Calculating breaker for a glycol chiller

[Psybion]

Alright, a quick background; I'm just an apprentice, so there's a lot I've got to learn.

To my question. I'm building a brewery and we are going to be installing a glycol chiller. I'm not familiar with this equipment but I've been told by everyone that is basically just motors. Its quite large and the FLA is 145A.

So my issue is that the electrical engineer put into the plans to use a 150A beaker. Now, the way that I understand the code is that this isn't right, I thought NEC says your branch circuit breaker size needs to be 250% of the FLA.

Can anyone tell me if I'm wrong; and why? It's something I'm not fully understanding

 

[texie]

Alright, a quick background; I'm just an apprentice, so there's a lot I've got to learn.

To my question. I'm building a brewery and we are going to be installing a glycol chiller. I'm not familiar with this equipment but I've been told by everyone that is basically just motors. Its quite large and the FLA is 145A.

So my issue is that the electrical engineer put into the plans to use a 150A beaker. Now, the way that I understand the code is that this isn't right, I thought NEC says your branch circuit breaker size needs to be 250% of the FLA.

Can anyone tell me if I'm wrong; and why? It's something I'm not fully understanding

This equipment should be marked with a value for "minimum circuit ampacity" (MCA) which you use to size the branch conductors and "maximum fuse or circuit breaker" which you use for the branch breaker. If the max indicated does not mention "breaker" you must use a fuse.

 

[don_resqcapt19]

If it is a chiller, it is most likely covered by Article 440 and not Article 430. Give us all of the information on the nameplate of the equipment.

 

[Psybion]

If it is a chiller, it is most likely covered by Article 440 and not Article 430. Give us all of the information on the nameplate of the equipment.

Oh I see. That sure does change quite a bit. The nameplate tells me it's 460v, 3 phase, 60hz. And that the MCA is 142. There's a little more on there, but primarily serial number and such

 

[suemarkp]

The breaker for a motor CAN be up to 250% of its rating, and sometimes more. But that doesn't mean you have to go that high. If it is easy to start, you may not need to oversize. If this an assembly of motors you only need to oversize for the largest one and add anything else that would be running at the same time. Because that could be complicated and you'd have to know how the machines controls work, the manufacturer should put a nameplate on it with MCA (what you size the wire to) and max breaker size (the largest breaker you can use but the minimum breaker should be at least the MCA rating).

 

[don_resqcapt19]

Oh I see. That sure does change quite a bit. The nameplate tells me it's 460v, 3 phase, 60hz. And that the MCA is 142. There's a little more on there, but primarily serial number and such

For most equipment there is also a maximum overcurrent device size shown on the nameplate. In general you size the conductor to the MCA and the OCPD to the maximum size shown on the nameplate.

 

[wallypiper]

If the nameplate doesn't have MOCP, you can probably work out a reasonable size. How many compressor motors are there? MCA = RLA of the largest compressor motor * 1.25 + RLA of all other compressor motors and other loads (control xfrmr for example). Using that you can back out the RLA of the motors and come up with a MOCP based on 440.21 and 22.

w piper

 

[StarCat]

Glycol and HVACR units

Glycol and HVACR units

Any HVACR unit is always better off being set up with the MAX breaker and breakers are ALWAYS better than fuses on ANY 3 phase unit.
Many units will have 3 pole common trip breakers wired to the compressor circuit right in the cabinet because this matter has been known about by the savvy Engineers for a very long time. ON a well designed machine, the on board protection will work in concert to save the very expensive " compressor."
Fuses are responsible for the destruction of countless refrigeration compressors that otherwise could have survived due to a fault somewhere else on the machine that is " correctable."
If you are going with fuses, then its advised to install a phase protector from the get go.
Going with MIN breaker size is a mistake, espically on Single Phase 208V.


All the best

 

[kingpb]

Alright, a quick background; I'm just an apprentice, so there's a lot I've got to learn.

To my question. I'm building a brewery and we are going to be installing a glycol chiller. I'm not familiar with this equipment but I've been told by everyone that is basically just motors. Its quite large and the FLA is 145A.

So my issue is that the electrical engineer put into the plans to use a 150A beaker. Now, the way that I understand the code is that this isn't right, I thought NEC says your branch circuit breaker size needs to be 250% of the FLA.

Can anyone tell me if I'm wrong; and why? It's something I'm not fully understanding

Two options, install what was put on the drawings (and get a change order later, MY CHOICE :happyyes, or issue an RFI raising the question to the engineer.

Other than for general understanding, learning, and knowledge it is not an apprentice's responsibility to install something different than what was specified.

 

[Psybion]

Thank you everyone for your help, it's much appreciated. In the end, I'm just an apprentice and I do whatever I'm told to do (within reason). There was just some stuff I didn't really seem to understand so I saw it as a good learning opportunity, or a chance to catch something before it went wrong. Unfortunately, the electrical engineer nor the architect seem to be too savvy (plans showed 2 panels and a receptacle going in the dead middle of a 20 ft wide door...) so I always like to check things, just in case ya know?