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Old 06-01-2009, 02:01 PM   #1
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I have a residential built in oven (or actually my son is doing the install). Three phase (220) setup, RST N and Earth, total of 380 volts +/-. The oven is actually segregated, three parts, each using a phase of 220 volt, there are no actually 380 volt components.
The electrician gave him five different colored wires (10 awg) in the dedicated oven wall outlet, us thinking it was a standard three phase setup. But after checking, they are actually three 220 volt wires, same phase, fused (16 amp) separate breakers, there is actually only a single phase (220) available in the house. Scratch my head, now why and the heck did the electrician do that?
My first impulse was to hook up a single wire with a bridge (in the installation kit) in the oven, along with neutral and ground and call it good. But then decided to hook up all three wires (fused separately) with a common neutral. Got to thinking later that the oven may be over fused, I sure don't know how the fuses will react, fused in parallel. Any thoughts?

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Old 06-01-2009, 02:23 PM   #2
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.... now why and the heck did the electrician do that?.....
Ask Him

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Old 06-01-2009, 02:38 PM   #3
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You should worry about overloading the shared neutral.
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Old 06-01-2009, 02:45 PM   #4
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Your not in the US. Search "frenchelectrician" on this forum and send him a PM. He will know what to do.
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Old 06-01-2009, 04:37 PM   #5
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Your not in the US.....
JV, I think he is in the US only for some reason he thinks our standard for for home ovens is 3 phase
He should read the Data Sheet on his new oven.

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......, us thinking it was a standard three phase setup............
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Last edited by PaliBob; 06-01-2009 at 04:39 PM.
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Old 06-01-2009, 04:50 PM   #6
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JV, I think he is in the US only for some reason he thinks our standard for for home ovens is 3 phase


.
No I'm in Germany, but the majority of my work is installing and maintaining U.S. manufactured equipment for the government (overseas). I'm used to odd hookups.
This is a typical German household setup (my son is installing the kitchen cabinets and such). I think I've answered my own question anyway, with a little help from the statement about overloading the blue/Neutral wire.
What threw me was the electrician running three fused (circuit breaker) wires to the dedicated stove outlet, all on the same phase. Maybe he ran the wiring before he checked the fuse box for the usual three phases and then found out there is only one phase in the box. I'm going to call the electrician, he may know something I don't.
I looked through the paperwork and even at the stove/range sticker, no useful info yet. Most household ranges here are fused for 16 amp single phase, though some are fused for 20 amp single phase (with larger gage wiring) and some wired for three phases of 220 volt/380 volt. They moved away from 380 volts over the years, but it is slowly coming back since the advent of the GFI (ground fault interrupter).

Last edited by Bigfoot; 06-01-2009 at 05:18 PM.
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Old 06-01-2009, 07:24 PM   #7
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If there are 3-220 volt elements in the oven, and they are wye connected (one side of each element is tied to a common point, usually the neutral), and each element is individually controlled, then the only difference in connecting them to a 3 phase supply vs. a single phase one is the current on the neutral.

Here's why. If the 3 elements are all powered by the same phase, neutral current will add. Suppose each element is 10 amps. With one element on, the current will be 10 amps on one of the hots, and 10 amps on the neutral. If 2 elements are on, the current is 10 amps on 2 of the hots, and 20 amps on the neutral. With all 3 elements on, the current is 10 amps on all 3 hots, and 30 amps on the neutral.

If the oven is connected to a 220/380 3 phase system, and all 3 phases are used, the neutral current will subtract, sort of. With one element on, the current will be 10 amps on phase R, and 10 amps on the neutral. With 2 elements on, the current will be 10 amps on phase R, 10 amps on phase S, and slightly less than 10 amps on the neutral. With all 3 elements on, the current will be 10 amps on R, 10 amps on S, and 10 amps on T. The neutral current will be around 2 amps. There will be 380 volts between the line side of each element, but this doesn't matter. Each element sees 220 volts.

The reason the neutral current doesn't fall much until all 3 phases are involved is difficult to explain, but it has to do with the 120 degree phase shift of a 3 phase system vs. the 180 degree phase shift of a single phase system.

All 3 of the elements can be powered by the same phase, but the neutral will need to be rated for 3X the breaker size.

Don't use the bridge if there are 3 breakers. It'll parallel the breakers, and you'll lose short circuit and overload protection. The bridge is meant to be used for one large single phase feed, not 3 small ones.

Rob

P.S. I had to laugh at myself, around here we use A, B, and C to identify 3 phase systems. I originally wrote A, B, and C. Then it dawned on me that Germany uses R, S, and T. So I went back and changed it all.

Last edited by micromind; 06-01-2009 at 07:28 PM. Reason: Added paragraph about using bridge.
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Old 06-01-2009, 09:05 PM   #8
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Originally Posted by micromind View Post
If there are 3-220 volt elements in the oven, and they are wye connected (one side of each element is tied to a common point, usually the neutral), and each element is individually controlled, then the only difference in connecting them to a 3 phase supply vs. a single phase one is the current on the neutral.

Here's why. If the 3 elements are all powered by the same phase, neutral current will add. Suppose each element is 10 amps. With one element on, the current will be 10 amps on one of the hots, and 10 amps on the neutral. If 2 elements are on, the current is 10 amps on 2 of the hots, and 20 amps on the neutral. With all 3 elements on, the current is 10 amps on all 3 hots, and 30 amps on the neutral.

If the oven is connected to a 220/380 3 phase system, and all 3 phases are used, the neutral current will subtract, sort of. With one element on, the current will be 10 amps on phase R, and 10 amps on the neutral. With 2 elements on, the current will be 10 amps on phase R, 10 amps on phase S, and slightly less than 10 amps on the neutral. With all 3 elements on, the current will be 10 amps on R, 10 amps on S, and 10 amps on T. The neutral current will be around 2 amps. There will be 380 volts between the line side of each element, but this doesn't matter. Each element sees 220 volts.

The reason the neutral current doesn't fall much until all 3 phases are involved is difficult to explain, but it has to do with the 120 degree phase shift of a 3 phase system vs. the 180 degree phase shift of a single phase system.

All 3 of the elements can be powered by the same phase, but the neutral will need to be rated for 3X the breaker size.

Don't use the bridge if there are 3 breakers. It'll parallel the breakers, and you'll lose short circuit and overload protection. The bridge is meant to be used for one large single phase feed, not 3 small ones.

Rob

P.S. I had to laugh at myself, around here we use A, B, and C to identify 3 phase systems. I originally wrote A, B, and C. Then it dawned on me that Germany uses R, S, and T. So I went back and changed it all.
Thanx for every bodies input. RST, ABC half a dozen different wire colors used as a standard. The oven/range has five different possible hook up configurations ( a whole party pack full of bridges and shunts), depending on which country it's shipped to. Life would be a lot simpler if they would adopt a single standard.
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Old 06-01-2009, 10:53 PM   #9
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Big,
Note that everyone but yourself has included their location in their profile. Make it easier for the rest of us.
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Old 06-01-2009, 11:30 PM   #10
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Big,
Note that everyone but yourself has included their location in their profile. Make it easier for the rest of us.
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Born and raised in the San Fernando Valley, been working for the Gov. overseas (mainly Europe) for quit awhile now.
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Old 06-01-2009, 11:46 PM   #11
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Thanks, Now we all know
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Old 06-01-2009, 11:55 PM   #12
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Thanks, Now we all know
Sorry about that, being a Europeon is a minus on some boards.
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Old 06-02-2009, 01:42 AM   #13
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Does the instructions have this wiring scheme selection in them or similar? We would need to determine which you need to convert to single phase 230 Volt. Looks like you are dealing with far left based on the 5 wires and 3 16 amp breakers only connecting to single phase. Normally R is brown, S is black, T is grey, blue is neutral and green/yellow is earth.

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Old 06-02-2009, 08:08 AM   #14
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Does the instructions have this wiring scheme selection in them or similar? We would need to determine which you need to convert to single phase 230 Volt. Looks like you are dealing with far left based on the 5 wires and 3 16 amp breakers only connecting to single phase. Normally R is brown, S is black, T is grey, blue is neutral and green/yellow is earth.

Outstanding idea, I'll shot a picture of the hookup schematic like you have and post it up. Or look in the destructions and see if they have hookup diagrams I can copy and post. I was looking for the (amperage draw) data in the provided paperwork or a data sticker yesterday (never did find any) and the thought (to bring home the paperwork) never crossed my mind.
Basically what I have, is like you have on the far left (in the picture). In the wall (and in the oven/range) five wires black, brown and gray (RST or L1 L2 L3 or A B C ) and blue neutral, Green/yellow earth. The supply cable (that came with the oven/range) for the wall outlet to the oven is also five wire flexible cable/ black, brown, grey/ blue/ and green with a yellow stripe.
There is also a drawing or stipulation for a single phase hookup in the back of the oven 1, 2, 3 are jumped (with the provided bridge) and the oven/range can be hooked up single phase 230 V.
The wiring is either 2.5 or 3 MM2. What threw me is, the black, brown and grey wires are all on the same phase (though fused separately, 3 separate 16 amp circuit breakers), there is no second and third phase available on this floor (likely not in the whole house). I looked in the fuse box.
It's been awhile since I have hooked up a residential oven and was wondering, three breakers on three wires (same phase) and a single neutral return line? I'd understand quick if only one of the three wires (black, brown or gray) were hot and the other two just dummies. Standard code installation or in case multiphase was to be added in the future. I'd even understand if two of the wires were hot (black and brown) and the gray wire was covered in blue tape. I just don't get the reasoning behind three hot wires running to the same oven/range, on three seprate 16 amp breakers, on the same phase and a single return (blue neutral) line?
Like I said, it's been awhile since I (attempted) hooked up a residential oven, maybe the code here has changed.
No big rush on the job, the counter work still has to be finished and half a dozen cabinets hung from the wall. I have some time to study the oven a bit.
I have my own project going on right now, new doors for the upstairs, my son asked for some help on this job.
Thanx again for your input and interest.


Last edited by Bigfoot; 06-02-2009 at 08:22 AM.
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