, some things are just a given in these discussions, some common sense applies and can go unstated. Do not look directly into the sun!

In AC wiring there is a Hot and a Neutral (and a ground). Often the Neutral is grounded (at the panel on 3-wire circuits), but never assume everything is wired correctly. Switching Hot and Neutral will do nothing to affect the working of the appliance, but will create a shock hazard as the Neutral and the ground are common at some point. Ask me how I know....

Usually, in all cases I have come across, in an RV or camper the White wires are ground wires, not the black. However, a technician might use a scrap piece of any color, black or white, to patch in positive or negative feed. In general, the long runs of White wire should always be ground. Do not assume this the rule for inside of an individual component's case; the furnace might have internal wiring that does not use color codes common to Rv's. White Ground only applies to the build-out of an RV, not everything and every item.

AC wires will be grounded to the frame the same as the DC wires. As you say, probably not at the same connection point or in the same box, but AC Neutral is connected to the DC ground, and AC ground on the frame. This should not be a concern at al

mr_andyj
Explorer
Explorer
Gdetrailer wrote:
larry cad wrote:
Gdetrailer wrote:
mr_andyj wrote:
Ground is ground. 2 amps is not a concern, but higher amperage might burn out the little tiny thermostat wire, not a concern here. Ground is ground, so if ground is issue with your pwm then any ground will be an issue. The steel camper frame is ground also, the entire frame of the camper is ground, all the ground wires are ground, they are all connected to the frame and to the negative post on the battery, ground is common to everything.
The only concern, as stated, is how much amperage will be flowing through your chosen ground wire.
I dont think there would be concern with your thermo wire, but try it, if it works then it works, job done.


Ground WIRE is not always "ground".

Yes it is!

That would be a blatant disregard of proper electrical wiring and a violation on NEC rules.

Can you please list the specific "NEC rule" that would be violated?

120V ground wires must terminate in the 120V breaker box on the ground buss. Yes, the ground buss must be bonded to to trailer frame but the 120V wiring has the potential for 120V currents which can cause voltage potentials on any of the ground wires that can cause issues like GFCIs false tripping or even higher voltage potential than 12V on your 12V system.

Gibberish! Voltage and Potential are the exact same thing. Voltage is potential.

The remainder of your comment makes no sense.


120V systems ground WIRE and 12V systems ground WIRE should never be exchanged or substituted or mixed.

We are back to "ground IS ground"

I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.

Wrong

Since there is no real 12V ground available OP will need to get creative on pulling an extra wire for the ground. If the location is close to wall trim you might be able to remove the trim carefully and carve out or drill a hole to thread the wire through the wall stud. Check at floor level to see if you can fish a wire from the floor up. Often you can drill holes just large enough to thread the wire but not too big to cause major damage that can't be hidden with some trim.

This is the closest you came to a sensible comment



Playing dumb is not an excuse.

NEC and "Common Sense" (yes, I realize Common Sense is dead but he was much smarter than anyone else on this planet) requires "separation" between "low voltage" items and "High voltage" items.

12V is considered and recognized as "low voltage" by NEC.

120V is considered and recognized as "high voltage" by NEC.

NEC requires "low voltage" and "high voltage" wiring to not be in the same space. You can plainly see this if you open up the breaker and fuse panel. All 120V wiring is in a separated compartment from the 12V wiring.

There is no DIRECT connection of the 120V wiring to the 12V wiring inside the breaker and fuse panel.

all 12V DC negative ground wiring is typically done outside of the breaker and fuse panel, all of the 12V negative ground wires will be found bunched together outside the panel under one huge wire nut. Under that wire nut one of the grounds is run to the trailer frame..

The 120V side, all grounds must terminate on a fully isolated ground buss bar, one of those wires will then run on its' own run separate from the 12V ground to the trailer frame.

While you might be "technically correct" that a 120V ground wire is at battery negative potential, it isn't what it was designed for or how it should be used.

The reality is the 120V ground wire is a safety ground for your 120V items, as such it has the potential to be carrying 120V voltages and currents under a fault situation.

The potential for 120V currents on the 120V safety ground is the reason in new builds that 240V items are no longer allowed to be wired as 2 HOT and only a safety ground and now are required to provide a Neutral wire.. In the old 3 wire scheme, things like driers would use the safety ground as a neutral for the motor and timer..

2112
Explorer II
Explorer II
enblethen wrote:
You must not confuse what you are calling ground.
A ground for the AC system is a safety wire that is not a current carrying conductor.
A "ground" for a DC system is a negative current carrying conductor.
Some thermostats have an isolated DC "negative" conductor.
Yea, I see what you're saying. The Tstat "ground" may not be common to the converter negative return, which is what I'm looking for. I'll investigate this further in a few weeks and let you know what I determine, if interested.

As far as you other guys, stop with the derogatory comments and insults. It's annoying. It's the main reason I stay away from this forum most of the time. I came here to get advice from Doug and Old Biscuit, not to be insulted or have to read insulting gibberish.

Thanks for everyone's input.
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857

Gdetrailer
Explorer III
Explorer III
larry cad wrote:
Gdetrailer wrote:
mr_andyj wrote:
Ground is ground. 2 amps is not a concern, but higher amperage might burn out the little tiny thermostat wire, not a concern here. Ground is ground, so if ground is issue with your pwm then any ground will be an issue. The steel camper frame is ground also, the entire frame of the camper is ground, all the ground wires are ground, they are all connected to the frame and to the negative post on the battery, ground is common to everything.
The only concern, as stated, is how much amperage will be flowing through your chosen ground wire.
I dont think there would be concern with your thermo wire, but try it, if it works then it works, job done.


Ground WIRE is not always "ground".

Yes it is!

That would be a blatant disregard of proper electrical wiring and a violation on NEC rules.

Can you please list the specific "NEC rule" that would be violated?

120V ground wires must terminate in the 120V breaker box on the ground buss. Yes, the ground buss must be bonded to to trailer frame but the 120V wiring has the potential for 120V currents which can cause voltage potentials on any of the ground wires that can cause issues like GFCIs false tripping or even higher voltage potential than 12V on your 12V system.

Gibberish! Voltage and Potential are the exact same thing. Voltage is potential.

The remainder of your comment makes no sense.


120V systems ground WIRE and 12V systems ground WIRE should never be exchanged or substituted or mixed.

We are back to "ground IS ground"

I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.

Wrong

Since there is no real 12V ground available OP will need to get creative on pulling an extra wire for the ground. If the location is close to wall trim you might be able to remove the trim carefully and carve out or drill a hole to thread the wire through the wall stud. Check at floor level to see if you can fish a wire from the floor up. Often you can drill holes just large enough to thread the wire but not too big to cause major damage that can't be hidden with some trim.

This is the closest you came to a sensible comment



Playing dumb is not an excuse.

NEC and "Common Sense" (yes, I realize Common Sense is dead but he was much smarter than anyone else on this planet) requires "separation" between "low voltage" items and "High voltage" items.

12V is considered and recognized as "low voltage" by NEC.

120V is considered and recognized as "high voltage" by NEC.

NEC requires "low voltage" and "high voltage" wiring to not be in the same space. You can plainly see this if you open up the breaker and fuse panel. All 120V wiring is in a separated compartment from the 12V wiring.

There is no DIRECT connection of the 120V wiring to the 12V wiring inside the breaker and fuse panel.

all 12V DC negative ground wiring is typically done outside of the breaker and fuse panel, all of the 12V negative ground wires will be found bunched together outside the panel under one huge wire nut. Under that wire nut one of the grounds is run to the trailer frame..

The 120V side, all grounds must terminate on a fully isolated ground buss bar, one of those wires will then run on its' own run separate from the 12V ground to the trailer frame.

While you might be "technically correct" that a 120V ground wire is at battery negative potential, it isn't what it was designed for or how it should be used.

The reality is the 120V ground wire is a safety ground for your 120V items, as such it has the potential to be carrying 120V voltages and currents under a fault situation.

The potential for 120V currents on the 120V safety ground is the reason in new builds that 240V items are no longer allowed to be wired as 2 HOT and only a safety ground and now are required to provide a Neutral wire.. In the old 3 wire scheme, things like driers would use the safety ground as a neutral for the motor and timer..

enblethen
Nomad
Nomad
You must not confuse what you are calling ground.
A ground for the AC system is a safety wire that is not a current carrying conductor.
A "ground" for a DC system is a negative current carrying conductor.
Some thermostats have an isolated DC "negative" conductor.

Bud
USAF Retired
Pace Arrow


2003 Chev Ice Road Tracker

2112
Explorer II
Explorer II
I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.
That's an interesting comment. I'll have to test this when I get back into it in a few weeks. We shove off tomorrow morning so I'll have to use the new LED strip at full brightness until I can install a dimmer.

My low side dimmer requires access to the LED to ground wire, which I can't easily access from inside. I ordered 2 of the dimmers Doug pointed to. If I can't use that outside I'll have to get a high side driver to make a high side dimmer. That 1 part costs $6 so that's almost a deal breaker right there. I usually design around parts I have on hand.
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857

larry_cad
Explorer
Explorer
Gdetrailer wrote:
mr_andyj wrote:
Ground is ground. 2 amps is not a concern, but higher amperage might burn out the little tiny thermostat wire, not a concern here. Ground is ground, so if ground is issue with your pwm then any ground will be an issue. The steel camper frame is ground also, the entire frame of the camper is ground, all the ground wires are ground, they are all connected to the frame and to the negative post on the battery, ground is common to everything.
The only concern, as stated, is how much amperage will be flowing through your chosen ground wire.
I dont think there would be concern with your thermo wire, but try it, if it works then it works, job done.


Ground WIRE is not always "ground".

Yes it is!

That would be a blatant disregard of proper electrical wiring and a violation on NEC rules.

Can you please list the specific "NEC rule" that would be violated?

120V ground wires must terminate in the 120V breaker box on the ground buss. Yes, the ground buss must be bonded to to trailer frame but the 120V wiring has the potential for 120V currents which can cause voltage potentials on any of the ground wires that can cause issues like GFCIs false tripping or even higher voltage potential than 12V on your 12V system.

Gibberish! Voltage and Potential are the exact same thing. Voltage is potential.

The remainder of your comment makes no sense.


120V systems ground WIRE and 12V systems ground WIRE should never be exchanged or substituted or mixed.

We are back to "ground IS ground"

I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.

Wrong

Since there is no real 12V ground available OP will need to get creative on pulling an extra wire for the ground. If the location is close to wall trim you might be able to remove the trim carefully and carve out or drill a hole to thread the wire through the wall stud. Check at floor level to see if you can fish a wire from the floor up. Often you can drill holes just large enough to thread the wire but not too big to cause major damage that can't be hidden with some trim.

This is the closest you came to a sensible comment

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2112
Explorer II
Explorer II
dougrainer wrote:

This is installed outside at the awning tube area where your 2 wires connect to the LED lights. Just 2 wires POS and NEG. You then turn the lights ON at your wall switch....... Doug

Oh, if this is water resistant that would be an easy install. Plus this would be nice for when we return in the dark. We could turn on some lights before we get out of the truck.

I can also use this for the above the bed lights my DW struggles to reach.

Thanks Doug
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857

dougrainer
Nomad
Nomad
2112 wrote:
dougrainer wrote:
Use this. For less than $30 and you control while outside. Doug

https://www.amazon.com/RV-LIGHTING-WS-01DC-Wireless-Controller/dp/B01LOIZ3Q2/ref=asc_df_B01LOIZ3Q2/?...
Thanks Doug
But doesn't this still require a ground wire? It looks like it wires up just like the one I have


This is installed outside at the awning tube area where your 2 wires connect to the LED lights. Just 2 wires POS and NEG. You then turn the lights ON at your wall switch. Then control the ON/OFF and Dimmer with the hand held remote. IF you are running a NEW wire to the outside LED, just get your ground from the Awning Arm. Doug

2112
Explorer II
Explorer II
DrewE wrote:
Is it a high side dimmer or a low side dimmer?
It's a low side dimmer I made with an ATtiny25.

Thanks
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857

Gdetrailer
Explorer III
Explorer III
mr_andyj wrote:
Ground is ground. 2 amps is not a concern, but higher amperage might burn out the little tiny thermostat wire, not a concern here. Ground is ground, so if ground is issue with your pwm then any ground will be an issue. The steel camper frame is ground also, the entire frame of the camper is ground, all the ground wires are ground, they are all connected to the frame and to the negative post on the battery, ground is common to everything.
The only concern, as stated, is how much amperage will be flowing through your chosen ground wire.
I dont think there would be concern with your thermo wire, but try it, if it works then it works, job done.


Ground WIRE is not always "ground".

That would be a blatant disregard of proper electrical wiring and a violation on NEC rules.

120V ground wires must terminate in the 120V breaker box on the ground buss. Yes, the ground buss must be bonded to to trailer frame but the 120V wiring has the potential for 120V currents which can cause voltage potentials on any of the ground wires that can cause issues like GFCIs false tripping or even higher voltage potential than 12V on your 12V system..

120V systems ground WIRE and 12V systems ground WIRE should never be exchanged or substituted or mixed.

I would also not recommend using the furnace T stat wires for 12V ground as the "ground" you find there goes through the furnace control board and will no longer be at ground potential when the T stat calls for heat.

Since there is no real 12V ground available OP will need to get creative on pulling an extra wire for the ground. If the location is close to wall trim you might be able to remove the trim carefully and carve out or drill a hole to thread the wire through the wall stud. Check at floor level to see if you can fish a wire from the floor up. Often you can drill holes just large enough to thread the wire but not too big to cause major damage that can't be hidden with some trim.

2112
Explorer II
Explorer II
I guess I hit the panic button and ran here too soon. I found ground, the black wire to the right connected to my awning motor control switch.



I can tap into that big black wire but that will be a more invasive effort than connecting to the thermostat. I'm going to try the thermostat ground 1st and see how that goes.

A little back story: My FW has a failed LED strip integrated into the awning tube. I'm replacing that with a strip that mounts onto the camper side under the awning. The power switch and wiring to the outside location already exists. I can use the ground wire on the outside for the LED side of the controller. I just needed to find a ground for the 12V input side of the controller.

Thanks
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857

DrewE
Explorer
Explorer
Is it a high side dimmer or a low side dimmer? In other words, do the instructions for the dimmer have the common connection between the LEDs and the dimmer on the ground side (which would mean it's a high side dimmer, as it is controlling the higher voltage lead) or the +12V side (a low side dimmer)?

If you have a low side dimmer, connecting the dimmer's +12V supply to the thermostat would probably not cause any problems because only minimal power is consumed there, and hence minimal noise produced; the 12V supply is only for the circuitry in the dimmer itself, not for the LEDs. However, in that case, you must have access to the ground lead from the LEDs for the dimmer to be able to control them; it won't work to switch/dim the positive line to them.

If it's a high side dimmer, I would avoid connecting it to the thermostat's 12V power, both from a noise point of view and from a current consumption point of view. From your description, it sounds like it might be a high side dimmer.

In either case, though, it really sounds like you'll probably need to pull a wire from somewhere (else).