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Old 09-14-2007, 11:57 AM   #1
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Electricity for water heater


Looking to go electric on-demand hot water, the unit we need requires 2 60amp breakers but has a maximum draw of 100amps (that's what the manufacturer tells me). I only have 100 amp service as it is in my home, so we're talking at least 50 if not 100 additional amps run from the pole. My question: knowing it won't draw more than 100amps at max load, can I put 2 60amp breakers in a 100amp panel?

......that thing they call "code" always gets in my way

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Old 09-14-2007, 12:29 PM   #2
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Originally Posted by moneymgmt View Post
Looking to go electric on-demand hot water, the unit we need requires 2 60amp breakers but has a maximum draw of 100amps (that's what the manufacturer tells me). I only have 100 amp service as it is in my home, so we're talking at least 50 if not 100 additional amps run from the pole. My question: knowing it won't draw more than 100amps at max load, can I put 2 60amp breakers in a 100amp panel?

......that thing they call "code" always gets in my way
What, exactly, are the ratings of the heater as listed on the ratings sticker/plate? I assume this is single phase at 110v.

A second question: why would you choose such an expensive device to heat your water? These things are only cost effective if the number of people using them is 1 or 2 people. If more than 2 people use this, a storage hot water service is recommended.

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Old 09-14-2007, 12:54 PM   #3
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can I put 2 60amp breakers in a 100amp panel?

Really, that's what I need to know. Forget the appliance attached to it, it doesn't matter.

I a bit insulted by your assumptions. What basis do you have for your recommendation? I do happen to only have 2 people in my house, but here's some info: there are tankless heaters that will raise water temp 55 degrees at a rate of 4.5gpm. Maybe I do not find them expensive in comparison.
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Old 09-14-2007, 01:19 PM   #4
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Originally Posted by moneymgmt View Post
Really, that's what I need to know. Forget the appliance attached to it, it doesn't matter.

I a bit insulted by your assumptions. What basis do you have for your recommendation? I do happen to only have 2 people in my house, but here's some info: there are tankless heaters that will raise water temp 55 degrees at a rate of 4.5gpm. Maybe I do not find them expensive in comparison.
Your sensitivities about being asked simple & harmless questions do not worry/concern me. If you wish to turn a simple question into a problem, go for it!

In the meantime, there is such a thing called 'maximum demand', which, in Australia, can answer your question.
Upon looking at your situation (the info you have provided), I think that you will have exceeded your 'maximum demand' & therefore cannot install such a device unless you upgrade the supply to your residence.
Mind you, this is from an Australian who is not familiar with US 'codes' but Amps are the same in Australia as they are anywhere.
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Old 09-14-2007, 02:23 PM   #5
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Yes, amps are the same. Forget increasing power to the house, it is not a part of the question. I agree with you, it is a "simple question": can I use breakers rated for more power than the box itself.

I'm laughing now, somebody please give me a yes or no.
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Old 09-14-2007, 02:30 PM   #6
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Originally Posted by moneymgmt View Post
Yes, amps are the same. Forget increasing power to the house, it is not a part of the question. I agree with you, it is a "simple question": can I use breakers rated for more power than the box itself.

I'm laughing now, somebody please give me a yes or no.

BUT whether or not it is part of the question is irrelevant. That is the proper solution --> increase the service.
With your lack of knowledge and especially attitude, I wouldn't let you wire up the Christmas tree lights .. there might be children in that house.
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Old 09-14-2007, 02:33 PM   #7
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Quote:
Originally Posted by moneymgmt View Post
Looking to go electric on-demand hot water, the unit we need requires 2 60amp breakers but has a maximum draw of 100amps (that's what the manufacturer tells me). I only have 100 amp service as it is in my home, so we're talking at least 50 if not 100 additional amps run from the pole. My question: knowing it won't draw more than 100amps at max load, can I put 2 60amp breakers in a 100amp panel?

......that thing they call "code" always gets in my way
Since you acknowledge that Amps are Amps, no matter where they are in the world, looking at your above statement tells me that you cannot do what you wish to do unless you upgrade you supply conductors.

On the other hand, tell me how many power points, lights, hot water heaters etc you have in your house & I will do a maximum demand calculation for you. This is the general way to calculate the size of the incoming mains. In Australia, most residences are single phase & generally are allowed 80 Amps (@ 240volts). In the US, this figure will be about double.
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Old 09-14-2007, 02:42 PM   #8
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Electricity for water heater


Quote:
Originally Posted by moneymgmt View Post
Looking to go electric on-demand hot water, the unit we need requires 2 60amp breakers but has a maximum draw of 100amps (that's what the manufacturer tells me). I only have 100 amp service as it is in my home, so we're talking at least 50 if not 100 additional amps run from the pole. My question: knowing it won't draw more than 100amps at max load, can I put 2 60amp breakers in a 100amp panel?

......that thing they call "code" always gets in my way
This will work only if you have no other electrical appliances in your house. Forget it. Your service is too small to support this appliance.
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Old 09-14-2007, 02:46 PM   #9
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This will work only if you have no other electrical appliances in your house. Forget it. Your service is too small to support this appliance.
I'm very much inclined to agree with you Househelper
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Old 09-14-2007, 02:47 PM   #10
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Ok, I seem to be miscommunicating, I appologize. Increasing service to the house is a GIVEN. That's why I'm not asking if I should, its common sense and I WILL. I am in the US, where few new houses are built with under 150 if not 200amps.... yes, we're rediculous energy wasters. So lets forget about the rest of my house, this unit will have its own meter (much like a hot tub or air conditioner).

So I'll re-phrase the actual question again in a little scenario: I have 100amps coming into a box with a 100amp main breaker. This box is feeding ONE appliance.... no other circuits.... which is rated for 100amps at max load. However, proper installation of this appliance requires 2 60amp breakers. Can I put 2 60amp breakers in a 100amp box.

Technically I would assume it to be ok, if it ever pulls over 100amp the main trips and so what. Code wise, I wonder if I'm going to be ok.
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Old 09-14-2007, 02:55 PM   #11
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Quote:
Originally Posted by moneymgmt View Post
Ok, I seem to be miscommunicating, I appologize. Increasing service to the house is a GIVEN. That's why I'm not asking if I should, its common sense and I WILL. I am in the US, where few new houses are built with under 150 if not 200amps.... yes, we're rediculous energy wasters. So lets forget about the rest of my house, this unit will have its own meter (much like a hot tub or air conditioner).

So I'll re-phrase the actual question again in a little scenario: I have 100amps coming into a box with a 100amp main breaker. This box is feeding ONE appliance.... no other circuits.... which is rated for 100amps at max load. However, proper installation of this appliance requires 2 60amp breakers. Can I put 2 60amp breakers in a 100amp box.

Technically I would assume it to be ok, if it ever pulls over 100amp the main trips and so what. Code wise, I wonder if I'm going to be ok.
I certainly can't answer this question because I'm not sure if the device actually uses 2 phases or otherwise. My guess is that Househelper may be able to answer this for you, although it still sounds like you will need to upgrade you supply (as you have acknowleged), but upgrade to what level? This is where a maximum demand calculation comes into play (unless this is not part of the US regs). Forgive me please if I am wrong.
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Old 09-14-2007, 03:09 PM   #12
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The panel with the 100 amp breaker will state the largest breaker that can be installed!
It should not be a problem to install 2 60 amp breakers in a 100 amp box.
The amperage of the breaker have nothing to do with the amount of power actually used.
If the water heater has a max draw of 100, then the panel will be able to handle that draw.
You may not be able to add anything else in the future to this panel.
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Old 09-14-2007, 03:50 PM   #13
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Money...
OK...that's a bit better.... not much, but you are trying....
I'd let you wire the lights on the Christmas tree now ....
nothing more .... so don't start smilin' yet ...
-----------------------------------------------------
I assume your present service is a 100a rated overhead drop. If different, other methods are used in our area.
In my area, electric water heaters are feed from a tap on the source side of the service (in the meter can).
(The electric water heater feed is NOT located in the indoor main service entrance panel).
That tap is fed from the meter can goes to a separate radio (frequency controlled) on demand "disconnecting device" which is NOT accessible to the homeowner. This is done with multiple # 6 1/C through a 2" rigid conduit nipple..
This "disconnecting device" is for load shedding during times of ultra high demands on the local power utility. How often is it used .... rarely .. .maybe 1-2 a summer for only 2 HOURS MAX at any given instance. Residential customers in our area also have this choice for their AC systems. Normally a reduced rate is given in otherwise "normal" operating times, which makes this service "rather" appealing.
The feed from the "disconnecting device" is routed to a dedicated 4 SPACE (2- pole brkr) panel usually mounted right next to the main service entrace cable. These 2 brkrs (generally upper & lower elements) act as the disconnect to the water heater.
The design and requirements in your area are probably different, but this is one very common scenario.
------------------------------------------
PS.... as far as increasing the service....do it...
go to 200a (40ckt panel)....150a is really not worth it....go to 200a....
And, get a lawn chair and watch the contractor do it....so your wife & children can sleep safely in that house...
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Old 09-14-2007, 06:01 PM   #14
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Quote:
Originally Posted by moneymgmt View Post
)

So I'll re-phrase the actual question again in a little scenario: I have 100amps coming into a box with a 100amp main breaker. This box is feeding ONE appliance.... no other circuits.... which is rated for 100amps at max load. However, proper installation of this appliance requires 2 60amp breakers. Can I put 2 60amp breakers in a 100amp box.
Here is the simple answer, yes you can. You could get a 84 space panel being fed from a 100A and put in 84 60A breakers in it, you would never do this but you could.

Once the total loads go over 100A your main breaker would trip.

Look at your 100A house panel and add up the amperage of each breaker. Your dryer and stove will bring it up to 70A alone.
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Old 09-14-2007, 06:19 PM   #15
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Here is the simple answer, yes you can. You could get a 84 space panel being fed from a 100A and put in 84 60A breakers in it, you would never do this but you could.

Once the total loads go over 100A your main breaker would trip.

Look at your 100A house panel and add up the amperage of each breaker. Your dryer and stove will bring it up to 70A alone.

That is absurd.
First...the largest panel APPROVED for residential service only has 40 single pole branch circuit spaces.
Second...the breaker rating has nothing to do with your actual total demand load. The breaker rating is for the safety/protection of the branch circuit conductors.
To get an accurate demand load .... you must do a load calculation, which includes the diversity factor....even for an electric range, etc...

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