'Water' ground - Garmin GMR radar

[Tomco]

I'm replacing my radar (and chartplotter) with a Garmin open array version. The install instructions require a ground be installed from the 'radar pedestal to a water ground location'.

I've not heard of 'water' ground before but after looking it up I believe that this would be the negative of the battery. Logic being the negative of the battery is connected to the engine, which is connected to the drive shaft (straight shaft configuration), which is in the water! So connecting to the common ground bus bar in the ER should do it.

Anyone else done this install and is this how you wired to a 'water ground' location?

 

[ttmott]

I'm replacing my radar (and chartplotter) with a Garmin open array version. The install instructions require a ground be installed from the 'radar pedestal to a water ground location'.

I've not heard of 'water' ground before but after looking it up I believe that this would be the negative of the battery. Logic being the negative of the battery is connected to the engine, which is connected to the drive shaft (straight shaft configuration), which is in the water! So connecting to the common ground bus bar in the ER should do it.

Anyone else done this install and is this how you wired to a 'water ground' location?

There is the power positive and negative to the batteries but then it needs to be bonded to the boat's bonding network. From the GMR housing bonding terminal run an 8 gauge green wire to where another bond is and connect the two. Usually the metal superstructure on your boat is bonded and a large green bonding wire is connected to one of the superstructure bolts. SR may have already routed the bonding wire and it may be stashed in your overhead electronic box. These green bonding wires have very low resistance to the hull zinc which is the "water ground". Some Sea Ray boats have a dedicated hull grounding plate sometimes called a Dynaplate that the green bonding wires and battery negative terminate on. My 400DA had a Dynaplate but my 52DB doesn't.

 

[techmitch]

There is the power positive and negative to the batteries but then it needs to be bonded to the boat's bonding network. From the GMR housing bonding terminal run an 8 gauge green wire to where another bond is and connect the two. Usually the metal superstructure on your boat is bonded and a large green bonding wire is connected to one of the superstructure bolts. SR may have already routed the bonding wire and it may be stashed in your overhead electronic box. These green bonding wires have very low resistance to the hull zinc which is the "water ground". Some Sea Ray boats have a dedicated hull grounding plate sometimes called a Dynaplate that the green bonding wires and battery negative terminate on. My 400DA had a Dynaplate but my 52DB doesn't.

"Dynaplate" Just had a flash back of you using that word before.

After initial search, thanks for many hours of reading. Lol

 

[Irie308]

I'm replacing my radar (and chartplotter) with a Garmin open array version. The install instructions require a ground be installed from the 'radar pedestal to a water ground location'.

I've not heard of 'water' ground before but after looking it up I believe that this would be the negative of the battery. Logic being the negative of the battery is connected to the engine, which is connected to the drive shaft (straight shaft configuration), which is in the water! So connecting to the common ground bus bar in the ER should do it.

Anyone else done this install and is this how you wired to a 'water ground' location?

Curious about this as well just installed the Fantom 54 and saw the grounding wire. There is a bonding wire in the starboard arch that was never run up to the arch. Planning on connecting this but also read in Garmin documentation that this doesn't necessarily protect you from lightning strike and only aids in reducing electrical interference if present. I'm thinking about extending the bonding wire to the arch and then connecting it to one of the bolts holding down the radar mount. Will then connect the grounding wire from the radar to the same bolt. But curious how useful this is as the old raymarine was never connected to the bonding wire from the factory. Curious as to what you end up doing Tom.

 

[ttmott]

Curious about this as well just installed the Fantom 54 and saw the grounding wire. There is a bonding wire in the starboard arch that was never run up to the arch. Planning on connecting this but also read in Garmin documentation that this doesn't necessarily protect you from lightning strike and only aids in reducing electrical interference if present. I'm thinking about extending the bonding wire to the arch and then connecting it to one of the bolts holding down the radar mount. Will then connect the grounding wire from the radar to the same bolt. But curious how useful this is as the old raymarine was never connected to the bonding wire from the factory. Curious as to what you end up doing Tom.

The bonding does a couple of things. First in an electrical surge like a lightning strike you want the entire boat as a unit to come up in potential then fall equally in potential. The idea is to avoid voltage differentials throughout the boat which are the cause of damage and electrocution hazard. In the rocket business we go to great lengths to ensure the flight hardware is bonded to the earth grounding system and all of the structures are equally bonded to the same grounding system; this ensures when lightning strikes (and it does quite often) everything comes up in potential (voltage) equally then drains to the ground system equally; We really want to avoid voltage differentials between any metal. This is why the bonding wires are such heavy gauge so they are the lowest resistance to ground.
Secondly, the bonding reduces galvanic corrosion as the bonding system is tied with low resistance to the hull zinc anode which is the less noble metal.
Lastly, as the bonding system also serves as a reference ground to the earth (water) electrical noise in sensitive electronic components becomes less of a concern.

 

[Tomco]

There is the power positive and negative to the batteries but then it needs to be bonded to the boat's bonding network. From the GMR housing bonding terminal run an 8 gauge green wire to where another bond is and connect the two. Usually the metal superstructure on your boat is bonded and a large green bonding wire is connected to one of the superstructure bolts. SR may have already routed the bonding wire and it may be stashed in your overhead electronic box. These green bonding wires have very low resistance to the hull zinc which is the "water ground". Some Sea Ray boats have a dedicated hull grounding plate sometimes called a Dynaplate that the green bonding wires and battery negative terminate on. My 400DA had a Dynaplate but my 52DB doesn't.

Thanks Tom! I understand your explanation. From previous work in the arch I don't remember any green bonding wire around ... but, I wasn't looking for one. It will be a few more weeks of melting snow before being able to get to the boat. If I have to run one from the ER that won't be a big deal.

 

[Irie308]

Tom, this is mine tucked into the panel behind the starboard backrest.

 

[Tomco]

Curious about this as well just installed the Fantom 54 and saw the grounding wire. There is a bonding wire in the starboard arch that was never run up to the arch. Planning on connecting this but also read in Garmin documentation that this doesn't necessarily protect you from lightning strike and only aids in reducing electrical interference if present. I'm thinking about extending the bonding wire to the arch and then connecting it to one of the bolts holding down the radar mount. Will then connect the grounding wire from the radar to the same bolt. But curious how useful this is as the old raymarine was never connected to the bonding wire from the factory. Curious as to what you end up doing Tom.

I have a ScanStrut pedestal that the sat dome and radar are mounted - I don't believe it is grounded (bonded?). If not, I'll likely run a bonding wire to the ScanStrut mounting bolts and then from there to the radar pedestal. If you get to yours before me, I'd appreciate knowing if you find a bonding wire already run to the bridge or arch.

Any tips for lifting up the new radar pedestal?

 

[Tomco]

Tom, this is mine tucked into the panel behind the starboard backrest.
View attachment 122999 View attachment 123000

Dean, didn't see your pics when I sent my message. Thanks for sharing! Are those running to the top of the arch?

 

[Tomco]

The bonding does a couple of things. First in an electrical surge like a lightning strike you want the entire boat as a unit to come up in potential then fall equally in potential. The idea is to avoid voltage differentials throughout the boat which are the cause of damage and electrocution hazard. In the rocket business we go to great lengths to ensure the flight hardware is bonded to the earth grounding system and all of the structures are equally bonded to the same grounding system; this ensures when lightning strikes (and it does quite often) everything comes up in potential (voltage) equally then drains to the ground system equally; We really want to avoid voltage differentials between any metal. This is why the bonding wires are such heavy gauge so they are the lowest resistance to ground.
Secondly, the bonding reduces galvanic corrosion as the bonding system is tied with low resistance to the hull zinc anode which is the less noble metal.
Lastly, as the bonding system also serves as a reference ground to the earth (water) electrical noise in sensitive electronic components becomes less of a concern.

Tom, I looked up the bonding/grounding wiring diagram for our boat and it shows the battery negative and the green bonding both attaching to the Main DC Negative Busbar. Not withstanding Dean finding the bonding wire extending up the arch, IF one had to run a wire, would it make sense to connect it to the Main DC negative busbar? I don't fully appreciate the nuance between 'ground' and 'bonding' ... to my mechanical mind, it seems the same.

 

[Irie308]

Dean, didn't see your pics when I sent my message. Thanks for sharing! Are those running to the top of the arch?

Currently no, its looks as if it was never extended to the arch. Its tucked in behind the star backrest assuming you also have the same back there. Should be easy to extend.

 

[ttmott]

Tom, I looked up the bonding/grounding wiring diagram for our boat and it shows the battery negative and the green bonding both attaching to the Main DC Negative Busbar. Not withstanding Dean finding the bonding wire extending up the arch, IF one had to run a wire, would it make sense to connect it to the Main DC negative busbar? I don't fully appreciate the nuance between 'ground' and 'bonding' ... to my mechanical mind, it seems the same.

View attachment 123004

They are interconnected at the main grounding buss (so is the AC Ground and AC Common when on generator or inverter) but the difference is there is less resistance through the bonding system and consequently the low level current will take the path of least resistance.
There were a couple of posts about a month ago maybe two where a member was failing his raw water HVAC pump; it was corroding through the bronze housing. He had been through at least a couple of pumps. His pump was grounded through the boat's AC/DC grounding system but not connected to his bonding system expecting the grounding system to take care of the galvanic corrosion; it didn't. The small gauge wiring for DC power (AC power in his case) lends to higher resistance consequently the low level current is not getting dissipated through the hull anode. On the other side of the equation where something on the boat is subjected to very high level current; If trying to dissipate that current again through small gauge DC wires large differential voltages will occur and things will be damaged; so, again the large gauge bonding wiring is the least path of resistance and will help save the day....

 

[ttmott]

As a side note - the importance of a robust bonding system with good corrosion free terminations cannot be overstated. It has always amazed me that surveyors don't thoroughly examine and test the bonding systems on boats for potential buyers. Gary Gellespie and Brian Stetler well-recognized surveyors who did my survey on the 52DB rung out the bonding system and then did some more when I asked if they tested things like handrails and superstructure. We discussed the bonding system on my boat on the post survey discussion; he (Gary) was pleased I wanted to spend some time going over it and noted that not many surveyors or potential owners understand the importance of the system. You know, to a potential buyer the bonding system condition is indicative of the condition of the boat from a corrosion aspect especially in locations that cannot be accessed. Everyone is more concerned with latent maintenance, lights that don't work, and hull moisture than that critical bonding system....

 

[Tomco]

They are interconnected at the main grounding buss (so is the AC Ground and AC Common when on generator or inverter) but the difference is there is less resistance through the bonding system and consequently the low level current will take the path of least resistance.
There were a couple of posts about a month ago maybe two where a member was failing his raw water HVAC pump; it was corroding through the bronze housing. He had been through at least a couple of pumps. His pump was grounded through the boat's AC/DC grounding system but not connected to his bonding system expecting the grounding system to take care of the galvanic corrosion; it didn't. The small gauge wiring for DC power (AC power in his case) lends to higher resistance consequently the low level current is not getting dissipated through the hull anode. On the other side of the equation where something on the boat is subjected to very high level current; If trying to dissipate that current again through small gauge DC wires large differential voltages will occur and things will be damaged; so, again the large gauge bonding wiring is the least path of resistance and will help save the day....

Got it! Thanks for the explanation.

 

[Irie308]

So from my checking all of the new Garmin gear has the similar grounding accessory. So now the question is if you're going to do the radar will will you also do the plotters?

 

[Tomco]

I’m not planning on bonding them unless I see some interference as well – this is what Garmin recommends. This is from the Garmin install guide:

Additional Grounding Consideration

This device should not need additional chassis grounding in most installation situations. If you experience interference, the grounding screw on the housing can be used to connect the device to the water ground of the boat to help avoid the interference.​