Selector Switch to avoid service upgrade

[TheDC]

I have many requests for new circuits for heat pumps replacing FAU, and for new electric car chargers. Most houses here have 100A services, If the house already has an electric range and clothes dryer, it cannot support the new load.
In the case of a car charger, customers have asked if I can install a selector switch that would enable the 240V/30A circuit to power either the charger or the dryer, thereby not increasing the load on the service. Seems reasonable, as most people would not run the dryer overnight with a car charger present or not. I cant find a Code section that is on point, I appreciate your thoughts.

 

[suemarkp]

I believe you could just install a double pole double throw snap switch to achieve the lock out required to eliminate something from a load calculation. I don't think there is an article specifically allowing or prohibiting it. Here's one from Home Depot, but it has a center off which may be a disadvantage (customer could land it there so neither work...). https://www.homedepot.com/p/Leviton...ed-Contact-Toggle-Switch-Brown-1288/301447057

Reliance also makes a transfer switch panel which is basically two double pole breakers with an intertie handle. That would work for ranges and 50A car chargers. The panel and breakers are eaton CH and you can use breakers up to 100A in it. It costs about $170, but if you could just get the interconnecting handle and use it in a normal panel with the two breakers side by side, that should be cheaper and easier (assuming customer has a CH panel). https://www.amazon.com/Reliance-Con...fCZFkT1nSBa8ZZ0YikBtx_a-oMWwGAfBoCWqoQAvD_BwE

 

[ron]

Smart splitter
Here is an example https://getneocharge.com/pages/smart-splitter

 

[augie47]

Here is another product that works as a load shed switch that might be of interest to you.

EVEMS which allows power sharing for full electric panels

Expand your full electric panel and add another high-power device such as a Type 2 EVSE Charger, a RV outlet, jacuzzi, steam shower, welder, A/C etc. No need to ask for more power from a already taxed grid. Use the power you already have more efficiently. Want to charge that Tesla in an...

simpleswitch.io

 

[TheDC]

Smart splitter
Here is an example https://getneocharge.com/pages/smart-splitter

Awesome product. In my experience if power is interrupted while an EV is charging, it will not resume the charging session without a reset once power is restored. This would make it a bad candidate for the charger on secondary plug. I do not know how the controller on a modern clothes dryer would handle that scenario, would it also require a re-start if power was needed by the primary side (charger).

 

[TheDC]

I believe you could just install a double pole double throw snap switch to achieve the lock out required to eliminate something from a load calculation. I don't think there is an article specifically allowing or prohibiting it. Here's one from Home Depot, but it has a center off which may be a disadvantage (customer could land it there so neither work...). https://www.homedepot.com/p/Leviton...ed-Contact-Toggle-Switch-Brown-1288/301447057

Reliance also makes a transfer switch panel which is basically two double pole breakers with an intertie handle. That would work for ranges and 50A car chargers. The panel and breakers are eaton CH and you can use breakers up to 100A in it. It costs about $170, but if you could just get the interconnecting handle and use it in a normal panel with the two breakers side by side, that should be cheaper and easier (assuming customer has a CH panel). https://www.amazon.com/Reliance-Con...fCZFkT1nSBa8ZZ0YikBtx_a-oMWwGAfBoCWqoQAvD_BwE

These are good ideas, but I have a different idea in mind. I would like to use a 2-position cam switch (no OFF position), to toggle power between 2-30A outlets. The normal state would be power to the charger, as it is used daily, when the user uses the dryer-change switch position to the dryer plug. As the Charger is cord and plug connected- would it require a permit? Can the smaller of the loads be eliminated from the Load Calc as the two loads could not operate simultaneously?

 

[texie]

These are good ideas, but I have a different idea in mind. I would like to use a 2-position cam switch (no OFF position), to toggle power between 2-30A outlets. The normal state would be power to the charger, as it is used daily, when the user uses the dryer-change switch position to the dryer plug. As the Charger is cord and plug connected- would it require a permit? Can the smaller of the loads be eliminated from the Load Calc as the two loads could not operate simultaneously?

There is no code issue with only sizing the service to supply only one of thee loads as long as they can't be energized at the same time. Your switch idea would be fine but I question if you can get a cam switch rated for 30 amps and be reliable. I would be inclined to use a non fused DPDT 30 amp safety switch. A little clunky but likely more reliable than a cam switch. But I guess that a safety switch may wear out pretty quickly as well if used multiple times a day.

 

[LarryFine]

I think suemarkup's DPDT toggle "snap" switch idea is elegant. Easy to operate and is a much cleaner install than a surface-mounted switch. It should last as it would rarely be switched under load.

 

[suemarkp]

Or maybe use a DPDT contactor that powers the charger when not energized. Use low voltage and switches at the charger and dryer locations to change the state of the contactor. If the dryer and car charger are near each other, a mechanical switch would be simplest.

If one of the circuits does not currently exist, then you most likely need a permit. I don't know what kind of permit I would buy here to add a switching mechanism to a circuit. Maybe just a branch circuit permit (don't think we have an altered branch circuit permit).

 

[jaggedben]

I have many requests for new circuits for heat pumps replacing FAU, and for new electric car chargers. Most houses here have 100A services, If the house already has an electric range and clothes dryer, it cannot support the new load.
...

Just gonna challenge you a bit on the given here...
And while I certainly don't advocate pushing an aging 100A service panel to its limit, it's still worth looking at a sample load calc under 220.82. (Under 220.83 it looks even better.)

VA item
6000 2000sq ft at 3VA/sq ft
4500 required (3) 1500VA branch circuits
1200 microwave
1200 dishwasher
9600 40A range
6000 25A dryer
7680 32A EV charger
5000 ~45,000 btu heat pump
=
41180 VA

After 40% demand factor for VA beyond the first 10k...
22,472 VA
93A

Add just about anything else, especially an electric or heat pump water heater, and indeed you're likely over the top. But still, worth having this perspective. (And 125A is likely fine. Have you ever actually seen a utility meter display 30kW?)

 

[wwhitney]

VA item
6000 2000sq ft at 3VA/sq ft
4500 required (3) 1500VA branch circuits
1200 microwave
1200 dishwasher
9600 40A range
6000 25A dryer
7680 32A EV charger
5000 ~45,000 btu heat pump
=
41180 VA

After 40% demand factor for VA beyond the first 10k...
22,472 VA
93A

I believe the heat pump is figured at 100% per 220.82(C)(2), so that should be 25,472 VA, or 106A. So you need to lose 1,353 VA.

Change the dryer to a heat pump dryer at 14A * 240V = 3360VA (the nameplate on my Whirlpool), and you're down 1,056 VA after the 40% factor. You need to lose another 300VA or go for 220.83 (which saves you 60% * 2000 VA = 1200 VA).

Cheers, Wayne

 

[ptonsparky]

No permit required here after original construction or at a service upgrade.

In practice, I doubt the charger will be an issue.