Is this fuse block suitable for use in a combiner box?

Plowman

I'm in the process of expanding my little DIY 12V off-grid system. Once I'm done it'll consist of:
--Three Dmsolar 158W panels
--Morningstar TS-45 charge controller
--Two Trojan T-105s

I'm trying to figure out a safe---and cheap---way of connecting and fusing my solar panel wires. This Blue Sea blade fuse block seems like it would work, though it's designed as a load center connected to a battery. $36 from Amazon.



Other suggestions in this price range?

Vic

Re: Is this fuse block suitable for use in a combiner box?

Hi Plowman,

This is a handsome little fuse holder,

It might be OK as a PV Combiner, but the ATC blade fuses often do not hold up well in PV battery-charging applications, as continuous current seems to stress the contacts, and thermal cycling takes its toll.

Perhaps at the 7-ish Amps that you might expect from each PV, it could be OK.

There are the MidNite Solar line of PV Combiners, and even the MN Big Baby box could be used. These would allow the use of MN DC DIN Rail breakers, this would about double the price, but would be Rated for the application.

MN Big Baby Box:
http://www.solar-electric.com/misobigbabox.html

MN Combiner:
http://www.solar-electric.com/mnpv3.html

You sill still need some additional circuit protection, and probably a Disconnect on the output of the CC, at a minimum.

And the Big Baby box should really have a negative, and positive busbar (as does a real Combiner,) but wire-nutting the common connections together is probably OK for a system that does not need inspection.

Just my opinions, FWIW, Good Luck, Vic

Photowhit

Re: Is this fuse block suitable for use in a combiner box?

You might look at a 'agu fused power distribution block', and then load it with the correct fuses. This takes the same 'midget sized' 13/32"x 1 1/2" or 10x38mm fuses used for solar.

niel

Re: Is this fuse block suitable for use in a combiner box?

plowman,
you could make up your own with bus bars and an old time car fuse holder.

http://www.radioshack.com/product/index.jsp?productId=2062258

these 1.25" x .25" fuses are more readily available for your 12v system as they usually have a 32v rating and your pvs if in parallel will not exceed this.

waynefromnscanada

Re: Is this fuse block suitable for use in a combiner box?

Vic wrote: »

Hi Plowman,

This is a handsome little fuse holder,

It might be OK as a PV Combiner, but the ATC blade fuses often do not hold up well in PV battery-charging applications, as continuous current seems to stress the contacts, and thermal cycling takes its toll.

Perhaps at the 7-ish Amps that you might expect from each PV, it could be OK.

There are the MidNite Solar line of PV Combiners, and even the MN Big Baby box could be used. These would allow the use of MN DC DIN Rail breakers, this would about double the price, but would be Rated for the application.

MN Big Baby Box:
http://www.solar-electric.com/misobigbabox.html

MN Combiner:
http://www.solar-electric.com/mnpv3.html

You sill still need some additional circuit protection, and probably a Disconnect on the output of the CC, at a minimum.

And the Big Baby box should really have a negative, and positive busbar (as does a real Combiner,) but wire-nutting the common connections together is probably OK for a system that does not need inspection.

Just my opinions, FWIW, Good Luck, Vic

I've also run into very serious problems with blade type fuses in long term solar applications. In time, for reasons I don't understand (were in clean, dry locations) resistance gradually built up in the contact area and produced heat that melted the fuses and holders. Even had it with the large 80 amp blade type automotive fuses and nearly caused a fire. Not kidding. I switched to bolt on fuses and had no more problems, but finally switched them out for DC circuit breakers that I can operate as disconnects when necessary. Wish I had done that first!

Plowman

Re: Is this fuse block suitable for use in a combiner box?

waynefromnscanada wrote: »

I've also run into very serious problems with blade type fuses in long term solar applications. In time, for reasons I don't understand (were in clean, dry locations) resistance gradually built up in the contact area and produced heat that melted the fuses and holders. Even had it with the large 80 amp blade type automotive fuses and nearly caused a fire. Not kidding. I switched to bolt on fuses and had no more problems, but finally switched them out for DC circuit breakers that I can operate as disconnects when necessary. Wish I had done that first!

I searched this board and I found other posts where you mentioned this (I think it was you). Someone else suggested it might be the fuse holder (a cheap inline fuse crimped in?). Nonetheless, blade fuses don't seem to be used much in these 12V systems.

How about a Square D QO load center (like this) and 3 QO 15-amp circuit breakers? Would also need a negative bus, so maybe $50 total. Think this would work better? My understanding is the QO line is rated for low voltage, but I didn't see any indication of this when I looked at them at Lowes today.

I had planned on putting a Blue Sea marine switch (which I already have) for a disconnect in the combiner box, but I could find other uses for this switch. I would prefer to use circuit breakers.

South Africa

Re: Is this fuse block suitable for use in a combiner box?

Do not use vehicle fuses. They do not last. I tried.

Another option is DIN Rail mounted fuse holders like these: http://www.em.co.za/product.htm?productID=914
Then get the right fuse for the cable, insert it and you are sorted.

Best for me is that they require no connectors. Crimping on connectors is another issue all on it's own if not done right.

In SA rands they are +-R80.00 for the holder and +-R70.00 for the fuse. Maybe R10.00 for the short DIN rail. Cheapest option I found to date.

waynefromnscanada

Re: Is this fuse block suitable for use in a combiner box?

Plowman wrote: »

How about a Square D QO circuit breakers.

I switched to these about a year ago and so far, so good. Happy with them and they also work great as disconnects - - as long as the voltage stays within their DC range.
Needed 80 amp, so used a double pole 40 amp breaker. So far excellent results.
BTW, I used blue sky bolt on fuses for a while, they were OK, but ran quite warm, dare I say hot. (100 amp fuse handling 60 amps) And no, it wasn't undersized wire or loose connections, it was the fuse itself. Two pole 40 Amp (80 amp total) Square D QO, same wires, handling same 60 amps, runs cool to cold.

westbranch

Re: Is this fuse block suitable for use in a combiner box?

Square D QO CB's are rated at/to 48V DC...

Vic

Re: Is this fuse block suitable for use in a combiner box?

Plowman wrote: »

How about a Square D QO load center (like this) and 3 QO 15-amp circuit breakers? Would also need a negative bus, so maybe $50 total.

YES the QO and QOB Square D breakers are rated to 48 VDC ONLY in sizes 10 - 70 A Handle Rating as Singles and Doubles (Three poles rated differently).

Had considered mentioning that, but did not have the time to deal with the details.

This is probably a pretty good approach on smaller 12 V systems, and these items are usually available locally. It would probably be better to not use QO breakers on the battery to CC connections or for the battery to inverter connections.

Not to nit-pic too much, just wanted to not that NOT every QO breaker is rated for DC Service.
Opinions, Vic

Plowman

Re: Is this fuse block suitable for use in a combiner box?

Thanks guys, I've decided on a Square D QO load center and circuit breakers for my combiner box. It'll look better than what I had in mind anyway and won't cost all that much more.

For circuit protection between the charge controller and battery bank, and between the battery bank and inverter, I'm planning on using these circuit breakers:



Will use Blue Sea marine switches for disconnects on these circuits.

Also thinking of adding a Blue Sea battery terminal fuse block to the battery bank, with maybe a 90 amp fuse (suitable for 6 AGW and a 1000W inverter I believe).

Any problem with this plan? I think this covers all my circuit protection aside from grounding, which I've already gotten great advice about in another thread here.

raymate

waynefromnscanada wrote: »

Re: Is this fuse block suitable for use in a combiner box?



I've also run into very serious problems with blade type fuses in long term solar applications. In time, for reasons I don't understand (were in clean, dry locations) resistance gradually built up in the contact area and produced heat that melted the fuses and holders. Even had it with the large 80 amp blade type automotive fuses and nearly caused a fire. Not kidding. I switched to bolt on fuses and had no more problems, but finally switched them out for DC circuit breakers that I can operate as disconnects when necessary. Wish I had done that first!

Sorry to hijack, but waynefromnscanada can you tell me where you got your DC breakers from and what brand and spec, I'm in Toronto and I'm finding it hard to get may hands on some. I want just small 5amp ones but the likes of Lowes, Home Depot give me blank faces when I ask about DC breakers. Thanks

westbranch

raymate, The QO line is double rated, go to the Schneider site and look up the exact model in the tables for the info you need...http://www.schneider-electric.com/products/ca/en/4200-circuit-breakers/4280-direct-current-dc-rated-circuit-breakers/7218-dual-rated-ac-dc-circuit-breakers/

hth

waynefromnscanada

raymate wrote: »

Sorry to hijack, but waynefromnscanada can you tell me where you got your DC breakers from and what brand and spec, I'm in Toronto and I'm finding it hard to get may hands on some. I want just small 5amp ones but the likes of Lowes, Home Depot give me blank faces when I ask about DC breakers. Thanks

As Westbranch noted, the Square D "QO" breakers are DC rated for up to 48 volts. These are standard AC breakers that are also rated for DC, but at reduced voltage compared to their AC rating. You should be able to get Square D, QO breakers at almost any hardware/building supply, or electrical supply store.
In most cases, the employees will not know these QO breakers are also DC rated, and may not even know what DC is, so to prevent the blank stares, questions and lectures, just insist on Square D, QO breakers, don't accept any substitutes, and don't mention DC at all.
Re "small 5 amp", I'm sure the "smallest" you'll find is 15 amp, and that could be a problem for you, depending on your needs.

Plowman

raymate wrote: »

Sorry to hijack, but waynefromnscanada can you tell me where you got your DC breakers from and what brand and spec, I'm in Toronto and I'm finding it hard to get may hands on some. I want just small 5amp ones but the likes of Lowes, Home Depot give me blank faces when I ask about DC breakers. Thanks

After getting the same blank stares and lack of options at the local big boxes, I ended up ordering Midnite Solar's 12V circuit breakers online. Our host appears to have the best prices on these, here's a 5-Amp. They're pretty handy, don't require special bus bars or anything, can use bare wire. They do require a DIN rail to mount them, but those are cheap. I got a 12" rail on eBay for a few bucks.

After starting this thread more than a year ago my circuit protection has become a mix-and-match of various sundry circuit breakers and fuses, but I plan on putting Midnite breakers on every circuit. Right now I just have them in my combiner box for each panel, plus a 63 Amp breaker on my batteries.

Mountain Don

NAWS also sells DIN rail material.

raymate

Plowman wrote: »

After getting the same blank stares and lack of options at the local big boxes, I ended up ordering Midnite Solar's 12V circuit breakers online. Our host appears to have the best prices on these, here's a 5-Amp. They're pretty handy, don't require special bus bars or anything, can use bare wire. They do require a DIN rail to mount them, but those are cheap. I got a 12" rail on eBay for a few bucks.

After starting this thread more than a year ago my circuit protection has become a mix-and-match of various sundry circuit breakers and fuses, but I plan on putting Midnite breakers on every circuit. Right now I just have them in my combiner box for each panel, plus a 63 Amp breaker on my batteries.

Thanks for all your replies, I just ordered a midnite baby box and 4 breakers from wind & sun 5,7,10 amps