200 amp service upgrade
Hi all,
Looking for some input. Planning to upgrade my homes electrical service to a 200 amp overhead. Trying to determine the best option for the electrical wire to use for the service lines. I know I can use 3/0 Copper but it’s way too expensive and not really necessary. So my other options from what I’ve found are 4/0 Aluminum, 4/0 Copper Clad Aluminum, and 250 MCM Aluminum. My understanding is 4/0 is not a true 200 amp, but along the lines of 189 Amp. 250 MCM Aluminum is a true 200 as is Copper Clad Aluminum. I would easily go with 250 MCM Aluminum but I’ve heard it might not fit in 2″ schedule 40 PVC conduit. Is that correct that it won’t fit? My dilemma is I’ve already purchased the 2″ conduit and the mast and meter socket have been installed at the side of my house, so I can’t return the conduit. I believe 4/0 Copper Clad Aluminum would fit in 2″ conduit but it doesn’t seem to be a common service wire electrical supply stores tend to carry and I don’t know if pricing is going to be more along the lines of true copper for that wire anyhow.
I’m based out of Ontario Canada, not sure if that might be of relevance to help better answer my questions.
Can anyhow answer my question re: 250 MCM fitting in 2″ PVC? Would be possible/to code to do 25o MCM Alu blacks x 2 and 4/0 Alu White and would that make it feasible fit?
Appreciate any suggestions and information.
Thank you,
John
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Replies
I think it would be good to understand why you think 4/0 is insufficient for your use. The NEC (and it sounds like the Canadian equivalent) make the provision for using 4/0 because it's more than sufficient for residential use.
Just remember... whatever you end up installing, the utility will likely light up your 200 amp service with a 1/0 AWG aluminum lateral.
Hi Insaneirish,
Thanks for the reply. Reasoning is, from what i've read, 4/0 Aluminum is technically not a true 200 amp service, and is more closer to 180-185 ampacity at 75 C/167 F. 250 MCM allows for up to 205 ampacity. Not that I will likely ever need to go to that maximum point, but I figure I'd like to have the full capacity of 200 since I am making this upgrade. 250 MCM is only a marginal amount more expensive, so cost wise I can justify it (copper not so much, far more exp). Just unsure if it will present a problem fitting 3 wires of 25o in 2" pvc conduit. Don't want to make the purchase to find out it won't make its way through the pipe.
Try this calculator: https://www.southwire.com/calculator-conduit. And this one: https://www.southwire.com/calculator-vdrop. The difficulty also depends on any sweeps, changes of direction, length of pull, will you be doing it by hand or by machine, etc.
Thanks James. Looking at these calculators, it seems to appear that it would fit. From the meter, there would be one 90 sweep for a 2-3' and then turn running perpendicular but would have a LB at this point to help pull and change the direction of the wire. From that point would be another 3-4' max to the panel box. All done via elbow grease.
Sure, that's not a hard pull, may as well dump a lot of the lube in there, which is cheap anyway.
You also need to check box fill rating of the LB. If I recall, some 2" LBs may be close to maxed out with 3 4/0 AWG conductors.
Having monitored power consumption on houses, I can say that you will never see anywhere near 200A, never mind for long enough to cause the wire to heat up. Unless you are looking to charge an EV city bus or a fleet of cars, you will never ever see much above 50A to 75A.
I wouldn't worry about the larger conductor unless you have a very long run.
I do agree. Ultimately if the 250 doesn't make sense, I am going with 4/0 Alum. Thanks for your feedback.
I think a lot of folks want to have a garage with several 220V devices, like an EV but also woodworking tools, welders, extra fridge/freezers, etc. They might have a hot tub which runs on electricity, and even convert the heat, hot water, and stove to electric. That warrants a bigger service, no?
Regarding the conductor size: you need to know if you are on 2021 code, and if Ontario kept Table 39 which was deleted from CEC 2021. And when you start putting wires in conduit you really need a copy of the CEC because you are working blind without the tables.
You can fit 250 mcm into 2" conduit (250 mcm hot, #2 bond) if you reduce the neutral.
HI Dalee, I do believe Ontario did delete Table 39 but not 100% sure. Would need to do more research to verify. Sorry, the #2 bond?
In BC we need a separate bond conductor now (as per CEC). I understand some provinces still allow the neutral to be used as the meter socket bond.
If table 39 is deleted I don't think you have a choice, 4/0 aluminum conductors are too small. Maybe talk to your inspector and see if they are strict about it?
I work with US code, but Canadian is usually pretty similiar. Our code book's conduit fill table shows 2" PVC conduit being good for 3 x 250MCM XHHW conductors (most aluminum wire will be XHHW), or 4 x 4/0 conductors. The fill table isn't an absolute though, since the real limit is based on cross sectional fill area. I know from experience that you can run 4 x 4/0 conductors and a #4 (a common three phase arrangement) ground in 2" conduit without any problems, satsifying both the rules in the code book and being practical in the field (although it is a tight fit).
Copper clad aluminum wire was never very common, and I've never seen it at all in larger sizes over maybe #12 or #10. Larger aluminum conductors in the "aught" range (1/0, 2/0, etc.) are bare aluminum, and you use no-ox paste at the connections (the gray "copper and aluminum" no-ox paste). That's the normal way to make these connections.
Aluminum prices have gone up recently, so aluminum wire is not as cheap relative to copper as it used to be, but it is still a little less money per unit current carried.
The code has an exception to go one size smaller for residential services. You basically get to size off of the 90*C table instead of the usual 75*C table. The reason is that residential services will pretty much never even approach the limits of the service in terms of current carrying capacity, and even if you do get close, it's likely to be for only a very short period of time. You don't have to worry about a "true" 200A service -- the breaker sets that anyway, not so much the wire. Just because you have a bunch of tools, for example, doesn't mean you'll have lots of load, since you probably won't be running all those tools under load all the time in a small home shop. If you really want to get into the details, even a "200A" breaker isn't a "true" 200A for long-term load, since the code says you can only use 80% of a typical breaker's rating for "continuous" (more than 3 hours) loads, which means "200A" is really "160A" for heavy use over long periods of time.
In a normal residential setting, just go with the code tables and residential service conductor ratings and don't worry about it. In commercial projects these load issues sometimes come up, but residential services tend to be very lightly loaded on average as a percentage of capacity.
Bill
Hi Bill,
Thanks for your reply. Very helpful information. Appreciate your reply on this.