ON electrical code - 2018 changes for vehicle charger load calcs

[richyrich]

So had another interesting chat with an electrician today. Apparently some ESA adjustments to code this year altered the load calculation to consider varying load during the day/night which might allow some of us to avoid an upgrade - you can install a device to monitor demand and throttle power to the charger if necessary - he talked about a "load shedder", code describes it as an "Electric Vehicle Energy Management Systems (EVEMS)".

Has anyone had one of these devices as part of their install?

The electrical code is paywalled but there's reference to these changes here and an excerpt below. Apologies if someone mentioned this already but it was news to me and very relevant as I am looking at a very pricey service upgrade.

2015 Code — EV supply equipment loads added to load calculations at 100% of rating
2018 Code — demand factors recognized where energy management system used.
Electric vehicle supply equipment (EVSE) can draw a substantial load when in the charging mode. For existing buildings, the addition of EVSE can result in the total load exceeding the existing service capacity. In this case, the first option is to increase the service size. A second option is to install a system to monitor the power being drawn by EVSEs and other building loads, and control the EVSE loads such that the overall load does not exceed the limits of the existing service, feeders, and branch circuits. In combination with new Rule 8-500 and new Subrules 8-106(11) and (12) such systems are now recognized in the Code as Electric Vehicle Energy Management Systems (EVEMS). Complementary to the introduction of EVEMS, a new Table of loads and demand factors has been added specifically for EVSE.​

 

[RAM_Eh]

The new code deals with load calculations for new dwellings. I don't believe it will force home owners to upgrade to 200A. I believe all new homes in Ontario will need to have a 200A service with this new set of rules.

 

[rdturner0]

So had another interesting chat with an electrician today. Apparently some ESA adjustments to code this year altered the load calculation to consider varying load during the day/night which might allow some of us to avoid an upgrade - you can install a device to monitor demand and throttle power to the charger if necessary - he talked about a "load shedder", code describes it as an "Electric Vehicle Energy Management Systems (EVEMS)".

Has anyone had one of these devices as part of their install?

The electrical code is paywalled but there's reference to these changes here and an excerpt below. Apologies if someone mentioned this already but it was news to me and very relevant as I am looking at a very pricey service upgrade.

2015 Code — EV supply equipment loads added to load calculations at 100% of rating
2018 Code — demand factors recognized where energy management system used.
Electric vehicle supply equipment (EVSE) can draw a substantial load when in the charging mode. For existing buildings, the addition of EVSE can result in the total load exceeding the existing service capacity. In this case, the first option is to increase the service size. A second option is to install a system to monitor the power being drawn by EVSEs and other building loads, and control the EVSE loads such that the overall load does not exceed the limits of the existing service, feeders, and branch circuits. In combination with new Rule 8-500 and new Subrules 8-106(11) and (12) such systems are now recognized in the Code as Electric Vehicle Energy Management Systems (EVEMS). Complementary to the introduction of EVEMS, a new Table of loads and demand factors has been added specifically for EVSE.​

Definitely interesting -- I hadn't come across that in my research but I might look into it further just to become educated on it.
The caveat is that a load monitoring system would likely require cooperation of the charger (i.e. HPWC) itself. This is certainly something Tesla could implement (especially with a Powerwall 2 setup as they have load monitors as part of that). There are also chargers, such as the Zappi (zappi | myenergi) that can adjust their charge rates based on monitoring of loads (such as the output of Solar or Wind).

 

[ItsNotAboutTheMoney]

Definitely interesting -- I hadn't come across that in my research but I might look into it further just to become educated on it.
The caveat is that a load monitoring system would likely require cooperation of the charger (i.e. HPWC) itself. This is certainly something Tesla could implement (especially with a Powerwall 2 setup as they have load monitors as part of that). There are also chargers, such as the Zappi (zappi | myenergi) that can adjust their charge rates based on monitoring of loads (such as the output of Solar or Wind).

You'd only need cooperation if you want to vary the EVSE load. If you're OK with powering the EVSE off in case of overload a cut-off would be enough.

 

[rdturner0]

You'd only need cooperation if you want to vary the EVSE load. If you're OK with powering the EVSE off in case of overload a cut-off would be enough.

Agreed -- I wasn't really thinking along those lines, but yes, that would probably be a lot simpler to get "off the shelf" and without custom chargers. However, longer term, we need a lot more of these devices cooperating....

 

[oshw]

I believe you do not need a service upgrade for existing houses (renovation) if you can show that you're under the limit with demonstrated load (12 month history from your utility) and the "nameplate" reading of the EVSE. This is how I would interpret the code. Need an official answer from the ESA.

 

[oshw]

The second idea at hand, is to modulate the charge current to the car to stay under the service rating limit.

I am working on an open source design that does this exactly and works with existing chargers. It relies on mains sensing (2 circuit cards) that reads the mains in current, and reduces the car limit dynamically. The same system can be used to modulate car charging based on generation swings (wind, solar).

 

[rypalmer]

Awesome. We need innovation on all fronts to drive costs down, and this should help.

 

[rdturner0]

The second idea at hand, is to modulate the charge current to the car to stay under the service rating limit.

I am working on an open source design that does this exactly and works with existing chargers. It relies on mains sensing (2 circuit cards) that reads the mains in current, and reduces the car limit dynamically. The same system can be used to modulate car charging based on generation swings (wind, solar).

That's more or less what the Zappi charger does, but having independent device will be nice. I might be able to encourage my father to help out (he likes doing this type of thing -- he builds custom charge circuits, monitors, etc for things...the electrical engineer in him doesn't want to retire...)

To what extent would modulating the current to the car cause the car or the charger to "back off" or detect faults?

While I have no first hand experience, I remember reading that the Teslas (charger in the car itself) will back off for a while if they detect too much voltage drop as a result of pulling current.

 

[oshw]

The device intercepts the control pilot signal, has the ability to reduce the duty cycle but not increase it. Doesn't get involved with the mains voltage or current path at all.

So it's a simple square wave pass through when the current does not need to be controlled, but will chop the square wave shorter as the mains input approaches the household limit.

 

[rdturner0]

The device intercepts the control pilot signal, has the ability to reduce the duty cycle but not increase it. Doesn't get involved with the mains voltage or current path at all.

So it's a simple square wave pass through when the current does not need to be controlled, but will chop the square wave shorter as the mains input approaches the household limit.

Sorry, pleading ignorance a bit here, but where is the control pilot signal? Is that on a separate conductor on the charger connectors? (I haven't looked at how they work) I think I understand the wave chopping, to control it, just didn't know such a signal was present in a standard way that could be used.

 

[RedSafari]

One device that would be suitable for EVSE load shedding is EV Charging Controlling System. Saw it featured in a condo installation video.