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I am not as sure as that as you seem to be.
Not having done rotary phase converters would I be correct in saying that you only supply three phase loads with them?
Rotory Phase Converter
- Thread starter Jkr3497
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I am not as sure as that as you seem to be.
Not having done rotary phase converters would I be correct in saying that you only supply three phase loads with them?
texie
Senior Member
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- Fort Collins, Colorado
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- Electrician, Contractor, Inspector
If so inclined, take a look at NEC ROP 5-120 Log #2506 NEC-P05. This explains that it must be a 1/4" X 2 busbar X required length and not a ground bar or similar such as pictured in the OP. This change was made to make clear that the installation as shown in the picture by the OP is not compliant. Also, the IAEI 2014 Analysis of Changes points this out as well on page 94.
kwired
Electron manager
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- NE Nebraska
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- EC
I am not as sure as that as you seem to be.
Not having done rotary phase converters would I be correct in saying that you only supply three phase loads with them?
My experience with them is mostly for center pivot irrigation machines. They are typically supplied with a 30 amp or less 480 volt three phase feeder. Often times the input to the unit is 30 amps and output is going to hit an overcurrent device on the machine so the load side overurrent is there whether needed or not. But I see it as no different then a feeder tap.
If you are not familiar with the design of such units - when you wire up a smaller unit like there is on the irrigation machines - incoming L1 and L2, are directly tied to outgoing L1 and L2 as well as some leads to the converter. Outgoing L3 is derived in the converter.
Any single phase load on load side needs to be tied to L1 and L2 - they are the same thing as they are on the input side. On the irrigation machines the single phase load is usually just a 480x120 control transformer, but you will not normally get 480 on the manufacture phase, not a stead reliable 480 anyway, but enough phase shift a three phase motor will have necessary torque to operate. These are not a good source for just any application, and motors may even need to be oversized in some instances from what they would be on a true three phase supply.
This may be a situation where you and I will just have to continue to disagree.
I have read the ROP and see the change to the buss bar requirement WHEN USED but the use of a listed grounding equipment still remains an option.
texie
Senior Member
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- Fort Collins, Colorado
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- Electrician, Contractor, Inspector
I'm not sure we disagree or not. I'm not saying that you must use 250.64(D)(1)(3) if you have multiple disconnects. One could run an unspliced GEC to the first disco. and use a split bolt from that GEC to go to another disco.per 250.64(D)(1)(2). What I am saying is that if you elect to use the option in 250.64(D)(1)(3) it must be a busbar 1/4" thick X 2" wide X required length for the number of connections. For example, the typical intersystem bonding bar used to comply with 250.94 could not be used to comply with 250.64(D)(1)(3).
cadpoint
Senior Member
- Location
- Durham, NC
OK Texie; OK Augie47, It looks to me that they took the guts out of a can and slapped it
on wood? I thought that if this type of installation was to happen that is it needs to have
isolation bushing, to raise this off application off the wood?
I'll admit, I didn't read any article listed.
Either care to comment?
on wood? I thought that if this type of installation was to happen that is it needs to have
isolation bushing, to raise this off application off the wood?
I'll admit, I didn't read any article listed.
Either care to comment?
kwired
Electron manager
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- NE Nebraska
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- EC
The OP is not using the (D)(1)(3) option he is using the (D)(1)(2) option, next question is whether it is listed for the grounding and bonding.
Why would it need to be isolated from wood?:?
I would say if it were bolted to building steel it could even serve as the method of bonding the building steel.
If the item pictured in OP is permitted as is - I also don't see why it can not serve as the required intersystem bonding terminal as well.
kVA isn't power. Power is kW or kVA times PF.
The input and output power factors could be different.
Most variable frequency inverters do......You can't output more kva than you put in.
kwired
Electron manager
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- NE Nebraska
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- EC
Most variable frequency inverters do......
My guess is they both were thinking kW but said kVA without really thinking.
But thanks for the correction.
jtinge
Senior Member
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- Hampton, VA
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- Sr. Elec. Engr
Power and KVA analogy:
Beer factor (pf) = Volume of beer (kW)/Volume of mug (kVA)
Mug (KVA) has to hold both beer and foam.
If you reduce your foam, the mug can hold more beer, and your can drive your beer factor towards 1.0.
I'll let you extend this line of thought to explain why equipment has to be sized larger for loads with poor power factors.
Attachments
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- Retired PV System Designer
Love the analogy! :thumbsup:
Now figure out how to get the motor efficiency into the picture.
Maybe the outside volume of the glass?
Outside volume to inside volume --> PF, beer to foam --> efficiency?
Now figure out how to get the motor efficiency into the picture.
Maybe the outside volume of the glass?
Outside volume to inside volume --> PF, beer to foam --> efficiency?
Last edited:
texie
Senior Member
- Location
- Fort Collins, Colorado
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- Electrician, Contractor, Inspector
Oh the sharp eye of the Brit.
Of course KVA is not power. In an effort not to use the term KW precisely because of unknown PF I slipped and used the term power along with it. My bad.texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
The OP is not using the (D)(1)(2) option. That would be such as a tap using a split bolt or a compression connector, etc. What he has is not a connector listed for grounding and bonding. In my view the OP is clearly (D)(1)(3) and it must be a 1/4" X 2" X xxxx busbar.
Somehow I'm going to convince you guys...I know it's petty, but somehow this has struck nerve with me.
- Location
- Massachusetts
Somehow I'm going to convince you guys...I know it's petty, but somehow this has struck nerve with me.
I am doubtful. I do not see any safety issue with using listed equipment.
kwired
Electron manager
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- NE Nebraska
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- EC
There are multiple port conectors, why couldn't this device be considered one of those? I feel it comes closer to that description then a bus bar. You attach the "connection devices" to a bus bar. (D)(1)(3) even seems to look at it that way by stating: "Connections shall be made by a listed connector or by the exothermic welding process." Meaning you need to add the connection device to the bus bar.The OP is not using the (D)(1)(2) option. That would be such as a tap using a split bolt or a compression connector, etc. What he has is not a connector listed for grounding and bonding. In my view the OP is clearly (D)(1)(3) and it must be a 1/4" X 2" X xxxx busbar.
Somehow I'm going to convince you guys...I know it's petty, but somehow this has struck nerve with me.
Without knowing the model number of what is pictured I will not claim it is or is not listed for grounding and bonding, but still think by design it utilizes (D)(1)(2) instead of (D)(1)(3). JMO.
I can't imagine a "neutral assembly" designed for a panelboard - especially one suitable for use as service equipment wouldn't be listed for grounding and bonding, but I may buy into it only being listed when installed within a panelboard it was tested with.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I think the difference is that (D)(1)(2) could be used in a tap situation but that would require connecting directly to the GEC. If you use (D)(1)(3) with the busbar the gives you the ability to stop the GEC at that point and run taps and/or bonding jumpers where ever needed. In other words it acts as a central connection point.
FWIW we had quite a discussion about this at a meeting attended by NEMA, NFPA and UL representatives and this was their view. In fact they maintain that the busbar option was reworded in the 2014 to make clear that it has to be a busbar of the cited dimensions. Under the old wording it was possible to use something like in the OP as it likely met the 1/4" and 2" dimensions the way it was worded. Note the new language makes it clear that it is 1/4" THICK X 2" WIDE X length required.
I'm doing my best to convince you guys.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
And I am doing my best to convince you that I don't believe the item in question is a "bus bar" but rather a "multiple port" terminal. If anything it needs to be attached to the required "bus bar", just like any other terminal used to land a conductor on the bus bar.I think the difference is that (D)(1)(2) could be used in a tap situation but that would require connecting directly to the GEC. If you use (D)(1)(3) with the busbar the gives you the ability to stop the GEC at that point and run taps and/or bonding jumpers where ever needed. In other words it acts as a central connection point.
FWIW we had quite a discussion about this at a meeting attended by NEMA, NFPA and UL representatives and this was their view. In fact they maintain that the busbar option was reworded in the 2014 to make clear that it has to be a busbar of the cited dimensions. Under the old wording it was possible to use something like in the OP as it likely met the 1/4" and 2" dimensions the way it was worded. Note the new language makes it clear that it is 1/4" THICK X 2" WIDE X length required.
I'm doing my best to convince you guys.
Without reading any ROP's I don't know what the intent was though, but IMO if the intent was to eliminate the type of install we are questioning, they have more work to do on wording.
Ah, it works the same in any country.Oh the sharp eye of the Brit.
OK.
Let's take the case of a fixed power (kW) at different power factors.
PF = kW/kVA
That's just the basic real power/apparent power definition.
From that:
kW = PF * kVA
Lower PF and you have to increase A for the same kW.
More A, bigger conductors, bigger switchgear.
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