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Old 03-21-2012, 11:26 PM   #1
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


I'll try to be succinct....

I need to install a new 100amp breaker panel for new air con, hot tub and pool.

Old house (1928) was entirely rewired 5 years ago (before I came on the scene).

Service goes from meter to an exterior breaker panel (is this called a main service panel?), which has 1 x 100amp breaker installed (with space for more). Then into basement to a 100amp main lug panel. Cabling from main service to main lug is 4AWG stranded AL (2 hot and 1 neutral).

I have a new Siemens (existing main lug is Siemens also) main breaker panel sitting here in a box (which has a 100amp main breaker installed). There is no ground bus in the panel.

The part I'm confused about is the grounding, I've read many posts on the subject but cannot wrap my head around it.

The existing main lug panel does not have the ground and neutral bus bars bonded. It does not have any ground running from the ground bus bar to anywhere (except the panel). I haven't opened the main service panel yet, but I can only assume that ground and neutral are bonded there.

Should this panel have something connected to the ground bus bar (to copper water pipe and ground rod)????

Should the new breaker panel, which will be cabled from the main service panel on a new 100amp breaker, be wired the same, and have a ground bus bar installed??

And lastly, can I run additional 4awg stranded AL cable in the existing (appears to be 2" diam.) metal conduit from the main service panel?

I tried to be brief, but wanted to include as much pertinent info to avoid too much back and forth questioning

Thanks for any advice you can provide.

edit:

with some further thought, it appears to me that the ground bus bar in the main lug panel should either be connected to the main service panel via a ground wire (in the case where the service panel has the neutral and ground bonded) or bonded to the neutral bus bar in the main lug panel. I'll open up the main service panel tomorrow to see what's going on in there.

Do I have the terminology correct and are initialisms ok for this type of thing? Main Lug Panel - MLP etc


Last edited by kalus; 03-21-2012 at 11:44 PM.
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Old 03-21-2012, 11:39 PM   #2
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


The first thing that sticks out to me is that the feeders to the existing SUB panel are undersized for the 100A breaker. #4 copper is only rated at 90 Amps when feeding a sub panel.

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Old 03-21-2012, 11:49 PM   #3
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


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The first thing that sticks out to me is that the feeders to the existing SUB panel are undersized for the 100A breaker. #4 copper is only rated at 90 Amps when feeding a sub panel.
I figured as much, which is why I included the cable specs. Easy enough to reduce that breaker to 90amp though.

Any other thoughts?
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Old 03-21-2012, 11:53 PM   #4
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


Without knowing what specific type of aluminum wire you have installed, all I can say is that the MAX rating on that wire would be 80 Amps.
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Old 03-21-2012, 11:55 PM   #5
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


Should be two hots a neutral and a ground four wires to the MLO panel and you should verify that you have more than 100 amps or you may not have enough to run what you are trying to run.

And #4 al is only rated for about 70 amps depending on cable rating.
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Last edited by rrolleston; 03-22-2012 at 12:00 AM.
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Old 03-21-2012, 11:55 PM   #6
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


If you say only single main breaker which it is a 100 amp size then I will seriouslly have you do the load demand caluation due the Hot Tub will useally seal the fate on small service ( they will typically required 120/240 volt 50 amp circuit ) plus there are few codes related to hot tub.

Now also you say Central Air that will go anywhere from 20 to 40 amp depending on what size the unit it is.

Pool is not too bad on powerwise beside the pump and there are a bit of code it will be covered ( there is not much leeway on pool set up simauir to hot tub but will address seperated due there is couple varations of code on that )

Really IMO for myself I will just pony up and upsize the service to 200 amp so you don't have to worry about the main breaker trip at all.

Merci,
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Old 03-22-2012, 01:12 AM   #7
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


I was told by the previous owner, that the service had been upgraded to 200amp... but the main service breaker is 100amp. So, assuming that everything is ok cabling-wise from the meter to the exterior breaker panel, I should be able to add a further 100amp breaker and cable to the new panel inside, correct? And yes, I will check the cable size and type coming from the meter.

The cable to the main lug panel is 4AWG Type SE Style XHHW-2 Aluminum, and from what I can find, will only handle 75amps.

The new air con is a 120v split system requiring 30amps, hot tubs tend to be 50amp from what I can see (haven't got one yet), and the pool is just a small 120v above ground unit (I allowed 20amps for it). This will all be running from the new breaker panel.

So......... Ideally, I should be replacing the 4AWG wire with cable to handle 100amps to the main lug panel (which I now know is the MLO) consisting of 2 hots, a neutral and a ground (as per rroleston above). Then, using the same cable, make a run to the new box as well and install a ground bus bar (which is not bonded to neutral).?????

My main issue is regarding the ground/neutral bonding which I'm hoping rroleston has answered correctly... thank you.
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Old 03-22-2012, 01:29 AM   #8
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


After the main disconnect panel in the Main lug panel and all other panels you install they require four wire feeds and neutral and ground separated.

Can you post a picture of the main disconnect panel?
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Old 03-22-2012, 01:52 AM   #9
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


Who is going to wire the hot tub? Who is going to install the HVAC? Are they going to be pulling a permit? Who is going to do the electric to the HVAC? Do you plan on pulling a permit? Can you pull an electrical permit?

What I am getting at is the liability if you do this work and do it incorrectly. What you are describing is a good amount of work for an electrician, much less a novice. With the jobs you are describing, you are dealing with many different codes and requirements. If you hire a qualified electrician to do the work, you won't have to worry about the liability. If you do it and something should happen and it is found to have something to do with your wiring, you are looking at a large problem...and I'm just talking monetarily. What you are talking about is mixing water and electricity, let's just hope its just property damage and not something far worse.
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Old 03-22-2012, 02:53 AM   #10
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


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Originally Posted by k_buz View Post
Who is going to wire the hot tub? Who is going to install the HVAC? Are they going to be pulling a permit? Who is going to do the electric to the HVAC? Do you plan on pulling a permit? Can you pull an electrical permit?

What I am getting at is the liability if you do this work and do it incorrectly. What you are describing is a good amount of work for an electrician, much less a novice. With the jobs you are describing, you are dealing with many different codes and requirements. If you hire a qualified electrician to do the work, you won't have to worry about the liability. If you do it and something should happen and it is found to have something to do with your wiring, you are looking at a large problem...and I'm just talking monetarily. What you are talking about is mixing water and electricity, let's just hope its just property damage and not something far worse.
I will wire the hot tub, I have installed the HVAC and getting a technician in to commission the sytem.

A novice I am not. I am aware of liability issues and requirements for permits etc.

My problem is that I am sick of fixing other "tradesmen's" crappy work, and have to do it all myself to make sure it is done right. I am a general contractor, have dealt with numerous tradespeople, and have been happy with very few.

This is my house, and the electrical panels are about the only thing I haven't fixed up yet. It has been a 3 year total renovation.

I realize that there are a lot of idiots out there, but rest assured, I won't blame you if something goes wrong. If you are worried about me doing something wrong and you feeling somehow responsible, the easiest way to avoid that is not to answer questions on a DIY forum.

Thanks to those who've helped.
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Old 03-22-2012, 06:12 AM   #11
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


Most of the guys touched on the main points.....I'll touch on the ground since I didn't see any comments on it...

For the most part, you have to terms correct...I prefer 'load center' or 'breaker panel'....but that is me.

At your main incomming power, ground and neutral buss bars should be bonded together. Any panels after that, they should NOT be bonded together.

And, yes....replace all those panels and just give yourself a single 200A panel....a few more bucks up front...but life will be much easier down the DIY path....
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Old 03-22-2012, 09:51 AM   #12
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


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Most of the guys touched on the main points.....I'll touch on the ground since I didn't see any comments on it...

For the most part, you have to terms correct...I prefer 'load center' or 'breaker panel'....but that is me.

At your main incomming power, ground and neutral buss bars should be bonded together. Any panels after that, they should NOT be bonded together.

And, yes....replace all those panels and just give yourself a single 200A panel....a few more bucks up front...but life will be much easier down the DIY path....
Very true that is why we love pictures so we can see or have a better idea what is going on. If there is a metal conduit from main outside to the panel inside and the neutral is floating and not bonded to the panel you may be ok but I prefer the four wire feed rather than rely on a pipe to continue that connection.
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Old 03-22-2012, 11:45 AM   #13
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


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Very true that is why we love pictures so we can see or have a better idea what is going on. If there is a metal conduit from main outside to the panel inside and the neutral is floating and not bonded to the panel you may be ok but I prefer the four wire feed rather than rely on a pipe to continue that connection.
I've been out to the house this morning and had a better look at things. It is a 200amp service, with 1 main 200amp breaker outside (see attached pic). The neutral and grounds are bonded in this panel, with a cable running to a ground bar below the panel and also inside to the copper water piping. The cable running from the outside panel is in fact 2 AWG. Writing on the cable is: AA8030 AL Type SE Cable Style U XHHW-2 600V 2 CDRS 2 AWG (33.6MM2) CDR 4 AWG (21.2MM2) SUN-RES (UL).... from a quick search, this cable will be ok, but, there is no ground running from the outside panel to the inside breaker panel, and no metal conduit between the two (the outside box has a hub in the rear which goes through the rim joist and into the basement).

Is the bare neutral ok (wrapped in white in pic)?

So, it seems to me that the thing to do is add metal conduit between the panels. I have enough access behind the panels to do so.

The existing MLO Panel has only 1 spare slot.*So I either replace the panel or use the new one I have as an additional sub panel.

I could then run another cable from the exterior panel to the new sub panel and install 2 100amp breakers in the panel outside. This is all without looking at load calculations in each panel, so please disregard that.

The main issue here is that there should be a ground between the panels. Am I right?
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Last edited by kalus; 03-22-2012 at 11:58 AM.
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Old 03-22-2012, 11:55 AM   #14
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


Looks to me that there is already a ground WIRE going inside the conduit with the wires. Maybe you will have to verify on the other end.
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Old 03-22-2012, 12:23 PM   #15
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Main Service Panel to 2 breaker panels - I can imagine you all rolling your eyes


If that conduit goes to the panel inside and has neutral floating I wouldn't worry about that. Just make sure you feed all other remote panels with four wires.

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