# Seen on the job: Overheating Busbar due to solar and AC



## Norske (Aug 23, 2020)

Browsing old threads I saw this comment: 









Looking for an all in one rated at 225A but will have a...


my parents are building their own house and are going to be putting up solar sometime in the near future. I was talking to my teacher and he said that they should get at least a panel rated for 225. The electrician that is wiring their house says he having a hard time finding a panel that will...




www.electriciantalk.com





I just came across this very situation, got a service call where they said the light circuit constantly tripped. Began diagnosing it and discovered the load on the circuit was only seven amps when fully loaded, but nonetheless the breaker was notably hot to the touch. I should have immediately cut the power and examined all the breakers but this being the first time seeing this I didn't think the situation described in the above comment was really likely, and figured it was a bad breaker. I prepared to replace it and as I killed the main power I noticed the main breaker was also noticeably hot. Finally got out my thermal camera and wow, Busbar read over 430F in some areas. Below is a picture that shows some tandem breakers and the Busbar temp. Unfortunately none of the captures showing the highest temps really capture what was going on, it just looks like a red blob. 

What's interesting as that the entire thing was installed and inspected just two years ago. If the 40A solar circuit were treated as a load the panel was still not over loaded - it did have some oxidation issues which likely lead to this. Even so I've seen many panels with far worse oxidation and nothing close to this sort of overheating issue. I strongly suspect the solar inverter backfeeding into the panel increases the amperage being transmitted more than a similar resistive load. Is there anything in the NEC to address this issue? 

I replaced the panel with the largest copper Busbar panel I could find, so I doubt they will have future issues.


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## oldsparky52 (Feb 25, 2020)

I have zero experience with solar. Is the solar system feeding into the bus through a breaker plugged onto the bus?


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## joe-nwt (Mar 28, 2019)

Were you actually able to determine the solar feed was the cause? Was the infeed breaker hot?


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## Norske (Aug 23, 2020)

joe-nwt said:


> Were you actually able to determine the solar feed was the cause? Was the infeed breaker hot?


Not directly, the heat was worst around the middle of the panel which was also where the infeed breaker was. My general impression was that I've seen a lot of similar panels with the same oxidation but never one with this sort of overheating issue before.


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## Norske (Aug 23, 2020)

oldsparky52 said:


> I have zero experience with solar. Is the solar system feeding into the bus through a breaker plugged onto the bus?


Yup, that's the standard way to do it here. The inverter is programmed to only feed in when it senses grid voltage so it doesn't require any other transfer switch.


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## oldsparky52 (Feb 25, 2020)

Norske said:


> Yup, that's the standard way to do it here. The inverter is programmed to only feed in when it senses grid voltage so it doesn't require any other transfer switch.


So if the grid goes down your house is isolated from the solar panels? No grid no power?


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## Quickservice (Apr 23, 2020)

oldsparky52 said:


> So if the grid goes down your house is isolated from the solar panels? *No grid no power?*


Why on earth would the inverter be programmed that way? If that is the standard.... it makes no sense to me.


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## Slay301 (Apr 23, 2018)

Quickservice said:


> Why on earth would the inverter be programmed that way? If that is the standard.... it makes no sense to me.


Most utilities require it they don’t want any chance of back feed onto grid in power outage


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## micromind (Aug 11, 2007)

Quickservice said:


> Why on earth would the inverter be programmed that way? If that is the standard.... it makes no sense to me.


During an outage, the PUCO is still connected to the bus so it'd be bad if the solar continued to backfeed energy into it. 

The PUCO around here has a list of approved inverters that will shut down during an outage, just for this reason.


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## Slay301 (Apr 23, 2018)

Also plus the standard array isn’t large enough to power a house at peak power


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## kb1jb1 (Nov 11, 2017)

Norske said:


> Not directly, the heat was worst around the middle of the panel which was also where the infeed breaker was. My general impression was that I've seen a lot of similar panels with the same oxidation but never one with this sort of overheating issue before.


The breaker for the photovoltaic system should be at the far end of the panel from the main circuit breaker. One reason I like line side taps.


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## HertzHound (Jan 22, 2019)

Quickservice said:


> Why on earth would the inverter be programmed that way? If that is the standard.... it makes no sense to me.


It’s called anti-islanding and every grid tie inverter has to meet the UL listing to prevent islanding.









UL 1741 Safety Testing of Inverters Includes Anti-Islanding Requirement - Eurofins E&E North America


In the event of a power failure on the electric grid, it is required that any independent power-producing inverters attached to the grid turn off in a short period of time. This prevents the DC-to-AC inverters from continuing to feed power into small sections of the grid, known as “islands.”...




www.google.com


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## HertzHound (Jan 22, 2019)

Like Kb1jb1 said, I hope the solar breaker was moved to the opposite end of the busbar, and there was a sticker next to the breaker to “not relocate”.

(b) Where two sources, one a primary power source and the other another power source, are located at opposite ends of a busbar that contains loads, the sum of 125 percent of the power source(s) output circuit current and the rating of the overcurrent device protecting the busbar shall not exceed 120 percent of the ampacity of the busbar. The busbar shall be sized for the loads connected in accordance with Article 220. A permanent warning
abel shall be applied to the distribution equipment adjacent to the back-fed breaker from the power source that displays the following or equivalent wording:
WARNING:
POWER SOURCE OUTPUT CONNECTION —DO NOT RELOCATE THIS OVERCURRENT DEVICE.
The warning sign(s) or label(s) shall comply with 110.21(B).


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## oldsparky52 (Feb 25, 2020)

Is there a system that will disconnect from the PoCo but still allow the house to use what electricity is generated? 

What happens to a solar panel if there is too much load for it to handle, and what happens if there is no load? Anything/nothing?


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## Slay301 (Apr 23, 2018)

oldsparky52 said:


> Is there a system that will disconnect from the PoCo but still allow the house to use what electricity is generated?
> 
> What happens to a solar panel if there is too much load for it to handle, and what happens if there is no load? Anything/nothing?


To much load = brown out you start undervolting and then as voltage goes down current goes down. Could damage equipment. And if theres
No load nothing happens and assuming the grid is up it’s sold back to the utility through the reversing meter. If the grids down it’s like a battery sitting on the shelf just waiting to be used.


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## Quickservice (Apr 23, 2020)

HertzHound said:


> It’s called anti-islanding and every grid tie inverter has to meet the UL listing to prevent islanding.
> 
> 
> 
> ...


So you are not allowed to have your own interlock that would disconnect you from the POCO/grid... thus letting you continue to use YOUR OWN solar power?


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## Slay301 (Apr 23, 2018)

Quickservice said:


> So you are not allowed to have your own interlock that would disconnect you from the POCO/grid... thus letting you continue to use YOUR OWN solar power?


The utilities regulate how much solar you can put on your house in a grid tied situation. So yes that is correct. You can do what u want if u were 100% off grid


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## kb1jb1 (Nov 11, 2017)

Quickservice said:


> So you are not allowed to have your own interlock that would disconnect you from the POCO/grid... thus letting you continue to use YOUR OWN solar power?


You can install a battery system or power wall for when the utility goes out you can have the solar charge the batteries which then feed the house. Expensive, sort of complicated, and uses wall space which many people do not have. Keep in mind all these fancy, green systems require proper maintenance. People do not maintain their HVAC, boilers, exhaust fans, cars... etc. Do you think people are going to have someone come in every 6 months to keep these items running ? I was at a house months back and the homeowner did not know his system was off line until I told him.


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## Quickservice (Apr 23, 2020)

kb1jb1 said:


> You can install a battery system or power wall for when the utility goes out you can have the solar charge the batteries which then feed the house. Expensive, sort of complicated, and uses wall space which many people do not have. Keep in mind all these fancy, green systems require proper maintenance. People do not maintain their HVAC, boilers, exhaust fans, cars... etc. Do you think people are going to have someone come in every 6 months to keep these items running ? I was at a house months back and the homeowner did not know his system was off line until I told him.


I should have kept my mouth shut so not to show my ignorance on solar. Very few companies or HO'ers have tried solar in our area, too many mountains, ridges, trees, and clouds. On top of that the smoke and humidity haze has been terrible this Summer.


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## Signal1 (Feb 10, 2016)

You stated that the infeed from solar was in the center of the bus?

What other loads are on the bus in relation to the main?
Could this be the scenario? If the utility and solar breakers were reversed you would still have the same issue.









EDIT: this image is Mike Holt's btw


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## joe-nwt (Mar 28, 2019)

Quickservice said:


> So you are not allowed to have your own interlock that would disconnect you from the POCO/grid... thus letting you continue to use YOUR OWN solar power?


Sure you can. You basically are creating a grid-tie ups system where the batteries are charged by solar.


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## kb1jb1 (Nov 11, 2017)

Quickservice said:


> I should have kept my mouth shut so not to show my ignorance on solar. Very few companies or HO'ers have tried solar in our area, too many mountains, ridges, trees, and clouds. On top of that the smoke and humidity haze has been terrible this Summer.


Don't feel bad. You are not alone.. Many electricians and inspectors don't know much about either the applications or installation. I have seen it on roofs that only have 3 or 4 hours of sun. DC ran with NM or Romex. Another thing about solar power is RFI. I listen to AM radio and I can tell when I drive past a house with a system on it.


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## argile_tile (Aug 12, 2021)

The original OP post says so little I'm unsure if he even said it was in the DC/AC converter or wave follower circuit and PF adjustment, where the solar comes in or where the AC leaves or where the power utility line comes in (which happens only on some models and depends on if installed up or down stream of disconnect) or ... PV systems have allot of boxes and boards these days.

The "IR photo" if that is using a chinese IR camera again means nothing. White could be 200 as easily as it coulbe be 500 with those things.

We don't know the PV system is installed or functioning correctly: it could be objectionable current heating it up not the PV maker's fault. It could be it's designed for heat in one area - there's no rule that says all boxes and panels are 75C.

_I would like to see a diagram. The image is not trust-worthy. Altering the factory components install voids your fire insurance of your home. And so on. You can see what direction I'm going. I'm saying your jumping around without mentioning specifically what causes the heating and altering the LISTED USE of the equpment: and that you should not be doing that. one reason is: if it fails it puts all blame on you for failure._


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## argile_tile (Aug 12, 2021)

Get with the manufacturer. Call them email them the picture.

I'm sure they'll have some response to it.


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## Norske (Aug 23, 2020)

Signal1 said:


> You stated that the infeed from solar was in the center of the bus?
> 
> What other loads are on the bus in relation to the main?
> Could this be the scenario? If the utility and solar breakers were reversed you would still have the same issue.
> ...


That’s helpful thanks, added that to my notes. That was similar to the situation I found, the higher load devices were at the far end with the PV and Utility inputs reversed compared to the above.

I wasn’t aware of the specification in the code to add a warning to not move feed in breakers and I’ve seen solar installs done by the leading companies in the area and they don’t - I definitely will though.


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## Norske (Aug 23, 2020)

argile_tile said:


> The original OP post says so little I'm unsure if he even said it was in the DC/AC converter or wave follower circuit and PF adjustment, where the solar comes in or where the AC leaves or where the power utility line comes in (which happens only on some models and depends on if installed up or down stream of disconnect) or ... PV systems have allot of boxes and boards these days.


DC/AC converter synchronized to the grid.



> The "IR photo" if that is using a chinese IR camera again means nothing. White could be 200 as easily as it coulbe be 500 with those things.


Seek Thermal pro but I found it matches what I get with a FLIR very closely, and it’s more convenient since it’s tiny and I can keep it in my test



> We don't know the PV system is installed or functioning correctly: it could be objectionable current heating it up not the PV maker's fault. It could be it's designed for heat in one area - there's no rule that says all boxes and panels are 75C.


.

Not one to argue there, if it had just been 90C and otherwise fine I’d have not charged them and told them not to worry. But the input breaker was melted and charred at the base, along with surrounding breakers. I also didn’t mean to imply it was the PV makers fault, rather whoever tried shoving another breaker to feed in to an overloaded aluminum bus breaker box in a damp basement.

_



would like to see a diagram. The image is not trust-worthy. Altering the factory components install voids your fire insurance of your home. And so on. You can see what direction I'm going. I'm saying your jumping around without mentioning specifically what causes the heating and altering the LISTED USE of the equpment: and that you should not be doing that. one reason is: if it fails it puts all blame on you for failure.

Click to expand...

_Agreed. I didn’t touch any of the solar equipment or modify it beyond moving the feed in breaker to the bottom of the panel and replacing the panel. If they wanted me to somehow modify the solar install I wouldn’t have taken the job. I appreciate the feedback. I do think I mentioned initially the busbar was aluminum and had oxidation issues, the panel was also overloaded with more tandem breakers than it’s listed maximum.

I didn’t exhaust all the possibilities though, it’s also possible the inverter was malfunctioning. I did follow up a few days later to check the temperature and it was barely warm (similar weather). I will take your advice to heart and examine the solar system function more closely in the future.


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## paulengr (Oct 8, 2017)

argile_tile said:


> The original OP post says so little I'm unsure if he even said it was in the DC/AC converter or wave follower circuit and PF adjustment, where the solar comes in or where the AC leaves or where the power utility line comes in (which happens only on some models and depends on if installed up or down stream of disconnect) or ... PV systems have allot of boxes and boards these days.
> 
> The "IR photo" if that is using a chinese IR camera again means nothing. White could be 200 as easily as it coulbe be 500 with those things.
> 
> ...


I think you are confused. Seek is an American company in California. They have been doing far better than say Flir One on the smaller sensors. Considering that the Seeks and Flir One are virtually the same price it’s obvious that Seek is buying the same stuff from the same or very similar source. Looking at their web site all their people are old white guys. No Charlie Wongs in the mix. The resolution beats most of the cheaper end of the Flir line. As far as where the sensors come from almost all companies, including Flir, are “fabless” as far as actual chip manufacturing. Over 75% of the chips in the world are made by just two companies: Taiwan Semiconductor (TMSC) and Samsung. There is a Chinese plant with just 3% market share.

It is easily possible to screw up temperature measurements with IR but this is with ANY camera or pyrometer. It’s best used as a relative measurement tool which is the case here. I don’t think it matters if it’s 90 C, 200 C, or 800 C. It just matters if it exceeds 75 C.


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## SomeJoe (Apr 9, 2021)

oldsparky52 said:


> Is there a system that will disconnect from the PoCo but still allow the house to use what electricity is generated?
> 
> What happens to a solar panel if there is too much load for it to handle, and what happens if there is no load? Anything/nothing?


Clearly I am late to the party, here are my two cents;

Many homeowners were bummed out in the years of 2016/2017 when the leased solar system would not generate when grid failure, even more so when some ho's decided to turn Off the main breaker thinking the solar would feed the house. 
Not the case obviously, this is why the solar industry took a while to lift off the ground. Some of the reasons where costly inverter designs / programming and finding ways to have control from a utility and manufacturing levels so homeowners would not tinker with it.

Jump to 2022 and we now have all sorts of solar manufactures with ATS's (controllers) and battery banks (Energy Storage System), one that our Canadian brothers might know of is Eguana Technologies from Calgary.
There are systems that can have a battery only, this means the battery will charge with solar production and discharge when sundown. This set up doesn't provide energy when grid fails, it needs an ATS still.

What's been trending for a few years now is the "critical loads" ESS, meaning, you have PV on roof with inverters / ATS / batteries and a load center which houses (4) circuits the homeowner chooses. 
This setup will allow energy stored in batteries to feed critical loads panel in the event grid fails. 
Typical loads are; fridge, Wi-Fi, GDO, and lights.
Whole home back-up systems are very costly because it involves installing ATS between MSP (which is converted to a meter main) and load center that houses all branch loads. 
Yes we have to separate the branch loads from MSP in states that have these combos. I would imagine other states resi setup is a bit easier because you see a meter socket and the load center is somewhere in the home. Which at that point it's intercepted somewhere in the middle.

I am certified to install most of these systems, I can't begin to tell you how complicated these can get real fast. You essentially have 3 sources of power. Utility, solar, and battery. Aside from the electrical and communications wiring, there's the programming which some systems take me a better half of the day to dial in. Keep in mind the measuring instruments, some have (5) CT's.

There is a new inverter on the market that has grid-forming capabilities, this device has an internal chip which allows it to create it's own micro-grid when utility grid fails (island). Paired up with the controller which has an NFT (Neutral Forming Transformer) and you now have a stand alone system. It does not need a battery to provide energy to the home when utility grid fails, they call this "solar-mode only".

To answer your 2nd question, on an Off grid mode; if there is too much power being pulled from branch circuitry that solar capacity can't handle then breakers will trip and possibly collapse the system. Some have relays that will open and send an "error" email message to ho & installer.
If batteries are fully charged, not enough consumption is happening, and production is high then a frequency shift will take place that shuts off the inverters until energy is needed.

Hope this answered your questions and more


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## joe-nwt (Mar 28, 2019)

SomeJoe said:


> It does not need a battery to provide energy to the home when utility grid fails, they call this "solar-mode only".


Awesome. If the grid fails during the day.


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## backstay (Feb 3, 2011)

joe-nwt said:


> Awesome. If the grid fails during the day.


I too thought it was a novelty at first. But have a wind storm or ice storm come through and that one receptacle that works 8 hours a day would be a god send to someone with no generator. I wouldn’t spend extra on it, a $1000 Honda generator is a much better option.

The hybrid battery/grid tie is just so expensive it’s hard to justify. There is so much going on in one. The Outback Radian can take power from a generator, the grid and the batteries at the same time. Controlling that based on the parameters of load, battery level, time of day or a multitude of inputs. There are seven inverter modes. Generator, support, grid tied, ups, backup, mini grid, grid zero. Three shunts monitoring power flow. Too complicated for a HO. Here’s a screen shot of the overview.


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## nrp3 (Jan 24, 2009)

That Radian is an intriguing product, but I can see that being a next step in the evolution of this. Some battery, some solar, and generator and the ability to use whatever you have in case of utility failure, or utility completely in the event of your system failure.


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## HertzHound (Jan 22, 2019)

Do you get the SRECs if there is a battery backup system?


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## backstay (Feb 3, 2011)

HertzHound said:


> Do you get the SRECs if there is a battery backup system?


Not every state has that. What are they based on. Production or selling back? I would think if you are grid tied they would be the same with or without batteries.


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