Replacing 240V 'double' breakers with two 120V ones?

[Ashyukun]

The electrical box in our new house is a bit of a head scratcher in multiple ways- there are for example breakers that I have been completely unable to determine what exactly they do- but one thing that is clear is that there are two 240 doubled-up breakers that have nothing at all hooked up to them. I'm looking to add some wired smoke detectors to the house and have been told that I need them on their own independant circuit- so I was hoping I could fairly easily just replace the big 240 breaker with two smaller 120 ones and use one for the new smoke detector circuit. Is it really just as simple as popping the old one out and putting two smaller ones in and then hooking up the wiring? Thanks!

[zolotiyeruki]

I believe it *is* really that simple.  See, you have two 120V lines coming into your house 180 degrees out of phase, and your dryer/oven/whatever connects to both of them in order to get the 240V.  So one half of that double breaker connects one 120V line, and the other half connects the other 120V line.  Single-height breakers will each connect one 120V line to the new circuit, so you'll be fine.

[Milspecstache]

Yes, it is that simple.  Just be careful messing inside the panel as it will always have something 'hot' in it, even if you flip the main breaker.  If we were at my toolbox I could show you some tools that got arced to give you some examples of what not to do (not entirely my fault as a bozo had sent 220v down 12/2 wiring).

I have my smoke detectors on my lighting circuit.  The benefit there is that if the breaker trips, securing power to the smoke detectors, I will know because the lights will be out also.  The load on modern lights (using CFL or LED) and smoke detectors is pretty minimal so not sure why you wouldn't want them together.

[zolotiyeruki]

I believe the reason they have to be on their own circuit is to minimize the chances of the breaker tripping due to other loads, and leaving you without working smoke detectors.

[paddedhat]

I believe the reason they have to be on their own circuit is to minimize the chances of the breaker tripping due to other loads, and leaving you without working smoke detectors.

Actually code requirements are that the smoke detectors share a circuit with a commonly used circuit. Most inspectors in my area check to confirm that the smokes are tied into a bedroom circuit. The smoke detector circuit then has a sort of monitoring system assuring that there is always power to the circuit.  If they were wired on a totally separate circuit they can trip and you wouldn't know. If they are tied to a bedroom circuit, when the circuit trips there is no power to lights and outlets in the room, and you will address the problem. The entire system, when in operation, has a negligible amp draw, and won't cause issues when added to another circuit. The only other thing I would add is to make sure that you have at least one smoke/CO detectors outside the bedroom doors if there are any fuel burning appliances in the home. Just to clarify, all of these unit are 110V with battery back-up, so even if they do lose power for extended periods they will function as an interconnected system until you allow the batteries to go dead.

[zolotiyeruki]

That's interesting--in our home, the smoke detectors are all on a dedicated circuit, with nothing else.

[Nords]

The electrical box in our new house is a bit of a head scratcher in multiple ways- there are for example breakers that I have been completely unable to determine what exactly they do- but one thing that is clear is that there are two 240 doubled-up breakers that have nothing at all hooked up to them. I'm looking to add some wired smoke detectors to the house and have been told that I need them on their own independant circuit- so I was hoping I could fairly easily just replace the big 240 breaker with two smaller 120 ones and use one for the new smoke detector circuit. Is it really just as simple as popping the old one out and putting two smaller ones in and then hooking up the wiring? Thanks!

Yes, it is that simple, and the bonus is that as soon as you take them out then someone in your household will suddenly learn what they were supplying...

When you say "nothing at all hooked up to them", are you saying that the panel doesn't even have wires connected to those breakers?  Because if the panel has wires connected to the breakers, then I'd wonder what's at the other end of the wires-- it might even be something unusual like exterior 240v for an EV or a photovoltaic feed.

[dragoncar]

Just be careful messing inside the panel as it will always have something 'hot' in it, even if you flip the main breaker. 

Can you elaborate on this? 

[paddedhat]

Just be careful messing inside the panel as it will always have something 'hot' in it, even if you flip the main breaker. 

Can you elaborate on this?

Typically when viewing the opened panel, there are two large wires coming in from the service cable. They are usually attached to large connectors at the top of the panel. These lugs are usually exposed and cannot be turned off, as they are on as long as the utility power is on. Typically you will see large flat aluminum colored bars at the bottom of the breaker attachment area. These bars are flat and have various bends and tabs attached. This is the "Bus" area where the breakers attach. Each bar is operating at 120 volts. The voltage from bar to bar is 240 volts, and they are hot and can only be turned off with the main breaker.

[dragoncar]

Just be careful messing inside the panel as it will always have something 'hot' in it, even if you flip the main breaker. 

Can you elaborate on this?

Typically when viewing the opened panel, there are two large wires coming in from the service cable. They are usually attached to large connectors at the top of the panel. These lugs are usually exposed and cannot be turned off, as they are on as long as the utility power is on. Typically you will see large flat aluminum colored bars at the bottom of the breaker attachment area. These bars are flat and have various bends and tabs attached. This is the "Bus" area where the breakers attach. Each bar is operating at 120 volts. The voltage from bar to bar is 240 volts, and they are hot and can only be turned off with the main breaker.

Ah, I see what you are saying.  Around here, we commonly have a large cutoff box outside the house.  I was confusing that "service shutoff" or whatever it's called with the "main breaker" you mentioned.  Seemed like that would adequately shut off power to the whole house.  Now I see you are just saying you can't shut off all power to the breaker box from within the breaker box itself.

edit: like so:

[paddedhat]

 That's why I tend to be a bit vague when describing a lot of residential work to a geographically diverse audience. In the states, a big percentage of residential work is the same for most areas, but there are some glaring exceptions. Most panels that I deal with are inside the home, as close as possible to the exterior meter base, and look like the attached pic.

That said, I have seen everything from main disconnects on a nearby power pole, to exterior panels that have a main panel and a built in sub-panel that cannot be disconnected with a main breaker. This sub-panel feeds any well or water pump on the property, for use in firefighting. Local codes and utilities can dictate some really odd installations in some places.

[Nords]

Most panels that I deal with are inside the home, as close as possible to the exterior meter base, and look like the attached pic.

That picture doesn't look right. 

The panel interior is clean & neat, there's no rust or water stains, and there's no cigarette butts or drywall screws adrift in the bottom.  I bet if you looked really closely and checked with a multimeter you'd even discover that everything is wired correctly and the lugs are tightened to the specified torque...

[GuitarStv]

Woah . . . there's a specific torque to tighten them to?

[paddedhat]

Most panels that I deal with are inside the home, as close as possible to the exterior meter base, and look like the attached pic.

That picture doesn't look right. 

The panel interior is clean & neat, there's no rust or water stains, and there's no cigarette butts or drywall screws adrift in the bottom.  I bet if you looked really closely and checked with a multimeter you'd even discover that everything is wired correctly and the lugs are tightened to the specified torque...

LOL, I know what you mean. That isn't my pic. but my work is always that neat. Over the years it has lead to some interesting side effects.  I had a customer call and ask if I could come and do the cable company's final hook-up at the media distribution center I had installed in his garage. I asked why he wanted to pay me to do something that the cable company is responsible for? He laughed and told me that the tech. looked at my install and told him that he wasn't even going to attempt to add a few cables to the box, since he had no idea how to do work that neat, and didn't want to screw it up.

On another job , I teamed up with two carpenter friends and spent a weekend wiring a new home for a buddy of mine. It was several states away, and in an area known for tough inspections. I really worked at getting my help to do everything neat, and squared away. I left before the rough in inspections, but I was nervous that I might of missed something, or failed to guess what goofy little quirk would piss off the inspector? My buddy called and told me it was the craziest inspection he ever walked through. The inspector checked everything in detail, pressure tests on the plumbing, framing details, etc... At that point my buddy asks if a different guy will be doing the electrical inspection? The inspector then tells him that the electrical passed. Since it was the neatest work he has ever seen,  and obviously done by somebody who knows what they are doing,  he didn't need to waste his time looking for problems. I have found this to be the case wherever I work. If you take a bit of time to do neat work, it really separates you from the
majority of residential electricians who tend to be quick and sloppy, at best.

 I've been attempting to fly under the radar and lead a low key FIRE existence, and I still get calls from other builders and contractors to troubleshoot the garbage that gets done by some of the residential electrical clowns. It can be challenging and sad to sort out some of the shit that passes for electrical work in these parts.  The worst ones are when you take the time to hunt down a wiring F-up and resolve it, only to be told be the homeowner that the original electrician came out several times, and was unable to figure out the problem.

[dragoncar]

Most panels that I deal with are inside the home, as close as possible to the exterior meter base, and look like the attached pic.

That picture doesn't look right. 

The panel interior is clean & neat, there's no rust or water stains, and there's no cigarette butts or drywall screws adrift in the bottom.  I bet if you looked really closely and checked with a multimeter you'd even discover that everything is wired correctly and the lugs are tightened to the specified torque...

LOL, I know what you mean. That isn't my pic. but my work is always that neat. Over the years it has lead to some interesting side effects.  I had a customer call and ask if I could come and do the cable company's final hook-up at the media distribution center I had installed in his garage. I asked why he wanted to pay me to do something that the cable company is responsible for? He laughed and told me that the tech. looked at my install and told him that he wasn't even going to attempt to add a few cables to the box, since he had no idea how to do work that neat, and didn't want to screw it up.

On another job , I teamed up with two carpenter friends and spent a weekend wiring a new home for a buddy of mine. It was several states away, and in an area known for tough inspections. I really worked at getting my help to do everything neat, and squared away. I left before the rough in inspections, but I was nervous that I might of missed something, or failed to guess what goofy little quirk would piss off the inspector? My buddy called and told me it was the craziest inspection he ever walked through. The inspector checked everything in detail, pressure tests on the plumbing, framing details, etc... At that point my buddy asks if a different guy will be doing the electrical inspection? The inspector then tells him that the electrical passed. Since it was the neatest work he has ever seen,  and obviously done by somebody who knows what they are doing,  he didn't need to waste his time looking for problems. I have found this to be the case wherever I work. If you take a bit of time to do neat work, it really separates you from the
majority of residential electricians who tend to be quick and sloppy, at best.

 I've been attempting to fly under the radar and lead a low key FIRE existence, and I still get calls from other builders and contractors to troubleshoot the garbage that gets done by some of the residential electrical clowns. It can be challenging and sad to sort out some of the shit that passes for electrical work in these parts.  The worst ones are when you take the time to hunt down a wiring F-up and resolve it, only to be told be the homeowner that the original electrician came out several times, and was unable to figure out the problem.

Wow can I hire you?  Lol, I'm super worried about contractors doing crap looking jobs (for example if I get solar panels... Routing it down the side of the house in big ugly conduit).  Seriously though any tips on finding tradespeople who have such attention to detail?  I assume they cost more, but any office beyond " ask around"?  Or maybe I'll do most work myself and have a licensed professional do final hookup

[Nords]

Lol, I'm super worried about contractors doing crap looking jobs (for example if I get solar panels... Routing it down the side of the house in big ugly conduit).  [...]  Or maybe I'll do most work myself and have a licensed professional do final hookup

I couldn't find a PV contractor willing to crawl through my garage attic routing 50 feet of wiring & conduit.  They wanted to go down the side of the house in big ugly conduit.

You might find a contractor willing to do "extra" work for substantially extra pay.  But you'd have to expect what you're willing to inspect.

[dragoncar]

Lol, I'm super worried about contractors doing crap looking jobs (for example if I get solar panels... Routing it down the side of the house in big ugly conduit).  [...]  Or maybe I'll do most work myself and have a licensed professional do final hookup

I couldn't find a PV contractor willing to crawl through my garage attic routing 50 feet of wiring & conduit.  They wanted to go down the side of the house in big ugly conduit.

You might find a contractor willing to do "extra" work for substantially extra pay.  But you'd have to expect what you're willing to inspect.

So what happened in the end?  Ugly conduit or DIY? 

[paddedhat]

Wow can I hire you?  Lol, I'm super worried about contractors doing crap looking jobs (for example if I get solar panels... Routing it down the side of the house in big ugly conduit).  Seriously though any tips on finding tradespeople who have such attention to detail?  I assume they cost more, but any office beyond " ask around"?  Or maybe I'll do most work myself and have a licensed professional do final hookup

The best thing I can offer is to find somebody that will be doing work "below their pay grade". For example a commercial or industrial electrician who does side work, and the older the better. Being older not only provides the usual benefits as a tradesman, but a lot of younger guys rarely get to see a job where skills are required. For example, most older commercial/institutional electricians are from a time when most work was done by running metal conduit and pulling wire in it. Most current work of this type has been replaced by Metal clad cable, which is a glorified Romex, and the installation usually looks like dog shit, hidden in walls and above drop ceilings.  A guy who knows how to run metal conduit, and wire industrial equipment, can easily transfer his skill set to doing neat and correct residential work. A lot of residential guys are a product of half-assed vo-tech schools, spend a few years riding shotgun with another semi-skilled Romex slinger, and suffer from the delusion that they are far better than they are.

[Nords]

Lol, I'm super worried about contractors doing crap looking jobs (for example if I get solar panels... Routing it down the side of the house in big ugly conduit).  [...]  Or maybe I'll do most work myself and have a licensed professional do final hookup

I couldn't find a PV contractor willing to crawl through my garage attic routing 50 feet of wiring & conduit.  They wanted to go down the side of the house in big ugly conduit.

You might find a contractor willing to do "extra" work for substantially extra pay.  But you'd have to expect what you're willing to inspect.

So what happened in the end?  Ugly conduit or DIY?

In late 2004 we found a PV electrician who was willing to tutor us on the code, and we did the labor.  We did all the mechanical and most of the electrical-- drilling holes in the roof, mounting racks & panels, and connecting the wiring together.  We strung all the wiring across the top of the roof to the attic (through conduit as required by code), drilled the hole in the attic wall, and routed everything through the attic (inside more conduit) back to the outside wall above the service connection panel by the electric meter.  I think it was a total of 70-80 feet, and only about 20 feet of conduit goes across our roof.  You can't even see it's there unless you're standing in the right location.

The electrician checked our work ("Did they do what I asked them to do?  OK."), mounted the inverter & manual disconnect, wired it to the service panel breaker, and then wired the panels to the inverter.  Then (and this is the really important part) they signed the net-metering request to HECO with their license number.  $750.

We tried to run our own PV permit through the city, but this was the early days of Oahu's residential net metering (we were permit #26).  The permit people didn't understand PV and kept trying to tell us we were doing solar water heating, so we had the electrician run the permit with his pre-approved plans.  That was worth every penny of the $150. 

When the system was connected, they flipped on the inverter and everything worked great.  We faxed the net-metering request to HECO that afternoon. 

Two weeks later we got an unannounced visit from HECO's fraud/theft division.  They had noticed that our electric bill had dropped and they thought we were stealing power.  I showed them the system, gave them a copy of the net-metering paperwork, and asked them to give their net-metering guy (a different depertment) a call.

Two weeks after that the city sent their "PV inspector".  He was actually an electrician, and this was the first residential PV array he'd ever seen.  He was fascinated, but I ended up entertaining the guy for nearly an hour before he felt that he "knew" enough to sign off the job.

It took HECO another year to formally approve the net-metering agreement.  I'm glad that I didn't wait on anyone's permission to flip the switch.

But that was nearly a decade and tens of thousands of PV installations ago, and today things move a little faster.  Hawaii has the nation's highest per-capita residential PV use, and I'd say that three out of every four homes on our street have an array.  HECO is now approving installations up to 120% grid penetration in most neighborhoods and is being pestered to go even higher. 

At a home show a few months ago I heard that there are over 200 PV companies servicing an island with a population of just under a million residents...

[phred]

Woah . . . there's a specific torque to tighten them to?

yes, new electrical code requires torque settings.  This was starting to be discussed down in Florida 20 years ago

[paddedhat]

Technically, everything has a torque spec. and needs to be installed "AMI" or according to manufacturer's instructions. That said, most residential and light commercial inspectors have better things to do than check your work with a torque wrench. Many will inspect a service panel with a large screwdriver and a set of hex wrenches and confirm that you at least gave the service cable lugs a good tightening.

One inspector that I deal with is really sharp and fair. He had an ongoing battle with some idiot that was going to "show him who's in charge". He resolved the issue on final inspection by bringing a small inch/lb wrench and checking proper torque on ALL the devices (switches, outlets, breakers, etc) As soon as he found one that was out of spec. he would red tag the job, and wait for the re-inspect fee to arrive at his desk. After a few weeks of wasted time, and a few hundred in red tag fees, the "electrician" apologized for being an ass, and the job passed.