3 Phase, Revisited.

[WyoDave]

First of all, thanks for the ideas last time. Talked to the power company. They'll upgrade me to a 3 phase service for free. They will provide my power to a 200 amp fusible disconnect, from there it is my responsibility.

My plan is to install a 200 amp outdoor 3 phase load center at the drop location, and use a 200 amp 3 phase sub feed lug, to feed the shop via a 200 amp 3 phase panel inside the shop. In the outdoor load center I will also feed the house via a 200 amp single phase sub feed lug, to a 200 amp panel in the house. Both of the interior panels will have main breakers for convenience. I understand they will both be sub panels, and need to run a separate ground wire to them as well.

Now the questions. Can the outside panel be just a main lug panel, since the fuse disconnect provides over current protection, or does it need a main breaker? Where would I bond? Also, using proper sized conductors are the 200 amp sub feed lugs acceptable, or would I need 200 amp branch breakers in the outdoor panel?

Honestly right now, it's kind of overkill with 200 amp setups in both structures, but this way I can always have the power company upgrade my service, and I will only have to swap out the outdoor panel, should I expand.

Thanks again, for working through this with me.

David

 

[dr sportster]

The disconnect can protect the panel without a breaker.Fuses are better than breakers anyway. Bond using bonding bushings. Often Called MIG bushings. The third question I would see what the inspector wants. The first means of disconnect may be fine but why do double work.Wire size is written on the lugs .[Not really a question but you were calling them 200 amp lugs]. So much for the guys that were telling you how much the power company was going to charge in thousands of dollars.The nice thing about a 200 amp panel is the breaker space . Not many homes need it amperage wise , but it is a selling point if you ever go to sell the house.

 

[WyoDave]

Thanks. Guess I'm pretty squared away. No inspection here. I'm not sure if it's special treatment, but my power company treats me good. Of course when you have 7 irrigation services, with big summer time bills tied to them, they may do things differently.

David

 

[dr sportster]

The bushings have to go on before you install the wire. They have lugs on them to take the ground wire which you can remove and relocate to the easiest location as there are several threaded holes. Thats just so you can get a screwdriver to tighten them and they don"t land in the back where they get hard to work on..After you go through the lug then ground to another lug on the back box without cutting at the bushing.

 

[Mike M]

For Free ?

Maybe they will make it up by charging a WAY HIGHER commerical rate on your KWH ?

 

[WyoDave]

Free might be the wrong word. The electric company pays the first $3100 of any new service, which is what they are considering this. That is enough to cover all the costs since no poles will need set. Monthly meter charge is a little higher, but KWH price is the same.

David

 

[John T]

Dave, youre havin fun !!!!!!!

SURE its safe and permissible to use a panelboard WITHOUT A MAIN BREAKER provided the feeders are still overcurrent protected. If you had say a fused disconnect that fed a panelboard, the feeders to that panel are sufficiently overcurrent protected. HOWEVER that's (feeder protection) not the whole story and concern. There are other SAFETY (NOT just overcurrent protection) concerns like a MAIN DISCONNECT MEANS (still could be a safety switch) at certain locations such as entry into a home AND THAT APPLIES REGARDLESS IF THERES OVERCURRENT PROTECTION ELSEWHERE!!!!!! I don't see it so much as a main breaker to protect the feeders versus a main disconnect method in a certain location!!!

If there's a fused safety switch outside right by a panel then I see no need for main breaker panel WELL DUH I was thinkin more above if youre running to a Service Entrance Panel inside a home/shop WHERE I WOULD WANT A MAIN for disconnect and safety purposes even if overcurrent was already dealt with

Even if theres no inspection authority I believe Id still check with the Utility provider regarding SAFETY AND DISCONNECT rules regardless of overcurrent protection (which you still need of course)

So whats the service??????

208 Y 120 Volt Three Phase Four Wire
120/240 Volt Three Phase Four Wired Red Leg Delta
Straight 240 Delta with dry transformers for 120

John T

 

[WyoDave]

Yes, the outdoor panel will be right at the fused disconnect, which is why I was wondering about needing a main breaker in that panel or not. Both the shop and house will have main breaker panels where it enters the building, for safety and convenience. Just wasn't sure whether I needed to spend the extra on a main breaker for the outside panel, it seems like double protection. Also was a little concerned by the sub feed lugs. They should be protected by the fused disconnect since they'll be capable of carrying 200 amps, but wasn't sure, if they needed branch breakers or not.

I'm putting in a 120/240 wild leg delta, and just not feeding the high leg to the house. Also going to sub panel the shop for lighting and 120 loads, so no possible way to get the high leg on them. Then use the rest of the 3 phase panel for 3 phase loads. Just got myself a 3 phase air conditioner for the shop, so if I get it done, I'll be nice and cool next summer working on antique tractors. Thanks for all your help.

David

David

 

[Greg 2N (TX)]

Is the stinger leg at 208V to neutral?
If so, some blower motors are rated for 208V single phase.

Unless you are going with 240V 3 phase for the blower or even 240V single phase.

Enjoy,

Greg

 

[Dusty MI]

Just be careful with that "Wild Leg" and understand all there is to know about it. I never liked them.
I would call that outdoor panel a Distribution Panel.
Bond Bushings were talked about but if your using pvc conduit bond bushings are useless.

Dusty

 

[John T]

YES on the 120/240 volt single phase four wire red leg delta system its 208 from the red leg to Neutral since 120 x 1.732 (Square Root of 3) = 208

In all my years of EE practice I never used that red leg for anything

John T

 

[buickanddeere]

I never seen the virtue in those wild Delta abominations to obtain 240 from a three phase system .
We just use a single phase 600-120/240 transformer for domestic loads.

 

[Bus Driver]

The wiring plan you describe could result in some unbalanced phases due to the house using two of them and the house has significant 120 volt loads. The 120/240 Delta ordinarily is expected to have only limited 120 volt loads.
Might be good to get an electrical PE on site to advise you.

 

[Greg 2N (TX)]

Oh Ok,
The reason I brought it up is that my uncle used to do commercial wiring with some buildings having the 240v open delta.
He said the AC blowers were using the 208v single phase stinger to neutral and that was an efficient use of the stinger.

Greg

 

[evilboweivel]

gotta disagree with you
did a lot of 7-11 stores back in the late 70's early 80's with delta service.
two big transformers, one smaller transformer.
buildings still standing and in use by other companies.
as long as the transformer bank is built correctly should not be a problem

 

[John T]

Im NOT saying it couldn't be used, heck its indeed still 208 volts, its just not the method we used where I practiced. Some of the electricians had a hard enough time the way it was let alone if one of the three legs was 208 instead of only 120 to Neutral !!!!!!!!!!

John T

 

[John T]

When I specified a 120/240 volt three phase four wire center tapped red leg delta service, it was in say an industrial shop where there were a ton of 240 both single and three phase loads and only a small 120 volt convenience load. HOWEVER as you know the system still works even if theres an imbalance (like if there were a lot of load on that center tapped transformer) but its just not the way we normally would specify a service be configured and that center tapped transformer could be specified at a larger KVA rating but again that's not the way we did it even if it would work.......

Fun sparky chattin with ya, good point you raised

John T Long retired from this practice so no warranty

 

[WyoDave]

Thanks for bringing that up. I'll give the electrician a call on Monday. Would running 3 phase to the house, and then tying the 240 volt loads (well, oven, drier, a/c) to the high leg help balance the loads?

David

 

[Greg 2N (TX)]

Yes, the stinger phase to another phase is 240v but you must be extra careful since the stinger is 208v to N and to equipment safety ground and not 120v !
I only meant that you may want to use it out at the shop.
I would only run the split phase 120/240 center tapped xfmr with N and Safety ground to the house.
I would feel uncomfortable having 3-ph at the house especially with a stinger to neutral hanging around.

Be careful,
Greg