electrical panel upgrade required?

Discussion in 'Prime Plug-in Charging' started by satsuke, May 20, 2021.

  1. satsuke

    satsuke Junior Member

    Joined:
    Apr 26, 2006
    67
    8
    0
    has anyone required a panel upgrade to service their PP?

    I have 100AMP service at my house. I haven't seen any drop outs yet, but the potential exists to overdraw the panel / meter if I end up getting a 240V circuit installed for my PP.

    My logic is ..
    PP will be drawing 240V ~ 12A
    House AC can be drawing 240V at 30A
    Stove/Oven can draw 240V at 30A
    Fridge and remainder of house can be ~120V at 30 amps

    I know its worst case scenario, but all this is very close or over the max panel draw.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    95,338
    43,220
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    agreed. 100 amps is prehistoric. i would upgrade to 200 if possible. it's not cheap, but it is worth it
     
  3. rdgrimes

    rdgrimes Senior Member

    Joined:
    Jun 7, 2013
    1,740
    438
    4
    Location:
    New Mexico, USA
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Advanced
    Its not about what will actually be drawn by this and that, its about the ratings and potential of all circuits. Here you can't get a permit for ANY work without upgrading to a 200A service. Anyways, keep in mind you should have a tax credit of up to $1000 for installing an charging station - and you can include the service upgrade in that calculation. To get that $1000 you have to spend $3000+.
     
  4. RobH

    RobH Senior Member

    Joined:
    Sep 18, 2006
    2,368
    970
    70
    Location:
    Sunnyvale, California
    Vehicle:
    2006 Prius
    Upgrading to 200 amp service would be more convenient, but necessary? To keep using the 100 amp service, you'll have to pay attention to which appliances you use at the same time. Our 1957 house has 100 amp service, and we juggle which kitchen appliances we use. Like we can't run the toaster and the microwave and the tea kettle and the dishwasher and the garbage disposal at the same time. It's not dangerous - it just pops a circuit breaker and the offender gets a trip out to the main box to reset the breaker.

    We did have an issue with the 100 amp main breaker a few years ago. It apparently degraded to the point that it tripped at much less than 100 amps. So if you do have problems, consider that it may be a sub-par breaker rather than a system design problem. The breaker in question is a Pushmatic brand, which is no longer carried in local stores. So it's online order or a local electrician's stock. I'd recommend keeping at least one breaker of each capacity used in your personal stock. Even if you use an electrician to do the install, they may not have local stock of older types like you have.

    I have to question why you would install a new 240V circuit for a PP. The ordinary 120V circuit in the garage will get the job done in 5 hours. Just don't run any large draw electrical equipment off the same circuit while you're charging. If you do install a new 240V circuit, what capacity would you get? All the PP needs is a 20 amp circuit, but your next car may need 50. Adding a 50 amp circuit on a 100 amp service is a no-go.

    So I say go with what you've already got. It's working. Upgrading would certainly make your electrician happy, perhaps with a holiday in Hawaii.
     
  5. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    5,955
    2,361
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    Assuming that it is a branch breaker that trips, that is NOT inherent with 100 amps service but indicates a piss poor electrician wired the house......putting all of the kitchen equipment and outlets on the same branch circuit.
    Fixing that might be a fairly simple operation, for a really competent electrician.
     
  6. jerrymildred

    jerrymildred Senior Member

    Joined:
    Oct 28, 2016
    10,251
    12,582
    0
    Location:
    Tampa, FL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    Are those the breaker trip ratings or the actual current drawn. If those are the breaker values, then the stuff on a 30A breaker should not pull more than 24A. Example, before I changed the breaker, my electric water heater was on a 40A breaker for some reason. It pulls about 16 amps (same as my L2 EVSE connected Prime).

    I also have a 100A service. If I add up all the breakers in the panel, they would come to way more than the 100A main breaker. Yet, I have never tripped any breakers while using the electric oven, the microwave, the water heater, and charging the car at the same time.

    In fact, looking at the numbers available now that I have solar power, since it went on line a month ago, I've never pulled more than just over 8 kW at any one time and it happened this week. Judging by the time, it consisted of charging the car for a drive to a meeting, cooking an early supper, and running the air conditioner.
    Screen Shot 2021-05-23 at 1.04.21 PM.png

    If you're concerned, I suggest you take to cover off the service panel, clamp an amp meter (they aren't all that expensive and come in super handy) on one of the incoming wires, and turn on a bunch of stuff. (BTW, I made my living as and industrial electrician and also have an EE bachelor's degree (for whatever that's worth :D)
     
  7. RobH

    RobH Senior Member

    Joined:
    Sep 18, 2006
    2,368
    970
    70
    Location:
    Sunnyvale, California
    Vehicle:
    2006 Prius
    The issue as I see it is the standards in effect when the system was installed. In 1957, microwaves were not kitchen appliances. This particular kitchen has three countertop outlets, which was a convenience that allowed you to plug in your toaster in a variety of places. You weren't expected to plug in multiple toasters.

    The first thing I'd do to upgrade the kitchen wiring would be to install ground wires. The plugs are all two prong, except the one for the microwave which was upgraded (I hope...). There's also a three prong plug for the dishwasher, which I guess indicates that the dishwasher was not in the original plan. None of the outlets have USB charging. Guess USB charged devices weren't on the radar in 1957...

    With regard to EV outlets, most of the discussion has been about do you wire for a current PP, or a full EV. But what about multiple EVs?
    One EV outlet isn't going to cut it when you have multiple EVs. What do you install now that will still work in 20 years? Will it still be monster cables or inductive coupling? Or robotic inserted connections?
     
  8. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    15,470
    8,728
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    It is completely normal for the sum of all the branch circuit ratings to substantially exceed the main panel rating, as virtually nobody has everything running full power at once. But I'm not an electrician (read Jerry's stuff for that), so don't have a good understanding of just what the limits should be for ordinary residences, despite having seen articles about it.

    Hopefully those 120V items are not all on the same side of the split-phase mains, but are shared between the sides, so that they are equivalent to just 15 amps at 240V.

    Are you counting actual appliance current loads, or just breaker ratings? If just the later, then it seems you should be fine. My 200 Amp service panel originally had 310 amps worth of branch circuits (240V equiv, but 420 amps of breakers if you count all the 120V breakers as-is, without adjust to 240V equivalent). But realistically, the house never draws anywhere close to that, not even momentarily, let alone steadily.

    The circuits have since increased to 340 amps worth of breakers. In 5 visits for various projects, the electrical inspector never winced at all. Though this electrical "expansion" has actually reduced the real-life load, as high efficiency heat pumps displace electric resistance heaters that still remain connected and functional but rarely used anymore.
    And it looks like your solar system was producing power at that time. That actually should have cooled your service panel bus bars.

    From my understanding of today's electrical codes, the solar PV breaker should be at the opposite end of the panel from the main service breaker. This is so that, during high load conditions approaching the panel rating limit, no portion of the bus bars are carrying the sum of the power source input currents (mains + solar). For a 2-source system, such a sum could exceed the panel rating, causing excessive I-squared-R heating in portions of the bus bars.

    With the two sources at opposite ends, then at any point along the bus bars, the total current is a difference between those two sources. Minus whatever load currents are tapped off at the various branch circuit points, of course.
     
    jerrymildred likes this.
  9. satsuke

    satsuke Junior Member

    Joined:
    Apr 26, 2006
    67
    8
    0
    Because I'm the kind of person who likes to use a device to its full potential, for better or worse.

    Getting this car is triggering a rethink of how I drive, as my previous 2 priuses I had put 470,000 miles on and really didn't care how much I ran the odometer up. This one is a little different since to get the maximum benefit means shorter trips to keep in all electric range (and displace gas usage in the process). I'd previously ran Uber at different times, and I'll be damned I do that on this new one (especially iwth the white seats).
     
  10. jerrymildred

    jerrymildred Senior Member

    Joined:
    Oct 28, 2016
    10,251
    12,582
    0
    Location:
    Tampa, FL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    No. The PV power is vampire tapped into the lines coming from the utility company's meter to my main breaker. So everything goes through the main breaker. It's called a supply-side or line-side connection. What you describe is a load-side connection.

    They CAN be at the opposite end, but if so, the new breaker has to conform to the 120% rule because of the concerns you mentioned.
    For example, a 200 Amp electrical panel is rated with a 200A busbar, and commonly has a 200A Main OCPD breaker. The 120% Rule back-feed limit for solar is calculated as:
      • (BUSBAR RATING x .20) + (BUSBAR - MAIN OCPD) = MAX PV (A)
      • (200A x .20) + (200A - 200A) = 40A MAX BACKFEED SOLAR
    • Therefore, 40A is the maximum solar output for a 200A panel with a 200A main OCPD, unless de-rated
    Replacing the main breaker with a smaller one would allow a larger breaker for the incoming PV electricity. For example, replacing the 200A main breaker with a 100A one would allow a 140A backfeed solar breaker. -- (200A x .20)+(200A-100A)=140A

    Supply-side connections don't have that problem since everything comes through the main breaker. Some jurisdictions don't allow this because they believe it voids the UL rating and the manufacturer's warranty on the service panel. I don't why that would void anything since there is no modification to the panel other than removing one more knock-out for the new conduit. But it would seem that your area is one that has that philosophy.

    My inverters max out a 4.8 kW, so that means they only supply 20A at peak. So far, that's providing over 50% more kWh than what I typically use. Considering the 120% load-side rule and my 100A panel, load side would have been possible if my panel wasn't already full.

    This is all stuff I'm just discovering myself since I'm so new to solar power.
     
    fuzzy1 likes this.
Loading...