Have a question for you sparkys out there, or any one else who knows. I have a home in Southern Calif. w/ 175 amp main panel. There is an additional sub panel#1 that feeds from the main and it is fed with #4 wire less than 50′ away. One neutral, two hot leads, and a ground. I have a 60 amp breaker on the main panel that feeds sub panel #1. In subpanel#1, it supplies power to my well(1 1/2hp submersible and a booster 200′ away)The feed from subpanel#1 to the well subpanel is also #4. I believe the breaker for the well system is 40amp. Also in the subpanel#1, there is a breaker that supplies another subpanel in my 1950sq.ft. shop that is located 50′ away. The wiring from subpanel#1 to subpanel#2 is also #4 wire and the breaker to the shop is also 40amp. I am assuming that the breaker sizing and/or wire sizing might be wrong and would like to get your feedback. The waterheater, stove and dryer are on propane. The air/heat pump are electric
In the 8 1/2 years of having the well and the shop, I have NEVER tripped a circuit breaker in the main or either subpanels. I have blown a fuse or two in the power disconnect box down in the shop and at the well, but this is normal, so I have been told. The largest machines I have run is a 8.8hp 3phase shaper and a 5hp table saw. These have been known to run concurrently, but never turned on at the same time. (I also have a 15hp rotory phase converter wired into the shop that does run 90% of the time when I am in the shop working). I never know when the well pump and/or booster. kick on, they just do on demand.
Can any of you tell me where I stand as to the correct requirements? I need to know since the property will be put up for sale with in the next few days.
I hope I explained this well enough and I thank all of you for your responses in advance. -Brian
Replies
According to the table, the lowest temperature rated insulation on #4 makes it good for 70 amps, so you're OK all around. Using #4 for that long run helps reduce voltage drop, which is a very good thing because motors don't like voltage drop at all.
-- J.S.
Never really had to worry about voltage drop, we are on the high side of the voltage sprectrum in this neck of the woods. -or should I say "in this neck of the dirt"
Brian,
Well, lessee here, you've never had an overload problem with breakers tripping. That in itself says volumes. Unless of course, the double pole breakers supplying the feeders are Federal Pacific Electric (FPE) brand--those are notorious for not tripping on overload and sometimes not even under short circuit conditions.
If the feeders are copper, and there are fewer than 4 conductors in the conduit (or in the cable), as John said, 70 amps is lowest ampacity rating.
As long as the panels aren't FPE, the design and execution of the system seems quite sound.
Cliff
As long as the panels aren't FPE,
FWIW, there are varying views on FPE Stab-lok panels, some people hate 'em, others don't.
I've been told by several very experinced electricians that they haven't seen any higher incidence of failure with them. (One is a consultant tyo the guys who draft the NEC!)
My own experience, having inspected several thousand panels, and probably a couple of hundred FPE's is the same.
I think there is a much higher degreee of risk from crummy, amateurish wiring than from FPE boxes.
OTOH, if I had an FPE, I'd probably change it out, but that would be a personal risk assessment - not a universal "truth."
_______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11
Edited 5/31/2003 11:18:02 AM ET by Bob Walker
I have seen more FPE breakers fail closed than any other brand. These units usually announce themselves by the circuit failing at the weakest connection, from what I hear there were a few law suits over fires caused by this, or when a hurried electrician, I know we should always double check, gets a shock from the still connected leg of a two pole breaker. Even though the handle is in the off position. A half dozen of these cases come immediately to mind.
Usually I find, after breaking open the case, that the contacts have welded closed. Breaking the case also keeps a bad breaker from being installed again and perpetuating a problem. This might be a design flaw, these breakers were never known for their sensitivity, or simple age. Federal Pacific was quite popular in the 50s and 60s so they might be just getting near the end of their service life. Nothing lasts forever.
The other point against FPE, and several other brands like Zinsco, is that the breakers are more difficult or expensive to get replacements for. Commonly these go for two or three times what a normal breaker goes for. Mains, particularly three phase, can easily exceed the cost of installing a new panel. If you can find them in good time. Given two weeks you can commonly have a rebuilt model shipped in for a small ransom.
4Lorn1
Thanks for that info/experience._______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11