You gotta be kidding me. Electricians won't add a Tesla wall connector on the backup side of ESS

[dareed1]

We have a 2100 sq ft house built in 1968. Since then we have added R-38 in the ceiling, double pane windows, and perhaps 1/2 of the walls are now insulated due to various remodeling. We installed a 2.5 ton Mitsubishi heat pump. I had to insist on such a small system (contractor recommended 3.5 or larger), and I did my own Manual J calculation using CoolCalc. It is free, but I paid $10 to allow me to output the calculations to a PDF file. Gathering the data for a Manual J calculation involves finding out the thermal properties and size of windows and the dimensions of the house. It took me a couple of hours to get through everything. The reason I wanted a small capacity heat pump is that smaller ones tend to be more efficient, and I want the PWs to last for a while during a power outage. I did the calculation myself to give me confidence that the numbers were reasonably correct.

I installed solar panels plus PWs first, while we still had a gas-fired furnace. Historical usage was about 12-14kWh per day, and Tesla recommended a 4kW solar system. I told Tesla that we planned to switch from a gas furnace to the heat pump, so they were willing to spec a 8kW system. I told the Tesla installers that I would need space in the electrical panel for a 20A breaker (240V) for the heat pump. They left the space, but still put the Add No Loads sticker on the panel. Later the HVAC contractor had no concerns installing an additional 20A breaker to power the heat pump in spite of the stickers.

That is a feature of inverter based compressors--low starting current. Mitsubishi doesn't even provide a LRA spec, but they do spec the recommended breaker size.

 

[zƬesla]

Mitsubishi doesn't even provide a LRA spec

They do provide it. For example, you can find the L.R.A. for the M-Series in the catalog (https://www.mitsubishipro.com/pdfs/m-series-catalog.pdf) and possibly the spec sheets as well. Or did you mean something else?

 

[dareed1]

That's a document from 2016. Here's the 2020 catalog: https://hvacdirect.com/hvac/pdf/Mitsubishi_Electric_M_and_P_Catalog_Spring_2020.pdf
The heat pump we installed (SUZ-KA30NA2 outdoor + SVZ-KP30NA indoor) was released in 2019, I believe.
I don't see a LRA spec in the newer literature. As part of the discussion regarding heat pump capacity, our contractor sent some more detailed performance curves, and that document also does not list LRA.

 

[CrazyRabbit]

..
View attachment 637545

perhaps the top breakers are miss labeled, as they are all 240v (trip in pairs).

@holeydonut
i wouldn't back the car charger...
look at page 54, using the non backup terminals in the gateway. or page 55 and add a non backup loads sub panel connected back to your main service panel and adding the CT so the load can be accounted for when using batteries on the grid.

 

[CrazyRabbit]

of the installation manual:
https://www.tesla.com/sites/default...erwall_2_AC_GW2_NA_EN_Installation_Manual.pdf

 

[jjrandorin]

perhaps the top breakers are miss labeled, as they are all 240v (trip in pairs).

Nothing is mis labeled, they do trip in pairs.

 

[MikeHolliday]

I do not believe this is a Sunrun issue. The Issue lies in the fact that he truly may not be able to add an additional load based on the total existing loads. In order to add a 50 Amp or 60 Amp breaker you may need to increase the size of the main panel and add a subpanel which then will effect your Sunrun System. Charging a Car and HVAC are considered Constant Loads. Constant loads are any loads that can last 3 or more hours. When calculating a circuit requirement instead of using the 80% as with most circuits, a Constant Load uses the 75% rule. So, if you have a HVAC circuit that requires 50 Amps then it must be on a 70 Amp breaker as shown in the above main panel and the wire must be rated for 70 Amps. I have seen a lost of people on this Forum trying to be electrical engineers. I highly suggest that you have a qualified individual look at the system. It may require the items that I mentioned above and then having Sunrun come back to make changes to their system to support the changes that were made. I have been involved with many Sports Venues prior to my retirement and when the equipment would arrive we would find that the individual responsible for the power requirement did not follow though with their responsibilities. Preplanning is vital and should always include expected changes over the next 10 to 15 years, adding outdoor kitchens, pools, saunas, heat driveway & walkways, electric cars, etc. They all be ground to a haul from failure to plan in advance...

 

[holeydonut]

I have seen a lost of people on this Forum trying to be electrical engineers. I highly suggest that you have a qualified individual look at the system.

Yeah I asked the mods to change the title of this post; Sunrun isn't the problem... the issue I'm having is qualified electricians don't want to touch the system since they're afraid of lawyers and liability/risk. My problem is I can't find a qualified individual because the Powerwall experts are all busy installing Powerwalls. And the run of the mill electricians are scared of the new tech.

This issue can be disaggregated into four sub-problems.


1) With the utility running, would a Tesla Gen 3 HPWC be ok for the home? The answer to this is yes. With my class 200 service and a properly set up 200A load, the NEC calc seems to support it. I even assume the air conditioners operate well above their nameplate rating RLA. Tesla's manual on their Gen 3 HPWC indicate it can't pull more than 48A on its max setting.

2) If the utility fails, would the loads explode my 3x Tesla Powerwalls? I think we have beat this topic to death in various threads here; but if I lose power while my house is on full load it's likely the Powerwalls are going to shut down even if the EV charger isn't running. I don't think Sunrun, myself, or Elon Musk intended a reasonably sized Powerwall backup to supply a home @ full load. But even in the absolute worst case scenario... the Powerwalls will go into that naughty-time-out mode which should give me a chance to manually load-shed my oven, stove, etc. I don't think the Powerwalls will explode or rupture like what someone may envision with a cobbled together array of car batteries.


3) Would Sunrun allow someone to touch "their equipment"? This shouldn't even be a thing. Sunrun doesn't own any of it. I made sure the guy on site installed the right sized conductors between the TEG2 and 200A Backup panel in the original pic. The original design of the system from Sunrun had the wrong sized copper conductor, but I asked for that change after posting here on TMC. But alas, I'm the idiot who didn't have the Tesla EV charger installed before Sunrun did their thing. Dumb. dumb. dumb.


4) Would an electrician be ok putting in a Tesla Gen 3 HPWC into that 200 A panel? Yes ... they said it looks super easy. I even have a giant gutterbox they can use instead of running anything in the wall. They just don't want to risk it since they personally don't know how Powerwalls would behave if overloaded, and they don't want to get into a litigation-issue with Sunrun.


PS. Contra Costa County requires a separate permit/inspection for any EV charger where the OCPD is over 50A. 50A and below can be e-permitted without the CAD stuff. So I guess the 5th issue is that a Tesla Gen 3 HPWC at its max setting has a way tougher permitting process and cannot be "owner/built".

 

[MikeHolliday]

There is your problem. By Code you cannot exceed 80% of total capacity of your Main Breaker. You need a minimum of a 250 Amp Service. 250 Amps times .80 equals = 200 Amps. So you barely squeak through with a 250 Amp Service. I had this exact situation and had to put in a new 225 Amp - 42 circuit Load Center.

Also, what company in there right mind would install a Panel and fill it totally up. You always leave room for both capacity (More amperage available) and space to add more circuits. One never know what come up in the future and when putting a panel in the extra cost for a larger panel is miniscule (less than $200) compared to the over project cost. Even if it meant adding a notification that additional changes that would be required before adding additional circuits.

 

[h2ofun]

There is your problem. By Code you cannot exceed 80% of total capacity of your Main Breaker. You need a minimum of a 250 Amp Service. 250 Amps times .80 equals = 200 Amps. So you barely squeak through with a 250 Amp Service. I had this exact situation and had to put in a new 225 Amp - 42 circuit Load Center.

Also, what company in there right mind would install a Panel and fill it totally up. You always leave room for both capacity (More amperage available) and space to add more circuits. One never know what come up in the future and when putting a panel in the extra cost for a larger panel is miniscule (less than $200) compared to the over project cost. Even if it meant adding a notification that additional changes that would be required before adding additional circuits.

My design sheets show 225 amp panels for my generation panels.

 

[wwhitney]

There is your problem. By Code you cannot exceed 80% of total capacity of your Main Breaker.

That's only true for continuous loads. In the above tally, only the EVSE is a continuous load.

And while it makes sense for the EVSE to be included in "Column 2" (loads figured at 100% instead of 40%), there's actually no language in Article 220 Part IV requiring that. Certainly the jetted tub belongs in Column 1, and arguably you could put the EVSE there. In which case, no problem with the load calc, even using the 125% factor for the continuous EVSE load.

Edit: gas water heater?

Cheers, Wayne

 

[MikeHolliday]

No, continuous loads are rated at 75%. All Breakers including a Main Breaker must have a minimum of 20% headroom, hence the .80 factor...

Yes, the Tesla Wall Connector draws 48 Amps maximum, but since it is a Continuous Load it must be on a 60Amp breakers and included in the calculations as a 60 Amp Load...

 

[wwhitney]

No, continuous loads are rated at 75%. All Breakers including a Main Breaker must have a minimum of 20% headroom, hence the .80 factor...

That's not correct. See NEC sections 215.2(A)(1)(a) (minimum feeder size), 215.3 (overcurrent protection), and 230.42(A)(1) (service-entrance conductors minimum size). They all tell you that the breaker and wire need to be sized to the non-continuous load plus 125% of the continuous load.

So a 200A breaker and wiring is good for (a) 200A of non-continuous load (b) 160A of continuous load, or (c) any scaled combination of the two, e.g. 48A of continuous load and 140A of non-continuous load. There's no additional 80% factor or requirement to leave headroom.

Cheers, Wayne

 

[holeydonut]

That's only true for continuous loads. In the above tally, only the EVSE is a continuous load.

And while it makes sense for the EVSE to be included in "Column 2" (loads figured at 100% instead of 40%), there's actually no language in Article 220 Part IV requiring that. Certainly the jetted tub belongs in Column 1, and arguably you could put the EVSE there. In which case, no problem with the load calc, even using the 125% factor for the continuous EVSE load.

Edit: gas water heater?

Cheers, Wayne

Thanks Wayne,

You are correct, the water heater is gas.

The sheet was actually based on one from one of the electricians that ultimately turned down the job. He was like “yeah man there’s plenty of amps left even after the Tesla charger.” But I re-calced and came up with a much different number.

He had the first 8,000 VA in column being calculated at 100% instead of the first 10,000 VA. He also had the bare minimum inputs for the microwave and stove and stuff, so I updated his sheet with the nameplate watts/VA from my installed appliances.

I was asking him to fix the circuit for my jetted tub in the master and he put it in column 2, so I left it there. I guess it’s assumed at 100% regardless where it goes.

But the comments from you and Mike now have me thinking I need to inspect the 200A breakers used in my home. Because of the redundantly redundant (lol) designing of Sunrun’s design team (double lol) I have three 200A breakers in my house all kind of stacked on top of each other.

I need to see if any of these Eaton/SquareD 200A are 200A continuous or if they’ll trip at 80%.

 

[wwhitney]

I need to see if any of these Eaton/SquareD 200A are 200A continuous or if they’ll trip at 80%.

There's no question those are normal breakers subject to the 125% continuous load factor. There are special breakers called "100% rated" where the breaker and the conductor can be sized at the non-continuous load plus 100% of the continuous load, but they are always one breaker per enclosure. They're not something you're going to have on your house.

However, all that means is that your 200A main breaker is not designed to avoid tripping at 160A continuous. It might trip at 160A continuous on a hot day, or it might hold at 220A continuous on a cold day. No guarantees either way.

Cheers, Wayne

 

[dhrivnak]

Yeah I'll need to find someone who is willing to do any of these (I think I know another guy.......)

These East Bay electricians won't touch the Gateway 2 so they can't add anything to the non-backup lug and they can't touch the Eaton 200A on the GW2. And they won't touch that pictured sub-panel since it's too precious.

So frustrating...

Have you considered installing yourself? I have installed at my home and Church with no issues.

 

[holeydonut]

Have you considered installing yourself? I have installed at my home and Church with no issues.

I tried... contra costa won’t allow an easy time for an owner/builder permit for EV chargers that require an OCPD over 50A. The Gen 3 HPWC needs a 60A breaker (48A max continuous x 1.25).

The permitting guy said if I applied for less juice, but it was just a software setting to make it unlock the full 48A max... he was going to assume the worst.

I don’t have a Tesla yet so I don’t actually know how to unlock/set that HPWC to use 48A or 40A.

Plus my wife won’t let me do my own electrical since she thinks the insurance company won’t allow it.

 

[dhrivnak]

I tried... contra costa won’t allow an easy time for an owner/builder permit for EV chargers that require an OCPD over 50A. The Gen 3 HPWC needs a 60A breaker (48A max continuous x 1.25).

The permitting guy said if I applied for less juice, but it was just a software setting to make it unlock the full 48A max... he was going to assume the worst.

I don’t have a Tesla yet so I don’t actually know how to unlock/set that HPWC to use 48A or 40A.

Plus my wife won’t let me do my own electrical since she thinks the insurance company won’t allow it.

Then put in a NEMA 14-50 and buy a second mobile connector. Even at 32 amps you will be fully charged in the morning.

 

[holeydonut]

Then put in a NEMA 14-50 and buy a second mobile connector. Even at 32 amps you will be fully charged in the morning.

But the Gen 3 HPWC is white and matches the Powerwalls... and I still have my wife to contend with.

 

[Electrph]

I tried... contra costa won’t allow an easy time for an owner/builder permit for EV chargers that require an OCPD over 50A. The Gen 3 HPWC needs a 60A breaker (48A max continuous x 1.25).

The permitting guy said if I applied for less juice, but it was just a software setting to make it unlock the full 48A max... he was going to assume the worst.

I don’t have a Tesla yet so I don’t actually know how to unlock/set that HPWC to use 48A or 40A.

Plus my wife won’t let me do my own electrical since she thinks the insurance company won’t allow it.

gen 2 hpwc easy to "hard set" max current just a lil potentiometer (?) marked with letters if i recall .. they correspond to max amps in manual i assume gen 3 similar or if not get a gen 2 / inspector can even put a lil security sticker on edge cover of HPWC if they are really worried about you cranking it up
HPWC very easy to DIY .. i don't consider myself expert electrician ..but our local inspector told me "looks great" .. that made me feel good .. for about 10min .. and got my gf to stop worrying