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Discussion Starter · #1 ·
Hey everyone new here,
So I currently have my house running on single phase from a generator. I want to switch the generator to 3 phase and was told I can add a 3 phase breaker box panel to run all the 240 shop lights and jump power from that panel to my single phase breaker box panel that’s already installed in my house. I want to avoid having to remove the whole single phase panel and rewire the whole house into a 3 phase. So my questions are;
1- can I just add the 3 phase panel to be the main box and jump power from it to the existing single phase panel?
2- if possible how do I jump the power from the 3 phase panel to the single phase panel?
3- Is there a diagram on how to do so?
any info on this subject and how to do it would be greatly appreciated. Thanks in advance
 

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Discussion Starter · #3 ·
3-phase isn't one thing. What specific type of 3-phase output is the generator set up for?

How did you come upon a 3-phase generator?
The generator is a MQ Whisperwatt 25kw generator. It has a switch for different settings “3 phase 480/277, 3 phase 240/139 and single phase 240/120” I only need the 240/139 as I won’t be running anything on 480
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You may not put (jump) 139/240 into your main electrical system.

Any 120 volt item or load will be damaged if switched on during such infusion of generator power.

If you must use the generator for 240 volt 3 phase loads then you will need a separate panel with branch circuits for 240 volt delta 3 phase with no neutral and/or 240 volt only single phase (no neutral). It would be simpler to manually move single phase plugs to "redundant" 240 volt receptacles fed by branch circuits from your house system as opposed to jumping (single phase) utility power from a house panel out to the generator 3 phase panel (interlock in the generator panel).
 
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You have a serious misunderstanding of electricity, and should really consult a pro.
There is no need to install a 3 phase panel, unless you have 3 phase equipment, which is highly unlikely.
 

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Discussion Starter · #8 ·
Well, you can power a lot of 240V loads.
Do you have ANY 120V loads you need to power?
My entire house is wired for 120/240 single phase like any normal house in the USA. The reason I need/want the generator on 3 phase is because the longevity of the motor will be better and the generator produces more power/kw. On single phase it only makes 14/15kw and on 3 phase it makes 20kw.


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Discussion Starter · #9 · (Edited)
You may not put (jump) 139/240 into your main electrical system.

Any 120 volt item or load will be damaged if switched on during such infusion of generator power.

If you must use the generator for 240 volt 3 phase loads then you will need a separate panel with branch circuits for 240 volt delta 3 phase with no neutral and/or 240 volt only single phase (no neutral). It would be simpler to manually move single phase plugs to "redundant" 240 volt receptacles fed by branch circuits from your house system as opposed to jumping (single phase) utility power from a house panel to the generator 3 phase panel (interlock in the generator panel).
Then generator has a voltage regulator to adjust the voltage for running on 3 phase. I know it is possible as many in my area run their generator on 3 phase to maximize the amount of lights it can hold. I think that by adjusting the voltage I’d be at 208/120. I’m trying to be able to add more shop lights to my shop. I know a 25kw (20kw) generator can hold 32 lights running 16 for 12hrs and 16 other 12hrs plus fans and exhaust fans but it can only do it on 3 phase as the generator only produces 14-15kw on single phase. Each light is 1000w and requires 240. I’m pretty sure I can switch the ballasts from 240 to 208. I would be using only the 3 phase panel to power all the shop lights and want to pull power from that panel to power up my single phase house panel to run all my 120/240 in house. Currently I’m only running 16 shop lights out of my houses main panel on 240 (8 lights/12hr). But as I stated before I can’t add 16 more lights on single phase as the generator will be over loaded.


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Discussion Starter · #10 ·
You have a serious misunderstanding of electricity, and should really consult a pro.
There is no need to install a 3 phase panel, unless you have 3 phase equipment, which is highly unlikely.
Being that I know it’s done a lot locally I know that what I’m trying to achieve is possible. So if I’m not running 3 phase equipment, how do I add the third hot to a single phase panel? I can’t as it only spots for 2 hots.


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Being that I know it’s done a lot locally I know that what I’m trying to achieve is possible. So if I’m not running 3 phase equipment, how do I add the third hot to a single phase panel? I can’t as it only spots for 2 hots.


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You have to replace the panel with a 3 phase panel.
 

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Discussion Starter · #12 ·
You have to replace the panel with a 3 phase panel.
Lol. Yes. I have a brand new 3 phase panel that will be my main panel for all my shop lights. But I want to jump power from the 3 phase panel to my houses single phase panel so I don’t have to completely remove the houses panel and rewire it into a 3 phase panel. It’d be easier to just add the 3 phase panel for all the shop lights then pull power from it to power up the houses single phase panel. Will you read my reply to the guy before you. Might explain what I’m trying to achieve


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You can take two of the hot legs from the generator panel and feed them to your house panel using the usual interlock in the house panel to use power from your generator during a utility outage. You will have to regulate the voltage down to no more than 125 hot to neutral each.

If the generator were powering all pure 3 phase motors and loads, how many amps can be drawn out of any one leg? Using just two of the legs you will probably be limited to half that because of the imbalance from the unused third leg.
 

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Discussion Starter · #14 ·
You can take two of the hot legs from the generator panel and feed them to your house panel using the usual interlock in the house panel to use power from your generator during a utility outage. You will have to regulate the voltage down to no more than 125 hot to neutral each.

If the generator were powering all pure 3 phase motors and loads, how many amps can be drawn out of any one leg? Using just two of the legs you will probably be limited to half that because of the imbalance from the unused third leg.
I guess I’m not understanding what you’re saying because my house is ran off generator. I do not have city power or any other power source. I’ll look into how many amps each leg holds as I don’t remember off the top of my head. But I know the breaker on generator for 3 phase says 60amps. Not sure if that’s 60 per leg or 60 total



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Sixty on the toggle of a breaker means that any one of the legs will trip when the load on that leg is a little over 60 amps. (Some breakers have more than one toggle with different amperes markings for what will trip each one.)

Run two of the hot legs of the generator (via a double breaker down the side of the new 3 phase panel), out to the existing single phase house main panel.

Run the third leg (via a single breaker in the new 3 phase panel) to the top of a new additional small single phase panel.

Move a few 120 volt only circuits from the main panel to new breakers in the new single phase panel. Select the circuits so that the usage on all three legs is somewhat balanced.
 

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On single phase it only makes 14/15kw and on 3 phase it makes 20kw.
Buut, you are trying to put it back to single phase which will limit you to 14 kW again
Can I get power from the 3 phase panel for the single phase panel like this?



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First of all, you may only have the neutral bonded to ground at a single point.
Second what would be the voltage from U-O and W-O in this situation?
 

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Discussion Starter · #18 ·
Run two of the hot legs of the generator (via a double breaker in the new 3 phase panel) to the existing single phase house main panel.

Run the third leg (via a single breaker in the new 3 phase panel) to a new single phase panel.

Move a few 120 volt only circuits from the main panel to new breakers in the new single phase panel. Select the circuits so that the usage on all three legs is somewhat balanced.
Ok so don’t get power from the main breaker on 3 phase panel to power the single phase panel, instead use a 240 breaker on the 3 phase panel to get power to the single phase panel? Wouldn’t that mean needing a big amp breaker. The single phase panel has a 200amp breaker. And you’re saying to even out load make sure I move some of the 120 breakers from the house to the 3 phase panel?


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Discussion Starter · #19 ·
Buut, you are trying to put it back to single phase which will limit you to 14 kW again

First of all, you may only have the neutral bonded to ground at a single point.
Second what would be the voltage from U-O and W-O in this situation?
I have a 3 phase panel. The 3 phase panel will have all the shop light breakers on it (so it’s still at 20kw). And to avoid having to remove the houses single phase panel to add everything onto a 3 phase panel I want to just add the 3 phase panel next to the houses and have the generator connected to it and just get power to the houses panel off of the 3 phase panel.

Voltage from U-O and W-O should be 120.

As for the ground you’re right I simply drew it wrong. It’ll be grounded from the 3 phase panel.


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Although your main panel has a 200 amp main breaker, given your 25 KW generator the most power any one of the legs will see is about 70 amps. (Most of the time the actual draw will be less than 30 amps on a leg). You could get a 75 amp double breaker to put in the 3 phase panel to feed the main panel with.
 
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