We have a Tesla solar + 3 PW system and right now everything in the house is backed up. We had the system put in nearly two years ago so they moved all the circuits from the main panel and a sub panel to feed from a new backup panel. We are now looking to add an electric hot tub 40A 220 but which I don't want backed up. Is it as simple as adding that to the main panel which for now has a single big breaker at the top and no individual circuits?
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Adding a hot tub after whole house Solar + Powerwalls, don't want it backed up
- Thread starter Cstreet
- Start date
aesculus
Still Trying to Figure This All Out
IMHO the answer is yes but we can get others to verify or refute my claim.
On my PW install Tesla moved all of my circuits, except my HPWC, from my main panel to the backup load panel. So in my case the only circuit that is not backed up and will only work if the grid is active is my HPWC. This would be the same as your hot tub.
But what I cannot tell you is what action might need to take place with your CT's. In my case I have an aggregated house load with whatever is in the backup circuit plus the HPWC. Not sure how that is done though. So Tesla or your installer MAY need to come and move some CT's around.
The answer is likely a "qualified yes", but depends on your specific configuration. I know in my case, with a setup similar to what you describe (its actually exactly like @aesculus mentions theirs is, with everything but my Tesla wall connector backed up), if I wanted to add anything at all from an electrical perspective, it would need to go in my "main" panel which has the HPWC, and my main breaker, and thats it.
Absent further analysis, the answer is no, no loads are to be supplied by the main panel.
For a service panelboard with a bus rated X (typically 100, 125, 150, 200, or 225), a main breaker rated X, and a branch breaker rated X supplying the Gateway, the 2017 NEC does not allow any other breakers in that panel (*). That is not to say that adding a single breaker to that panel actually provides an opportunity for the bus to be overloaded. But the NEC provides a limited set of rules for ensuring that the bus is not overloaded, and that configuration does not fit any of them.
(*) Unless the inverter continuous output current ratings sum to no more than 16% of X, e.g. X=200 and there's only one Powerwall (24A) and the only PV inverter is 1.92 kW (8A) or smaller.
The 2020 NEC recognizes that the Powerwall can be configured to limit the total export from the Gateway, which allows for some additional options, but that would require further details and consideration.
Cheers, Wayne
For a service panelboard with a bus rated X (typically 100, 125, 150, 200, or 225), a main breaker rated X, and a branch breaker rated X supplying the Gateway, the 2017 NEC does not allow any other breakers in that panel (*). That is not to say that adding a single breaker to that panel actually provides an opportunity for the bus to be overloaded. But the NEC provides a limited set of rules for ensuring that the bus is not overloaded, and that configuration does not fit any of them.
(*) Unless the inverter continuous output current ratings sum to no more than 16% of X, e.g. X=200 and there's only one Powerwall (24A) and the only PV inverter is 1.92 kW (8A) or smaller.
The 2020 NEC recognizes that the Powerwall can be configured to limit the total export from the Gateway, which allows for some additional options, but that would require further details and consideration.
Cheers, Wayne
With your timeframe of installation, I assume you have the Gateway 1 (grey box that looks like your other subpanels) and not the Gateway 2 (black box with glass face on it)
The GW1 does not have an easy way to add non-backup loads. However the GW2 does, and so might be your easiest way to do this upgrade. Unfortunately the old CT's are not compatible with the new CT's so those will also need to change, which should be simple.
Any way you slice it will be something like $1-2k to add the capacity to put this on the non-backup side. Another option would be a large 400A subpanel with 200A subfeed inserted between the GW and the MSP, or a 225A panel with a 175A subfeed done the same way.
The GW1 does not have an easy way to add non-backup loads. However the GW2 does, and so might be your easiest way to do this upgrade. Unfortunately the old CT's are not compatible with the new CT's so those will also need to change, which should be simple.
Any way you slice it will be something like $1-2k to add the capacity to put this on the non-backup side. Another option would be a large 400A subpanel with 200A subfeed inserted between the GW and the MSP, or a 225A panel with a 175A subfeed done the same way.
You say that you don't want the hot tub to be backed up, but do you really mean that you don't need the hot tub to be backed up? If you have space for the new 40A 2P circuit breaker in the new panel where all the circuits moved, just add it there and don't turn on the hot tub during a grid outage. If that panel is full but you have an existing 40A 2P circuit breaker you could change that one out for a quad 40A breaker to supply both circuits.
Another option for keeping the hot tub deenergized during an outage is to put it behind the Gateway with a load shed device that kills power when the grid is out.
Cheers, Wayne
Cheers, Wayne
Do you have an example of such a device that you have used for a 40A 2P circuit and worked well?
No, I know more theory than practice, but surely they exist? The tricky thing NEC wise would be to get a signal from the grid side of the Gateway, as additional breakers are not to be added to the service panel (for the general case).
One example of the inconsistency of the rules in NEC Article 705 is that an unbacked up loads main breaker panel can be added by intercepting the feeder from the service panel to the Gateway with, say, 3 port polaris connectors for a splice. [If a 200A main breaker panel with sub feed lugs, or double lugs on the main breaker, were available, that would be even easier.] Even though electrically that feeder with splice would be equivalent to a panel busbar with just 3 breakers (including the main breaker), the rules for wire type feeders and for busbars are different.
Cheers, Wayne
PS FWIW, I proposed a 2023 amendment to 2020 705.12(B)(3) to expand it slightly by excluding the main breaker plus one breaker of the smallest size present. That allowance would be directly useful in a situation like this, and still protects the busbar from overload (obvious in the case of just 3 breakers total (including main), but true in general). Unfortunately, I doubt it will be adopted; the initial committee response was "Adding additional features to this very simple rule creates unnecessary confusion for the enforcement and marking requirements." Which I took to mean "the full set of electrically safe configurations is too hard to describe, so we'll stick with the easier to describe subsets currently allowed."
I have always assumed the difference in levels of code enforced safety with what is otherwise electrically similar to be more about breakers being an easy plug-on device, and code users expect backyard repairs and additions with new breakers regardless of rules. Tapping a 200A Feeder with polaris connectors to make a new service is significant, and not a typical backyard upgrade I hope.
Getting the voltage sense otherwise might be able to be read wirelessly from the smart meter, but there isn't an easy NEC compliant way otherwise to do it with those 100% rule panels.
PS: I am just stepping into the world of code making and going to my first IAEI meeting in a couple weeks. It's been interesting to see how the sausage is made.
The first piece of code I helped to write is getting comments which we have addressed: https://www.iccsafe.org/wp-content/uploads/IFC-2021-Group-A-2021-Group-A-Aug-13.pdf See F155-21
We have in the meantime made and installed some truly awesome 12k bollards! I turned my frustration with this process into real code that is widely accepted and snuck in a couple of model 3's in the garage image while I was at it. It was interesting to see earlier, draft images of this turn up at various building departments.
RKCRLR
Active Member
I have a hot tub with a whole house backup. I was considering making it so the hot tub didn't run when the power is out. I manually control that now during an outage by flipping the breaker. But that doesn't work if I'm not at home.
My hot tub controller has a low amperage fuse inside the controller box that makes the hot not not run when it is blown. Depending on the model yours may even have some terminals to control it.
I was considering replacing the fuse with an inline fuse and relay. If your Gateway has load shedding terminals (mine does but I don't know if they all do), the terminals could be used to control the relay. But I haven't done much more than thinking about it.
My hot tub controller has a low amperage fuse inside the controller box that makes the hot not not run when it is blown. Depending on the model yours may even have some terminals to control it.
I was considering replacing the fuse with an inline fuse and relay. If your Gateway has load shedding terminals (mine does but I don't know if they all do), the terminals could be used to control the relay. But I haven't done much more than thinking about it.
aesculus
Still Trying to Figure This All Out
Some of us have circuitry that cannot be isolated and therefore gets backed up. It's the price you pay, but the events are rare enough it hardly counts.
Ideally there would be a way to remotely (ie no wires) isolate certain devices but my fairly extensive investigation in this domain returned sketchy results. Some solutions work for very specific environments but nothing works in every situation. Still a virgin industry.
None of my whole house stuff can be isolated. My spa is and everything else is connected to whole house. One cannot design for every possible situation.
Sounds like poster might want something like this : grid goes down, hut tub running, kill hot tub.
Could try a relay attached to somewhere on the supply side of the gateway (E. G. Feeder) with relay (NC) output run to a shunt trip breaker installed for the hot tub. Use opto isolator or whatever ppl think is need to separate the relay which is being used here as a sensor. Or maybe some o ne knows of say a CT triggered output to use as a sensor.
Could try a relay attached to somewhere on the supply side of the gateway (E. G. Feeder) with relay (NC) output run to a shunt trip breaker installed for the hot tub. Use opto isolator or whatever ppl think is need to separate the relay which is being used here as a sensor. Or maybe some o ne knows of say a CT triggered output to use as a sensor.
I did something "similar". Everything in house is backed up (including HPWC) except for one of my AC units (lower level which doesn't need to be on if upper level is cooled). That 2nd AC unit breaker was left in my main panel, all other circuits were moved to a new sub-panel and are being backed up in the event of an outage. I wanted to add a new 24V NEMA 14-50 outlet and charger (Wallbox) in preparation for a second EV (Rivian R1S) and wanted to take advantage of the 30% tax credit for this year. For me it was as simple as adding a new 50AMP breaker and running 6/3 wire in a conduit in my garage to a new outlet. The one issue I found is that when Tesla installed the system, they didn't put Neurio CTs around the incoming power from the Grid in my old panel, they only put the CT around the remaining breaker for the AC unit. This means that the new outlet is not being monitored. Research on here has shown that I "should" be able to double up the loads from the two breakers through the CTs to be able to measure the sum of the loads. That'll be this weekend's project to test.
So what is the bus rating of your main panel, and what size are all the breakers in it? I count 4 now--main breaker, A/C breaker, breaker for 14-50 receptacle, and breaker supplying the Gateway and new subpanel.
Cheers, Wayne
My Main Panel is 200Amp. The only breakers left in my main panel are AC (40A), new 14-50 outlet (50A), Gateway (don't recall amperage) and one that the Neurio is connected to (Don't recall amperage, but draw has to be VERY low for Neurio).
The NEC has some requirements to ensure that your main panel 200A busbar is not overloaded. [Check the label closely, there's a chance the busbar is 225A even though the main breaker is 200A.] Now, in practice, with only 2 sources of supply (the grid and the Gateway), and only 3 load breakers that add up to less than 200A, there's no way for that busbar to be overloaded.
However, the NEC options for compliance are more limited and don't include adding up the possible load breakers as above. So assuming a 200A busbar, there are just 2 possible options:
a) All the breakers except the main add up (per leg) to 200A or less. That would work if your Neurio breaker is 10A and your Gateway breaker is 100A.
b) The Gateway is configured to never allow more than 32A continuous to flow towards the grid from it. [That's a new compliance allowance in the 2020 NEC, and CA is on the 2017 NEC, but many AHJs are allowing its use early.] The Gateway breaker needs to be at the opposite end of the bus from the main breaker.
The reason I bring this up is that you mentioned adding the 50A breaker for the 14-50 receptacle. If prior to that the configuration was 40A A/C breaker, 10A Neurio breaker, and 150A breaker for the Gateway (or perhaps more likely, 40A / 15A / 125A), then it was compliant under option (a). And by adding that 50A breaker, it's no longer compliant. In this case, it's a technical violation that doesn't actually allow the main panel bus to be overloaded.
Cheers, Wayne
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