# Jumping together DIN ground terminal blocks



## splatz (May 23, 2015)

Mbit said:


> Do you guys run jumper wires on the green/yellow dedicated DIN rail grounding terminals to bond them all together or do you rely on the DIN rail?
> 
> 
> The specific one's I have don't have a spot in the middle for a conventional DIN style jumper pin, they just have the screw which bonds it to the rail. I don't really trust them and think I'll daisy chain all mine together. I guess I could order some old school style forked jumpers for next time. I know this is in the weeds a little just curious how everyone else does it.



I actually trust those ground terminal blocks connection bonding to the DIN rail more than I trust a jumper. 

If you're not going to trust them, why not just use regular terminal blocks? You can buy them in green, although I am not aware of any requirement that the terminal blocks be green.


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## bill39 (Sep 4, 2009)

I used to run a UL508 shop and our UL inspector had no problem with us using wires or jumper bars to connect ground terminals together, then back to the main ground bar.


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## just the cowboy (Sep 4, 2013)

*One or the other*

I have done both but not together. I like the self bonding ones better because I know it is bonded. I have seen the bonding jumper get removed for what ever reason and have a ungrounded strip. 

Cowboy


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## joe-nwt (Mar 28, 2019)

I see no reason to ground grounding blocks. Most I normally do is bond the backpan.


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## MotoGP1199 (Aug 11, 2014)

I use the screw down grounding terminal blocks and those things are solid. The whole purpose is so you can ground the rail, the back panel and what ever else you want. I see no reason to jumper them. Do you trust grounds from a conduit that are tied into a panel that is grounded with a lug? If so its about the same situation.


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## John Valdes (May 17, 2007)

What are you doing for your neutrals?


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## Cow (Jan 16, 2008)

I don't use the grounding terminals blocks 95% of the time. 

I grind paint and install a 10-20 space ground bar down at the bottom somewhere usually.


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## gpop (May 14, 2018)

MotoGP1199 said:


> I use the screw down grounding terminal blocks and those things are solid.


Mess up the clamp screw you will be amazed at how solid that connection is.

5 minute job and all you need to do is move the ground 1/2" and add 2 extra blocks but the person who built the panel farm tightened the clamp screw :crying:.


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## Mbit (Feb 28, 2020)

splatz said:


> I actually trust those ground terminal blocks connection bonding to the DIN rail more than I trust a jumper.
> 
> If you're not going to trust them, why not just use regular terminal blocks? You can buy them in green, although I am not aware of any requirement that the terminal blocks be green.



Lot's of salt spray here so I don''t really trust the steel DIN rail. I probably should just use regular terminal blocks you're right.


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## Mbit (Feb 28, 2020)

John Valdes said:


> What are you doing for your neutrals?



Don't have any just 2 pole breakers and terminals for some dry contacts and modbus. The ground blocks are for the EGC's and the panel grounding.


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## bill39 (Sep 4, 2009)

bill39 said:


> I used to run a UL508 shop and our UL inspector had no problem with us using wires or jumper bars to connect ground terminals together, then back to the main ground bar.


I think I misunderstood the original post. If you’re talking about using the clamp on the self-grounding terminals then I need to change my previous comment a bit.

Our UL guy made us connect a ground wire to the mounting screw on each dinrail. Those ground wires could be jumpered from one dinrail to another, ending up at the main ground bar.


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## MotoGP1199 (Aug 11, 2014)

bill39 said:


> I think I misunderstood the original post. If you’re talking about using the clamp on the self-grounding terminals then I need to change my previous comment a bit.
> 
> Our UL guy made us connect a ground wire to the mounting screw on each dinrail. Those ground wires could be jumpered from one dinrail to another, ending up at the main ground bar.


Serious question. IF your UL guy is correct then what is the purpose of using the grounding block if you still have to run jumper wires from mounting screws? Why not just run the wire to a lug with a screw. I was under the impression these grounding blocks were an approved method of grounding the din rail, and the back panel was approved to be grounded through a machine screw connecting the din rail to the back panel. One of the sales advantages to using these grounding blocks was that you could just mount a grounding block on any din in a large cabinet and run a ground to an individual PSU with out having to run ground wires all over the place.


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## John Valdes (May 17, 2007)

Mbit said:


> Don't have any just 2 pole breakers and terminals for some dry contacts and modbus. The ground blocks are for the EGC's and the panel grounding.


 What voltage are the controls? 120? 230? 460?


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## bill39 (Sep 4, 2009)

MotoGP1199 said:


> Serious question. IF your UL guy is correct then what is the purpose of using the grounding block if you still have to run jumper wires from mounting screws? Why not just run the wire to a lug with a screw. I was under the impression these grounding blocks were an approved method of grounding the din rail, and the back panel was approved to be grounded through a machine screw connecting the din rail to the back panel. One of the sales advantages to using these grounding blocks was that you could just mount a grounding block on any din in a large cabinet and run a ground to an individual PSU with out having to run ground wires all over the place.


Two things, 
1) This was a place where I decided to pick my battle and & I didn't want to fight it. 

2) I believe his point was to ensure that the dinrail was grounded properly. We typically don’t grind the paint off behind the dinrail so the grounding was through the screws to the back panel. It simply was not a big deal so we ran the jumpers.


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## Mbit (Feb 28, 2020)

John Valdes said:


> What voltage are the controls? 120? 230? 460?[/QUOTE
> 
> 
> 120/240 single phase 3 wire ungrounded system with neutral switched on the main and all the feeder breakers via the B phase. Yes sir.


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## just the cowboy (Sep 4, 2013)

Mbit said:


> John Valdes said:
> 
> 
> > What voltage are the controls? 120? 230? 460?[/QUOTE
> ...


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## joe-nwt (Mar 28, 2019)

just the cowboy said:


> Mbit said:
> 
> 
> > Now I'll ask a question. Are these control system ground wires or Power system Ground wires?
> ...


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## dronai (Apr 11, 2011)

Ground the dinrail ? the dinrail is already grounded by your attachent screws ? I use the jumpers that you buy. Haven't seen the other type yet you described.


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## paulengr (Oct 8, 2017)

What’s missing here is surface area. Steel has about 1/10th of the conductivity of copper but usually we make up for this with massively larger components, even screws. Try this. Attach a couple pigtails to your ground terminal strip. Take a micro ohm meter and measure from the main power grounding lug on the panel to each of the pigtails and also measure between them both with and without the extra shorting bar. What I suspect you will find is either not much difference or it’s there but it’s all in the range of milli ohms so it’s an argument about nothing.


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## Mbit (Feb 28, 2020)

> Now I'll ask a question. Are these control system ground wires or Power system Ground wires?
> 
> If the are power system ground wires I would not put them on the din rail, I would use a Ground BAR as said by *cow*
> 
> Control wire grounds I would use the self bonding ones.



Power. The controls just have shields, no grounds. I don't have room in the boxes for a ground bar but I just got thrown a curve ball.



After doing a little investigating and opening the xfmr, panelboard and some branch circuit JB's I found this particular system was built ungrounded. Basically 3 phase panel running 120/240 with the neutral switched via the B phase on the main and branch CBs. lain:



According to the CFR's (not subject to the NEC here unfortunately) switching the neutral is allowed as long as all conductors are broken at the same time. The rules do state though that any neutral has to be solidly grounded which it's not. And the neutral is grounded all over the place on the branch circuits after I opened a few JBs.



The system has been operating this way for 40 years so it's not an emergency but this circuit is running all over the place out on deck and I would like to ground it solidly for future personnel safety when we have a long enough shutdown.


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## gpop (May 14, 2018)

Mbit said:


> Power. The controls just have shields, no grounds. I don't have room in the boxes for a ground bar but I just got thrown a curve ball.
> 
> 
> 
> ...


Not grounded or no visible green wire. Back in the day the conduit could have been the ground then later when things went bad someone got lazy and simply bugged the neutral to patch a ground path. 

Also try to figure out why someone wanted a disconnect on the neutral wire. Is anything classified as flammable and do the breakers have shunt trips?

I guess what im saying is don't fix what you think is a problem until you understand why it was done that way. No one payed extra for a 3 pole breaker when a cheaper 2 pole would have worked.


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## Mbit (Feb 28, 2020)

> Not grounded or no visible green wire. Back in the day the conduit could have been the ground then later when things went bad someone got lazy and simply bugged the neutral to patch a ground path.
> 
> Also try to figure out why someone wanted a disconnect on the neutral wire. Is anything classified as flammable and do the breakers have shunt trips?
> 
> I guess what im saying is don't fix what you think is a problem until you understand why it was done that way. No one payed extra for a 3 pole breaker when a cheaper 2 pole would have worked.



Yeah I hear you, unfortunately this is on a ship that runs almost exclusively ungrounded everything. No conduit or EGC's onboard. The only time you will see a green wire is on vendor equipment. On previous vessels I've even seen X2 grounds on control circuits lifted to clear ground faults. No hazardous areas for our particular vessel.


This is a small 120/240 system just for some laundry and galley equipment. Over the years stuff was added out of convenience, and now there's a few circuits run out on deck. There is not a single ground bus on the entire ship and that's actually common. 



When I started this thread I kind of assumed that it was a grounded system because the red wire(the 3rd wire in our 14/3 color scheme) was landed on the ground lug in each one of the silo sensors (there are 10 daisy chained on one circuit). Then I opened everything up and found this gem.



Currently the system is not correct according to the regs but I'm guessing that just like the NEC a lot has changed since it was built. Currently I have a system that was built ungrounded but has since had the neutral grounded in a lot of places(JBs, enclosures). I also have 3 dryers hooked up 3 wire being fed by this panel I'm not really comfortable with that. There is 0 advantage to ungrounded systems in this application but that's just how they did things back in the day.


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## glen1971 (Oct 10, 2012)

Cow said:


> I don't use the grounding terminals blocks 95% of the time.
> 
> I grind paint and install a 10-20 space ground bar down at the bottom somewhere usually.


I've seen them used lots in PLC and DCS cabinets on the shields on the AI/AO terminals. Little less jumpering to do.


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## paulengr (Oct 8, 2017)

Navy regulations mandate ungrounded systems due to corrosion concerns. Since those guys often retire and get civilian jobs, it spills over into all other vessels.

However not grounded and not bonded are two different things. You can be ungrounded but you must be bonded, period. In an ungrounded system even if it’s 3 phase 4 wire wye, ALL conductors are potentially energized. Even if there is a “neutral” it is not a grounded wire or shouldn’t be (ungrounded) so it’s a hot too. Where things get a little crazy is OSHA requires breaking all ungrounded current carrying conductors. So that means 3 pole breakers on 240/120 feeds and 2 pole on 240 or 120 only. It can be done with 3 phase MDPs and careful marking but it’s nuts to do it.

NEC is fine with ungrounded systems, as long as they are above 240 V and have phase lights. This was popular industrially in the 1950s. It is still allowed below that in limited circumstances like control power and VTs in switchgear (typically 120 V ungrounded) as long as you break both phases. So it does exist. It’s quite common, especially in other countries and some systems in the US. Just not for what passes as “residential” style North American systems,

Don’t get hung up on CFR/OSHA regulations. Most ship builders choose a Code such as ABS to follow. Pleasure boats and yachts have their own. Fishing boats tend to be a mess of whatever hack did it last. CAT has a way they like to do things too. This goes beyond CFR and fleshes our details. For example contrary to popular belief on construction sites OSHA has just 2 sentences for LOTO. Locks aren’t even required! That’s why you need a Code. This avoids the mess with explaining what you are doing to USCG inspectors. You’ve already got mixed grounded/ungrounded systems with no rhyme or reason. Likely it needs to be all one or the other. Pay attention to why ships are ungrounded. There is a good reason. NEC is a good standard to use even in places where it is not mandatory (power plants, mines) because it keeps you out of trouble. It just might not be appropriate due to corrosion concerns in this case. I’ve looked at Navy’s stance on this before. Not sure I entirely agree but they have way more experience than I do. And my opinion might change if I’m on a fiberglass or aluminum hull vs a steel one, and salt vs fresh water.

I’m telling you this because maritime is not black and white like commercial/industrial. When you work outside NEC that doesn’t mean there is NO Code. It’s just different from what you are used to. In maritime to some degree you get to pick one. I wouldn’t apply the yacht Code to a dredge but no state mandated Code means you have more flexibility to not follow some things if they don’t apply. And just like a lot of unlicensed residential work there is a lot of jack leg stuff. Inspectors struggle with it too. There is a reason that BOAT stands for Break Out Another Thousand.


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## Mbit (Feb 28, 2020)

paulengr said:


> Navy regulations mandate ungrounded systems due to corrosion concerns. Since those guys often retire and get civilian jobs, it spills over into all other vessels.
> 
> However not grounded and not bonded are two different things. You can be ungrounded but you must be bonded, period. In an ungrounded system even if it’s 3 phase 4 wire wye, ALL conductors are potentially energized. Even if there is a “neutral” it is not a grounded wire or shouldn’t be (ungrounded) so it’s a hot too. Where things get a little crazy is OSHA requires breaking all ungrounded current carrying conductors. So that means 3 pole breakers on 240/120 feeds and 2 pole on 240 or 120 only. It can be done with 3 phase MDPs and careful marking but it’s nuts to do it.
> 
> ...



46 CFR § 111.05-15 does require solidly grounding the neutral.


I will say you are right on with everything else, you've obviously spent some time around the industry. We do have to follow ABS steel vessel rules since we are ABS classed. But as an US flag vessel when built we are subject to the CFRs as they are law. The CFRs do however incorporate by reference IEEE 45, the NEC and some IEC standards.


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## gpop (May 14, 2018)

Mbit said:


> 46 CFR § 111.05-15 does require solidly grounding the neutral.
> 
> 
> I will say you are right on with everything else, you've obviously spent some time around the industry. We do have to follow ABS steel vessel rules since we are ABS classed. But as an US flag vessel when built we are subject to the CFRs as they are law. The CFRs do however incorporate by reference IEEE 45, the NEC and some IEC standards.


If ground is free floating until its connected to shore power and its not connected to the bonding then how do you solidly connect neutral to ground while running on a generator. 

seems confusing.


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## Mbit (Feb 28, 2020)

gpop said:


> If ground is free floating until its connected to shore power and its not connected to the bonding then how do you solidly connect neutral to ground while running on a generator.
> 
> seems confusing.



Just connect the neutral to the hull. Usually there is a welded pad or sometimes a stud, that makes it solidly grounded.


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## paulengr (Oct 8, 2017)

Mbit said:


> Just connect the neutral to the hull. Usually there is a welded pad or sometimes a stud, that makes it solidly grounded.



Not so easy. Especially with DC systems but even AC can be tricky. Navy spends billions on corrosion control. It’s a big part of their budget.

https://www.wired.com/2011/06/shipbuilder-blames-navy-as-brand-new-warship-disintegrates/


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## just the cowboy (Sep 4, 2013)

I saw a control panel built by an ex navy guy. All the starters coils common side were tied direct to the back-plane. That was how the did it on the ships, manufactures even built starters that way. As a base electrician we would have to pull that wire off if we got one from stock.

Cowboy


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## QMED (Sep 14, 2016)

just the cowboy said:


> I saw a control panel built by an ex navy guy. All the starters coils common side were tied direct to the back-plane. That was how the did it on the ships, manufactures even built starters that way. As a base electrician we would have to pull that wire off if we got one from stock.
> 
> Cowboy


Weird. I’ve never seen that on ships. With MCCs it’s a tossup between the CPTs having having grounded secondaries and one fuse or ungrounded with 2.


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## just the cowboy (Sep 4, 2013)

QMED said:


> Weird. I’ve never seen that on ships. With MCCs it’s a tossup between the CPTs having having grounded secondaries and one fuse or ungrounded with 2.


I saw this back in the seventies, when I asked they said it more reliable because they never had to worry about losing one side since the ship was the return. 
I was in controls maintenance in the ship yard, never worked on the ships.


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