Odd intriguing and perhaps dangerous multi unit grounding question/problem: JUMPER??

[docj67]

main bldg service feeders size unknown at this time

main bldg service feeders size unknown at this time

the feeders running to gutter that feed taps to the 4 sevices size
is unknown, have not yet opened gutter. an associate whom i may hire to reground building suggested the 1.5" rmc that they run down from weather head was small considering it supports 4 services.....

thx for your interest!!

js

 

[al hildenbrand]

he has a 100amp
service fed by 2awg alum

each 50amp
sub feeder is currently 4awg copper

thx

What about the Service Entrance conductors?

The conductors in what appears to be a 2 inch conduit? The ampacity of those conductors is possibly the limiting factor. . . not the size of the four (or five) Service Disconnect Overcurrent Protective Devices, or the current carrying capacity of the subpanel feeder conductors.

When a multiple service disconnecting means (your 4 or 5 disconnects) is supplied by a single set of service entrance conductors, the size of the service entrance conductors must be determined by calculating the existing load via Article 220. Your client added an additional 50 A feeder, yes. . . but that doesn't give us any information about what the connected load is. Did your client actually add load that is new and additional to the original calculation done by the electrician that designed the original four-meter/disconnect?

See, a lot of time has passed from the original FPE installation. How many new loads have been added/changed beyond the original as-built loads? The only way to tell, whether the Service Mast Conductors are up to today's load, is to ask after the present day loads, get the habitable area dimensions and to do the Calc. The amperage of the Service Disconnect Overcurrent Protective Devices and/or the current carrying capacity of the Feeders has nothing to do with the outcome.

Edit To Add: I just saw your response about possible 1-1/2" size Service Mast !! The Calculation is even more important as the conductors get smaller. It sounds like the client's adding of the fifth feeder may be a real problem for the Service Mast conductors.

 

[docj67]

appreciate this new inquiry but

appreciate this new inquiry but

there's a missing piece

we are not adding any more load to his service at this time we r replacing old fpe sub w new one: like for like replacement.

new non fpe
sub in NEC allowed location and replacing his master disconnect w new non fpe unit.

id love to dialog more and will follow up more in the next few days.
i have a brief window for a few days off between this project and several others on deck.

thx,js

 

[docj67]

and you are right but

and you are right but

my mandate has not been to analyze entire building. its a 4 unit condo complex w out a formal HOA.

your points are great,thx

js




QUOTE=al hildenbrand;1884658]What about the Service Entrance conductors?

The conductors in what appears to be a 2 inch conduit? The ampacity of those conductors is possibly the limiting factor. . . not the size of the four (or five) Service Disconnect Overcurrent Protective Devices, or the current carrying capacity of the subpanel feeder conductors.

When a multiple service disconnecting means (your 4 or 5 disconnects) is supplied by a single set of service entrance conductors, the size of the service entrance conductors must be determined by calculating the existing load via Article 220. Your client added an additional 50 A feeder, yes. . . but that doesn't give us any information about what the connected load is. Did your client actually add load that is new and additional to the original calculation done by the electrician that designed the original four-meter/disconnect?

See, a lot of time has passed from the original FPE installation. How many new loads have been added/changed beyond the original as-built loads? The only way to tell, whether the Service Mast Conductors are up to today's load, is to ask after the present day loads, get the habitable area dimensions and to do the Calc. The amperage of the Service Disconnect Overcurrent Protective Devices and/or the current carrying capacity of the Feeders has nothing to do with the outcome.

Edit To Add: I just saw your response about possible 1-1/2" size Service Mast !! The Calculation is even more important as the conductors get smaller. It sounds like the client's adding of the fifth feeder may be a real problem for the Service Mast conductors.[/QUOTE]

 

[docj67]

nothing is being added, no 5th service/feeder

nothing is being added, no 5th service/feeder

thx!!!

my mandate has not been to analyze entire building. its a 4 unit condo complex w out a formal HOA.

your points are great,thx

js




QUOTE=al hildenbrand;1884658]What about the Service Entrance conductors?

The conductors in what appears to be a 2 inch conduit? The ampacity of those conductors is possibly the limiting factor. . . not the size of the four (or five) Service Disconnect Overcurrent Protective Devices, or the current carrying capacity of the subpanel feeder conductors.

When a multiple service disconnecting means (your 4 or 5 disconnects) is supplied by a single set of service entrance conductors, the size of the service entrance conductors must be determined by calculating the existing load via Article 220. Your client added an additional 50 A feeder, yes. . . but that doesn't give us any information about what the connected load is. Did your client actually add load that is new and additional to the original calculation done by the electrician that designed the original four-meter/disconnect?

See, a lot of time has passed from the original FPE installation. How many new loads have been added/changed beyond the original as-built loads? The only way to tell, whether the Service Mast Conductors are up to today's load, is to ask after the present day loads, get the habitable area dimensions and to do the Calc. The amperage of the Service Disconnect Overcurrent Protective Devices and/or the current carrying capacity of the Feeders has nothing to do with the outcome.

Edit To Add: I just saw your response about possible 1-1/2" size Service Mast !! The Calculation is even more important as the conductors get smaller. It sounds like the client's adding of the fifth feeder may be a real problem for the Service Mast conductors.

[/QUOTE]

 

[al hildenbrand]

my mandate has not been to analyze entire building. its a 4 unit condo complex w out a formal HOA.

your points are great,thx

js

I'd be cautious. As you've described the situation, your client created the possible overload on the Service Entrance Conductors and directly affects the other attached condos. Your working on it opens you to a liability.

 

[docj67]

confused

confused

Hi, i'm appreciative of reminding of liability but I'm not sure what overload you are talking about?

My client did not build the place.........I'm confused. He's another innocent homeowner victim of some wonky electric work. My analysis of his service and loads other then the entire building ground issues that began this thread shows correct breakering and wire sizing. It would be good to SEC size for sure, but we are not adding anything.

I will mention to him that it was suggested that entire building SEC be inquired of. He's trying to get a hold of the contractor who built the place. If he can't then we are going to get a more veteran company to reground the building and I will make sure they audit the loading of the entire place per your advice as part of their scope of work.

How does that sound?

I'd be cautious. As you've described the situation, your client created the possible overload on the Service Entrance Conductors and directly affects the other attached condos. Your working on it opens you to a liability.

 

[jumper]

Okay, back to this grounding issue.

You have the service panel with two 50A breakers feeding two sub panels in unit.

Panel A and Panel B. Both are fed with #4 copper. 3 wire feed with metallic raceway EGC. Good.

Panel A has what as far as odd GECs and Panel B,the FPE one, has what?

 

[docj67]

panel a and b

panel a and b

A has two #8's
B has nothing ( no EGC visible ) (FPE PANEL)

 

[al hildenbrand]

nothing is being added, no 5th service/feeder

OK. I hear (read, really) that. But again, the current in the Service Entrance Mast Conductors is caused by ( and only by ) the connected LOAD.

There's a reason the additional panel and feeder were installed. . . I can't see it from this side of my screen. Why was additional branch circuit OCPD space required? Is it because the new branch circuits go to new loads?

 

[docj67]

There has been no new panel installed and feeder installed in my working on this proj

There has been no new panel installed and feeder installed in my working on this proj

~

 

[jumper]

OK. I hear (read, really) that. But again, the current in the Service Entrance Mast Conductors is caused by ( and only by ) the connected LOAD.

There's a reason the additional panel and feeder were installed. . . I can't see it from this side of my screen. Why was additional branch circuit OCPD space required? Is it because the new branch circuits go to new loads?

Al, you have great points, but he cannot possibly answer those questions and it falls outside his scope of work. The guy is not getting paid to fix the whole shebang.

 

[jumper]

There's a reason the additional panel and feeder were installed. . . I can't see it from this side of my screen. Why was additional branch circuit OCPD space required? Is it because the new branch circuits go to new loads?

How do we know there was not two panels to begin with?

 

[jumper]

A has two #8's
B has nothing ( no EGC visible ) (FPE PANEL)

The conduit is the EGC.

If panel B is the one you are replacing and there are no mysterious bare #8 wires, it can be replaced.

Panel A may or may not have a problem. Hardest part is not knowing where the other ends are.

Two wires are puzzling. If they simply were unneeded GECs that went to part of the building GES, they would be harmless. Assuming they land in the EGC bus and not the neutral bus.

A connection at the service equipment to a GES still has to be done. Fixing your customers stuff without fixing the others there is problematic.

You said you were going to sub this part out?

 

[docj67]

yes most likely

yes most likely

sub to one of
my mentors
or
my hopeful new journeyman's current boss

15 and 30 years experience respectively

can one conduit be an egc for two feeders?

and yes my intention and conmunication to client

from start hass included entire building: all units inclusive -thx.
appreciate reminders to make sure Service equipment is included, thats partially why i want a veteran to handle it under my management.

I request closure of thread and further dialogue to occur off line .....thx for continued moderatinf

The conduit is the EGC.

If panel B is the one you are replacing and there are no mysterious bare #8 wires, it can be replaced.

Panel A may or may not have a problem. Hardest part is not knowing where the other ends are.

Two wires are puzzling. If they simply were unneeded GECs that went to part of the building GES, they would be harmless. Assuming they land in the EGC bus and not the neutral bus.

A connection at the service equipment to a GES still has to be done. Fixing your customers stuff without fixing the others there is problematic.

You said you were going to sub this part out?

 

[al hildenbrand]

There has been no new panel installed and feeder installed in my working on this proj

Ahh, I apologize. By typing "new panel", and 'new loads", I am only referring to the Sq D HOM subpanel and the load connected to the branch circuits that come from it. That Sq D HOM subpanel is "new" to the as-built decades-old FPE assembly.

I never meant to say the "new" is the project you are doing right now, nor that you are causing a problem. As you say, Doc, in the opening post ( OP ) title: "perhaps dangerous". The four-service multi-condo existing Premises Wiring (System), as first seen by you before you did anything, seems to be in a heavily loaded state with respect to the Service Entrance Mast Conductors. Whether the Service Entrance Mast Conductors are overloaded, in fact, requires more information than we've yet seen in this thread.

I am used to seeing this kind of old service in the multidwelling fourplexes that are common in the inner City of my work area. The FPE equipment dates the service/subpanel assembly in your posts as several decades old or older.

The original FPE service/subpanel assembly connected load will tend to creep larger over time as dishwashers, microwaves, hot tubs, whatever, are added. I'm not trying to say that has, in fact, happened, BUT that addition of the Sq D HOM subpanel was for more branch circuit overcurrent protective devices. . . no?

 

[al hildenbrand]

How do we know there was not two panels to begin with?

Yes, perhaps an old FPE subpanel was replaced with a Sq D HOM panel. . . one can hope this is the case and that no appreciable new load has been added since the original Service Conductor sizing calculation occurred 3 to 5 decades ago.

I may be over cautious. . .

My field experience with the fourplexes in my area have taught be to be cautious.

 

[docj67]

cautious and conservative is how i run my business:egc question reasked

cautious and conservative is how i run my business:egc question reasked

and just a last
comment for Derek; new subpanel will have new feeders w egc as old one is impractical to chase

Im on vacation to Oregon!!! Yahoo!!

thx all!! was fun!!!!


(still curious if one conduit can be used as egc for two sets of feeders)

best regards,js

Yes, perhaps an old FPE subpanel was replaced with a Sq D HOM panel. . . one can hope this is the case and that no appreciable new load has been added since the original Service Conductor sizing calculation occurred 3 to 5 decades ago.

I may be over cautious. . .

My field experience with the fourplexes in my area have taught be to be cautious.

 

[al hildenbrand]

(still curious if one conduit can be used as egc for two sets of feeders)

When all the conductors of two sets of feeders are contained within a metallic raceway, a raceway identified in 250.118 as a suitable EGC (Equipment Grounding Conductor), the single raceway is acceptable as the EGC for both feeders.

Have a great vacation.

If you wish, at some point in the future, it would be fun to hear the outcome of the project described in this thread.

 

[docj67]

grateful to both of you

grateful to both of you

When all the conductors of two sets of feeders are contained within a metallic raceway, a raceway identified in 250.118 as a suitable EGC (Equipment Grounding Conductor), the single raceway is acceptable as the EGC for both feeders.

Have a great vacation.

If you wish, at some point in the future, it would be fun to hear the outcome of the project described in this thread.

Will do!!! For sure!!! Thx for Egc info

Newbie Nate is sharp but needs some down time to recharge his batteries bc that
4plex has kicked my u know what
plus i need more time to dry behind the ears!

In gratitude,js