200A Panel in Garage Craziness

[Diezul]

Hi everyone, I had posted something similar on a DIY forum, but the feedback I received for the most part was to have a qualified electrician do everything. I am planning to have electrician do the work, but wanted to try and understand as much possible what is needed to get it done so that I don't have to just rely on 'trust' from an electrician. I came across this forum and observed that the active members are very helpful and detailed. I thought I would try my luck here and hopefully it can be useful to others who may try something similar.

I’m trying to plan/design the layout for having electrical work done inside my garage. I will hire a licensed electrician to have the work completed (I’m in the Orange County area of Southern California), but wanted to shop around and buy the different components myself not only to save costs, but to try for higher quality components that may not be available at typical hardware stores. I’ve researched quite a bit and have most of components required except for the wiring and conduit. I have included a diagram of what I’m hoping to have completed (attached). I have no experience with electrical work so I was hoping to get some feedback from experts to help point out any flaws or better recommendations.

My goal is basically to have a 200A Garage panel (or at least 150A; ~125Ft run from Main Service Panel) that feeds three 1ϕ 250V 50A outlets, six 120V 20A outlets, and a 20HP digital phase converter (which will provide three 3ϕ 250V 50A outlets). My MSP is 200A and upgrading to 400A is not feasible for me as the power company quoted about 30K to do so. I don’t expect the continuous load to be very high, but the machinery/tools that I’m planning to run may draw high current in short bursts (ex. Taking a deep cut on the CNC machine will increase the load momentarily or the air compressor turning on) and want to ensure that I have a more than adequate circuit to safely handle the various conditions. For example, the 20HP Digital Phase Converter recommends a 125A breaker as it can supply a maximum steady state 3ϕ 240V 64A , and my CNC machine states it can draw up to 3ϕ 240V 40A . It should rarely ever be even near this load under normal operating conditions. The number of outlets desired is more for ease of accessibility rather than trying to load them all. I'm planning to put on energy monitors to make sure the loads are within safe operating norms.

Some questions and concerns I have:

1) The 200A Main Service Panel I have is the Square D Homeline SC2040M200C. Problem is that spec says that max branch breaker is 100A. I don’t believe this model has any feed through lugs. It looks like my only option is to upgrade to another MSP such as the SC3042M200PS which would be able to use a 200A breaker (HOM2200BB) to feed the garage panel?

2) The Safety Throw disconnect I have (Siemens GNF324) is a 3ϕ model and the ratings are in Horsepower (rated for 15HP for 1ϕ and 25HP for 3ϕ). Can I safely use this as the disconnect between my 200A MSP and 200A Garage panel? I’m assuming it’s perfectly okay for the 3ϕ load between the digital phase converter and 100A 3ϕ panel, but not too sure of it’s application for a 200A 1ϕ load. Probably not.

3) I’m planning to use 2.0” EMT Conduit for the majority including when running the 6 AWG and two 10 AWG wiring sets for the 1ϕ 250V 50A outlet and 120V 20A outlet. According to the conduit sizing charts I've referenced, 2.0” size conduit should be okay for this size/number of conductors. I just wanted to make sure this is the optimal/recommended way to run this type of circuit by putting it all inside same conduit if possible.

4) From various threads on various forums, it seems like it would be safe and normal to run SER AL wire from the MSP to garage sub panel. I'm planning to use SER AL 250-250-250- 3/0 Ground rated at 230A. Conduit would be used from the MSP to entry to attic space. No conduit in the attic space but properly secured. Then more conduit when entry into the garage and into the sub panel. I understand it's a big conductor bundle even if I end up having to go with 150A only, but I want to be on the safer side if possible assuming everything fits. And also to future proof it in case I'm able to do something later to utilize capacity of the wires, I wouldn't want to have to repurchase/install again.

5) If possible to estimate, how much do you think an electrician might charge for a project like this assuming I already have all the components except for wire and conduit? I've gotten a couple quotes so far from opposite ends of the spectrum (2K to 30K) with different views of what's possible. This is another whole issue I'm struggling with which I can detail with another post if interested, but hopefully the feedback received from this community will help give me more insight on how to proceed.

Thank you so much for everyone’s help in advance and please let me know if you need any additional information.

 

[wyliesdiesels]

Geez thats way too much to read

Is the garage attached or detached?

If youre hiring an electrician, you should have him buy the materials. This way you dont waste his time buying the wrong stuff.

 

[Diezul]

attached garage. Understand having electrician buying materials, but trying to save thousands by getting the main components used. Trying to be detailed but I feel you. Thanks.

 

[pattenp]

I think you are asking a lot to get any meaningful cost input from people on this board. Your project is not small and you really need to get the best detailed estimates from electrical contractors in your area. One thing that sticks out to me is if your service is large enough. Second is running 250mil SER up and over through the attic isn't going to be a cake walk. Have you done actual load calculations to know the current 200A service is enough to handle the added loads?

 

[wyliesdiesels]

SER does not need to be in conduit.

I would forget the conduit

 

[Diezul]

I think you are asking a lot to get any meaningful cost input from people on this board. Your project is not small and you really need to get the best detailed estimates from electrical contractors in your area. One thing that sticks out to me is if your service is large enough. Second is running 250mil SER up and over through the attic isn't going to be a cake walk. Have you done actual load calculations to know the current 200A service is enough to handle the added loads?

Yeah, wasn’t really expecting to get cost estimate, just that the range is so wide as mentioned from what I’ve gotten so far. Yes, should be no problem as of now. Concern would be in future if I add more machines and have car chargers going at the same time. I doubt I would realistically use over 100 amps average at any given time in garage, it’s just the peak spike loads that I’m worried about that may trip breakers if I just go with more typical 100A panel Install. For example the phase converter specs to use 125A breaker already, but typical operating draw shouldn’t be anywhere near that. In regards to 250mil SER, it should be a bit easier if not in conduit correct? But I understand as contractor mentioned that would be most time consuming part. Thank you.

 

[Diezul]

SER does not need to be in conduit.

I would forget the conduit

Appreciate the confirmation.

 

[brewchief]

If I understand correctly you want to run a 2" conduit and run all your circuits through it? That is possible but not practical, over 3 current carrying wires in a conduit will require you to derate the wire and reduce its ampacity.

I also see aluminum wire used for branch circuits with the ampacity listed wrong, need to use the 75 degree column as that is what your breakers and other terminations will be rated at.

Sent from my SM-G965U using Tapatalk

 

[theoldwizard1]

My goal is basically to have a 200A Garage panel (or at least 150A; ~125Ft run from Main Service Panel) that feeds three 1ϕ 250V 50A outlets, six 120V 20A outlets, and a 20HP digital phase converter (which will provide three 3ϕ 250V 50A outlets).

I think you are shooting way too high !

Of those three 250V 50A outlets how many are likely to be powered up at any one time and how much will the load really draw ? Welders do come with 250V 50A plugs, but most will not draw more than 30A and most have no more than a 50% duty cycle. A plasma cutter is in the same ball park for current and duty cycle, but of course, a plasma cutter requires an air compressor, also under 50A and a 50% duty cycle.

My MSP is 200A and upgrading to 400A is not feasible for me as the power company quoted about 30K to do so. I don’t expect the continuous load to be very high, but the machinery/tools that I’m planning to run may draw high current in short bursts

Exactly what I am saying. You do NOT need to size the main in the sub-panel for something that will likely not happen on a CONTINUOUS basis.

The real critical issue is the size of the branch breaker at the main panel and the size of the wire ! If you are using MHF cable from the main, because it is considered a branch circuit, I believe the max current is 90A.

1) The 200A Main Service Panel I have is the Square D Homeline SC2040M200C. Problem is that spec says that max branch breaker is 100A. I don’t believe this model has any feed through lugs. It looks like my only option is to upgrade to another MSP such as the SC3042M200PS which would be able to use a 200A breaker (HOM2200BB) to feed the garage panel?

IMHO, this is overkill, unless you are going to be running your CNC and 3 welders at the same time.

2) The Safety Throw disconnect I have (Siemens GNF324) is a 3ϕ model and the ratings are in Horsepower (rated for 15HP for 1ϕ and 25HP for 3ϕ). Can I safely use this as the disconnect between my 200A MSP and 200A Garage panel?

Not required if you have a breaker for the branch at the MSP and a "main" breaker in the panel in the shop.

3) I’m planning to use 2.0” EMT Conduit for the majority including when running the 6 AWG and two 10 AWG wiring sets for the 1ϕ 250V 50A outlet and 120V 20A outlet.

I ASSUME these separate circuits ! No need for anything larger than 12 AWG for a 20A branch circuit. 10AWG might not pass muster if that was a 50A continuous load (adequate for a welder), as we discussed before.

4) From various threads on various forums, it seems like it would be safe and normal to run SER AL wire from the MSP to garage sub panel. I'm planning to use SER AL 250-250-250- 3/0 Ground rated at 230A.

WOW ! It is you money !! Terminating 250 will be a challenge. 2/0 MHF would be adequate if the breake in the MSP was 90A.

And also to future proof it in case I'm able to do something later to utilize capacity of the wires, I wouldn't want to have to repurchase/install again.

Are you going to open a professional shop or have fabrication parties with multiple people running multiple welders at the same time ?


EDIT : 250 Al SER is $7.90/ft ; 2/0 MHF is $1.92/ft That is about $750 difference for just the cable !

 

[Jim greengo]

attached garage. Understand having electrician buying materials, but trying to save thousands by getting the main components used. Trying to be detailed but I feel you. Thanks.

I dont reccomend buying/using used electrical materials myself anyway.
Materials are not that expensive new.

 

[Diezul]

If I understand correctly you want to run a 2" conduit and run all your circuits through it? That is possible but not practical, over 3 current carrying wires in a conduit will require you to derate the wire and reduce its ampacity.

I also see aluminum wire used for branch circuits with the ampacity listed wrong, need to use the 75 degree column as that is what your breakers and other terminations will be rated at.

Sent from my SM-G965U using Tapatalk

Hi, just planned to have the three sets of two 120V circuits and one 240V single phase in the same conduit if possible when spaced along the wall since I would like them next to each other if possible. This would save on additional conduit. This would be the only situation where more than 3 current carrying conductors are in the same conduit. Thanks for pointing this out so that I can make sure for reduced amperage. I believe I only checked the appropriate conduit size for the size/number of wires.

I just checked again for the aluminum wire using the 75 degree column and it seems to still check out fine as I sized up one size initially. Thanks.

 

[Diezul]

I dont reccomend buying/using used electrical materials myself anyway.
Materials are not that expensive new.

To be specific, the used items are only the digital phase converter and 240V outlets. The DPC can run ~6K new and the Hubbell brand outlets can be ~$100 each. I've read some horror stories online about cheaper brand outlets and decided to try and get higher quality ones that are still in good shape for a reasonable price. But I understand the concern and hopefully there will be minimized issues.

 

[Diezul]

I think you are shooting way too high !

Of those three 250V 50A outlets how many are likely to be powered up at any one time and how much will the load really draw ? Welders do come with 250V 50A plugs, but most will not draw more than 30A and most have no more than a 50% duty cycle. A plasma cutter is in the same ball park for current and duty cycle, but of course, a plasma cutter requires an air compressor, also under 50A and a 50% duty cycle.



Exactly what I am saying. You do NOT need to size the main in the sub-panel for something that will likely not happen on a CONTINUOUS basis.

The real critical issue is the size of the branch breaker at the main panel and the size of the wire ! If you are using MHF cable from the main, because it is considered a branch circuit, I believe the max current is 90A.



IMHO, this is overkill, unless you are going to be running your CNC and 3 welders at the same time.


Not required if you have a breaker for the branch at the MSP and a "main" breaker in the panel in the shop.



I ASSUME these separate circuits ! No need for anything larger than 12 AWG for a 20A branch circuit. 10AWG might not pass muster if that was a 50A continuous load (adequate for a welder), as we discussed before.



WOW ! It is you money !! Terminating 250 will be a challenge. 2/0 MHF would be adequate if the breake in the MSP was 90A.



Are you going to open a professional shop or have fabrication parties with multiple people running multiple welders at the same time ?


EDIT : 250 Al SER is $7.90/ft ; 2/0 MHF is $1.92/ft That is about $750 difference for just the cable !

Thanks for your insight. I know it seems like overkill for now, but my worst fear is that I will need a little extra something more later and might regret it. I wouldn't want to spend the time/resources to upgrade it again. Sacrificing a little bit more upfront costs now. I just moved into my home recently and plan to be here for a while, so in the event I actually am able to get 400A service by having my electric provider subsidize some of the costs, I would be set already for the garage/workshop.

In the near future, I'm only planning to maybe run a 15HP CNC Mill, 10-15HP CNC Lathe, 10-15HP Air Compressor, and charging an electric car. Yes, I will try to time/space everything out as much as possible but I don't want to have to stop what I'm doing if my wife decides she needs to charge her car. I understand under normal operating conditions, the load will be much lower than stated max. But I don't think a 100A panel would be sufficient for this, or otherwise not give me much wiggle room? Do you feel 150A Panel is more reasonable?

I'm planning to use 250mil ALU SER and not MHF. If I upgrade my MSP, the max branch breaker size that can be used per spec is 200A.

Affirmative on the Saftey Throw Switch, I will skip this as it's pretty large anyways.

Another member touched on the 120V circuit with Single Phase 240V circuit in the same conduit. Are you recommending that I definitely separate the two? It's just that it would greatly increase the amount of conduit needed as I was planning to have 3 sets of this.

In regards to the 12AWG wire for 20A circuit, this might be too unnecessarily detailed for you, but I decided to size one up to 10AWG because I have a 3D printer that needs to be powered on 24/7 to keep the resin in the printheads by use of vacuum pump. And when it is printing, it consumes ~1800 Watts. Since this POS will always be putting a load on the circuit, I thought it would be wise to size one up.

You bring up another valid concern I have that 250mil SER AL will be difficult and maybe not possible to fit in certain situations. The garage sub panel model I have says it can accept up to 250mil wire, but IIRC it stated up to 2/0 ground whereas the 250mil AL SER comes with 3/0 ground. From the various online sources I shopped, it seems ~$4.30/ft. for 250 AL SER. If purchasing a 150' roll, it may be a little cheaper.

No, this is just for hobby/prototyping for now. You're welcome to come stop by if you're ever in the area. I have an extra guest room, but might limit you to only using one power device at a time if I'm running a machine Thank you.

 

[brewchief]

You need to talk to your power company if you are planning motors that large, many will have a restriction on size.

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[alfredeneuman]

So CA Edison (which should be the OP's PoCo, unless he's in Anaheim, or the extreme southern limit of OC) has a 10HP maximum limit to residential customers

 

[theoldwizard1]

But I don't think a 100A panel would be sufficient for this, or otherwise not give me much wiggle room? Do you feel 150A Panel is more reasonable?

The size of the panel doesn't matter except for the number of circuiot that can be terminated in it !

I'm planning to use 250mil ALU SER and not MHF. If I upgrade my MSP, the max branch breaker size that can be used per spec is 200A.

It is the size of the wire from the "first disconnect" and the size of the breaker in that disconnect that matters.

I said "first disconnect" because if you insist on that size wire, then your best solution might be to install a 2-4 circuit breaker panel between the meter socket and your house load center and then tap off from there. Or possibly replace the meter socket with a combination meter socket/load center that can handle 4-8 circuits.

Another member touched on the 120V circuit with Single Phase 240V circuit in the same conduit. Are you recommending that I definitely separate the two? It's just that it would greatly increase the amount of conduit needed as I was planning to have 3 sets of this.

As long as these are separate circuits back to the load center and you are not exceeding the "fill" on the conduit, one conduit is adequate.

In regards to the 12AWG wire for 20A circuit, this might be too unnecessarily detailed for you, but I decided to size one up to 10AWG because I have a 3D printer that needs to be powered on 24/7 to keep the resin in the printheads by use of vacuum pump. And when it is printing, it consumes ~1800 Watts. Since this POS will always be putting a load on the circuit, I thought it would be wise to size one up.

IMHO, it is still a waste of money ! A 20A circuit with 12 AWG wire can handle 2400 watts all day. The problem with 10 AWG is connecting it to the outlet. I'll bet that 3D printer has a NEMA 5-15 (15A) plug on it ! If you are worried about it, put it on a separate circuit.

You bring up another valid concern I have that 250mil SER AL will be difficult and maybe not possible to fit in certain situations.

and don't be surprised if your sparky charges extra for that !

No, this is just for hobby/prototyping for now. You're welcome to come stop by if you're ever in the area. I have an extra guest room, but might limit you to only using one power device at a time if I'm running a machine Thank you.

It is YOUR MONEY ! Spend it how you like. "Joe Average" can get by with 240V 60A in a garage workshop even with A/C. (Might have to turn off the A/C for a few minutes when running a plasma cutter.)

 

[ard]

I would size the circuit from the 200A main panel to be able to handle 200A, but only use a 125A breaker to begin. So the breaker in the main is the only limit onwards...

The idea of 'changing the MSP to handle 200A sub' seem flaweds IF YOU DONT ALSO UPSIZE THE SERVICE. To upgrade a 200A MSP top handle a 20)A lug or sub, now, before you really have lived in the shop, seems wasteful if you may than need to turn around and upgrade the service anyway.

Draw a box around that project: "Upgrade MSP and service as required" and do it when/if it is needed.

And also agree that your POCO will need to be involved with this from the get go. Would not be surprised in the least that your 200A service will not be able to actually deliver 200.

Consider sizing the conduit to only one of two 'sets' of conductors/circuits. So dont run everything in a 2"... run receptacles in one; run #6 to XYZ in another and a few #10 to ZYX in a third.

Finally, is that a 6000 square foot attached garage?!?!?

Oh, you are going to need to find a VERY special electrician to put up with this. Its one think being an OCD perfectionist...its another to do that AND be cheap AND have a pile of used parts for them to install. Its the story of my life, its why I wind up doing 99% of my own work. (Mortar bed shower stall kicked my ***...) Just saying.

 

[pattenp]

There was mention of MHF cable vs. SER. There is noway you would want to use MHF cable for the sub feed. MHF is a direct bury cable and would require conduit from panel to panel. I did not read the entire comment about MHF and don't know why it was commented on.

 

[Diezul]

So CA Edison (which should be the OP's PoCo, unless he's in Anaheim, or the extreme southern limit of OC) has a 10HP maximum limit to residential customers

I've never even thought of this or think that they would care as long as the circuit can support it properly. Isn't 10HP roughly 240V 50A Single Phase rounded up? Same as maybe a double oven or EV charger? I think the newest Tesla charger can use up to 80A, so would that be an issue?

How would they verify or ding you for something larger? Thanks so much for bringing this up so that I can try to keep everything to 10HP or lower. Luckily a lot of CNC machines market overstated HP. Advertises as 15HP, but the motor is actually only 10HP.

 

[Diezul]

The size of the panel doesn't matter except for the number of circuiot that can be terminated in it !


It is the size of the wire from the "first disconnect" and the size of the breaker in that disconnect that matters.

I said "first disconnect" because if you insist on that size wire, then your best solution might be to install a 2-4 circuit breaker panel between the meter socket and your house load center and then tap off from there. Or possibly replace the meter socket with a combination meter socket/load center that can handle 4-8 circuits.


As long as these are separate circuits back to the load center and you are not exceeding the "fill" on the conduit, one conduit is adequate.


IMHO, it is still a waste of money ! A 20A circuit with 12 AWG wire can handle 2400 watts all day. The problem with 10 AWG is connecting it to the outlet. I'll bet that 3D printer has a NEMA 5-15 (15A) plug on it ! If you are worried about it, put it on a separate circuit.


and don't be surprised if your sparky charges extra for that !



It is YOUR MONEY ! Spend it how you like. "Joe Average" can get by with 240V 60A in a garage workshop even with A/C. (Might have to turn off the A/C for a few minutes when running a plasma cutter.)

Thanks again everyone for your input and help.

Just to clarify, my current MSP setup is a combination meter socket/load center with 20 space 40 circuit. So if my understanding is correct of what you suggested, this should already be satisfied?

You mentioned that the problem with 10AWG is connecting it to the outlet. Do you mean to say that it is physically difficult (or impossible) to connect this size wire to the terminals of the outlet? If so, thanks again for catching this.

 

[alfredeneuman]

Isn't 10HP roughly 240V 50A Single Phase rounded up? Same as maybe a double oven or EV charger? I think the newest Tesla charger can use up to 80A, so would that be an issue?

10HP= Exactly 50A at 230V 1Ø.

Car charger and oven loads differ with motor loads due to the momentary massive inrush starting currents of the motor. It would cause a voltage dip on their lines.
Commercial and industrial facilities are supplied with enough to take this strain. Houses aren't.

 

[Diezul]

I would size the circuit from the 200A main panel to be able to handle 200A, but only use a 125A breaker to begin. So the breaker in the main is the only limit onwards...

The idea of 'changing the MSP to handle 200A sub' seem flaweds IF YOU DONT ALSO UPSIZE THE SERVICE. To upgrade a 200A MSP top handle a 20)A lug or sub, now, before you really have lived in the shop, seems wasteful if you may than need to turn around and upgrade the service anyway.

Draw a box around that project: "Upgrade MSP and service as required" and do it when/if it is needed.

And also agree that your POCO will need to be involved with this from the get go. Would not be surprised in the least that your 200A service will not be able to actually deliver 200.

Consider sizing the conduit to only one of two 'sets' of conductors/circuits. So dont run everything in a 2"... run receptacles in one; run #6 to XYZ in another and a few #10 to ZYX in a third.

Finally, is that a 6000 square foot attached garage?!?!?

Oh, you are going to need to find a VERY special electrician to put up with this. Its one think being an OCD perfectionist...its another to do that AND be cheap AND have a pile of used parts for them to install. Its the story of my life, its why I wind up doing 99% of my own work. (Mortar bed shower stall kicked my ***...) Just saying.

Thanks so much for chiming in and it helped me get a new perspective on this project. I like the idea of sizing the circuit for 200A, but starting with a lower breaker. I feel I would be comfortable with 125A to start, but my concern is with the breaker size with the current MSP. I had a Master Electrician come out to check the project, and he insisted that I could put a 125A breaker in my MSP even though I pointed out the spec of that particular models says max of only 100A (hence the reason of me thinking I need to replace the MSP in first place). Is there any truth to this? Is it okay and common practice to use 125A Breaker and not be safety hazard? This will be crucial in determining which route I will take and having to avoid replacing the MSP.

My other concern would be whether the 250mil SER AL wire size would physically be able to connect to the current MSP with 125A breaker, so that I can have the garage circuit sized for 200A.

Could you please elaborate on your comment that "Would not be surprised in the least that your 200A service will not be able to actually deliver 200." I had one Electrician mention something similar in regards to the size of the wire coming from the pole and that it couldn't even handle 100A. I'm not sure I fully understood what he was saying or if I misheard, but he still wanted to use 125A breaker to branch to garage panel. I was under full assumption that if I had 200A service, that the circuit could support 200A from power company side at the least.

No, it's just a standard 2-car garage, but have thoughts of expanding it should the need arise and funds available. Are you my VERY special Electrician? I can buy your plane ticket here if you desire to visit beautiful South OC, Disneyland is only ~15 minutes away

 

[theoldwizard1]

Thanks again everyone for your input and help.

Just to clarify, my current MSP setup is a combination meter socket/load center with 20 space 40 circuit. So if my understanding is correct of what you suggested, this should already be satisfied?

Probably not, unless you can find a breaker that will handle 250 MCM wire !

As stupid as this sounds, you could run COPPER SER (1/0 ???) over to a 12x12 J-box and splice it to the aluminum SER, just use the proper splices. I am not certain how easy it is to find a breaker that size.

 

[Kevin Essiambre]

You mentioned that the problem with 10AWG is connecting it to the outlet. Do you mean to say that it is physically difficult (or impossible) to connect this size wire to the terminals of the outlet? If so, thanks again for catching this.

Most receptacles will accept 14-10AWG solid with no issues. At least all the ones I have seen will.


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[Kevin Essiambre]

I've never even thought of this or think that they would care as long as the circuit can support it properly. Isn't 10HP roughly 240V 50A Single Phase rounded up? Same as maybe a double oven or EV charger? I think the newest Tesla charger can use up to 80A, so would that be an issue?



How would they verify or ding you for something larger? Thanks so much for bringing this up so that I can try to keep everything to 10HP or lower. Luckily a lot of CNC machines market overstated HP. Advertises as 15HP, but the motor is actually only 10HP.

The starting current of a large motor can be huge (like, some can be 600% more current on start up). This starting current is why they will limit your motor sizes. If you start a large motor (let's say 30hp), they're gonna notice a voltage drop at the sub-station, and with these new fangled smart meters, they could probably trace it back to you.

This is why soft starts exist (and VFD's).

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[Diezul]

The starting current of a large motor can be huge (like, some can be 600% more current on start up). This starting current is why they will limit your motor sizes. If you start a large motor (let's say 30hp), they're gonna notice a voltage drop at the sub-station, and with these new fangled smart meters, they could probably trace it back to you.

This is why soft starts exist (and VFD's).

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Thanks for this info. Any large motor load would come from the Phase converter's 3 phase outlets. I don't know the science behind it, but I just read some info about my particular phase converter and someone mentioned that a rep said "single phase input line would have minimal inrush current on it while starting a load as long as it's within the 4 sec overload rating". Hopefully I won't have any issues.

 

[Diezul]

10HP= Exactly 50A at 230V 1Ø.

Car charger and oven loads differ with motor loads due to the momentary massive inrush starting currents of the motor. It would cause a voltage dip on their lines.
Commercial and industrial facilities are supplied with enough to take this strain. Houses aren't.

Thank you. Something to consider and be mindful of.

 

[wyliesdiesels]

The real critical issue is the size of the branch breaker at the main panel and the size of the wire ! If you are using MHF cable from the main, because it is considered a branch circuit, I believe the max current is 90A.

That is for #2 AL MHF only. MHF comes in several sizes larger than #2...

Not required if you have a breaker for the branch at the MSP and a "main" breaker in the panel in the shop.

Incorrect.

A breaker in the garage subpanel is not required either since this is an attached garage.

WOW ! It is you money !! Terminating 250 will be a challenge. 2/0 MHF would be adequate if the breaker in the MSP was 90A.

you keep mixing up wire sizes. #2/0 AL is NOT 90a max. You're thinking of #2 AL

 

[Diezul]

Probably not, unless you can find a breaker that will handle 250 MCM wire !

As stupid as this sounds, you could run COPPER SER (1/0 ???) over to a 12x12 J-box and splice it to the aluminum SER, just use the proper splices. I am not certain how easy it is to find a breaker that size.

I looked into this a little further. You're correct, the 125A Breaker (HOM125CP) can only handle up to wire size 2/0 . The breakers for 150A and 200A (HOM2150BB and HOM2200BB) can handle up to 300kcmil.

I see what you're saying, so in theory I could use a 125A Breaker at the MSP, run 2/0 ALU SER (rated for 135A @ 75C) from it to a J-box, then splice it to the 250kcmil ALU SER for the main run to the garage panel? Would this technically break any NEC code?

This is assuming I can safely use a 125A Breaker on my current MSP. I mentioned before that my MSP SC2040M200C spec states max breaker of 100A, but a Master Electrician that came out insisted I could use 125A Breaker. Can you confirm or deny this recommendation? Does it have anything to do with some overhead built in?

 

[alfredeneuman]

states max breaker of 100A, but a Master Electrician that came out insisted I could use 125A Breaker. Can you confirm or deny this recommendation? Does it have anything to do with some overhead built in?

You'd better get a new "Master Electrician".
When the panel label says 100A max, it means just that.
It may physically fit but is against the Code to do anything inconsistent with the panel's listing or labeling (NEC 110.3).

 

[mm08822]

In regards to the 12AWG wire for 20A circuit, this might be too unnecessarily detailed for you, but I decided to size one up to 10AWG because I have a 3D printer that needs to be powered on 24/7 to keep the resin in the printheads by use of vacuum pump. And when it is printing, it consumes ~1800 Watts. Since this POS will always be putting a load on the circuit, I thought it would be wise to size one up.

1800w = 15a @120v. This should go on its own 20a ckt. #12's will cover that. Going to #10 has no added value.

What you really need is the printer plugged into a UPS so it can ride thru momentary power-blips. Consider additional UPS capacity if you experience longer term interruptions. It all depends on how long your print jobs are, critically of the job and power disturbance frequency.

 

[wyliesdiesels]

I looked into this a little further. You're correct, the 125A Breaker (HOM125CP) can only handle up to wire size 2/0 . The breakers for 150A and 200A (HOM2150BB and HOM2200BB) can handle up to 300kcmil.

I see what you're saying, so in theory I could use a 125A Breaker at the MSP, run 2/0 ALU SER (rated for 135A @ 75C) from it to a J-box, then splice it to the 250kcmil ALU SER for the main run to the garage panel? Would this technically break any NEC code?

This is assuming I can safely use a 125A Breaker on my current MSP. I mentioned before that my MSP SC2040M200C spec states max breaker of 100A, but a Master Electrician that came out insisted I could use 125A Breaker. Can you confirm or deny this recommendation? Does it have anything to do with some overhead built in?

Did he bother to read the panel label? Obviously not. Is this guy really a master electrician?

You already answered your own question by reading the panel specs...

 

[Bert_]

Should probably do some more reading on the HOM2200bb and HOM2150bb. The spec sheet simply says they are for load centers and combo units rated 150a or more. No reason it shouldn't be allowed, those breakers use 4 stabs which keeps the current at or below 100a per stab. Might be worth a phone call to Square D.

150a breaker with 2/0 aluminum wouldn't be bad to install as long as you don't predict your load going over 135A.

Otherwise the 200a with 4/0 will give you 180a of allowable load. I wouldn't mess with 250mcm, your whole house isn't fed with wire that big.

With that phase converter 100 feeder isn't enough. Full load on it is like 110A.

 

[Bert_]

Any halfway modern 10hp motor is no where near 50a. Most are around 40a. Lowest I've seen is 38a. Doesn't matter though, inrush is the concern.

 

[Kevin Essiambre]

Any halfway modern 10hp motor is no where near 50a. Most are around 40a. Lowest I've seen is 38a. Doesn't matter though, inrush is the concern.

1 hp = 746 watts
10 hp = 7460 watts
7460 ÷ 240 = 31.083
31.083 amps without losses and inefficiencies.

You are right, I haven't seen any modern 10hp motors that are 50 amps.

Sent from my SM-G920W8 using Tapatalk

 

[wyliesdiesels]

50a is the NEC FLC rating listed in table 430.248.

It hasnt been updated in a long while.

The wire for the circuit must be sized by that but it doesnt mean the motor draws that amount of current.

As Bert said, in-rush is the concern here

 

[ard]

snip

Could you please elaborate on your comment that "Would not be surprised in the least that your 200A service will not be able to actually deliver 200." I had one Electrician mention something similar in regards to the size of the wire coming from the pole and that it couldn't even handle 100A. I'm not sure I fully understood what he was saying or if I misheard, but he still wanted to use 125A breaker to branch to garage panel. I was under full assumption that if I had 200A service, that the circuit could support 200A from power company side at the least.

Folks have been saying 'do a load calc'...

When a new home is built, the builder provides a load calc on the home to the poco engineer. That engineer then decides on what size wire to run from the transformer to the meter. THEY ARE NOT BOUND BY NEC. They are not bound by the numbers on the main breaker handle. They can violate wire sizes and voltage drops. They need to size the wire to serve the home as built, with a bit of slop built in (add a pool, a spa, a heater etc). By PUC regs they need to deliver 120V +- whatever... thats what they try and do

If you were to read the rules and regulations here in CA, the poco has something that requires you to inform them if the loads will be changing. This is so they can, if necessary, upgrade the service. While one might think If it say 200 on the switch I should have 200', the poco has negotiated other rules (that in fact reduce costs and therefore rates to the homeowners.) This is why large loads, large motors, etc, all require poco notice

No, it's just a standard 2-car garage, but have thoughts of expanding it should the need arise and funds available. Are you my VERY special Electrician? I can buy your plane ticket here if you desire to visit beautiful South OC, Disneyland is only ~15 minutes away

lol. not hardly. A med dev guy that used to be a sparky a good many years ago


In terms of wire sizes breakers and lugs... looks like that is well in hand.

 

[Diezul]

Folks have been saying 'do a load calc'...

When a new home is built, the builder provides a load calc on the home to the poco engineer. That engineer then decides on what size wire to run from the transformer to the meter. THEY ARE NOT BOUND BY NEC. They are not bound by the numbers on the main breaker handle. They can violate wire sizes and voltage drops. They need to size the wire to serve the home as built, with a bit of slop built in (add a pool, a spa, a heater etc). By PUC regs they need to deliver 120V +- whatever... thats what they try and do

If you were to read the rules and regulations here in CA, the poco has something that requires you to inform them if the loads will be changing. This is so they can, if necessary, upgrade the service. While one might think If it say 200 on the switch I should have 200', the poco has negotiated other rules (that in fact reduce costs and therefore rates to the homeowners.) This is why large loads, large motors, etc, all require poco notice



lol. not hardly. A med dev guy that used to be a sparky a good many years ago


In terms of wire sizes breakers and lugs... looks like that is well in hand.

Thanks for this explanation, it's really helpful and not something I've came across or considered. This is what my POCO planner is alluding to when I last spoke to her. When I inquired about service upgrade months back, I was upfront with everything and they didn't seem to care one bit, just gave me options and potential costs.

 

[Diezul]

Did he bother to read the panel label? Obviously not. Is this guy really a master electrician?

You already answered your own question by reading the panel specs...

He said he didn't care and was very adamant, he's been doing this for so long and to trust him... Also must use Copper wire, not aluminum, otherwise my house will burn down.

I also indicated my phase converter called for a 110-125A Breaker and max steady state 3 phase output would be ~64A per spec. He says that would be magic and math doesn't lie, busts out his calculator and says max ~40A 3 Phase output given ~120A single phase input. Again, very adamant. I believe his math to be misguided by using 3 as the multiplier, and not sqrt(3).

What's scary is that he is a highly reviewed Master Electrician that works on a lot of commercial/industrial projects also. This is exactly the reason why I try to research and sometimes turn to an online community for help/guidance instead of just trusting an 'Expert' to do everything. As funny as it sounds, I only trust the internet because you can usually find the answer/truth if you filter through enough. I'm greatly appreciative of everyone's help and contribution.

 

[Diezul]

1800w = 15a @120v. This should go on its own 20a ckt. #12's will cover that. Going to #10 has no added value.

What you really need is the printer plugged into a UPS so it can ride thru momentary power-blips. Consider additional UPS capacity if you experience longer term interruptions. It all depends on how long your print jobs are, critically of the job and power disturbance frequency.

Thanks for the reassurance. I do have it plugged into a UPS.