Fuse vs breaker protection on Taps

[SunNinja]

Looking for code reference that proves a line (or load) side tap must terminate at a fused disconnect, not a breaker?

Something to do with OCPD definition??

I’m looking at doing a load side tap for a new company in a new state. I am accustomed to always using a Fused Disconnect… They are saying they have done it all the time, terminating in a breaker, and that in fact I would be required by the utility to put a breaker in between the actual tap and the fused disconnect… I went to go prove why you have to hit a fused disco, ideally within 10’ so I can just use a 60A fused disco, but I am not finding the proof in 705 or 240 (or anywhere else I could think of). Thanks in advance!

 

[augie47]

The only possible reasons I can think of would be if the load required fusible protection or the fuses helped in reducing a high fault current.

 

[don_resqcapt19]

No such rule. Nothing in the definition of OCPD even suggests what type of device can be used.
Also a load line side connection does not use the tap rules in 240.21(B) as those conductors are service conductors and they terminate in a service disconnect. That disconnect can be an enclosed breaker or a fused disconnect.

Corrected as I typed load when I wanted to type line

 

[ggunn]

No such rule. Nothing in the definition of OCPD even suggests what type of device can be used.
Also a load side connection does not use the tap rules in 240.21(B) as those conductors are service conductors and they terminate in a service disconnect. That disconnect can be an enclosed breaker or a fused disconnect.

You mean a line side connection, I presume. Tap rules are for taps on feeders (load side connections).

Code only says PV AC conductors require OCPD, but many (most? all?) AHJs want a bladed disconnect for a PV AC disco. By code it doesn't have to be fused if the conductors are otherwise protected, but again, the AHJ may want it to be fused, anyway.

 

[Carultch]

You mean a line side connection, I presume. Tap rules are for taps on feeders (load side connections).

Code only says PV AC conductors require OCPD, but many (most? all?) AHJs want a bladed disconnect for a PV AC disco. By code it doesn't have to be fused if the conductors are otherwise protected, but again, the AHJ may want it to be fused, anyway.

That's usually a utility requirement, rather than an AHJ requirement. This device that the OP is asking about, isn't necessarily the same device that a utility would require. The OP is asking about the first disconnect from tap conductors on a feeder tap, or first disconnect from a supply-side interconnection. Code-wise, all it has to be is an OCPD and disconnecting means, in some form or another. Most likely with both purposes as part of the same device, like an ECB or fused disconnect.

It is a likely situation that one properly placed disconnect in a situation allowing it, could serve both purposes. But it is also just as likely that you may have the kind of disconnect the OP is asking about as an indoor device, and the device the utility requires as an outdoor device.

 

[electrofelon]

I have never used a fused disco in a PV system.

 

[BackCountry]

Looking for code reference that proves a line (or load) side tap must terminate at a fused disconnect, not a breaker?

Something to do with OCPD definition??

I’m looking at doing a load side tap for a new company in a new state. I am accustomed to always using a Fused Disconnect… They are saying they have done it all the time, terminating in a breaker, and that in fact I would be required by the utility to put a breaker in between the actual tap and the fused disconnect… I went to go prove why you have to hit a fused disco, ideally within 10’ so I can just use a 60A fused disco, but I am not finding the proof in 705 or 240 (or anywhere else I could think of). Thanks in advance!

I do this often by using a main breaker AC combiner panel with a feeder tap if I’ve got more than one inverter. Otherwise, we do a fused disconnect if it’s just a single inverter.

The feeder tap rule only talks about an OCPD, no specific language on disconnect versus breaker.

I don’t see any application where I’d need a fused disconnect and a breaker.

I do see a safety switch and a breaker if the utility requires a lockable blade safety switch. Where I’m at, that’s only required on 400a and above services.

Safety switches are expensive albeit very obvious. With Enphase, they’re frustrating if they require one because you have to put in a ton of breakers AND a $150+ safety switch.

 

[don_resqcapt19]

You mean a line side connection, I presume. Tap rules are for taps on feeders (load side connections).

Code only says PV AC conductors require OCPD, but many (most? all?) AHJs want a bladed disconnect for a PV AC disco. By code it doesn't have to be fused if the conductors are otherwise protected, but again, the AHJ may want it to be fused, anyway.

yes I do mean line side

 

[ggunn]

I have never used a fused disco in a PV system.

Have you done commercial supply side interconnected PV? I use them all the time in such systems.

 

[electrofelon]

Have you done commercial supply side interconnected PV? I use them all the time in such systems.

Yes quite a bit, although they were not "my" jobs, I was working with another crew. Most of those were around 300kw and some of those did have safety switches to meet a utility requirement. What I meant was there does seem to be an excessive proclivity in the pv industry to use safety fused switches, even when not utility required - in my experience anyway.

 

[ggunn]

Yes quite a bit, although they were not "my" jobs, I was working with another crew. Most of those were around 300kw and some of those did have safety switches to meet a utility requirement. What I meant was there does seem to be an excessive proclivity in the pv industry to use safety fused switches, even when not utility required - in my experience anyway.

Are ECBs (enclosed circuit breakers) significantly cheaper than fused bladed disconnects? For supply side connected PV systems you have to have one or the other.

 

[electrofelon]

Are ECBs (enclosed circuit breakers) significantly cheaper than fused bladed disconnects? For supply side connected PV systems you have to have one or the other.

I think so. I just got prices on these 30A 600v:

3 pole

HF361N -- $230.70/ea

HF361NR (Nema 3R) -- $315.20/ea



2 pole

HF261 -- $197.20/ea

HF261R (Nema 3R) -- $353.90/ea

Not including fuses. Not sure offhand what a small 2 space panelboard is, pretty cheap tho.

If you recall, I mostly do ground mounts now and use 230.40 ex #3 to feed a service panelboard at the array so I don't need a disconnect (utilities here dont require blades disco for resi < 25kw systems). If I was doing a interconnect at the same structure, I would typically use 230.40 ex 2 to feed a panelboard too .

 

[electrofelon]

Here is a 3r mini panelboard, $40

Square D Homeline 70 Amp 2-Space 4-Circuit Outdoor Main Lug Load Center(HOM24L70RBCP) HOM24L70RBCP - The Home Depot

The Square D Homeline 70 Amp 2-Space 4-Circuit Outdoor Main Lugs Load Center is UL listed for residential and commercial power distribution. This load center is built with a plated, aluminum bus bar that

www.homedepot.com

 

[kwired]

"Line side taps" are nothing more than tapping of service conductors. Your taps are still "service conductors". 240.21(D) would apply to those and it basically sends you to 230.91 for more on what is required for service conductor overcurrent protection.

"Load side taps" are "feeder taps" and the protection rules of 240.21(B) apply. Those tap rules there all just say "overcurrent protection" and don't specify fuse or breaker types for any the tap rule situations.

 

[Carultch]

Are ECBs (enclosed circuit breakers) significantly cheaper than fused bladed disconnects? For supply side connected PV systems you have to have one or the other.

Not in my experience. Maybe in 100A/less applications, but it's a rare case for me to have this issue come up on a system that small. I'd normally specify a fused disconnect, if all I need is a disconnecting means / OCPD as the only device in an enclosure. Unless there were a compelling reason to specify a breaker.

Examples:
1. A shunt trip is needed for another application, such as controlling the device via an e-stop button the fire department requires.
2. The breaker is paired with a relay
3. A space-constrained situation, where an ECB fits better.

 

[BackCountry]

Here is a 3r mini panelboard, $40

Square D Homeline 70 Amp 2-Space 4-Circuit Outdoor Main Lug Load Center(HOM24L70RBCP) HOM24L70RBCP - The Home Depot

The Square D Homeline 70 Amp 2-Space 4-Circuit Outdoor Main Lugs Load Center is UL listed for residential and commercial power distribution. This load center is built with a plated, aluminum bus bar that

www.homedepot.com

We use those sometimes on smaller applications.

I stick with a fused disconnect on anything larger purely because the wire size gets too big for the small single breaker panel boards.

One resource I’ve found is Amazon Business for Siemens fused disconnects, they’re cheaper than any vendor we have.

An HNF363R Nema 3R three pole heavy duty 100A fused disco is $391 on Amazon (with prime delivery). About $50 cheaper than our dealer.

Square D and Eaton are more expensive and harder to get in my experience.

Square D does make a 100A rated single breaker enclosure, I haven’t found any other manufacturers that make a 100A enclosure, most top out at 70A, it’s the QO2100BNF. They make a 3 phase version too, but still 240v max. The single phase version goes for about $50, plus a QO2100 breaker at about $80, so $130 is your cost to do a 100A disconnect vs an GF223N 100A fused disconnect is about $140 plus two fuses at about $50 (both indoor rated).

So, $130 for a single breaker panel with a QO2100 versus $190 for a fused disconnect. The only caveat is that the QO load center is 6” wide and 13” tall, whereas a GF223N is 12” wide and 23” tall. For #2 wire, I sure like that safety switch can size a lot better.

Clearly when you move up to a 480V service, things change and you’re back to fused disconnects, while you could get a single breaker enclosure and a bolt on rated breaker — my utility wouldn’t accept that for an interconnection application, it has to be a visible blade disconnect. We’re only allowed to use a breaker for 320A single phase service and below.

 

[ggunn]

Most of the services I deal with are 480/277V, a few are 208/120V, and a very few are 240V high leg, We have a 100kW minimum for commercial PV systems, which is all I design. I only rarely use an enclosed breaker for a PV disco, and that is virtually always for enclosure size considerations.

 

[kwired]

Are ECBs (enclosed circuit breakers) significantly cheaper than fused bladed disconnects? For supply side connected PV systems you have to have one or the other.

Depends, miniature 120/240 volt 2 pole breakers that are 100 amp or less will likely be less than a 2 pole fused disconnect. 3R or higher rating will be higher priced for fuse or breaker enclosures.

 

[kwired]

We use those sometimes on smaller applications.

I stick with a fused disconnect on anything larger purely because the wire size gets too big for the small single breaker panel boards.

One resource I’ve found is Amazon Business for Siemens fused disconnects, they’re cheaper than any vendor we have.

An HNF363R Nema 3R three pole heavy duty 100A fused disco is $391 on Amazon (with prime delivery). About $50 cheaper than our dealer.

Square D and Eaton are more expensive and harder to get in my experience.

Square D does make a 100A rated single breaker enclosure, I haven’t found any other manufacturers that make a 100A enclosure, most top out at 70A, it’s the QO2100BNF. They make a 3 phase version too, but still 240v max. The single phase version goes for about $50, plus a QO2100 breaker at about $80, so $130 is your cost to do a 100A disconnect vs an GF223N 100A fused disconnect is about $140 plus two fuses at about $50 (both indoor rated).

So, $130 for a single breaker panel with a QO2100 versus $190 for a fused disconnect. The only caveat is that the QO load center is 6” wide and 13” tall, whereas a GF223N is 12” wide and 23” tall. For #2 wire, I sure like that safety switch can size a lot better.

Clearly when you move up to a 480V service, things change and you’re back to fused disconnects, while you could get a single breaker enclosure and a bolt on rated breaker — my utility wouldn’t accept that for an interconnection application, it has to be a visible blade disconnect. We’re only allowed to use a breaker for 320A single phase service and below.

A 100 amp fused disconnect won't as a general rule accept conductors over ~ 2/0 AWG nor will a fused disconnect. The bigger issue might be wire bending space if you are running larger conductors even though you only need a 100 amp device.

As far as that 70 amp version pictured, you can get a QO2100BN(+RB for N3R) that has quite a bit more wire bending space than those 70 amp versions have.

 

[SunNinja]

We are using a lot of Siemens outdoor 125A 4-space panels to tie in the solar. Mostly 100A services out here (so weird to me)
Small & cheap. Good for aesthetic, bad for wire bending space.

Original question was answered early on there. Yep, OCPD can be OCPD, doesn't need to be a fuse. It was the most effective way to serve a few functions. Utility required knife handle disconnect, busbar not rated for size of system and we did not prefer to downsize main breaker, OCPD required on inverter.