Wall charger install issue HELP!

[CharleyBC]

If you have truly maxed out your panel, there's a box that cuts off the car if the house pulls too much current:

DCC Electric – Simplifying Electric Vehicle Charging In Condos

They're not cheap, but it is a solution.

I didn't know there was such a product. Pretty cool. So, OP, this could salve your problem for a lot less than $3500. If you're at risk of overloading your panel (cooking and AC and everything going at the same time), it just cuts off the power to the car until the load drops. Simple and clever. If you usually charge overnight, even with Arizona AC running, you'll be fine.

I'm going to remember this product if I ever install a 14-50 at my in-law's summer cabin...

 

[davewill]

I didn't know there was such a product. Pretty cool. So, OP, this could salve your problem for a lot less than $3500. If you're at risk of overloading your panel (cooking and AC and everything going at the same time), it just cuts off the power to the car until the load drops. Simple and clever. If you usually charge overnight, even with Arizona AC running, you'll be fine.

I'm going to remember this product if I ever install a 14-50 at my in-law's summer cabin...

Yeah, a couple of folks on here have installed them. There's two flavors, the DCC-9 is used when you need to tap into the feed in a remote meter room. It installs between your meter and your panel, and has the breaker for the EVSE built into it. This is useful when installing in common area parking that's close to the meter room, but far from your unit's panel.

The DCC-10 is designed when you have a more normal install, where your parking is near your panel and you can install the box next to the panel and it has physical room for another breaker. The breaker and current sensors are installed inside the existing panel.

The OP could install the DCC-10, and chances are good that it would rarely, if ever, trip. Especially if he schedules his charging for late at night.

 

[MidnightPerfAZ]

Okay, i think i may have my solution. Was hoping somebody could confirm im not an idiot here in my calculations, and thanks all for your help:

i looked online at my electric usage through my electric company (APS) and found basically my highest energy consumption point was in the summer sometimes i got up to 6.0 kw hours. (August summer here in Arizona)

From my understanding to convert that to amps, then 6.0 x 1,000=6,000. 6,000/200=30 amps

i used 200 Just as a rough idea because some appliances are 240 volt and somw 120 volt.

In other words, is it possible that im only actually consuming 30 amps at my peak usage?

Seems incredibly low. I dont have any gas appliances, only major thing is in the summer here in AZ the AC is blasting pretty much day and night. Only thing i can think of is appliances now a days just way more efficient (new AC unit, LED bulbs everywhere, LED TVs etc)

 

[Sophias_dad]

is that 6kwh in a day, or peak usage was 6kw in one hour, or are they measuring it even more precisely?

None of your breakers works by averaging an hour's use... overrun by 25% or something like that and the breaker should trip in 10's of seconds or less.

If you get a model number from your AC unit, you can measure its normal power usage, which is frequently much less than the breaker its on.

But yeah, its sounding like you have a decent amount of excess capacity.

 

[MidnightPerfAZ]

is that 6kwh in a day, or peak usage was 6kw in one hour, or are they measuring it even more precisely?

None of your breakers works by averaging an hour's use... overrun by 25% or something like that and the breaker should trip in 10's of seconds or less.

If you get a model number from your AC unit, you can measure its normal power usage, which is frequently much less than the breaker its on.

But yeah, its sounding like you have a decent amount of excess capacity.

thanks, that actually somewhat provides some clarity on another thought i was having. I believe they are measuring all the kwh and dividing by 60 to get the average for the specific hour. The highest i could find was about 6kwh

my follow up question which you sort of brought on, if that is an average for the hour, that would still mean for an extremely short spurt it could still be 100+ amps right? For instance if the AC kicks on dont they draw a ton for a few seconds and i have tesla charging at 48 amps couldnt that trip the breaker?

 

[Sophias_dad]

if that is an average for the hour, that would still mean for an extremely short spurt it could still be 100+ amps right?

If its just an AC starting, the breaker(s) should be able to deal with that startup time. That 100 amp breaker will notice the extra 20 amps of AC startup draw than the smaller individual breaker driving the AC.

But it could be >much< worse than that, in theory. There could be some subset of loads that run at 90 amps for one minute, then they go away and you use 20 amps for the rest of the hour. If you add even 24 amps to that load, you might see 'correct' tripping action on the main.

If you have a clip-on ammeter, you can actually measure the current flow through your main wires in real time(gotta take the cover off the panel and know what not to touch in there to do it!). If you are REALLY interested, there are some really neat products that will do that in real time and remotely(Efergy is one, Sense is another, EnergyCloud is a third... the list goes on). Efergy's and Sense's products are full-time clamped onto the supply cables in the panel, EnergyCloud clamps onto the outside electric meter itself and physically reads the spinning disk..... I've found the outdoor meter reader part of this to fail after two years, which sucks, but maybe they've improved it.)

Even if you don't have a clip-on ammeter and don't want to get one of the above, you should be able to do a decent job of checking the power flow just using the electric meter. Some digital ones will actually display real-time power usage, if you have the spinning disk type, you could count the spins-per-minute of the disk and then do the math... sadly there doesn't seem to be a 'standard' for the spins per kwh... Electricity meter - Wikipedia ... but it isn't hard to figure out....

Your AC isn't the only load in your house by any means... Imagine you are doing some clothes drying while cooking your Thanksgiving turkey and your refrigerator decides its time to defrost, and the hot water heater is heating water because you just cooked or took a shower and your 3 is out in the garage drawing 48 amps because you just gotta drive over to grandma's house after the turkey is done.... its unlikely, but also perhaps the worst time to have a nuisance trip of your main.

 

[MidnightPerfAZ]

If its just an AC starting, the breaker(s) should be able to deal with that startup time. That 100 amp breaker will notice the extra 20 amps of AC startup draw than the smaller individual breaker driving the AC.

But it could be >much< worse than that, in theory. There could be some subset of loads that run at 90 amps for one minute, then they go away and you use 20 amps for the rest of the hour. If you add even 24 amps to that load, you might see 'correct' tripping action on the main.

If you have a clip-on ammeter, you can actually measure the current flow through your main wires in real time(gotta take the cover off the panel and know what not to touch in there to do it!). If you are REALLY interested, there are some really neat products that will do that in real time and remotely(Efergy is one, Sense is another, EnergyCloud is a third... the list goes on). Efergy's and Sense's products are full-time clamped onto the supply cables in the panel, EnergyCloud clamps onto the outside electric meter itself and physically reads the spinning disk..... I've found the outdoor meter reader part of this to fail after two years, which sucks, but maybe they've improved it.)

Even if you don't have a clip-on ammeter and don't want to get one of the above, you should be able to do a decent job of checking the power flow just using the electric meter. Some digital ones will actually display real-time power usage, if you have the spinning disk type, you could count the spins-per-minute of the disk and then do the math... sadly there doesn't seem to be a 'standard' for the spins per kwh... Electricity meter - Wikipedia ... but it isn't hard to figure out....

Your AC isn't the only load in your house by any means... Imagine you are doing some clothes drying while cooking your Thanksgiving turkey and your refrigerator decides its time to defrost, and the hot water heater is heating water because you just cooked or took a shower and your 3 is out in the garage drawing 48 amps because you just gotta drive over to grandma's house after the turkey is done.... its unlikely, but also perhaps the worst time to have a nuisance trip of your main.

thanks for this. It almost seems like some of these AC units take a lot more than additional 20 amps to fire up. Some late night reading i saw numbers like 80 amps. Mine is a new Trane middle of the road 4 ton AC unit sonits probably better than some.

sounds like i should have the electrician measure it as you mentioned when the AC is kicking on and maybe run the tesla charger at lower than 48 amps :/

 

[Sophias_dad]

thanks for this. It almost seems like some of these AC units take a lot more than additional 20 amps to fire up. Some late night reading i saw numbers like 80 amps. Mine is a new Trane middle of the road 4 ton AC unit sonits probably better than some.

sounds like i should have the electrician measure it as you mentioned when the AC is kicking on and maybe run the tesla charger at lower than 48 amps :/

I just used 20 as an example. The point was that the 100 main isn't gonna be the first thing to trip due to your AC. The one-second startup of even 80 amps is probably far more than double the normal operating current of that AC breaker, while its nowhere near double the normal operating current of the 100 amp main. Its pretty common (and I'm sure there's a well defined specification for it) for big breakers to have to deal with much higher motor startup currents for short periods.

There's really nothing wrong with tripping a breaker, that's what they're for. A nuisance trip or two before you decide to turn it down isn't gonna kill it. That said, unless you have a really long commute there's little to be gained from charging at 48 instead of even 40, 32, or even 24 amps.

 

[Sophias_dad]

Apologies... somewhere along the way I changed to thinking your panel was only 100 amps, when its really 150. I also totally missed your pictures of the panel and load calculations....

There are several 'dubious' entries in the load calculations.... someone should go and look at the plate-ratings of each of the big appliances... particularly the range and dryer... I found mine(a decent dual oven Gemini) was considerably less than the 12000 being used by default by the load calculation pictured(that could be 4000 watts(aka 16.5 amps!) freed up, just from one appliance read).

The load calculation picture shows that they didn't even glance at the plate rating of the compressor, and because they just took 65% of the breakers they are wildly overestimating the power usage (32.5+22.75 amps)... right there you have a ~30 amp error, since we know for sure the expected running load of the compressor is 21 amps and the breaker is inexplicably 50 amps instead of the 40 amp max breaker specified by the motor plate. It isn't really clear what 'F.A.U.' is, but the only logical thing is the air-handler, but it has a 35 amp breaker, which is just ludicrous for a fan-only... based on the fact you are in Arizona I bet that FAU is a combination of the air handler PLUS a decent pile of electric resistance heat. But you gotta do a little thinking here... the fan itself is only about 5 amps, so when you are cooling, you'll use the 21 amps of the outdoor unit, plus the 5 amps of the fan (total of 26 amps, notably ALOT less than 55.25 amps). Interestingly, when heating, you might actually use all 35 amps of the fan unit circuit, but would not use the compressor circuit at all, so you would probably want to calculate that at 35 amps instead of the 55.25 amps combined) The NEC actually allows you to do this consideration in load calculations, where the heat and cooling modes will obviously never by used together.

The bathrooms aren't supposed to be considered separately from the 'general lighting' arena, so there's 3000 watts that could be ignored.

So yeah... read some appliance plates/models, and see if you can determine the actual expected usage of your fan/heater unit.. I bet the fan/heater isn't >really< rated to take 35 amps.

And don't worry at all about AC startup issues... they are so short lived and small compared to the main breaker, they can be ignored even if the rest of your home is running flat-out...

I initially ran the numbers and came out to 120 amps with a 40 amp HPWC, but have now redone them and found it to be more like 161 amps... I'm more than a little surprised at that result, and might make another response later. I bet with a few more real plate readings you'll get down to 150.