Feeding Chiller Module

[Tainted]

In a 208V 3-phase building I am feeding chiller module. The available fault current at the service is 128,000 amps.

The chiller module has these specs:

LRA: 1359 amps
MCA: 930 amps
MOP: 986 amps
Recommended fuse size: 800 amps

The short circuit rating of the chiller module control panel is 10,000 amps. The chiller module will be 120 feet away from the power source.

How the heck do I get 10,000 amps from 128,000 amps? The length of the run would be astronomical with terrible voltage drop.

If I need a line reactor, which one do I get? Wouldn't the line reactor be extremely large? I'm also worried about the voltage drop too if the line reactor is installed. I am not even sure if this installation is feasible..

 

[petersonra]

I don't see you getting anywhere near 10 ka of scc at the chiller control panel.

I also don't see much chance of even getting a reworked chiller control panel to get to the level of available short circuit current you have.

First off, I would be looking real close at where the 128 ka number came from.

If that is real, you probably can't ever install this chiller module here. You might be able to install a transformer to just feed the chiller. It seems to me someone screwed up and their professional liability insurance is going to take a big hit.

By the way, do they make reactors for this purpose for low voltage? I thought they were only made for medium voltage systems.

 

[petersonra]

If I am thinking about this right a 300 kva xfmr would have something less than 25 ka of scc available assuming an infinite bus.

Anyway to add one as another service xfmr?

 

[electrofelon]

How was the chiller speced or obtained without any coordination to the AFC? Looks like you have about 35-40k at the equipment if that 128k Is accurate. Can you prod the POCO for a more accurate number? Often they throw out the lazy number that is 50-100% more than the actual. You sure there are no series ratings for the equipment?

 

[infinity]

LRA: 1359 amps
MCA: 930 amps
MOP: 986 amps
Recommended fuse size: 800 amps

The short circuit rating of the chiller module control panel is 10,000 amps.

Are you sure that all or any of these numbers are correct? If the minimum circuit ampacity is 930 amps why a fuse size of 800 amps?

 

[Tainted]

I don't see you getting anywhere near 10 ka of scc at the chiller control panel.

I also don't see much chance of even getting a reworked chiller control panel to get to the level of available short circuit current you have.

First off, I would be looking real close at where the 128 ka number came from.

If that is real, you probably can't ever install this chiller module here. You might be able to install a transformer to just feed the chiller. It seems to me someone screwed up and their professional liability insurance is going to take a big hit.

By the way, do they make reactors for this purpose for low voltage? I thought they were only made for medium voltage systems.

128kA came from Con-Edison. Which transformer should I use? I never speced a 1 to 1 transformer before...

Nobody bought anything yet, my mechanical engineer did the chiller design and wants me to design the electrical for it.

How was the chiller speced or obtained without any coordination to the AFC? Looks like you have about 35-40k at the equipment if that 128k Is accurate. Can you prod the POCO for a more accurate number? Often they throw out the lazy number that is 50-100% more than the actual. You sure there are no series ratings for the equipment?

My engineer speced it, after he did the whole design, I looked at the cutsheet and realized the SCCR what way too small.

I don't think POCO will go out of their way to give me a more accurate number and they will probably stand their ground, dealing with Con-Ed is a pain. I didn't check any series, I don't even know what equipment is inside the control panel.

Are you sure that all or any of these numbers are correct? If the minimum circuit ampacity is 930 amps why a fuse size of 800 amps?

I had suspicioun of this too. I'm not making these numbers up, it's in their cutsheet. We're doing 8 stacked

https://global.aermec.com/en/produc...60HZ_NA&f=chiller_water&Code=WWM_1709_60HZ_CO

 

[augie47]

The saving factor is:
Nobody bought anything yet, my mechanical engineer did the chiller design and wants me to design the electrical for it.

Time to go back to the chiller manufacturer. Should not be the 1st time this has happened.

 

[Tainted]

The saving factor is:
Nobody bought anything yet, my mechanical engineer did the chiller design and wants me to design the electrical for it.

Time to go back to the chiller manufacturer. Should not be the 1st time this has happened.

Would it be a possibility that they will just say they don’t have anything more than 10000 amps?

Explaining this to my mechanical engineer and boss will such a pain.

I even calculated it with a transformer with a generous 5% impedance and it still is literally impossible to design this

 

[petersonra]

128kA came from Con-Edison. Which transformer should I use? I never speced a 1 to 1 transformer before...

I was thinking more of adding another smaller MV to 208/120 transformer to the service just for the chiller to get to a more realistic level of scc. But you might be able to get a one to one transformer. But it sounds like the poco owns the existing MV to 208/120 xfmr so probably that won't work.

I would guess this is not the only sccr issue you are going to run across with so much available scc.

 

[Tainted]

I was thinking more of adding another smaller MV to 208/120 transformer to the service just for the chiller to get to a more realistic level of scc. But you might be able to get a one to one transformer. But it sounds like the poco owns the existing MV to 208/120 xfmr so probably that won't work.

I would guess this is not the only sccr issue you are going to run across with so much available scc.

Even with a 1 to 1 transformer this design is impossible… i keep getting more than 3% voltage drop with the wires needed to reduce fault to 10000 amps. Unless I am doing the calculations incorrectly

 

[Tainted]

I have an Idea... I can just use stacks that are less than 8 for example 3 stack + 3 stack + 2 stack. I would need like 250 feet of wire while maintaining 2% voltage drop for each stack. But now I have to worry about motor contribution from these modules + the rest of the building...

 

[petersonra]

I have an Idea... I can just use stacks that are less than 8 for example 3 stack + 3 stack + 2 stack. I would need like 250 feet of wire while maintaining 2% voltage drop for each stack. But now I have to worry about motor contribution from these modules + the rest of the building...

Do the chillers use vfds? I don't see how you get any motor contribution if it is a motor run by a vfd.

 

[augie47]

I was thinking more of adding another smaller MV to 208/120 transformer to the service just for the chiller to get to a more realistic level of scc. But you might be able to get a one to one transformer. But it sounds like the poco owns the existing MV to 208/120 xfmr so probably that won't work.

I would guess this is not the only sccr issue you are going to run across with so much available scc.

Seemingly that might be a realistic solution. If you could get POCO (or customer) to provide a separate service transformer you could possibly come up with a SCA you could work with. A typical 750kva would have close to 30k available.

 

[Tainted]

Seemingly that might be a realistic solution. If you could get POCO (or customer) to provide a separate service transformer you could possibly come up with a SCA you could work with. A typical 750kva would have close to 30k available.

The building is currently being fed by (2) 1000kVA transformers. 750kVA is huge, we would need to make a whole vault just for that and including ventilation. I think my idea in post #11 might work, I am trying to figure out motor contribution

 

[Tainted]

Do the chillers use vfds? I don't see how you get any motor contribution if it is a motor run by a vfd.

I am not sure because their cutsheet doesn't say anything about VFDs.

 

[electrofelon]

The saving factor is:
Nobody bought anything yet, my mechanical engineer did the chiller design and wants me to design the electrical for it.

Time to go back to the chiller manufacturer. Should not be the 1st time this has happened.

Yeah I would first see what the chiller mfg can do before anything else.

 

[MyCleveland]

How the heck do I get 10,000 amps from 128,000 amps? The length of the run would be astronomical with terrible voltage drop.

I have never seen a CP rated at 10k. It always was 5k, if the EE did not inform the ME in advance of spec. If I had told the ME the AFC was 10,001, the manufacturer always came back with a SCCR of 65k. Maybe they have more options now, but doubtful they can get to 100k.

I would recommend breaking the equipment package down into smaller pieces....then your feeder sizes go down significantly and you can choke the SCC down hopefully to 65k at connection points.

 

[electrofelon]

I have never seen a CP rated at 10k. It always was 5k, if the EE did not inform the ME in advance of spec. If I had told the ME the AFC was 10,001, the manufacturer always came back with a SCCR of 65k. Maybe they have more options now, but doubtful they can get to 100k.

I would recommend breaking the equipment package down into smaller pieces....then your feeder sizes go down significantly and you can choke the SCC down hopefully to 65k at connection points.

65k is no problem, note OP said 120' run so AFC will be about 40k +/- at the end.

 

[Tainted]

65k is no problem, note OP said 120' run so AFC will be about 40k +/- at the end.

I will go ask the rep tomorrow... I hope it's possible to get 65k.

If not possible, I will tell my mech engineer to give me 3 stack + 3 stack + 2 stack modules.

For each 3 stack module I would need 1 set of 500kcmil with 260 feet of wire minimum to get the fault current below 10k. I would also be able to maintain 2% voltage drop.

260 feet is a lot but doable, they have a large garage I can just run it around the garage.

 

[MyCleveland]

65k is no problem, note OP said 120' run so AFC will be about 40k +/- at the end.

Look like he can below 65k without doing anything special...