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-   -   3 phase panels and sub panels (http://www.diychatroom.com/f18/3-phase-panels-sub-panels-115532/)

michael825 08-28-2011 03:44 PM

3 phase panels and sub panels
 
just bought a house that a doctor had put in an xray machine and had three phase power brought in. its a 100 year old house and some of the changes over the years are terrifying. im gut renovating from top floor down. i am creating 2 apartments on top floor and will live on lower three floors.
there are currently 2 main panels both fed from same meter with 250 wire 3 hots and a nuetral one has a integral main 200 breaker / cut off the other a seperate switch with three 200 fuses at first i thought the second panel might be a sub because it was not diurectly grounded but realized it grounds through the other panel and it is definitely fed directly from service.
i want to install new panels for each of these apartments the run would be less than 100' want to do it in a way that for now they are sub panels but eventually they would be converted to their own meters. i think utility will not let me mix 3 and 2 phase service and ive come to apreciate the 3 phase advantages and would like to pass that advantage on to apartments that may get central air of panels. intend to run #2 wire from 3pole breakers rated 100 amps -150amps depending on panels i find 3ph panels turn out to be expensive however i do heavy construction [hvac] and often come across 200 amp 3 phase 240v panels being taken out of service two i could have now have 200 amp main cut off breaker could i simply replace that breaker these panels are quite large for my purpose but the panels would each cost $600 without the 40 breakers. i understand when those panels become mains they must have shut offs in reach so those main breaker style helps. understand about bonding difference between subs and mains and 3 phase load balance but really im a novice think i will need to run 3 hots and nuetral and ground

Jim Port 08-28-2011 03:52 PM

Before going any further you need to find out if the power company will even supply 3 phase to your unit again. What is the voltage of the 3 phase?

michael825 08-28-2011 04:00 PM

when i say the un grounded second main panel is grounded through the other panel its because the service wires come through a race where they are divided with a splice before they go into each panel so it seems the nuetral is "grounding" the second one to the first which has a green ground going to earth. i admit im a bit hazy on 3 phase ground vs nuetral and on second thought i dont think i would need a fifth ground wire up to apartment panels but must only tie their nuetral into the nuetral bar of main i sub them from and later wnen they are disconected to get ther own meters ide have a problem lol or since i thought to use #2 bx could that serve as panel ground i doubt it but its probably cheaper to run a separate smaller ground then

michael825 08-28-2011 04:03 PM

i would have thought they would not be supplying again so much as splicing in a couple new meters i have this system already running now and 3 hot legs 225 amp #250 service wire is more than sufficient for 3 separate domestic panels no?

michael825 08-28-2011 04:10 PM

its 120 240 v

kbsparky 08-28-2011 07:01 PM

Are you SURE you have 120/240 and not 208Y/120?

There is a big difference in how sub-panels would be connected ....

michael825 08-28-2011 09:19 PM

yes all poles are 120 and when scrounging for panels at work ive stayed away from 208 though i wasnt sure how much it would matter in a panel rating

kbsparky 08-28-2011 09:21 PM

IF all poles are 120 as you have stated, then your three phase service is 208Y/120 Volts.

You do NOT have any 240 Volts available.

Have you used a digital meter to confirm your phase-to-phase voltage?

michael825 08-28-2011 09:22 PM

its kind of why i want to keep it seems only upside more efficient more power in same amperage more power int house more versatile im already pulling 3 phase for tools and expect the ac will be three p[ole

a7ecorsair 08-28-2011 09:22 PM

Quote:

Originally Posted by michael825 (Post 716983)
yes all poles are 120 and when scrounging for panels at work ive stayed away from 208 though i wasnt sure how much it would matter in a panel rating

You didn't answer the question completely. What do you read for voltage pole to pole? This should be three separate readings.
A to B
A to C
B to C

michael825 08-28-2011 09:25 PM

hmm i did a while back but can not be certain except the meter and panels all say 120/240 which i assumed meant 120 per leg i have pulled 220 of a 2 pole breaker

michael825 08-28-2011 09:29 PM

multi meter was stolen i will have to get back on that

kbsparky 08-29-2011 07:01 AM

Quote:

Originally Posted by michael825 (Post 716995)
hmm i did a while back but can not be certain except the meter and panels all say 120/240 which i assumed meant 120 per leg i have pulled 220 of a 2 pole breaker


In the US there is no such thing as "220" -- either you have 208 or 240 available.

You can have 208 volts on a panel rated for 120/240. The nameplate rating is the maximum that the panel can safely handle. It is not verification of your available system voltage.

AllanJ 08-29-2011 07:44 AM

If you measure 220 between two hot legs and 110 volts between hot and neutral, then this is a 120/240 system and not a 208 volt system.

michael825 08-29-2011 03:29 PM

ok got a meter so i want reading from two hot legs,every combination of hot legs and also each leg to nuetra if its 208 to determine which is the high leg?l


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