Home |
Search |
Today's Posts |
![]() |
|
Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
|
#1
![]() |
|||
|
|||
![]()
Ok, I've got the opposite problem that most of the people here have
with regards to AC power. I've got a 400 amp 3 phase service in the back half of the building I moved into a few months ago. I'm going to be leasing out this portion of the building and the electric company bills me separately for this panel. What I want to be able to do is have this panel supply the power for this portion of the building so I can have an accurate record of the electrical use for the tenant. I have another 200 amp 3 phase service and 200 amp single phase service for the other portion of the building that I'm using for the shop (RCM related) and living space. My question is how can I tap single phase 110VAC off this panel for regular power for this portion of the building? I've checked the panel in question with a VOM and I get 240 VAC to ground off of each of the two hot leads coming in and the neutral and ground are both connect to the same bus inside the panel. Checking the between both hot leads I also get 240VAC. What am I going to have to do or install to meet my needs? Thanks in advanced for the help. I know some of you guys know what I need to do. Jack Fisher |
#2
![]() |
|||
|
|||
![]()
Jack,
Maybe, it's me and I've only had coffee #2 this morning ... but your question reads as if you want to somehow meter 3-phase service and single-phase service for both areas from your location. It would seem the logical solution would be to have the leased area billing put in your tenant's name. Otherwise, combining single-phase and 3-phase service in the same panel would involve the use of transformer(s). This type of question would be much better put to your electric utility. Bob Swinney "Jack Fisher" wrote in message om... Ok, I've got the opposite problem that most of the people here have with regards to AC power. I've got a 400 amp 3 phase service in the back half of the building I moved into a few months ago. I'm going to be leasing out this portion of the building and the electric company bills me separately for this panel. What I want to be able to do is have this panel supply the power for this portion of the building so I can have an accurate record of the electrical use for the tenant. I have another 200 amp 3 phase service and 200 amp single phase service for the other portion of the building that I'm using for the shop (RCM related) and living space. My question is how can I tap single phase 110VAC off this panel for regular power for this portion of the building? I've checked the panel in question with a VOM and I get 240 VAC to ground off of each of the two hot leads coming in and the neutral and ground are both connect to the same bus inside the panel. Checking the between both hot leads I also get 240VAC. What am I going to have to do or install to meet my needs? Thanks in advanced for the help. I know some of you guys know what I need to do. Jack Fisher |
#3
![]() |
|||
|
|||
![]() |
#4
![]() |
|||
|
|||
![]() Gary Coffman wrote: The third leg, called the high or wild leg in this configuration, will read more than 240 to ground. Not so. The high leg or wild leg, also called the power leg, will be 208 volts to ground. I have some pictures of transformer connections on a web page. Scroll to the bottom of the page to see them. http://murrayranch.com/Electricity.htm . This was found a lot in older installations, but most power companies don't want to provide this any more. Gary Not so, again. This is still widely in use. At the power company I work for we install a lot of these, many in strip malls, supermarkets and small office buildings. Anyplace that has a large 120 load, and need some 3-phase for refrigeration and air conditioning. Don |
#5
![]() |
|||
|
|||
![]() Not so. Semantics. The "third leg", often called the "high leg" or "red leg" really should be called the "orange leg" as all new work is required to indicate this leg with orange wire (small gauges) or orange tape (large gauges). No single-phase loads are permitted on such a leg. |
#6
![]() |
|||
|
|||
![]()
On Fri, 11 Jul 2003 01:50:43 GMT, Don Murray wrote:
Gary Coffman wrote: The third leg, called the high or wild leg in this configuration, will read more than 240 to ground. Not so. The high leg or wild leg, also called the power leg, will be 208 volts to ground. I have some pictures of transformer connections on a web page. Scroll to the bottom of the page to see them. http://murrayranch.com/Electricity.htm You're right, sqrt(240^2 - 120^2) = 207.846 volts. . This was found a lot in older installations, but most power companies don't want to provide this any more. Gary Not so, again. This is still widely in use. At the power company I work for we install a lot of these, many in strip malls, supermarkets and small office buildings. Anyplace that has a large 120 load, and need some 3-phase for refrigeration and air conditioning. Nope, you took that one out of a different context. I'm talking about 208 delta there. Your power company may still support it for new work, but none of the ones I know will (though they continue to support it in old work). They want to supply 480 wye instead. It saves them money via smaller cheaper transformers. In a stretched out facility it saves you money too, in reduced copper costs. Gary |
#7
![]() |
|||
|
|||
![]() I'm talking about 208 delta there. Your power company may still support it for new work, but none of the ones I know will (though they continue to support it in old work). They want to supply 480 wye instead. 120/208Y is still the bulk of the new Wye installations, far outpacing 277/480Y. Installations usually follow this sequence (as a function of intended usage and total premises volume): 1) 120/240 center-tap grounded Delta (mixed use, small to medium volume), 2) 120/208 Wye (mostly power, small to medium volume), and 3) 277/480 Wye (industrial, large volume). In (3), a customer-owned "dry type" transformer or transformers is (are) required to provide 120 single-phase, 120/240 single phase or 120/208 Wye and/or 240 Delta three-phase. |
#8
![]() |
|||
|
|||
![]() Gary Coffman wrote: Nope, you took that one out of a different context. I'm talking about 208 delta there. Your power company may still support it for new work, but none of the ones I know will (though they continue to support it in old work). They want to supply 480 wye instead. It saves them money via smaller cheaper transformers. In a stretched out facility it saves you money too, in reduced copper costs. Gary Gary, I don't think I took anything out of context, I am going to cut and paste the paragraph from your original post so you can see why I thought you were talking about 208 wye. "Note you probably don't want to change to 4 wire wye service. That would give you 120 volts to neutral from any leg, but the leg to leg 3 ph voltage would drop to 208. That would require rewiring all your 3 ph motors for 208 instead of 240. This was found a lot in older installations, but most power companies don't want to provide this any more." I've never heard of a 208 delta, other than the high leg on a 240 bank. The determining factor in whether you will get a wye or delta secondary is the voltage of the service. You can see the wye secondary transformer connections on my web page have the secondary coils paralleled. What determines whether the high side is delta or wye is the actual primary voltage of the line and the nameplate rating of the transformer. Where I work, we have a lot of 12KV primary and a 20.8KV primary that we use the same transformers on. The company stocks a lot of 12KV 120/240 transformers. So if you are going to hang a bank to serve a 208V 3-phase service in the 20.8KV you pop the lid off the transformers, parallel the secondary coils, and hang a wye-wye bank. If you wanted a 240V 3-phase bank in the 20.8KV, it would be a wye-delta. If you are hanging these 12KV transformers in the 12KV primary, it would be a delta high-side. And again the secondary configuration would be determined by the secondary voltage you want, 120-208V requires you to parallel the secondary coils and wye the secondary side. 120-240V would be delta secondary. The 20.8KV system is a common neutral system. That is the neutral carried in the secondary position is shared by the primary and secondary, and is a metallic return to the substation. Don |
#9
![]() |
|||
|
|||
![]()
On Sun, 13 Jul 2003 18:42:32 GMT, Don Murray wrote:
Gary Coffman wrote: Nope, you took that one out of a different context. I'm talking about 208 delta there. Your power company may still support it for new work, but none of the ones I know will (though they continue to support it in old work). They want to supply 480 wye instead. It saves them money via smaller cheaper transformers. In a stretched out facility it saves you money too, in reduced copper costs. Gary Gary, I don't think I took anything out of context, I am going to cut and paste the paragraph from your original post so you can see why I thought you were talking about 208 wye. "Note you probably don't want to change to 4 wire wye service. That would give you 120 volts to neutral from any leg, but the leg to leg 3 ph voltage would drop to 208. That would require rewiring all your 3 ph motors for 208 instead of 240. This was found a lot in older installations, but most power companies don't want to provide this any more." I've never heard of a 208 delta, other than the high leg on a 240 bank. I misspoke (miswrote), I meant 208 wye. Gary |
#11
![]() |
|||
|
|||
![]() But then the building is supplied with two 13.8 kV feeders. I think we do our own on-site transformations from there on down. Most likely. While at my former employer we NEVER allowed one of our customers to connect to our transmission systems (115 kV ac through 500 kW ac, and 800/1,000 kV dc), we DID allow our large industrial customers/municipal partners to connect to our subtransmission systems (34.5 kV, most, and 69 kV, a few). Note that MOST (but not all) system voltages are multiples of 115 ... 13.8 kV = 120 X 34.5 kV = 300 X 69 kV = 600 X 115 kV = 1,000 X 138 kV = 1,200 X 230 kV = 2,000 X 287.5 kV = 2,500 X (Hoover to L.A., Circuits 1 and 2, e.g., in L.A.'s system) 345 kV = 3,000 X (not used in L.A.'s system, but used within the "Western System", APS, e.g.) But ... 500 kV / 115 = 4347.8261 (Hoover to L.A., Circuit 3, e.g. and the "Western System" ac Intertie, e.g.), and 765 kV / 115 = 6652.1739 ("Eastern System" ac Intertie, e.g.). Oh, well. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
Cable colours for 110v fixed wiring | UK diy | |||
3 phase electrics | UK diy | |||
3 phase armoured used for single phase supply? | UK diy | |||
Upgrade to a three phase domestic supply? | UK diy | |||
Three phase installation ....? | UK diy |