/diy/ - Do It Yourself

Because:
1. It's code
2. HVAC monkeys are not electricians and require a local disconnect.
3. You can't fuck up the LOTO that easy if it's right there. But it happens. You can't fix stupid and that rule is written in blood.

Thanks for killing a thread to ask a dumbass question you could of googled you dumb fuck.

>>1755289
>Because:

>1. It's code

Begs the question. Why is it code?

>2. HVAC monkeys are not electricians and require a local disconnect.

Understand the need/utility for a local disconnect but the fuses are redundant.

It is redundant on purpose. The extra fuses are a safety device should something else fail.

>>1755294
1. Because people died. They fucked up the lockout by choosing the wrong breaker if at all and got maimed and/or killed. Now it's mandatory to have local disconnect device near HVAC equipment.

2. It's a fused disconnect. Some equipment needs it some not. Depends on what you're working with. Some of those boxes just have a plastic jumper block instead of fusing.

>>1755279
redundancy is safety, retard.

>>1755294
why the hell are you still using fuses anyways?? switch to a circuit breaker already.

Fuses are significantly faster than circuit breakers. Circuit breakers save equipment, fuses save lives.

>>1755279
>Seems redundant.

The fuse box is a means of disconnecting the service within sight, dum dum.

>>1755494
>Circuit breakers save equipment, fuses save lives.

Where does this sort of nonsense come from? I realize most of /diy/ has the electrical understanding of a fruit fly, but damn.

>>1755601
Are you kidding? 50 amps can flow through your body and blow a fuse without you feeling it, but by the time it trips a breaker you'd be dead.

>>1755294
>>1755279
why not just have a safety switch.

>>1755612
Youre an actual dumb cunt

>>1755612
Kill yourself faggot

>>1755279
>Why do I need an additional fuse box behind the circuit breakers for 220V equipment (Air Conditioners, Hot Water Heaters, etc).
Because the equipment is up in a very inconvenient location, and the disconnect and fuse box allow the power to be shut off at the unit as it is being serviced without having to dick around with determining which breaker is feeding it.
You would understand why they're convenient if you have done any HVAC work yourself. Breaker boxes are almost never labeled accurately or conveniently. And they're usually a long way away from where you need to work.

>>1755297
So my coffee pot needs a fuse box?

>>1755830
No just that assholes' short temper when he tries to talk about something he knows nothing about. He's probably a failed electrician who became a plumber and needs to give people stupid electrical advice.
>>1755469
No it's not dumbass, it's actually a hazard.
>>1755490
Breakers are not an isolation devices you fucktard.
>>1755494
No.. They're not. Not anymore boomer. Also fuses are more hazardous because dumbfucks always put in the wrong ones when they blow. Please neck yourself you walking accident waiting to happen.
>>1755504
Based smrt smrt anon
>>1755612
Dumb strawman argument and you know it basedboy.
>>1755631
That's what a disconnect is. It's a "safety switch" when it has a lock.
>>1755646
A very worthy answer, better than my reply >>1755300
>>1755612
>the most honest post in the thread.

I like how diy is full of armchair EEs with a chip on their shoulders.

local breaker or fuse at equipment is to keep safe so if out of sight breaker is turned on the tech will not get shocked/dead... just a safety thing...

If you don't have a disconnect outside for your AC, the bill just went up because now I have to waste time walking in and out of your house to kill/regain power to the uint.

If your breaker box/fuse box inside isn't labeled. Fuck you. I ain't even looking at it til you get an electrician out there to label all that shit. I'm not playing a guessing game of which 30-60amp breaker is the AC only for your dumbass to call back in the next day because one of the breakers I flipped happen to shit the bed and now your fridge isn't/wasn't running and all your food spoiled.

>crawl 30 feet in a tight crawl/attic only to find out the furnace/airhandler has no blower door kill switch or power disconnect
Fuck you fuck you fuck you I hope your house freezes, pipes burst, and then the fucker burns to the ground.

>>1755900
>Breakers are not an isolation devices
infact they are and the common amp range is sometimes cheaper than a dedicated switch

>>1755601
why does /diy/ think it's okay to talk shit to me? i'll fucking find you and turn you into a fruit fly bro. where do you live?

>>1755601
A circuit breaker takes 5 ac sine waves to trip, fuses take half a cycle. On a 60hz line thats 5ms vs .5ms

>>1757760
No licensed electrician in the world will ever agree with you. Molded case breakers are not switches and they are by no means cheaper than a switch.

>>1755612

try this theory out yourself .

>>1758070
And to clarify on this. If a person shorts to ground, they dont only pull the 50 amps the breaker is labeled for, they pull all of the amperage the transformer can put out, so if you have a breaker it will allow 5 cycles of possibly 20k amperage (commercial) or more, vs half a cycle.

>>1758070
Do you normally talk out of your ass or did you have a special dish of steamy bullshit for breakfast today?

>>1758077
>what is ohms law

>>1758080
What are you talking about?

>>1758079
Here you go

>>1755279
It probably also serves as overload protection for motor loads like your AC unit.Your breakers might not be capable of being sized to the correct size to accomplish this. In cases like I just mentioned you will need 1 of the following, a thermal protection integrated into the motor/compressor/pump, STO, SSU, mag starter, or fuses.. Often times the motors are thermally protected but when we get to 3 phase its usually fuses as that is the cheap option if it doesn't need something to control it like an elaborate heating control system.

I will be honest I am a little shaky in this area of the code since I do bigger jobs that have engineers spec everything. Also lots of times engineers will spec things over and above code just for peace of mind.

oh and a disconnect within sight is a big one. 2 birds 1 stone.
So I will refer you to Part 4 of section 440 in the 2020 NEC for your AC units.

With your water heater its usually just a switch for convenience, but in the off chance your water heater has an overcurrent rating that doesn't match up with a standard breaker size then you need to fuse it to the proper size.... typically when talking electric water heaters you can have them be 220 rated and it will need like a full load of 8A and then you x 125% = 10A.. well they don't make a 2 pole 10A breaker so it will be a 2 pole 15A and fused down to 10A.. just an example don't beat me up.. I haven't wired a normal water heater in years. Or just go read through section 422.

>>1758086
So you lied about everything here >>1758070, but cherry picked fusing time, which you couldn't even calculate correctly. What was the point of this Toilet humor?

>>1758088
Is there a market for used Square D I-Line Busway switches and quick disconnects. 270/480 models. I

>>1758336
Explain how its a lie.

>>1755279
I like how almost no one answer the actual question.

Clearly, OP is asking why its fused rather than just a disconnect.

Its definitely not code here (Canada) and I doubt its code anywhere else as long as the circuit breaker is dedicated to the AC (code) and sized correctly (code).

Assuming the fuses in the disconnect are lower than the circuit breaker they are fed from, that means the circuit breaker would only be protecting the wire from the breaker to the fuse, which is stupid.

This is actually against code in certain situations.

>>1758415
doubt it, pretty much trash, gut it and recycle if you can.

there is a used market for used breakers/refurbished breakers. Nobody really wants to do a panel/gear change if we can find a working breaker that fits the needs. Some of them get kind of costly actually since they know you need it and are trying to avoid doing a $2k panel change so they market it up pretty good. You can also usually sell the old breakers to them too, granted at like $2/ breaker but when you do 2-300 at a time it adds up.

>>1758572
Totally legal in Canada if the fuses were the "overload device", or is a requirement by the manufacturer (which trumps csa). Also, circuit breakers, particularly molded case, thermo electric breakers only protect the wire, not the device, as per code in canada (arc detect, or just oc). Gfi is only for humans. It's relays that protect devices (differential, ngr, overloads, undervoltage, thermo and start inhibits). Tbh I don't know where it even says you have to electrically protect equipment. Protect humans from equipment, protect cables from humans, but not protect equipment itself from an electrical standpoint.

>>1758086
>0.5 cycle fault clearing time
Does this mean it'll blow within ~8ms@60Hz and 10ms@50Hz? Or what is a cycle?
Haven't posted itt yet and no opinion on fuses so no need for an angry reply. Just curious. Thanks.

fuse probably saves more lives than a breaker does but I think this is code to prevent catastrophic equipment failure. if someone doesn't maintain their unit then that fuse should fail before anything else does.

>>1755294
>Begs the question. Why is it code?

Code is generally not for you. Code is for the stupidest person you can think of. Code is for the low cogs that will do dumb shit like apply tape to a breaker so it can't flip during the hot summer months or sheisty slumlords that would rather pay their retard cousin 30 bucks to do some work than licensed tradesmen.

Making something convenient a building regulation is important too, Nobody goes above and beyond code standards besides when it's convenient or when the homeowner is willing to pay for it. HVAC guys have no idea what they are getting into when they go to a house call. This makes isolation simple and easy for them. for what might cost an extra hundred bucks of parts and labor during construction will save thousands down the line for the homeowner. If it weren't a strict code then nobody would do it and HVAC guys would have to isolate breakers until they found the correct one- which could potentially take an hour or so.

>>1758888
>HVAC guys have no idea what they are getting into when they go to a house call. This makes isolation simple and easy for them. for what might cost an extra hundred bucks of parts and labor during construction will save thousands down the line for the homeowner. If it weren't a strict code then nobody would do it and HVAC guys would have to isolate breakers until they found the correct one- which could potentially take an hour or so.
Czeched, and I never thought about it this way.

>>1758563
Because panel breakers don't do that. No fucking breaker does, not with a thermo trips. Your weenie lighting panel breakers are based on i2t. Could take hundreds of cycles, depending on the amplitude of the current. Furthermore half cycle on 60hz is 8ms. That rating for a fuse is based on a known current and its clearing time is proportional to that current, again i2t, its just alot less tolerant when it crosses the sensitivity threshold. But I can show you plenty of fuses that are slower than breakers, and that's why engineers do coordination studies.
>how is it a lie
Because you went to a code class and started spewing potentially life saving/ending numbers without a clue like your some sort of "pro" to people who will. Take this as gospel now. As much as I'd like to see the trolls fry themselves here, your shitty advice is a danger to the uneducated.

>>1755279
Because if you need to quickly shut off power to the condenser you’re not gonna run 200 feet to the main panel to shut it off, occasionally the condenser comes miswired from the factory. Once I was installing a heat pump and the reversing valve didn’t have the leads connected to it in the factory and we turned it on and suddenly it’s running at 450psi. If I had to run to switch it off it could have burned up the compressor and turned their brand new unit into a paperweight. Also a lot of old ones are just a non fused disconnect, fused ones are a relatively recent thing.