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What fuses/ breakers to use for 48V Growatt

Madizell

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Nov 29, 2021
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Hi all,

I just bought a Growatt 48V SPF 3000 TL LVM. I have 8

ET Solar Group ET-P672280 (280W) panels connected in series. Can I use a simple fuse on the wires from my panels, or do I need a combiner box? Does anyone have a fuse recommendation?​

 
Hi all,

I just bought a Growatt 48V SPF 3000 TL LVM. I have 8

ET Solar Group ET-P672280 (280W) panels connected in series. Can I use a simple fuse on the wires from my panels, or do I need a combiner box? Does anyone have a fuse recommendation?​

If you you only have 1 string of panels you don't need a fuse.
Having said that, it is good to have a means of disconnect.
A double pole breaker is often used for this situation.
 
If you you only have 1 string of panels you don't need a fuse.
Having said that, it is good to have a means of disconnect.
A double pole breaker is often used for this situation.
Thank you. What size pole breaker would suffice?
 
  • Isc 7.98A

  • Voc 43.8V
8 * 43.8 = 350.4 volts.
Generally you want to add some headroom for low temperature voltage increase.
350.4 volts / .8 low temp fudge factor = 438 volts
7.98 amps /.8 fuse headroom = 9.975 amps
You want a double pole breaker that is rated for at least 10 amps at at least 438 volts direct current.
 
Hi all,

I just bought a Growatt 48V SPF 3000 TL LVM. I have 8

ET Solar Group ET-P672280 (280W) panels connected in series. Can I use a simple fuse on the wires from my panels, or do I need a combiner box? Does anyone have a fuse recommendation?​

Stop please, unless you want to try putting the smoke back into the charge controller once you hook it up. The Growatt 48V SPF 3000 TL LVM is only rated for 60-115V PV input.

You can only put 2 panels in series with 4 parallel strings, 2S4P . This will require fuses or use a 4 string combiner box with built in fuses.
 
Thank you @Zwy and @smoothJoey . That was a huge oversight on my part. So I'm planning now to wire 2 panels in series and then four in parallel.

The the voltage of each of the 4 series will be 73.44 v/7.63 a. In this case, should I use a combiner box for the 4 series or mc4 branch cables?





16382444748614858183899512629374.jpg
 
If you want something cheap, use one of these, I used one on my truck camper build. https://www.amazon.com/gp/product/B07F5HDP2W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Take the MC4's out of it if you don't mount it vertical, the wire is too small for the compression part of the fitting. I removed mine and just ran the wire into the fuse terminals thru glands. https://www.amazon.com/gp/product/B07KFCGFYF/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Be sure to check all the connections in this box, whomever assembles these doesn't always get everything tight. This box gives you everything you need, fusing, lightning arrest and DC double pole breaker.
 
If you want something cheap, use one of these, I used one on my truck camper build. https://www.amazon.com/gp/product/B07F5HDP2W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Take the MC4's out of it if you don't mount it vertical, the wire is too small for the compression part of the fitting. I removed mine and just ran the wire into the fuse terminals thru glands. https://www.amazon.com/gp/product/B07KFCGFYF/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Be sure to check all the connections in this box, whomever assembles these doesn't always get everything tight. This box gives you everything you need, fusing, lightning arrest and DC double pole breaker.
I looked at this one. The only thing is, with the way I'll have the panels wired, each parallel wire should run 15.26 A. So I figure each fuse should be rated at 20a. Are the 10a fuses in these boxes replaceable?

Thank you for your help. This is all very new to me.
 
I looked at this one. The only thing is, with the way I'll have the panels wired, each parallel wire should run 15.26 A. So I figure each fuse should be rated at 20a. Are the 10a fuses in these boxes replaceable?

Thank you for your help. This is all very new to me.
Amps for 2 panels series connected will be 7.63a. You even show it on your diagram.

Series connections the amps stay the same, voltage doubles. In parallel connections, the amps double, voltage stays the same.

The combiner has the correct fuses at 10a per string, size your wire accordingly for length to prevent voltage drop.
 
I'm trying to setup my Growatt 48V SPF 3000 TL LVM array and wondered why you couldn't do 3 in series? the range goes up to 115V for PV input and each panel is 36.7V, so if you put 3 in series you'd be at 110V and below the 115V rating. Is it the cold temp adjustment?
 
I'm trying to setup my Growatt 48V SPF 3000 TL LVM array and wondered why you couldn't do 3 in series? the range goes up to 115V for PV input and each panel is 36.7V, so if you put 3 in series you'd be at 110V and below the 115V rating. Is it the cold temp adjustment?
Cold weather will put it over the 115V rating. Midnite Solar has a calculator for this. https://www.midnitesolar.com/sizingTool_kid/index.php
 
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