3 pole breakers

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Old 07-31-02, 09:24 PM
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3 pole breakers

I have seen these 3 pole breakers, what is there purpose
 
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Old 08-01-02, 03:48 AM
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Hatteras
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They are for 3-phase loads, such as some motors, compressors, etc.

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Old 08-01-02, 11:58 AM
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I have seen them in standard 200 amp service residential panels
 
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Old 08-01-02, 12:12 PM
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This is just a guess as I have never seen a 3 pole on a residential.

But I would guess they could be used in an application where one 240 volt circuit and 120 circuit were run for the same device. The only thing I can think of would be a hot tub or pool, where the pump would be on 120 and the heater would be on 240 or opposite. If the pump stopped you wouldn't want the heater to run because it would destroy something. However the heater doesn't share a circuit with the pump, and the wire sizes (and max amps) wouldn't have to be as large.

This is a total guess, I was just trying to come up with an instance. I'm curious to hear an answer.
 
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Old 08-01-02, 12:15 PM
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You may be thinking of a gfci breaker,, that might look sort of the same,, maybe There are also shunted breakers that fit in single phase panels but are not very common and are mostly used in commercial apps.
 
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Old 08-01-02, 01:41 PM
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Hatteras
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[QUOTE]Originally posted by PentaVolvo
I have seen them in standard 200 amp service residential panels

How can a 3-phase breaker be made to work in a single phase panel? Each leg of the 3-phase breaker comes off of a seperate secondary buss. Am I missing something?

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Old 08-01-02, 04:16 PM
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There is no use for a 3 pole breaker in a panel that has only two hots (residential).
 
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Old 08-02-02, 04:37 AM
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joeh20
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every other breaker is the same leg, saying the three 3 phase breaker is in spaces 1,3,5, 1 and 3 give 240vac, 5 gives 110vac, 3 and 5 give 240vac and 1 gives 110vac hense how it would work. If all three legs are tied by a pin through the handle and 1 and 3 trip on the 240vac load then the handle in 5 will open with them. and therefore kill the separate 110vac to load to the equipment also. Might be safe like that, though I've never seen it done before. If the handles aren't pinned together and just the cases are connected it will function as three separate single pole breakers. Other than transferring heat from case to case by the connecting means they will perform the same.
 
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Old 08-02-02, 06:39 AM
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Ok not sure if they still make them but, it used to be that you cold purchase a three-phase breaker that could be installed in a single-phase panel and you had to bring in a third leg and could run it directly through the breaker and take it to the load.
Second, there are residential installations that have three-phase systems. For instance, here in south Florida, there are many homes in older subdivisions that have three-phase services with a high leg. This was done in the early days to accomodate chilled water air conditioning systems.
So beware, not all residential services have to be single phase.
 
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Old 08-02-02, 11:42 AM
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DaveB.inVa
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Sparksone42,
Isnt what your talking about called a "Delta Breaker"? It could be used with a rotary phase converter and would allow you to bring the manufactured phase in and give it overcurrent protection.
 
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Old 08-02-02, 09:39 PM
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3 poe breaker

Gentlemen:
Some one mentioned a high leg in the florida system. This is a dangerous application which is called Open Delta. It was used to supply 3 phase power to an area that did not required all the power that a fullblown closed Delta could supply. They simply leave out one transformer. The danger her is that the voltage are different.
eg. A - B =120 vac
b - C = 120 vac
C -A = 208 vac c -a = 208 vac

208 v is the phazer sum of these two voltage which are 120 degrees displaced. If c is the 208 vac wire do not use it for normalm120 v appliances (burn up)
Jafro Be care ful with this system since it has killed a few electricians
 
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Old 08-02-02, 10:57 PM
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There is nothing wrong at all with a three phase delta configuration with a high leg!! I dont see why people get so freaked out about it, there are applications where a 120/240v Delta can really be more useful than a 120/208v Wye. The perfect example is shops. Most welders are single phase 240v, so is a lot of other smaller equipment. This is good because you dont have to search for 208v equipment. True they are harder to balance, but its not saying it cant be done, you just have to think a little more to do so!!! Their use is beneficial where line to line loads are more common than line to neutral loads.

A high leg delta is no more dangerous than any other single or 3 phase system and a closed delta is just as dangerous as an open delta!!

The voltages for an open delta are the same as for a closed delta.

A-B-C 240v

A-B 240v
A-C 240v
B-C 240v

A-N 120v
B-N 208v
C-N 120v

The High Leg is required by code to be landed on the center "B" phase in panelboards (408.3(E)) and required to be effectively tagged or marked orange in color (110.15)

The Delta configuration is particularly useful in the event one of the transformers fail service can be maintained at reduced load by the two remaining transformers.
The Open Delta is also useful in that you can get 3 phase with just two transformers, plus the fact that you can get 3 phase using just TWO phases and the Neutral of a Wye high voltage system.

If you had a full closed delta secondary with a wye primary you can lose any one of the incoming lines and still maintain service!!
 
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Old 08-03-02, 07:13 AM
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Electrical equipment is required to be used for the purpose that they are listed and labeled. A single phase panel is not designed, listed or labeled to have a three phase breaker installed in it.

A three phase panel is only listed to be used in a three phase panel.

An open delta is only force feeding a motor to operate without the use of the third transformer. No more dagerous nor less dangerouse than a wye or full delta system. The hang up of a three phase open delta system is lack of efficiency. The motors will have to work harder and it is more expensive in KW cost than a full delta system.

A high leg is a commonly used system. Only dangerous part of a high leg three phase system is an untrained electrician trying to connect a 120 volt rated piece of equipment on that high leg. Two out of the three legs will run 120 volt equpment but that high leg would burn out the equipment becuase of the excess voltage.

A roto phase acts much like a high leg during no load condition. The generated leg would read 250 volts to ground. Yet when loaded the generated leg will filter down to also reading 120 volts to ground.

What might have been mistaken for a three phase breaker may have been a double 240 volt piggy back breaker.

It very well could have been a three phase breaker in that single phase panel. As far as I know a three phase breaker will connect into a single phase panel. However it would be a Code violation if a three phase breaker was installed in a single phase panel due to the listing and labeling.

Wg
 
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Old 08-03-02, 08:30 AM
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DaveB.inVa
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True an open delta has about 58% the efficiency of a closed delta or about 87% the efficiency of the total of the two transformers. But if the transformers are properly sized the motors are just as powerful and efficient as ones ran on a closed delta. Problems occur when more and more load is added to an open delta, then the open sides voltage starts to droop. This is a great time for the 3rd transformer to be added.

Around here in rural Va you will see a lot of open deltas being fed with 2 hots and the neutral of a wye primary. It keeps cost down for the customer because the power company only has to pull one more phase in. The loads here are usually just one piece of 3 phase equipment so just about any transformer combination provided is enough to reliably and efficiently power it. Some examples are remote water plants that only have a couple 3 phase pumps. Another big one around here is an open delta feeding gas stations. The only 3 phase motors they have are just running the pumps.

I guess this area is fortunate to have engineers that realize the flexiblity of a delta system, arent scared to use it and havent gone "wye" crazy.
 
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