- First Name
- A. J.
- Dec 8, 2019
- Reaction score
- Tesla X LR+, Lexus SUV, Toyota SR5, Toyota Landcruiser
- EE (Retired)
No problem. Use 400 or any other number if you want to. But your load factor is 100%? That's really, really high.I'm not sure I agree with the 800 pole Amps. IMO, it should be closer to 400.
Most people's load factor is way less than 50%, hence the doubling I suggested. My EVSE is in a 400 pole amp panel with 1360 pole amps of breakers in it. That is a factor of 3.4 times the panel capacity well over the factor of 2 I recommend and corresponds to a load factor of 29%. In fact, in the last year, my average draw from that panel was 3.37% of capacity. That's my real load factor. But my maximum draw (while charging the car) was 239 pole Amp which is 59.6% of that panel's rating.To use 800, you'd have to make sure both side (H1 & H2 are balanced, AND your actual use is only at most 50% of the circuit breakers combined capacity).
Did the inspector arch an eyebrow at 3.4? Yes he did. So how was I able to get away with this? The answer is by being able to show the inspector what the nominal and peak loads on the panel actually are. I didn't even have to do that. The electrician just told the inspector "this guy measures everything" and as the panel was dripping with CT's he accepted this.
The code is, IMO, pretty vague about how to size a panel. There are detailed requirements about so many VA per square foot and how many for an electric range etc. but when it comes to a welder outlet in the garage the guidance is less clear. Obviously while the welder could be on at the same time as the emergency heat in all the house's air handlers at the same time your Mrs. is using both electric ovens and drying laundry such an event is very very rare. My average load (for the whole house) is 4 % of the service. Given this in a complex situation (and modern houses are getting pretty complex) rather than a detailed load calculation the code permits submission of actual consumption data. Obviously there are considerations as to how you get this but ultimately it is the best way to go. An awful lot depends on the jurisdiction. In Virginia I got by with the 400 A service that was already installed because even though the factor for one panel was 3.4 time capacity most of the loads are not in use most of the time. In Quebec I was forced to upgrade to 600A service where half that proved to be plenty.Does the Code allow for this?
You didn't say what the main breaker was rated, Assuming it is 200 A you have 400 pole amp capacity and 620 pole amp installed. Installing a single 120 pole amp EVSE would get you to 740 which is under 800 so you should be able to do that. I don't know your local jurisdiction's policies but a local electrician will. In fact you might be able to install two EVSE for a total of 860. If the inspector balks (actually you want any balking done when you pull the permit - not after the work is complete and billable) you can try pointing out that of the 120 pole amps worth of breaker installed for each EVSE the unit will never draw more than 96 and that it can be set to limit its draw to less than that.Maybe it does. I don't know. I just checked, and my home pannel has 320 A on one side and 300 A on the other; based on Circuit Beaker Capacity. So maybe it can be pushed further.
Yes, that's the best way for sure. Check eGauge if interested in this approach.Perhaps if one can demonstrate the actual loads a Household will be using at maximum, to an Inspector, They will be okay with it.
Balance isn't that big a deal. As long as reasonable attention has been paid to distributing single pole loads you will be OK. Keep in mind that the dual pole loads are already, by their very nature, balanced.Also, any 240V CB's will draw current on both H1 & H2 when in use, unless it is a Sub Panel; in which case you'd need to do a load balance on that as well.
This is the kind of information that comes from an energy recording system. Here are some representative data from the past year for chez moi,At the end of the day, the goal is to not have your CB's ever trip, under use. So you have to ask yourself, what's the worst case (Max current) situation you'll likely have happen. Say you are Chrging the CT, running Microwave, Oven, other Kitchen appliances; Refrigerator and Freezer both kick on, and you are running lights ,TV and other devices; meanwhile you are running laundry, which also means the hot water Tank is on; What does this equal? Is it over 200 Amps thru either H1 or H2?
%iles: 50% > 2.67kW; 1% > 13.12kW; 0.1% > 20.64kW; 0.01% > 25.06kW; 0.0050% > 25.69kW; 0.001% > 27.41kW;
My service is 400 A (800 pole amps) so 1 kW represents about 1 % of the service. Note that my draw was less than 27.4 kW (28.5% of capacity) for 99.999% of the time but also note that 0.001% of a year is 5.3 minutes. The peak (1 minute average) demand for the year was 31.62 kW which represents 32.9% of service capacity,