to piggy or not

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solaeros

solaeros

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I've allready asked one member this question but I'll throw it out to the world as well.
I recently had a contractor ask me to wire a 2500 sq.' cabin. without really thinking I went ahead and threw a 200 A. meter/ main and, a 200 A. 30/40 subpanel on. two weeks later when I went to rough the place in, he had 11 240v. wall heaters he wanted to install. Anyway by the time I had all my home runs pulled I came up with too many wires for the allowable 30 spaces.
My question is this would it be considered poor practice to instal 4 piggyback breakers to free up the space I need in the subpanel? or do I need to tear out the subpanel and feeders and put in a 40/40 panel.

(I know what you guys are thinking...."Dumb Rookie")

Dana
 
solaeros said:
I've allready asked one member this question but I'll throw it out to the world as well.
I recently had a contractor ask me to wire a 2500 sq.' cabin. without really thinking I went ahead and threw a 200 A. meter/ main and, a 200 A. 30/40 subpanel on. two weeks later when I went to rough the place in, he had 11 240v. wall heaters he wanted to install. Anyway by the time I had all my home runs pulled I came up with too many wires for the allowable 30 spaces.
My question is this would it be considered poor practice to instal 4 piggyback breakers to free up the space I need in the subpanel? or do I need to tear out the subpanel and feeders and put in a 40/40 panel.

(I know what you guys are thinking...."Dumb Rookie")

Dana
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A 30/40 panel means 30 position 40 circuits so your allowed to put in 10 piggybacks. IMO. So speaking you'll get no more circuits with a 40/40 then you will with a 30/40.;)
 
It's a 30/40 panel, so what's the problem with tandems? Nothing that I can see. Too bad you got caught with your pants down this time. Better luck on the next job.
 
If the panel is rated for more than 30 breakers (i.e. a 30/40), than you would be foolish to rip it out and install a new one.
 
stickboy1375 said:
Your allowed 42 OCD in each cabinet...I don't have a problem with twin breakers as long as your not over the limit...
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I have a problem with tandems in a panel not rated for tandems. I see non CTL "cheater" tandems in panels every day that were never rated for tandems. They're not over the 42, but they're not rated for tandems either.
 
stickboy1375 said:
Your allowed 42 OCD in each cabinet...I don't have a problem with twin breakers as long as your not over the limit...
Click to expand...

The panel would have to be rated as a panel that accepts tandems to 42 OCPD.12/24. 30/40 etc..dont think I`ve seem a 30/42.
 
My next question would be if there are 11 240 volt heaters I would question the load calc on the residence.What is the total load calc going to be.If using nothing but electric heat then i would doubt that there would be gas stove/cook top. wall ovens etc.You might want to look at that aspect.Then decide if there needs to be a change order given.KACHING !!!!!!!
 
stickboy1375 said:
The only time I see tandems installed is when the last guy didnt want to install a sub-panel....
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Eh, I dunno. I often want to. More often, I am not permitted to by the property owner. I always present the tandem option if it's permissable. Let them make a fully informed decision.
 
mdshunk said:
Oh, shame shame. I'm betting that the neutral/ground bar in those panels is screaming for mercy too.
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Yep... and some guys are not good at making up panels... its funny how I never struggle when I go back to a panel I did, but WOW it takes forever with someone elses....
 
stickboy1375 said:
Yep... and some guys are not good at making up panels... its funny how I never struggle when I go back to a panel I did, but WOW it takes forever with someone elses....
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There's allready a subpanel, it's just a standard "homeline" panel, yes it's rated for tandems, i'm just questioning wether or not it would be seen as poor worksmanship on a new residence
 
solaeros said:
... i'm just questioning wether or not it would be seen as poor worksmanship on a new residence
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If you planned all along to use tandems, maybe so. You kinda got blindsided, so your pre-planning in using a 30/40 panel paid off. This is among the reasons why you plan with a little wiggle room, in case things like this crop up. Don't sweat it.

(All that electric heat, though... how's your demand load calc look now?)
 
solaeros said:
I recently had a contractor ask me to wire a 2500 sq.' cabin. without really thinking I went ahead and threw a 200 A. meter/ main and, a 200 A. 30/40 subpanel on. two weeks later when I went to rough the place in, he had 11 240v. wall heaters he wanted to install. Anyway by the time I had all my home runs pulled I came up with too many wires for the allowable 30 spaces.
Click to expand...
Two thoughts:

A) You should always discuss the expected load before deciding anything else, as you have discovered.

2) You don't need separate circuits for each heater; split them up evenly, with 3840 watts as a limit per circuit.*

D) I have no problem with properly-used tandems, even in new work. I always start with the lowest-current breakers first.


As Allen mentioned, what is the total heater load wattage? You may have a non-issue.

*If the load can be considered non-continuous, you can go to the full 4800 watts per circuit.


mdshunk said:
Oh, shame shame. I'm betting that the neutral/ground bar in those panels is screaming for mercy too.
Click to expand...
Not necessarily; line-to-line loads don't affect the neutral bar, and multiple EGC buses can be added relatively easily.
 
solaeros said:
There's allready a subpanel, it's just a standard "homeline" panel, yes it's rated for tandems, i'm just questioning wether or not it would be seen as poor worksmanship on a new residence
Click to expand...

I know a few EIs who "frown" on tandems in new work.

As to whether it's "poor workmanship" - beauty is in the eye of the beholder...and who be holdin' the final payment :)
 
LarryFine said:
Not necessarily; line-to-line loads don't affect the neutral bar, and multiple EGC buses can be added relatively easily.
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Yeah, but do you really think that the knucklehead who took the panel over 42 circuits bothered to put in another ground bar? Very seldom in these non-compliant panels. Plus, when they're that full, they often have some age on them. Older panels had notoriously small neutral/ground bars. If you see a panel with more than 42 circuits, you're more than likely also looking at a panel with double and tripled up ground buss holes.
 
The tandem CBs are fine. I never PLAN to use 'em and end up using "em alot. The thing that is most important to me is the actual load on the panelboard. I tend to use quite a few lightly loaded circuits rather than very few heavily loaded ones. At the end of the day, though, who really cares?
 
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