Adding 6-20 or 14-50 to a 100 amp service

[flai54]

Don't understand.....100 amp 240 volt service is only 24,000 watts. 100 x 240 = 24,000.

You are not running everything at 240 volts in the USA. The only thing in my panel that runs at 240 volts and utilizes both hot wires now are the EV charger and my central AC condenser unit (20A breaker) neither of which are ever pulling large current at the same time. Regular plugs are only using 120 volts which means the circuit breakers are tapping only 1 side of the hot wires in alternating fashion in the panel. If you look at your own electrical panel you will have way more circuit breakers than theoretically the electrical panel capacity.

The city permit process must be accounting for extra circuits that you can have in your panel since no circuit breaker will be maxed out at all times. Also I was looking at the back of my stove, AC condenser, microwave, sink erator, etc spec books for trying to provide accurate measures of how much current is being used. Its not an exact science but I had to fill out this electrical usage worksheet to see it if met the requirements as part of the process.

At the end of the day, it was fine for the permit process and with the way I charge with off peak charging due to lower rates, there is never a temptation to charge during the day which could conflict with my charging but not likely. I also use the mobile connector as my charging unit so its not even drawing the full 40A that is is allowed but only 32A max and during off peak hours where most of your house is running on minimum current.

 

[Eric33432]

You are not running everything at 240 volts in the USA. The only thing in my panel that runs at 240 volts and utilizes both hot wires now are the EV charger and my central AC condenser unit (20A breaker) neither of which are ever pulling large current at the same time. Regular plugs are only using 120 volts which means the circuit breakers are tapping only 1 side of the hot wires in alternating fashion in the panel. If you look at your own electrical panel you will have way more circuit breakers than theoretically the electrical panel capacity.

The city permit process must be accounting for extra circuits that you can have in your panel since no circuit breaker will be maxed out at all times. Also I was looking at the back of my stove, AC condenser, microwave, sink erator, etc spec books for trying to provide accurate measures of how much current is being used. Its not an exact science but I had to fill out this electrical usage worksheet to see it if met the requirements as part of the process.

At the end of the day, it was fine for the permit process and with the way I charge with off peak charging due to lower rates, there is never a temptation to charge during the day which could conflict with my charging but not likely. I also use the mobile connector as my charging unit so its not even drawing the full 40A that is is allowed but only 32A max and during off peak hours where most of your house is running on minimum current.

Yes, I understand how split phase power works in North America. But if you have 100 amp service, I promise you that you only have 24,000 watts of power available if you have 240 volt service. If you submitted a load calculation showing about 25,000 watts of calculated load I am surprised the city would issue a permit to install your EVSE circuit.

That said, with the EVSE only pulling 32 amps and a relatively small air conditioner as your only 240 volt loads, I agree the 120 volt loads at your house will be minimal, and you are fine with 100 amp service.

To do a load calculation, you need to convert all your fixed in place appliances, air conditioners, motors, etc., to watts. If an appliance nameplate specifies how many amps it uses, you will multiply volts times amps and you will get the "volt-amps" for that appliance which for the purpose of the load calculation is the same as watts. For example, an air conditioner that draws 12 amps at 240 volts would be listed as using 2,880 watts (240 x 12). But a 120 volt dishwasher that uses 11 amps would be listed as using 1,320 watts (120 x 11).

Another thing that would not be allowed is for you to promise not to run the A/C, or any other heavy load, while you are charging your car. At least this would not be allowed by any jurisdiction I am aware of in the United States.

If your air-conditioning is window units, those would not need to be considered in your load calculation because they are not fixed in place appliances. But if your home is equipped with central air conditioning, which you have said it is, you have to list it when you do your load calculation even if you never use it.

Based on what you have said in your earlier posts, you have a disposer, dishwasher, washer, central air conditioner and an EVSE. Being a curious person, I did a quick calculation, assuming a 1500 square foot condo, and understanding your water heater, dryer and stove are gas. Of course I made some assumptions about how much power these devices use and your square footage. The EVSE is shown on the "other" part of the form. You did not mention heating, so I did not include any provision for heating in my load calculation.

And the load calculation I ran shows you are fine with 100 amp service. If you came up with about 25,000 watts of calculated load, perhaps there are other things that you have that you did not mention in your earlier posts.

Thanks for reading!

 

[Watts_Up]

Wow, three pages already on this topic!!!

My short answer, and what i would
If I didn't want to upgrade to a 200 A panel:

I would add a new 30A plug (24 A charging).
But I would use a relay to stop charging when the split air conditioning is running.

 

[Eric33432]

@jcanoe said it best. If you can live with the charging speeds he outlined, then just do a 20A/240V circuit.

Always best to do a load calculation. Then you KNOW what you can install.

 

[flai54]

Yes, I understand how split phase power works in North America. But if you have 100 amp service, I promise you that you only have 24,000 watts of power available if you have 240 volt service. If you submitted a load calculation showing about 25,000 watts of calculated load I am surprised the city would issue a permit to install your EVSE circuit.

That said, with the EVSE only pulling 32 amps and a relatively small air conditioner as your only 240 volt loads, I agree the 120 volt loads at your house will be minimal, and you are fine with 100 amp service.

To do a load calculation, you need to convert all your fixed in place appliances, air conditioners, motors, etc., to watts. If an appliance nameplate specifies how many amps it uses, you will multiply volts times amps and you will get the "volt-amps" for that appliance which for the purpose of the load calculation is the same as watts. For example, an air conditioner that draws 12 amps at 240 volts would be listed as using 2,880 watts (240 x 12). But a 120 volt dishwasher that uses 11 amps would be listed as using 1,320 watts (120 x 11).

Another thing that would not be allowed is for you to promise not to run the A/C, or any other heavy load, while you are charging your car. At least this would not be allowed by any jurisdiction I am aware of in the United States.

If your air-conditioning is window units, those would not need to be considered in your load calculation because they are not fixed in place appliances. But if your home is equipped with central air conditioning, which you have said it is, you have to list it when you do your load calculation even if you never use it.

Based on what you have said in your earlier posts, you have a disposer, dishwasher, washer, central air conditioner and an EVSE. Being a curious person, I did a quick calculation, assuming a 1500 square foot condo, and understanding your water heater, dryer and stove are gas. Of course I made some assumptions about how much power these devices use and your square footage. The EVSE is shown on the "other" part of the form. You did not mention heating, so I did not include any provision for heating in my load calculation.

And the load calculation I ran shows you are fine with 100 amp service. If you came up with about 25,000 watts of calculated load, perhaps there are other things that you have that you did not mention in your earlier posts.

Thanks for reading!

View attachment 982108

The 2 pictures below are a few pages out my local municipality EV permit application as part of the electrical permit process. On that 2nd page it says up to 48000 watts for a 100A service. Take this attachments of the Service Load Estimate and the audit that one has to do of their housing loads as you will. Not trying to get into a debate over what the local municipality has vetted.

By the way, the 27500 total watts I put down includes on the first page at the bottom under "Level 2 Electric Vehicle Charging rating" with 12000 watts (240V/50A) even though we know it will pull 32A max when using the Tesla mobile connector. But of course this is EVSE specific with the Tesla mobile connector so its best not to assume you will always have that since it can draw 40A with other EVSE units. In reality my non-EV watts estimate is really around 15500 potential watts. Again this is an estimate that they do and is not 100% exact science but they are mostly concerned with the heavy hitter circuits in a typical home.

Like I said in another post, my water heater, laundry dryer and kitchen stove are all gas based so that relives the majority of the strain of an electrical panel. The only thing other than the EV charger that uses 240V is the central AC condenser (13.8A nominal based on the spec sheet and verifying on the AC condenser label) which is on a 20A breaker.

The first page

The second page

 

[flai54]

Wow, three pages already on this topic!!!

My short answer, and what i would
If I didn't want to upgrade to a 200 A panel:

I would add a new 30A plug (24 A charging).
But I would use a relay to stop charging when the split air conditioning is running.

I don't think that is a good idea. Why not just add a new 30A breaker in the panel just dedicated to the EV charger. Your AC is already dedicated on its own breaker and won't draw current if it is not on. You are basically relying on a relay to do the switching for you when you shouldn't have to do that. I mean if you are charging late at night during off peak hours when you sleep, is that really a need?

 

[Eric33432]

Thanks for this. It explains our disconnect as we were each discussing different (although related) things.

This worksheet is NOT saying that 100 amp service will deliver 48,000 watts of electrical power. What it IS saying is that due to the fact that all loads are not all on at the same time, if the total of all devices in your home are 48,000 watts you need 100 amp service.

It is assuming the total load will be only 50% of the total of ALL devices in your home, just like the load calculation I did allows for derating due to the diversity of all the potential loads not being on at the same time.

The worksheet makes a reference to the type of load calculation I did in the "CAUTION" statement near the end of the second page.

As I said, you are good. But I did not want anyone reading this to somehow think 100 amp service would provide power equal to 48,000 watts. The electrical formula for that is very simple:

Power = volts x amps.

(Actually it is Volt Amps = volts x amps, but the two are close enough for the purposes of a load calculation.)

 

[Eric33432]

Wow, three pages already on this topic!!!

My short answer, and what i would
If I didn't want to upgrade to a 200 A panel:

I would add a new 30A plug (24 A charging).
But I would use a relay to stop charging when the split air conditioning is running.

Load calculation potentially shows such a relay is not necessary and that 32 amp charging is OK.

Really, in all these threads, the answer to the question being discussed can only be determined with a load calculation.

 

[flai54]

Thanks for this. It explains our disconnect as we were each discussing different (although related) things.

This worksheet is NOT saying that 100 amp service will deliver 48,000 watts of electrical power. What it IS saying is that due to the fact that all loads are not all on at the same time, if the total of all devices in your home are 48,000 watts you need 100 amp service.

It is assuming the total load will be only 50% of the total of ALL devices in your home, just like the load calculation I did allows for derating due to the diversity of all the potential loads not being on at the same time.

The worksheet makes a reference to the type of load calculation I did in the "CAUTION" statement near the end of the second page.

As I said, you are good. But I did not want anyone reading this to somehow think 100 amp service would provide power equal to 48,000 watts. The electrical formula for that is very simple:

Power = volts x amps.

(Actually it is Volt Amps = volts x amps, but the two are close enough for the purposes of a load calculation.)

Correct I understand what you said and glad we are on the same page now. But the reality is nobody is running everything at full capacity in their electrical panel anyways all day. I get that yes based on the calculation it should just be 24000 watts but they are doubling that since they are not expecting you to be running at 100% and maxing the full amperage on all your plugs and circuits in the house. 24/7 That is why like I said in an electrical panel lets say you have say 200A service you don't just have like 10 breakers of 20A that total of 200A since each breaker is not going to be running at full capacity just for normal house usage.

 

[Tronguy]

Minor comment. This idea of, "Not Everything Is In Use At The Same Time" carries over to lots of different places. In particular, telecommunications. On Ye Olde POTS systems, they were definitely not build for everybody going off-hook at the same time: Too Darned Expensive. Which led to typical situations (of which us older types have memories) of trying to call home on Mother's Day, or during a hurricane: No dial tone. Sometimes for hours. Or fast busy.

 

[Eric33432]

Minor comment. This idea of, "Not Everything Is In Use At The Same Time" carries over to lots of different places. In particular, telecommunications. On Ye Olde POTS systems, they were definitely not build for everybody going off-hook at the same time: Too Darned Expensive. Which led to typical situations (of which us older types have memories) of trying to call home on Mother's Day, or during a hurricane: No dial tone. Sometimes for hours. Or fast busy.

Or the old "Please Wait for Dial Tone" on some older phones. Old DMS 100 (among other switches) guy here. But my favorite is Panel, and I am old enough to remember the old revertive pulsing when calling between central offices in the big city I grew up in.