Costing of 3ph panels, transformer selection

[bryanbdp]

Hi. I need a number of 240 3ph panels and 208/120 panels. Home Depot sells GE powermark panels TL30420C for $159 and TL42420C $167 with free shipping. These panels are also supposed to be rated for 240v 3 phase.

The price seems great, these same numbers sell for $500+ on other sites. I plan to use several of them as subpanels to power various single and 3 phase equipment. These panels also use the inexpensive THQL style breakers.

It would be nice to have a 300 or 400 amp panel, but the costs seem to be in the $800 to $1000 dollar range for these. I run out of load capacity on the panel way before I run out of spaces...

Are these panels a good deal? Are they unsuitable for light industrial use for any reason?

In one area I have a 240V 1ph coating oven with 60A requirement. Are commercial ovens non-continuous or continuous?
In this same area, I have two 50a 220v 1ph plugs for use with welders or other equipment. There is no dedicated equipment for these plugs.
In my 240V 200A 3ph panel, I have the 60A oven load, and the two 50A plugs = 160A
If oven is considered continuous, then the total is 75 + 100 = 175A
My panel is basically near capacity, even though the oven is the only load that will be used regularly.
Is this correct? I have to size for the 3 loads as above for the feeder circuit and panel capacity criteria?
Or is there some exception I don't know about...

I need a transformer to switch from the building 208Y120 power to 240v 3ph. I plan to supply several subpanels which will have both 1ph and 3ph branch circuits, using a main panel near the transformer. I need a 150kVA transformer, but a 300kVA is only a couple hundred dollars more... If I use an autotransformer.
https://canadatransformers.com/auto...-kva/primary:240-volt/secondary:208-volt.html

Is there any reason not to use the bigger transformer? It isn't much bigger (dimensions), either. I'd probably use a smaller than maximum OCPD and conductors, but could always upgrade them later for increased capacity. I would assume the amount of parasitic power is pretty much the same for any capacity transformer (no load current).
Also, I'm not sure if these transformers meet the latest energy code, or even if they have to in CT. I think the bigger unit would also last much longer, not being used near its rated capacity...

Any help on these questions would be most appreciated!
Thank you,
Bryan

 

[JFletcher]

While the panels may be rated for 240V 3ph, standard (slash rated) breaker are not. You cannot use 120/240V breakers in a 240V 3ph panel, which Im not sure you even need based on your loads. Are there any 240V 3ph loads?

 

[dionysius]

I need a transformer to switch from the building 208Y120 power to 240v 3ph. I plan to supply several subpanels which will have both 1ph and 3ph branch circuits, using a main panel near the transformer. I need a 150kVA transformer, but a 300kVA is only a couple hundred dollars more... If I use an autotransformer.
https://canadatransformers.com/auto...-kva/primary:240-volt/secondary:208-volt.html

Is there any reason not to use the bigger transformer? It isn't much bigger (dimensions), either. I'd probably use a smaller than maximum OCPD and conductors, but could always upgrade them later for increased capacity. I would assume the amount of parasitic power is pretty much the same for any capacity transformer (no load current).
Also, I'm not sure if these transformers meet the latest energy code, or even if they have to in CT. I think the bigger unit would also last much longer, not being used near its rated capacity...

Any help on these questions would be most appreciated!
Thank you,
Bryan

You might state which specific xfr you are thinking of. The caveat is as stated in their site:

Three phase Autotransformer has common primary-secondary windings which are not insulated from each other, offers no interference or disturbance isolation between primary and secondary circuits. It is an economical solution but is not suitable for sensitive equipment with electronic components and perfectly suitable for simple motor and heater applications.

Since you are possibly feeding more elaborate equipment should you not be looking at distribution transformers?????

 

[JFletcher]

Also, you are not calculating your loads correctly. 2 1ph 50A receptacles with no welders = 0 load, and even if there were 2 50A welders,coupled with your oven load, one recep would be AB, one BC, and one AC, giving 60A 3ph load (roughly), not 160A.

 

[Saturn_Europa]

Also, you are not calculating your loads correctly. 2 1ph 50A receptacles with no welders = 0 load, and even if there were 2 50A welders,coupled with your oven load, one recep would be AB, one BC, and one AC, giving 60A 3ph load (roughly), not 160A.

Wouldn't it be roughly a 100A , 3 phase load?

 

[JFletcher]

Wouldn't it be roughly a 100A , 3 phase load?

w/o welders it would be a single phase (AB or AN if not a delta panel) load of 75A, if a continuous load oven. With two single phase 50A welders running simultaneously and wide open (unlikely unless you are building a ship or boat) with that 1ph oven, I stand by my ~60A max load calc. If any of those loads are 3ph, all bets are off. I may be off a bit on my 3ph calcs, but w/o a calculator, I dont see how I'd be 40A off.

How did you arrive at 100A 3ph load based on the OP's information?

 

[Saturn_Europa]

w/o welders it would be a single phase (AB or AN if not a delta panel) load of 75A, if a continuous load oven. With two single phase 50A welders running simultaneously and wide open (unlikely unless you are building a ship or boat) with that 1ph oven, I stand by my ~60A max load calc. If any of those loads are 3ph, all bets are off. I may be off a bit on my 3ph calcs, but w/o a calculator, I dont see how I'd be 40A off.

How did you arrive at 100A 3ph load based on the OP's information?

Sir, for better or worse this is what I have. I put everything in kW per phase then converted back to Amps.

A B C 18000 18000 oven kw 12000 12000 welder 1 kw 12000 12000 welder 2 kw 30000 30000 24000 total kw 125 A 125A 100A

Excuse the import errors on the table.

 

[Fnewman]

You seem to be getting plenty of help with the panel sizing, but I can offer a few questions:
1. Do you know that the capacity of the existing service to the building is adequate for the new loads?
2. If not (or,in any event) would it make more sense to have the POCO change out the service transformers?
3. If the service has to be changed, are there any new or existing 3 phase loads, or would a larger single phase service make more sense?
4. Are there any additional 120 v single phase loads to be considered?

Just thoughts for consideration.

 

[bryanbdp]

You seem to be getting plenty of help with the panel sizing, but I can offer a few questions:
1. Do you know that the capacity of the existing service to the building is adequate for the new loads?
2. If not (or,in any event) would it make more sense to have the POCO change out the service transformers?
3. If the service has to be changed, are there any new or existing 3 phase loads, or would a larger single phase service make more sense?
4. Are there any additional 120 v single phase loads to be considered?

Just thoughts for consideration.

Per the design/build electricians, the existing main building service is sufficient. The outdoor transformer is a 500kVA 208/120 output, the meter panel has a 1600A main breaker. There are multiple meter sockets open, including two 400a and one 200a. I plan to use one of the larger meters to supply the 208/120 circuits, and the other with an auto transformer to supply 240v 3ph, which will supply several subpanels with mixed 1ph and 3ph loads. The 200a meter I plan to use with a 480v transformer, which will supply a handful of 3 phase loads.

I plan to use the 208/120 panel for lighting at 208v, and a slew of general purpose 120v receptacles. The HVAC units are 208 3ph, with 208/240 1ph 10kW aux heaters. A few machines also run on 208 3ph.

To give you an idea, the facility contains a number of shops, all with light industrial equipment. Woodshop, welding shop, metal fab, plastics, waterjet cutter, various milling and turning machines, including a Haas TM3P. A few of the machines are dual rated for 208/240, but the majority of them require 220 (240).

I THINK the autotransformers make sense in this situation. Most of the sensitive loads will be on the 208/120 panel. The 240 and 480 circuits are all for machinery, and the few that have VFD controls would be built to run concurrently with other motor loads, I would think, as far as interference and harmonics go... The panel feeders are all 130' or more in length, I don't know if this helps to dampen harmonics and noise or not.

The computers and other 120v loads will all have decent surge protectors, are there other steps I should take to help protect this equipment?

Thanks,
Bryan

 

[dionysius]

Sir, for better or worse this is what I have. I put everything in kW per phase then converted back to Amps.

A B C 18000 18000 oven kw 12000 12000 welder 1 kw 12000 12000 welder 2 kw 30000 30000 24000 total kw 125 A 125A 100A

Excuse the import errors on the table.

You would have been best to have had this dgm in your OP.

It is still unclear if these are 240V 3 phase loads.

What trafo are you using???? I am not convinced this dgm is correct!!

If they are then here is where you are headed.......

Based on this and allowing for about (200-125)/125 = 60% growth you need a 200A 240V 3 phase panel.

Please chime in on voltage and phase spec if my assumptions are off.

 

[Fnewman]

Your additional information clarifies a lot - looks like a pretty good-sized project. Here are a few comments:

if if you are planning to use LEDs for the lighting, 208v may be an overkill given the very low currents of those. You can run A lot of LEDs on a 120v circuit!

I have a general dislike for autotransformers, primarily because I prefer the isolating qualities of the two winding units. Haven't priced it, but for a sizeable project, the difference may be fairly small as a percentage of the total. In addition, I would not want to take the risk or responsibility for the problems possibly created by harmonics for other users on the same service.

You are planning to use several meters to serve one user? If those are meters the POCO will be reading (and billing) I don't think they would allow. Maybe I am still misunderstanding something- a one-line diagram would help.

Back to your original question - I'm not sure why you would see such large price differences for panels of the same catalog #. In my experience, prices from my local electrical supply house usually beat the big box stores. Sounds like some misunderstanding somewhere in the mix.

 

[Saturn_Europa]

You would have been best to have had this dgm in your OP.

It is still unclear if these are 240V 3 phase loads.

What trafo are you using???? I am not convinced this dgm is correct!!

If they are then here is where you are headed.......

Based on this and allowing for about (200-125)/125 = 60% growth you need a 200A 240V 3 phase panel.

Please chime in on voltage and phase spec if my assumptions are off.

The OP didn't post this chart. It's something that I came up with to clarify my load calculations based on the OP having two welders and an oven on 240v single phase.

 

[dionysius]

The OP didn't post this chart. It's something that I came up with to clarify my load calculations based on the OP having two welders and an oven on 240v single phase.

I missed that. Sounds like the OP needs to weigh in and give us a one line drawing.

 

[JFletcher]

Sir, for better or worse this is what I have. I put everything in kW per phase then converted back to Amps.

A B C 18000 18000 oven kw 12000 12000 welder 1 kw 12000 12000 welder 2 kw 30000 30000 24000 total kw 125 A 125A 100A

Excuse the import errors on the table.

You are correct. I've gotta stop doing math at midnight....