Strange electrical/Breaker issue (solar related??)

[SJ-Chris]

This is on my 2015 Thor Majestic 28a. I've owned for over a year and haven't had any fuse/breaker/electrical issues. Everything works exactly as it is supposed to.

My battery bank consists of two Group 29D 100AH lead acid batteries. I will be adding one more to help with heavier loads on the inverter.

Recently, I added 500w of solar and a 2000w pure sine wave inverter. Here is what the setup looks like...

Two 250w residential solar panels wired in parallel on the roof (~36v @ 8.2a each under ideal conditions).
Connected through a 40 amp resettable fuse to an EPEVER 30 amp MPPT solar charge controller.
The output of the solar charge controller goes through a 40 amp resettable fuse. After about 2 feet, it connects to the +/- terminals on the 2000w inverter. From there there are a double pair of 2/0 cables going ~8 feet to my battery bank (to be able to carry the potentially heavy load of the 2000w inverter).

I have an Aili battery monitor hooked up so I can monitor the battery bank voltage and current flowing in/out of the batteries. Works great and as expected.

Everything seemed to be functioning fine and as expected. I could see that the solar is charging the batteries (highest amps I have seen so far going into the batteries is about 23 amps, but I never looked yet at high noon). The 2000w inverter works when I plug various things in up to about 600-700w (I've only got two deep cycle Group 29D lead acid batteries and will be adding another soon to help with heavier loads).

I wanted to do a solar charging test recently, so overnight I drained my 200AH battery bank to about 50%. I wanted to see if the next day (which was sunny) the solar would charge the batteries all the way up to full. Nothing was on inside the RV and nothing was plugged into the 2000w inverter. Well, I went to check on the batteries in the afternoon. The battery monitor was at ~80-85% (can't remember exactly). But the interesting thing was that the 40 amp resettable fuse between the solar charge controller output and the inverter +/- terminals (which are hooked up to the battery bank) had popped. I thought this was strange as the MPPT controller is 30amp and I assumed had a maximum output of 30 amps.

I wondered...could there have been anything driving the current back towards the solar charge controller and popping the 40amp breaker? I didn't think so. Could the 30amp charge controller have delivered more than 40 amps??

Let's do some math... The panels (in parallel) each have a max voltage of 36v and max output of 8.2amps. If the solar charge controller during a particular stage is trying to charge the batteries at 13.6v, then (if I'm not mistaken) the 36v at 16.4amps could get converted into 36v/13.6v = 2.65 multiply the 16.4 amps could generate 43.46 amps. (Yes, I know my charge controller could be limiting my solar output, but I don't really care about efficiency as I was only planning on putting on 250w in the first place and I've only got 200AH of battery bank for now). I suppose if the 30a MPPT controller actually delivers this ~43 amps, it would in fact pop the 40a resettable breaker. Do you think this is what happened?? Do any of you have a MPPT solar charge controller that actually delivers ABOVE the advertised max output?

Then I thought, well...since the solar charge controller output is connected to the battery bank (via the terminals of the 2000w inverter), I really don't care if it is delivering MORE than 40 amps to the batteries, so I changed the 40 amp breaker (between the solar charge controller and the terminals on the inverter) to 50 amps. I was hoping this would fix the issue. Maybe there was a spike of some sort(?) on the charge controller output that was more than 40amp that popped the breaker and maybe going to a 50amp breaker would resolve the issue.

But then, just today there was a new issue I had never seen before. And this one has me scratching my head...and I wonder if it has anything to do with the solar/inverter install I recently did. I have a friend using my RV and he was at a full hookup campsite last night. Note: He is very unexperienced at RVing so who knows if he plugged in/out correctly, etc. This morning when he unhooked everything he told me that all of the 12v items were no longer working (interior lights, water pump, refrigerator on propane). As a test, I had him turn on the generator...everything worked (120v and 12v lights, water pump, etc). But as soon as he turned off the generator the 12v items stopped working. I ran him through all the usual things to check. I was able to find the fix. The main CONVERTER BREAKER (I believe it is also 40 amps) had popped. I believe this breaker is the master control for the 12v wire going into the converter that goes to all 12v systems. Here is a picture:



*** What are the most typical situations that pop this CONVERTER BREAKER? ***

Note: Because of their lack of experience, I suppose it is possible that this actually popped anytime in the last 24hrs (and maybe they only noticed it after they unplugged in the morning). If they got to the campsite yesterday in the daylight, they might not have even noticed (before plugging in to shore power) that the 12v wasn't working. To me, it doesn't seem like anything from the solar/inverter install should cause this. Afterall, the solar/inverter simply tie into the battery bank much the same as, for example, the chassis alternator (which can deliver 50-100 amps). What do you think?

I welcome your thoughts on the matter.

Thanks!
Chris

[FWC]

SJ-Chris wrote:
Could this be possible?.....

Under my dinette bench seat is the converter. The resettable Converter Breaker is in this compartment also. It has never popped before, but did yesterday for the first time.

I did install in this same compartment (under the dinette bench seat) my solar charge controller and my 2000w pure sine wave inverter.

Someone in these posts, someone mentioned "thermal" and/or heat. Is it possible that the HEAT from the solar charge controller and the HEAT from the 2000w inverter could be making this compartment hot enough to pop the resettable Converter Breaker? My first reaction/thought is "No way". I don't know for a fact, but I'm pretty sure the solar charge controller wasn't really doing much (...the RV batteries were full when it left my house, my friend drove the RV for 4 hours, then plugged in to shore power at a campsite) so it should not have gotten hot at all. It is possible they had the inverter on watching the TV and a DVD (~150w ?). Doesn't seem like that would cause the inverter to heat up much at all.

Do you think I should install a small fan in this compartment under the dinette bench seat to blow hot air out (and pull cooler air in from the coach)? I could put it on a temperature controlled switch so it would only come on when that chamber under the bench seat gets to a certain temp. Necessary or overkill??

Just still thinking, not sure yet what caused that resettable Converter Breaker to pop...

-Chris

The heat shouldn't make the circuit breaker trip on its own, but it will cause it to trip at a lower current. There are 'derating' curves for thermal circuit breakers at higher temperatures.

As the circuit breaker is also being used as a junction block (which is bad practice) if the connections on either stud are not great, then they can have some resistance, which will produce heat that will be conducted into the bi-metal strip in the breaker also lowering the trip current.

[CA_Traveler]

On your next trip with shore power disconnected make heavy use of the inverter discharging the battery to 50% and measure the temperature. Then charge the battery with the converter and measure the temperature.

[SJ-Chris]

Could this be possible?.....

Under my dinette bench seat is the converter. The resettable Converter Breaker is in this compartment also. It has never popped before, but did yesterday for the first time.

I did install in this same compartment (under the dinette bench seat) my solar charge controller and my 2000w pure sine wave inverter.

Someone in these posts, someone mentioned "thermal" and/or heat. Is it possible that the HEAT from the solar charge controller and the HEAT from the 2000w inverter could be making this compartment hot enough to pop the resettable Converter Breaker? My first reaction/thought is "No way". I don't know for a fact, but I'm pretty sure the solar charge controller wasn't really doing much (...the RV batteries were full when it left my house, my friend drove the RV for 4 hours, then plugged in to shore power at a campsite) so it should not have gotten hot at all. It is possible they had the inverter on watching the TV and a DVD (~150w ?). Doesn't seem like that would cause the inverter to heat up much at all.

Do you think I should install a small fan in this compartment under the dinette bench seat to blow hot air out (and pull cooler air in from the coach)? I could put it on a temperature controlled switch so it would only come on when that chamber under the bench seat gets to a certain temp. Necessary or overkill??

Just still thinking, not sure yet what caused that resettable Converter Breaker to pop...

-Chris

[CA_Traveler]

SJ-Chris wrote:
If I see "30amps" on my battery monitor flowing into my batteries sometime this summer, I'll smile knowing that I paid only $225 for my 500w system and it's generating lots of power for me :C

Realistically though....If I'm in Phoenix in June at noon, there is GONNA be some AC involved where ever I'm at which means plugged in or generator on!! When I was moving my daughter into the dorms at ASU several years ago it was a cool 114 degrees!

Copy that. I paid $1550 in 2014 and then did a bunch of testing to confirm the setup and the Phoenix one was brief :B as I wanted to be cool. :C

At that time most of this boards native knowledge which wasn't always correct was focused 12V 100W panels and PWM controllers.

[pianotuna]

SJ-Chris wrote:
The one in the photo (Converter Main Breaker) has never popped in the ~1.5 years that I've owned the RV. Until yesterday. After feedback here and thinking about it more, I don't see how the solar/inverter install could have caused this since those components are basically hooked up directly to the batteries and not through this breaker.
Thanks!
Chris

I can say, that in the old days when I used "double conversion" (plug in only the converter to shore power, and use an inverter to run the rest of the RV loads), that I did cause the reverse polarity fuses to deform.

You might want to have a look and see if your fuses are pristine or not.

The converter in mind is a 30 amp unit--with 30 amp fuses.

[SJ-Chris]

FWC wrote:
I would guess your breakers are tripping at below their rated current, and it is an issue with low quality thermal breakers. This would also explain two apparently unrelated faults, if they are using the same breakers. I can't see from the photo, but is there a manufacturer and part number on the breaker? Not to be rude, but based on the photo of the installation, this does not appear to have been done by a careful professional.

The breaker from the solar charge controller to the batteries is now 50amps (it blew one time when it was 40amps). It is one of these:
https://www.amazon.com/gp/product/B07K4ZK4VP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The one in the photo is the one that came from the manufacturer (Thor) install. I have not touched or added to it, so as far as I know it came exactly like this (with all the wires) directly from the manufacturer.

The one in the photo (Converter Main Breaker) has never popped in the ~1.5 years that I've owned the RV. Until yesterday. After feedback here and thinking about it more, I don't see how the solar/inverter install could have caused this since those components are basically hooked up directly to the batteries and not through this breaker.

Until I see it happen again (which could very well happen), I'm going to caulk it up to user error or fluke. If it happens again, I'll try to get more details about what was going on just before it popped.

Thanks!
Chris

[SJ-Chris]

CA Traveler wrote:
BFL13 Reasonable analysis for warmer temps but designs should include lower temps which raise panel power. Interesting that you didn't again bring up lens or cloud effect. I agree that it's likey a panel CB fault which can be eliminated as it serves no purpose.

For general estimating purposes I use 66% of panel power for 4+ hours. On a clear hot Phoenix sky in June I pushed my loads and got 53A from the controller with 750W panels. But I designed for for cold temps as well.

And it seems likely the OPs 2 problems are unrelated but w/o details who knows?

OP Recommend you replace both CBs with better quality ones if not eliminate the panel CB. Then see if you repro the issues.

Thanks for the info and suggestions CA Traveler

I have not seen any issue with the panel to solar controller circuit breaker (...I'm mostly using it as an on/off switch right next to my controller for ease of use).

Using your Phoenix sun at high noon in June numbers, 53amps with 750w of solar would translate roughly to 35amps if it was a 500w solar system. That's just a little above my 30amp controller's capability so if it limits the output (and basically wastes a bit of the solar panel's potential) under a mostly optimal scenario I'm okay with that. If I see "30amps" on my battery monitor flowing into my batteries sometime this summer, I'll smile knowing that I paid only $225 for my 500w system and it's generating lots of power for me :C

Realistically though....If I'm in Phoenix in June at noon, there is GONNA be some AC involved where ever I'm at which means plugged in or generator on!! When I was moving my daughter into the dorms at ASU several years ago it was a cool 114 degrees!

[SJ-Chris]

BFL13 wrote:
500w panels aimed at the sun at high noon with a high sun calculation, adjusted for being flat on the roof in March when the sun is only half way up at high noon compared with June's altitude.

500w loses 10% in the heat, so 450W, loses say 3% wiring loss to controller, say 13w loss, so input to the controller is 437w.

Aimed vs flat maybe 13% loss and some for March, WAG is 20%, so 80% of 437 =350w input. Controller is say 95% efficient doing 24-12. so another 5% loss to make output 333W. Say no wiring loss to battery to be generous.

output amps (loads first, battery gets what is left over)
333/12.2v = 27.3 amps
333/ 13.2v= 25.2 amps
333/ 14.2 = 23.5 amps

OP says he sees about 25 amps.

Say it is 21 June at high noon, and panels aimed not flat or he moves South till sun is overhead.

437w input with 5% controller loss (22w) = 415w output so amps output:

415/12.2 = 34 amps
415/ 13.2 = 31.4 amps
415/14.2 = 29.2 amps

OP's 30 amp Tracer is just fine for amps size, and yes, it does clip the amps . I don't know why he had the various breakers fail, but it could not have been too many amps from the controller.

Great analysis. This is why I'm comfortable with the 30amp controller. Bumping up to the 40amp controller was an extra ~$60-70, and as mentioned I was really fine with the idea of a 200-250w system originally so the 500w system should be a total overkill for me (...I have a 200AH battery bank and will grow it to 300AH, but anything close to 500w of solar will more than handle that).

-Chris

[SJ-Chris]

CA Traveler wrote:
There is no reason for a fuse or CB for 1 or 2 parallel panels as a short will not blow the fuse or damage the panels. A switch can be helpful however.

3 or more parallel panels should be individually fused to protect a shorted panel.

Each of my panels are individually fused with a 15amp inline MC4 fuse.
I also installed a breaker from the panels to the solar charge controller right next to the solar charge controller, PRIMARILY just to act as an on/off switch so that I can "turn off" the panels anytime I need/want to. That is also primarily why I put a fuse between the solar charge controller and the batteries. I wanted to have a way of disconnecting it from the system if I ever needed to (ie. doing any electrical work and want there to be no power source on the line while doing so).

-Chris

[FWC]

I would guess your breakers are tripping at below their rated current, and it is an issue with low quality thermal breakers. This would also explain two apparently unrelated faults, if they are using the same breakers. I can't see from the photo, but is there a manufacturer and part number on the breaker? Not to be rude, but based on the photo of the installation, this does not appear to have been done by a careful professional.

[CA_Traveler]

BFL13 Reasonable analysis for warmer temps but designs should include lower temps which raise panel power. Interesting that you didn't again bring up lens or cloud effect. I agree that it's likey a panel CB fault which can be eliminated as it serves no purpose.

For general estimating purposes I use 66% of panel power for 4+ hours. On a clear hot Phoenix sky in June I pushed my loads and got 53A from the controller with 750W panels. But I designed for for cold temps as well.

And it seems likely the OPs 2 problems are unrelated but w/o details who knows?

OP Recommend you replace both CBs with better quality ones if not eliminate the panel CB. Then see if you repro the issues.

[BFL13]

500w panels aimed at the sun at high noon with a high sun calculation, adjusted for being flat on the roof in March when the sun is only half way up at high noon compared with June's altitude.

500w loses 10% in the heat, so 450W, loses say 3% wiring loss to controller, say 13w loss, so input to the controller is 437w.

Aimed vs flat maybe 13% loss and some for March, WAG is 20%, so 80% of 437 =350w input. Controller is say 95% efficient doing 24-12. so another 5% loss to make output 333W. Say no wiring loss to battery to be generous.

output amps (loads first, battery gets what is left over)
333/12.2v = 27.3 amps
333/ 13.2v= 25.2 amps
333/ 14.2 = 23.5 amps

OP says he sees about 25 amps.

Say it is 21 June at high noon, and panels aimed not flat or he moves South till sun is overhead.

437w input with 5% controller loss (22w) = 415w output so amps output:

415/12.2 = 34 amps
415/ 13.2 = 31.4 amps
415/14.2 = 29.2 amps

OP's 30 amp Tracer is just fine for amps size, and yes, it does clip the amps . I don't know why he had the various breakers fail, but it could not have been too many amps from the controller.

[CA_Traveler]

There is no reason for a fuse or CB for 1 or 2 parallel panels as a short will not blow the fuse or damage the panels. A switch can be helpful however.

3 or more parallel panels should be individually fused to protect a shorted panel.

[CA_Traveler]

3 tons - MPPT controllers seek the panels maximum power point on the IV curve, ie voltage and amps or watts. This point is less than the panels Isc but at a higher voltage, hence greater watts. This maximum input power is then converted to power for the battery to charge at it's voltage and amps. The controller continually seeks this point and adjusts the output as the input changes. As the battery becomes charged the controller output is reduced as needed.

PWM controllers use Isc to charge a battery.