[crossrite]

In my home Breaker Panel there are two breakers connected by a bar (labeled "Service Disconnect"), each breaker has a "100" written on them. Is this a 100 amp or 200amp Breaker box? Salesman wants to know what size Breaker Box I have in order to order to correct tankless water heater.

[donf]

Service Disconnect Box is not the box you should be worried about. Your Main Panel Box should have to feeder cables coming in to a 200 Amp Breaker.

The service disconnect is part of the utility companies equipment and is used to disconnect the service VAC the supplies the house.

What is this salesman trying to sell you and why doesn't he have an electrician in hand if he doesn't have a clue about what he needs?

[KISS]

You cannot determine the size of the "breaker box", by the size of the main breaker which is in your case 100. You can infer that you have a 100 amp service from your utility.

The box itself COULD be rated for 200 amps and a 100 amp main breaker was installed. Not likely, but possible.

Salesman wants to know what size Breaker Box I have in order to order to correct tankless water heater.

Did you ask him/her why?

If you take a look here: iTankless.com - Bosch Tankless Water Heater, Rheem Tankless Water Heaters, Takagi, Stiebel Eltron @ iTankless.com

And there is lots of stuff at iTankless.com - Bosch Tankless Water Heater, Rheem Tankless Water Heaters, Takagi, Stiebel Eltron @ iTankless.com

That model requires a 200 amp service for the house. That is, what I believe, why he is asking.

Your probably going to take a performance hit if this is a whole house tankless water heater and you have a 100 A service.

The ganged (2 breakers operated simultaneously) 100 Amp Service disconnect says that you have 100 Amps of usually 240 volt single phase service for residential. This also means that you have 200 amps of 120 V single phase service available, but the industry practice rates it on the highest voltage. Thus you have a 100 Amp service.

[donf]

Crossrite,

Help me out here, please? Is this a new question on your part or are you sending a Private Message to obtain additional information? Now for the smart a** in me. Do not do this again. Either continue the original posting or start a new one. You'll get your question answered faster and probably better written then waiting for me to wake up from a medicine induced 3 hour nap! :(

Also, I'm going to post this response into the original post where it belongs.

The simple answer is you are looking at two individual 120 VAC cables. There is also another wire to the Neutral Bus to supply a neutral or (Zero) tap between the two 120 VAC leads.

Connect two 120 VAC leads to Two different breakers using a shared Neutral and presto, changeo you now have a 240 VAC circuit.

If it is the former and in fact you are looking inside your main panel box, you will see a Single Throw Breaker at the Top of the box, usually in the center. That is a main power breaker to kill all circuits beyond that breaker within the Main Panel Box. If you open (switch the breaker to "OFF") and start playing inside the main panel box, you can get very dead, very quick and quite permanently, if you stick your hands on the Supply in Lugs. There is no margin for error. First Time is usually final time. (My Personal Opinion)

A "Service Disconnect" is external to the Main Panel Box. One of it's purposes is to kill electricity to the main panel box.
So, what exactly are you looking at and what are you trying to do?

If you have removed the Main Panel Box, and are looking at two adjacent breakers (for example the circuit breakers for the range, and we can use the 40 amp range, for educational purposes only). Now this is a standard design to provide you with a 240 VAC @ max 40 amps for range / oven unit.

For ease of conversation, we will use a four conductor cable for the run from the breaker to the kitchen female receptacle.

Okay, here we are bright eyed and dressed for safety, standing on a mildly firm rubber mat, that is clean and dry.

Are your safety glasses on? You have already completed all of the prep work, see it didn't take all that long. The Four copper stranded conductor #8 AWG has been pulled from the kitchen receptacle work box. The 50 Amp female cap has been connected and mounted and the face plate added.

Our resident expert, TK Russell, says to leave and additional 18 inches for the cable work inside the Main Panel Box. Because I don't trust myself, I leave about 24 inches. I don't mind having waste, I hate being 2 inches too short (Kiss, don't hammer me about the missing 2 inches. I put where I hoped I can find it again :))!

Find two adjacent breaker slots to use for the range breaker.

With the main breaker "OFF", you would connect the Black lead to one breaker, the Red lead to the 2nd breaker. White would go to the Neutral Bus Bar and Ground Bus Bar. Do not make a mistake here. White has to go to Neutral, period! Install the new breaker into the Main Panel Box, leave this breaker turned off. Turn on the Main Panel breaker and if everything looks stable, turn on the new breaker.

Hi donf

Please tell me how I Know what size the Breakers are if two breakers, with a bar across them, are labeled with 100 on each is that a 100amp or do you add the two and that makes it a 200amp

[tkrussell]

When have I stated this?:

Our resident expert, TK Russell, says to leave and additional 18 inches for the cable work inside the Main Panel Box.

[donf]

TK,

Are you throwing down the metaphorical gauntlet?

Either in a PM to me during a visit to the woodshed for something dumb that I said or in a posting. It was something along the lines of,"..make sure to leave at least 18 inches of cable to allow for connection points inside the main panel box."

Do I need to stop imbibing in the cough syrup, muscle relaxes and pain killers that are keeping me alive, so to speak? Or do you want me out of electricity and electronics until I'm off that stuff. I must say, I've had several enjoyable trips, leaving every three hours from the spare bedroom, but I always end up flat backed and wondering when in the devil am I!

[tkrussell]

No gauntlet here, this is not that big a deal.

Sorry but I do not recall ever saying leave 18 in in a panel. I know better because panels are all varying sizes, and there is no spec for that. I, if asked, would advice to leave the length and width of the panel.

Don't matter, just wanted to point out that there is no spec or code on this dimension.

As far as the meds you mention... um.. no comment.

[tkrussell]

Cross, I really don't see where Don was rude, but that may only be my perception.

He can be a bit overzealous and colorful with his explanation.

He really does mean well.

Seems he was reprimanding you due to a PM you sent him. It is better to post questions here in the forum, but not absolute law.

P.S. SAFETY NOTE:

While safety glasses should always be worn while doing any work, please do not assume that simple safety glasses are even close to sufficient when working on a live panelboard.

The amount of energy available that will produce an arc blast due to a short circuit in a panel can melt the standard glasses, along with delivering crippling flesh wounds and burns. Proper protective apparel working hot is a whole another topic.

As Don mentions, always shut the Main Breaker off, and if that breaker is in the panel being repaired, the large wires feeding the breaker are still hot. This would require the meter be pulled to kill these feeders,

To anyone reading this,

AND NO DIY"ER SHOULD EVER PULL A METER, leave that to a pro.

To outfit a tech with the proper hot work clothing costs approx. $500.00.

Again, Don meant only the best for you and your project.

Now to the real problem, the tankless water heater. These are power hogs, so careful calculations are needed to insure this will fit on your service.

Best to consult with a pro, it will be worth a service call to size the service and estimate cost for the wiring and any upgrades needed.

[donf]

Okay,

Guys, back to square 1. The only issue I've raised as a concern is the use of a private message back to a responder rather than using the forum posting for that purpose.

I know I sound very caustic currently, however it's just not true. It's like I've beamed backwards in time and I stuck in the hell of the Bronx. For that I do apologize and I work on that as best I can.

Crossrite, If I was severely ticked, I never would have responded back to via the PM. However, I also posted to the forum because that's where both your question and my response needed to be there. I should never get so unhinged that I'm intentionally rude. That's not me, NYC Sarcastic, yeah that's me, but it's genetic and totally without malice.

TK knows me, and when I say to him, are you tossing the metaphorical gauntlet down, I'm not attacking him, I'm bantering with him. I'm trying to find out if he actually wants me to try to find such a statement from him. Either way, I win because I get to learn something new.

This vein of electricity/electronics are an absolute fascination for me and have been so since just after diapers.

I ask for the foreseeable future, until I get off some of this "stuff", tolerate me, within norms. I am definitely not a petty, spiteful prissy little b******. Normally, I the kid in the room full of pony poop, looking for the pony and having a blast doing it.

[sirjamzalot]

Direct and shortform, good answer!

[Stratmando]

I believe I have seen 2 100 amp breakers paralled to equal a 200 Amp breaker.
As for length of wire to leave in a panel or box, Commonly used is length + heigth of panel.
If you know exactly where the wires are going, this number could be shorter, can save wire and money.