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One thing I really don’t get in the discussion around EVs and charging is, why are people so afraid of tripping the main breaker? If you have a total of e.g. 17 kW available and happen to go over, just reset the main breaker (or replace it in case it’s still a traditional one). It’s there precisely so that you wouldn’t need to care about overloading the connection.
In my experience people get by with a 3x25A (17 kW available, matches approximately a 70A service in the US) while using the available power to
heat/cool a single family home (in -20 °C weather mind you)
run all appliances (including the oven, stove, dryer etc.)
heat up a sauna
charge an EV
whatever else you typically would want to plug in, kettles and such
While it’s true you can trip the main breaker if you have everything on at the same time, typically it never happens even if there are no lockouts in place preventing overuse. And it’s not like tripping it causes any permanent harm.
Why is an electrical service upgrade constantly brought up as a solution when any home with >15 kW of available power won’t need it? Is it against code to purposefully overcommit your mains in the US or something?
Edit: there were valid concerns raised over how long-lived the breakers are (probably won’t be rated for tens of fault-condition related trips), also that these smaller service specs aren’t as common as I’ve gathered from the media. That might have something to do with this at least. Thanks for the replies – it’s been an interesting discussion.
why are people so afraid of tripping the main breaker?
Not everyone know as much as electricity as you, I think is natural to be afraid of something you not know so much and that potentially can burn your house.
In my experience people get by with a 3x25A (17 kW available, matches approximately a 70A service in the US)
Wow, how do you do that?
Of course over-provisioning is a thing but that’s crazy. Maybe you have much smaller appliances or assume much lower usage, but 70a basically assumes 2 major appliances at a time, using close to max load, and with nothing else turned on.
Typical 240v major appliances
level 2 EV charger: 50a
stove: 50a
central ac: 40a
dryer: 40a
heat pump: 50a+
water heater: 50a
Of course you won’t use them all at once and they won’t usually be drawing their full rated load but I would not want to deal with being limited to one at a time so I can also turn on the lights or use the microwave
That can theoretically draw 280a, before you even count things like lights and small appliances. If you added up all possible circuits, you may be hitting 1000a theoretical in a modern house. I’m comfortable that My 200a service will handle any combination I might use, but 70a definitely not
By contrast I once lived in an apartment with 60a service. It did not have most of these large appliances but I frequently tripped the main with combinations like stove + window ac + microwave + lights
As a European those power draws listed sound absolutely absurd to me. I mean, I can easily believe you, but a stove pulling 50 A at 240 V, so 12 kW, sounds like a complete overkill in normal use. The dryer power use also sounds comically high, when viewed from a country where heat pump dryers are the norm.
Let’s go for a standard single family home example. Level 2 charger is either 8 A (5.5 kW) or 16 A (11 kW) three phase. On top of that, typical sauna is 6-7.5 kW, 1-2 heat pumps (approx. 1.5 kW a piece), stove (8.5 kW max), water heater (2-3 kW), + other appliances like dishwasher, washing machine etc.
It would seem like that easily trips the breaker, but you won’t be charging the car and warming up the sauna at the same time, unless opting to 5.5 kW charging. However, you typically charge the car at night, when the other things running are the heat pumps and the water heater – this will end up drawing around 16 kW total (in the worst case scenario) which fits in the limit. When you don’t count the car into the mix, there’s plenty of power to go around.
There are multiple reasons behind this. One is our homes are relatively well insulated, which means that we can get by with a lot less AC and heating. Appliances in the EU are also generally more efficient – as an example, our dryers are typically based on heat pumps and pull a lot less amperage for the same performance. Lot of homes also don’t have a dryer. Stoves have generally lower power requirements as well, and practically never draw peak power. Here’s an example washer+dryer combo where the suggested fuse for the whole thing is 10 A (meaning 2.3 kW available for the combo).
So listing the same appliances you have (at 230 V single phase equivalent for simplicity, i.e. 75 A available (3 * 25))
level 2 EV charger: 24-48 A depending on chosen speed
stove: 20 A
Heat pumps (also used for AC) worst case scenario approx. 15 A, practically only reached for longer periods in extreme cold
dryer and washing machine: 10 A
water heater: 16 A
Which will result in 79 A total worst case or 103 A depending on the car charger spec. A bit over the 75 A available, and not calculating additional smaller loads like the microwave, kettle, TV, lighting etc. That worst case will in practice never be reached, though, and even the main breaker typically has some tolerance before it trips (usually main breaker is using a slow-blow fuse equivalent profile, which doesn’t immediately trip with a minor overload or a short spike). Our code mandates enough tolerance in wiring gauges that this doesn’t pose any risk.
Why don’t we want the added headroom then? Upgrading the service from 3x25A to 3x35A isn’t really that expensive in urban areas, and can be done relatively simply? Well – Finns are stingy and depending on who happens to own your local distribution grid you can get heavily penalized monetarily in the long term, when upgrading the service to a higher tier. Caruna owns a lot of the Finnish distribution grid nowadays, and as an example from their pricing chart going from 3x25A to 3x35A raises your monthly base rate from 29.71 € to 51.68 €. That’s 240 € extra per year, which is a pretty high cost for a just in case that’s easily avoided. In cities that still have municipally owned distribution (Lahti, Turku, Helsinki as an example) the costs are typically much lower, both for upgrading the service and monthly costs, compared to the privately owned grids.
Then you’d round up to the nearest service level. Realistically, I believe most recent-ish houses are 200a service now with larger ones or hot climates tending to 300a+
At least here the electrical service base rate is largely set by the max amperage you can draw from the grid. I’ll use my own home’s electricity cost breakdown as an example (all listed prices, even the additional tax, include our 25.5 % VAT)
Monthly base rate for your main breaker, depends on your grid operator – mine is 7.63€ for 3x25 A connection (among the cheapest grids in Finland, I previously used another example often seen in smaller cities, which is 29.71 €/month)
Transfer costs, 0.0187 €/kWh during day, 0.0089 €/kWh during night
Electricity tax, 0.0282752 €/kWh, includes national energy security taxes as well
Cost of the actual electricity, typically ranges from -0.05 €/kWh to 0.20 €/kWh with yearly average being about 0.055 €/kWh
Electricity company’s margin for spot prices, 0.004 €/kWh
Electricity company’s base rate, 4.90 €/Month
For many cities in Finland the base rate for grid connection is considerably higher, and especially for apartments tends to be the majority of your electricity bill outside major urban centers. Even in cities it makes up a large percentage, so there’s a big incentive to not overspec your service.
The way that it works in most countries is that the breakers are per circuit in your wall. The breakers trip in order to prevent that single circuit from overheating and starting a fire in your walls.
Let’s say you have a wire that’s rated for 16amps. More than that and it becomes a fire risk just threw overheating. @230v that gives you 3680w per circuit.
If you have your industrial microwave, water heater, and car charger all going at the same time on that same circuit. This will draw way more than 3680w and thus would go over that 16a limit.
The breakers trips once you go over that 16a limit for safety. It’s a good thing. This all being said no sane electrician would put those three things on the same circuit. lol.
Circuit breakers are actually what enable you to safely over provision. Without them fires would just be a matter of time.
I know it works this way in the U.S. and Germany at least.
Also worth noting that breaker ratings are for instantaneous usage. A 15A 120v breaker can only actually support 12A of continuous usage. But it says 15, because most things use a little extra power when they first turn on. AC system spinning up the fans and compressor, for instance. Spinning things up takes more power than keeping it moving. If you put a 15A device on a 15A breaker, it would likely trip as soon as that device turned on. In that instance, you’d likely use a 20A breaker to support the 15A device instead. But that 20A breaker would also call for upgraded wiring and outlets which could support 20A.
Ok – that works a bit differently for our code then. Standard breakers are 10 A and 16 A, which means 10 A and 16 A constant load. Load characteristics affect which profile you use, typical residential alternatives are B and C profile breakers. B trips quicker, C trips slower and is meant for circuits with more reactive load characteristics. 16 A C profile breaker can take up to an hour to trip under 18-19 A load as an example. Your standard breaker can deal with quite a lot of inrush current – even with the faster B profile.
Wiring is built to withstand approximately 15 A when using a 10 A breaker, and 20 A when using a 16 A breaker. As such, the fuses display the value for constant loads, not for the peak. The most commonly used outlets in the EU (i.e. Schuko) are rated for 8 A continuous, 16 A peak, and are typically put on a 16 A circuit. 10 A circuits are mainly used for lighting nowadays, at least in Finland – 16 A being the standard for most things.
The voltage difference might have something to do with this, as 230 V will be capable of driving much more power though a potential short. As such any actual fault condition will most likely cause the fuse to trip quite quickly. Also current code mandates GFCI on all outlets in a house, which will help with smaller faults that aren’t enough for the breaker to trip.
Not talking about the circuits, but the main electrical connection to the grid. To me it often seems like there’s reluctance in overcommitting overprovisioning that capacity: as an example, four 16A circuits on a 25A main breaker. Here that’s quite common, but even in Tech connections videos I’ve seen him bring up smart electric cabinets or automatic load monitoring when putting enough capacity on the mains to possibly go over.
What I’m asking is, why bother? If you trip the mains by having too much load, just reset the breaker and be done with it. No need to automate things to not run into that situation, one will learn to not have the oven on while charging the car full blast. No need to gimp the charger amperage since you’re running a new circuit anyway, and it’s not like it’s much different running a 20A circuit vs a 40A one. If that’s 70% of your total available capacity, it doesn’t matter – worst you have to do is walk downstairs and flip a switch.
Sometimes breakers don’t trip, so there’s a small risk of fire
Restarting the whole house may have large initial loads as everything starts at once: more chance of it happening again or potentially damaging some appliances
Risk of heat damage to wiring with repeated trips, risk of broken connections from more frequent expansion from heat/cool cycles
Inconvenience, especially in the old days when you’d have to go through to set clocks. If while asleep you might not be awoken in time. If you weren’t home, maybe food gone bad
Occasional home health appliances are critical to keep going
Realistically it comes down to how conservative you are with over-provisioning. You might also expect it to handle the load for 50 years of growing usage. In the US we have the expectation of rarely to never tripping the main and when that happens it’s more likely an electrician call
Hadn’t considered that one TBH, no practical limits with actuations (rated in the thousands) but they’re probably not rated for that many trips under a fault condition – now I’m curious, will have to dig up a spec sheet at some point
Not really, unless you have equipment that’s poorly designed everything should be fine. It’s not much different from a brownout, and things should be configured to deal with that anyways if you don’t have a UPS
If there are a lot of reactive loads, then yes – e.g. electric motors, large capacitors. Those will have a large inrush when started again. Typically there isn’t that much reactive loading in a residential home though, and it should be covered by the latency designed into the breaker.
The first point is actually a really good one, and one I didn’t really remember to consider. I’d guess it has at least something to do with that (and would explain why many homes around here are still configured with traditional fuses for the main connection – no need to worry about lifetime when you have to replace them anyways)
I don’t think overprovisioning is a thing that is realistically is a problem in the U.S. or in Germany. I know that modern homes tend to have 300amp mains. Older homes 100amps. You would have to have a house that was wired in 1920 in order to have a 20amp mains available. In that case you have bigger issues safety wise.
One thing I really don’t get in the discussion around EVs and charging is, why are people so afraid of tripping the main breaker? If you have a total of e.g. 17 kW available and happen to go over, just reset the main breaker (or replace it in case it’s still a traditional one). It’s there precisely so that you wouldn’t need to care about overloading the connection.
In my experience people get by with a 3x25A (17 kW available, matches approximately a 70A service in the US) while using the available power to
While it’s true you can trip the main breaker if you have everything on at the same time, typically it never happens even if there are no lockouts in place preventing overuse. And it’s not like tripping it causes any permanent harm.
Why is an electrical service upgrade constantly brought up as a solution when any home with >15 kW of available power won’t need it? Is it against code to purposefully overcommit your mains in the US or something?
Edit: there were valid concerns raised over how long-lived the breakers are (probably won’t be rated for tens of fault-condition related trips), also that these smaller service specs aren’t as common as I’ve gathered from the media. That might have something to do with this at least. Thanks for the replies – it’s been an interesting discussion.
Where I live, there is a pole fuse, which is, as the name implies, on the pole, and only a linesman can change it.
Massive pain in the ass if that pops.
Not everyone know as much as electricity as you, I think is natural to be afraid of something you not know so much and that potentially can burn your house.
Wow, how do you do that?
Of course over-provisioning is a thing but that’s crazy. Maybe you have much smaller appliances or assume much lower usage, but 70a basically assumes 2 major appliances at a time, using close to max load, and with nothing else turned on.
Typical 240v major appliances
Of course you won’t use them all at once and they won’t usually be drawing their full rated load but I would not want to deal with being limited to one at a time so I can also turn on the lights or use the microwave
That can theoretically draw 280a, before you even count things like lights and small appliances. If you added up all possible circuits, you may be hitting 1000a theoretical in a modern house. I’m comfortable that My 200a service will handle any combination I might use, but 70a definitely not
By contrast I once lived in an apartment with 60a service. It did not have most of these large appliances but I frequently tripped the main with combinations like stove + window ac + microwave + lights
As a European those power draws listed sound absolutely absurd to me. I mean, I can easily believe you, but a stove pulling 50 A at 240 V, so 12 kW, sounds like a complete overkill in normal use. The dryer power use also sounds comically high, when viewed from a country where heat pump dryers are the norm.
Let’s go for a standard single family home example. Level 2 charger is either 8 A (5.5 kW) or 16 A (11 kW) three phase. On top of that, typical sauna is 6-7.5 kW, 1-2 heat pumps (approx. 1.5 kW a piece), stove (8.5 kW max), water heater (2-3 kW), + other appliances like dishwasher, washing machine etc.
It would seem like that easily trips the breaker, but you won’t be charging the car and warming up the sauna at the same time, unless opting to 5.5 kW charging. However, you typically charge the car at night, when the other things running are the heat pumps and the water heater – this will end up drawing around 16 kW total (in the worst case scenario) which fits in the limit. When you don’t count the car into the mix, there’s plenty of power to go around.
There are multiple reasons behind this. One is our homes are relatively well insulated, which means that we can get by with a lot less AC and heating. Appliances in the EU are also generally more efficient – as an example, our dryers are typically based on heat pumps and pull a lot less amperage for the same performance. Lot of homes also don’t have a dryer. Stoves have generally lower power requirements as well, and practically never draw peak power. Here’s an example washer+dryer combo where the suggested fuse for the whole thing is 10 A (meaning 2.3 kW available for the combo).
So listing the same appliances you have (at 230 V single phase equivalent for simplicity, i.e. 75 A available (3 * 25))
Which will result in 79 A total worst case or 103 A depending on the car charger spec. A bit over the 75 A available, and not calculating additional smaller loads like the microwave, kettle, TV, lighting etc. That worst case will in practice never be reached, though, and even the main breaker typically has some tolerance before it trips (usually main breaker is using a slow-blow fuse equivalent profile, which doesn’t immediately trip with a minor overload or a short spike). Our code mandates enough tolerance in wiring gauges that this doesn’t pose any risk.
Why don’t we want the added headroom then? Upgrading the service from 3x25A to 3x35A isn’t really that expensive in urban areas, and can be done relatively simply? Well – Finns are stingy and depending on who happens to own your local distribution grid you can get heavily penalized monetarily in the long term, when upgrading the service to a higher tier. Caruna owns a lot of the Finnish distribution grid nowadays, and as an example from their pricing chart going from 3x25A to 3x35A raises your monthly base rate from 29.71 € to 51.68 €. That’s 240 € extra per year, which is a pretty high cost for a just in case that’s easily avoided. In cities that still have municipally owned distribution (Lahti, Turku, Helsinki as an example) the costs are typically much lower, both for upgrading the service and monthly costs, compared to the privately owned grids.
Aside from the heat pump we have all of these things and they’re often running all at once. Never had an outside
There’s a standard
Then you’d round up to the nearest service level. Realistically, I believe most recent-ish houses are 200a service now with larger ones or hot climates tending to 300a+
At least here the electrical service base rate is largely set by the max amperage you can draw from the grid. I’ll use my own home’s electricity cost breakdown as an example (all listed prices, even the additional tax, include our 25.5 % VAT)
For many cities in Finland the base rate for grid connection is considerably higher, and especially for apartments tends to be the majority of your electricity bill outside major urban centers. Even in cities it makes up a large percentage, so there’s a big incentive to not overspec your service.
The way that it works in most countries is that the breakers are per circuit in your wall. The breakers trip in order to prevent that single circuit from overheating and starting a fire in your walls.
Let’s say you have a wire that’s rated for 16amps. More than that and it becomes a fire risk just threw overheating. @230v that gives you 3680w per circuit.
If you have your industrial microwave, water heater, and car charger all going at the same time on that same circuit. This will draw way more than 3680w and thus would go over that 16a limit.
The breakers trips once you go over that 16a limit for safety. It’s a good thing. This all being said no sane electrician would put those three things on the same circuit. lol.
Circuit breakers are actually what enable you to safely over provision. Without them fires would just be a matter of time.
I know it works this way in the U.S. and Germany at least.
Also worth noting that breaker ratings are for instantaneous usage. A 15A 120v breaker can only actually support 12A of continuous usage. But it says 15, because most things use a little extra power when they first turn on. AC system spinning up the fans and compressor, for instance. Spinning things up takes more power than keeping it moving. If you put a 15A device on a 15A breaker, it would likely trip as soon as that device turned on. In that instance, you’d likely use a 20A breaker to support the 15A device instead. But that 20A breaker would also call for upgraded wiring and outlets which could support 20A.
Ok – that works a bit differently for our code then. Standard breakers are 10 A and 16 A, which means 10 A and 16 A constant load. Load characteristics affect which profile you use, typical residential alternatives are B and C profile breakers. B trips quicker, C trips slower and is meant for circuits with more reactive load characteristics. 16 A C profile breaker can take up to an hour to trip under 18-19 A load as an example. Your standard breaker can deal with quite a lot of inrush current – even with the faster B profile.
Wiring is built to withstand approximately 15 A when using a 10 A breaker, and 20 A when using a 16 A breaker. As such, the fuses display the value for constant loads, not for the peak. The most commonly used outlets in the EU (i.e. Schuko) are rated for 8 A continuous, 16 A peak, and are typically put on a 16 A circuit. 10 A circuits are mainly used for lighting nowadays, at least in Finland – 16 A being the standard for most things.
The voltage difference might have something to do with this, as 230 V will be capable of driving much more power though a potential short. As such any actual fault condition will most likely cause the fuse to trip quite quickly. Also current code mandates GFCI on all outlets in a house, which will help with smaller faults that aren’t enough for the breaker to trip.
Not talking about the circuits, but the main electrical connection to the grid. To me it often seems like there’s reluctance in
overcommittingoverprovisioning that capacity: as an example, four 16A circuits on a 25A main breaker. Here that’s quite common, but even in Tech connections videos I’ve seen him bring up smart electric cabinets or automatic load monitoring when putting enough capacity on the mains to possibly go over.What I’m asking is, why bother? If you trip the mains by having too much load, just reset the breaker and be done with it. No need to automate things to not run into that situation, one will learn to not have the oven on while charging the car full blast. No need to gimp the charger amperage since you’re running a new circuit anyway, and it’s not like it’s much different running a 20A circuit vs a 40A one. If that’s 70% of your total available capacity, it doesn’t matter – worst you have to do is walk downstairs and flip a switch.
Realistically it comes down to how conservative you are with over-provisioning. You might also expect it to handle the load for 50 years of growing usage. In the US we have the expectation of rarely to never tripping the main and when that happens it’s more likely an electrician call
The infinitely easier solution is to let the car charger know how much power is available to draw.
Well, true. Fair enough
ADHD guy here.
Wondering if these are reasons but need someone knowledgable to answer
one of us
The first point is actually a really good one, and one I didn’t really remember to consider. I’d guess it has at least something to do with that (and would explain why many homes around here are still configured with traditional fuses for the main connection – no need to worry about lifetime when you have to replace them anyways)
I don’t think overprovisioning is a thing that is realistically is a problem in the U.S. or in Germany. I know that modern homes tend to have 300amp mains. Older homes 100amps. You would have to have a house that was wired in 1920 in order to have a 20amp mains available. In that case you have bigger issues safety wise.