Solar Combiner Box Help

macc2323

looking for help picking a solar combiner box. Not sure when to use fuses or circuit breakers. Im looking at the boxes for sale at www.solarpowercombinerbox.com and not sure what I need. I have a 6 string setup, each string has six 120 watt 12V panels in series. any advice would be great.

Vic

macc..,

Here are some mainstream PV Combiners:

http://www.solar-electric.com/installation-parts-and-equipment/midnite/pvarco.html

Generally, circuit breakers are more convenient that fuses, in Combiners.

Strings of six PVs often approach the limit of many Charge Controllers when the PVs are cool/cold. This mostly depends upon your climate.

Please tell us more about your system, or plans for it.

Thanks, Vic

Photowhit

macc2323 wrote: »

looking for help picking a solar combiner box. Not sure when to use fuses or circuit breakers. Im looking at the boxes for sale at www.solarpowercombinerbox.com and not sure what I need. I have a 6 string setup, each string has six 120 watt 12V panels in series. any advice would be great.

I am not familiar with those boxes, but they don't appear to be 'dead front' boxes, which are required to meet current code. A dead front box allows access to the breaker or fuse, with out exposed wires. It is not uncommon to find pictures of combiner boxes, including Midnite's, that don't show the 'dead front'. This doesn't mean they are unsafe, only that they require more care in handling. I think this was just in the last couple revisions.

From what you said it appears you have 6 strings of 6 panels for 36 - 120 watt panels? What is your system voltage?

glentaybow

Hello:
Trying to ask a question but don't know how to do it. So, I'll try here. I'm running PV wire from the array directly down to the inverter for connection (two strings of 10). No junction boxes, No combiner boxes. Does the PV wire need to be in conduit? If so, can it be PVC?

Thanks

Photowhit

glentaybow wrote: »

Trying to ask a question but don't know how to do it. So, I'll try here. I'm running PV wire from the array directly down to the inverter for connection (two strings of 10). No junction boxes, No combiner boxes. Does the PV wire need to be in conduit? If so, can it be PVC?

USE 2 is the most common wire used for PV installations (at least around here) and is sunlight resistant. It does not Need to be in conduit. That said there are codes that require limited access to connections above 30 volts DC. Also local codes may require any wire to be in conduit. There is an exterior PVC (grey around here) that works pretty well. Is this a grid tied system? Your local Power company and local electrical inspector may flag improper wiring...

glentaybow

Thanks for reply. It's a grid tie system. My electrician (who will make the electrical connections) doesn't do many solar systems so is not familiar with requirements. Most installations do not run PV wire all the way down to inverter due to costs or other reasons. Hence the uncertainty (at least with my electrician) regarding what the conduit requirements are. The only connections are at the array (MC4) for the home runs and near runs. I have two pluses and two minuses (4 PV wires total) running to inverter in PVC. The system is mounted to my barn/carport. Perhaps a call to the local inspector would be in order to discuss conduit requirements? I just want it to pass inspection.

inetdog

glentaybow wrote: »

Thanks for reply. It's a grid tie system. My electrician (who will make the electrical connections) doesn't do many solar systems so is not familiar with requirements. Most installations do not run PV wire all the way down to inverter due to costs or other reasons. Hence the uncertainty (at least with my electrician) regarding what the conduit requirements are. The only connections are at the array (MC4) for the home runs and near runs. I have two pluses and two minuses (4 PV wires total) running to inverter in PVC. The system is mounted to my barn/carport. Perhaps a call to the local inspector would be in order to discuss conduit requirements? I just want it to pass inspection.

The PV wire can be run exposed on the roof, but it must also be run in such a way that it is protected from physical damage. For example behind the racking or attached to a running board across the roof.

Once the wire comes inside the building without first going through a disconnect with overcurrent protection, my belief is that it must be in raceway.

glentaybow

My wiring enters PVC on roof under PV panels through water tight strain relief. (see picture) From there, it runs through PVC directly to inverter and terminates there. (see photo)

BB.

I am not sure--But you may need metal EMT (sorry, I am not a code guy) when the PV cables enter the home to the PV disconnect switch--Then plastic is OK after that (I think).

-Bill

glentaybow

Bill, thanks for reply. When I began researching this project back in January of this year, I wanted to design something that was simple, and that I could do myself, with the exception of the electrical connections, which my grid tie agreement requires a licensed electrician to perform. I decided on two strings only using Solaredge Inverter and Optimizers. Although most systems use combiner boxes, with fusing or circuit breakers in the DC part of the system, it was my contention that two strings require none of that. Do I have that right? To me, less connections mean less problems down the road. So, I figured I could use the PV wire to make the home run and near run direct to the inverter. In fact, my inverter will accommodate 2 dc's and 2 ac's, which is what I have. I understand the high voltage wires must be protected from physical damage as per NEC. I believe the schedule 40 PVC does that, plus I have routed the conduit in places where physical damage is not likely to occur. My electrician, who hasn't done much solar, is now telling me I need a combiner box where the PV wire first comes into my barn, then Schedule 80 PVC or EMT needs to be run after that to the inverter.

BB.

Yes, you are correct. You do not need a combiner box/fuses for two series strings of solar panels. However, the NEC requires metal upon entering the home prior to the first solar disconnect if the disconnect is inside the home.

Hopefully others here can help with the details.

-Bill

glentaybow

Thanks, BB. My system is mounted on my barn/carport if that makes any difference. Also, there is no solar disconnect, only at the inverter. One continuous PV wire from the last panel connected in the string on the roof to the inverter.

glentaybow

My electrician is also telling me that a combiner is required per NEC to run only one circuit down to the inverter. If that's the case, then why does SolarEdge provide terminations for two circuits in the inverter? (two positives and two negatives)

BB.

Don't know. Ask what version of nec and what chapter.paragraph number requires this.

Many times the nec is quite readable. You should understand why it is required, or understand that the code is being looked at wrong.

-Bill

glentaybow

Can anyone on this forum provide a NEC reference that stipulates only one circuit can run to the inverter?

Thanks, Glenn