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Old 08-24-2009, 02:27 PM   #1
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How to determine amps coming to main panel?


I apologize if this is an easy question--I don't know a great deal about amps. I am looking at a hot water heater that requires at least 200 amps coming to the main panel. The door of my panel cover says, "200A Main Breaker," and the ratings section says, "200A Max; 120/240 VAC, 3 wire, single phase; 208Y/120 VAC, 3 wire, single phase," so I assume I am okay, but I wonder if that's too close? I'll put a link to the heater, and I read about the 200A requirement in the comments section. Thanks!
Ryan

http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

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Old 08-24-2009, 02:42 PM   #2
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How to determine amps coming to main panel?


That tankless system, needs 120a JUST to run
That's 60% of the available power in your house

What else do you have that uses electric?
That will determine if you have enough spare power
But most will recommend not going with an electric tankless

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Old 08-24-2009, 02:48 PM   #3
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How to determine amps coming to main panel?


The specs say 3 seperate 40amp breakers so that is 120 amps, and 6 #8 wires plus a ground with 200amp min breaker box. Is your house all electric as far as big ticket items? One thing for sure when it fires up and the AC, Range, Dryer, & what ever else is going the electric meter is going to be spinning mighty fast! over 50%of the power coming in to the home just for WH. I could never see the advantage of the tankless heaters gas or electric. The new tank type models are super insulated and Energy Star rated, and a lot less expensive in price, less maintenance also. But that is just my opinion for what that is worth.

(Quote):


The PowerStar AE-125 electric tankless water heater is designed to replace an electric storage tank heater. Advantages include endless hot water, reduced electricity costs and substantial space savings. Provides 4.0 gal. per minute for water usage at 105 F (assumes 60 F inlet temp.) for 1 shower or bathtub or 2 sinks simultaneously. 240 volt. 95% efficiency rating. 10 year warranty on unit, 1 year on parts. REQUIRES Hard Wiring and 120AMPS
  • Requires 240V Hard Wiring and 120 Amps
  • This Model Requires 3 Separate 40 Amp 2-Pole Circuit Breakers and Six #8 Awg Wires + Ground (Min. 200 Amp Breaker Panel)
  • 95% Efficiency Rating
  • External Temperature Control Knob
  • Flow Sensor to Provide a Constant Output Temperature
  • MFG Brand Name : PowerStar
  • MFG Model # : AE-125
  • MFG Part # : AE-125
Specifications
  • ADA Compliant : No
  • Amperage : 120 A.
  • Assembled Depth (In Inches) : 4.5 In.
  • Assembled Height (In Inches) : 15.5 In.
  • Assembled Weight (In LBS) : 22
  • Assembled Width (In Inches) : 15.25 In.
  • BTU Heat Rating : 0 Btu/h
  • CSA Certified : Yes
  • Commercial/Residential : Residential
  • Draft Hood Size : 0 In.
  • ETL Safety Listing : No
  • Energy Star Compliant : No
  • EnergyPlus : False
  • Flow Rate @ 45F Rise : 4 GPM
  • Fuel Type : Electric
  • Gas Connection Size : N/A
  • Gas Or Electric : Electric
  • Gas Type : Other
  • Height : 15.5 In.
  • Maximum BTU : 0 Btu.
  • Tank Capacity : N/A Gal.
  • Temperature Range : up to 131F
  • Voltage : 240 V.
  • Warranty (Labor) : 0.00
  • Warranty (Parts) : some
  • Water Connection Size : 3/4"
  • Watts : 26850 W.
  • Weight : 22 Lbs.

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Old 08-24-2009, 02:51 PM   #4
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How to determine amps coming to main panel?


It's going to depend on what else you have running in the household full time. If you don't have any gas utilities or geothermal heating/cooling you might run into issues.

Scuba is correct, unless I were building a new home, I don't know that I'd install an electric tankless system.
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Old 08-24-2009, 03:24 PM   #5
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How to determine amps coming to main panel?


You quite possibly will need to install another 200 amp service just for the tankless. Add that into the cost of the tankless install before you decide to pursue this avenue.

You should also let your power company know about this new load.
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Old 08-24-2009, 07:53 PM   #6
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How to determine amps coming to main panel?


Quote:
...Energy Star Compliant : No....
Your actual load on this thing is 3 x 8950 watts = 26850 watts total. Approx. 112 Amps. (3)-40 Amp circuits sounds normal for this type of thing.

Depending on the other loads on your electric service, you may or may not have sufficient capacity for such an appliance.
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Old 08-24-2009, 08:02 PM   #7
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Stick with a tank type water heater and you won't regret it.
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Old 08-24-2009, 08:06 PM   #8
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How to determine amps coming to main panel?


Quote:
Originally Posted by junkcollector View Post
Stick with a tank type water heater and you won't regret it.
1000% agree.
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Old 08-24-2009, 08:32 PM   #9
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How to determine amps coming to main panel?


Woah, I hope you're planing to buy a couple hydro dams to power that thing!

120 amps, really? That's a LOT of power for a single device. I would be concerned about how much it's going to cost to run that.
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Old 08-24-2009, 09:26 PM   #10
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How to determine amps coming to main panel?


How can your BTU rating be zero? It's supposed to be
4.0 gal. per minute for water usage at 105 F (assumes 60 F inlet temp) makes 89,640/hr
@ 91% efficient at 120A [about the same as a tank heater].

Last edited by Yoyizit; 08-24-2009 at 09:35 PM.
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Old 08-24-2009, 10:37 PM   #11
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How to determine amps coming to main panel?


Ryan.,

If you are serious about going tankless waterheater just goggle or search it in this fourm look up word " tankless waterheater " you will get a bit of past infomation including myself I did make few comments and I know few members here allready dealt with that before so.

Few members here make a good points here

If you going tankless route you will need to increase the service size to at least 400 amp singlephase { some area may force you go with three phase due the distubation size }

There are few quirks with tankless heater no matter what the manufacter tell ya they leave few info out so we will fill in the blanks here

Check on the price going from 200 to 400 amp service you will say Holy crap and we are not kidding on price and most common way to deal with it is install the class 320 meter socket basically a 400 amp resdential meter socket { some POCO may not allowed to use the 320 socket }

The other thing with electric tankless waterheaters that it will make the light flicker no question asked that why many POCO is getting strict with this.

I have one service call not too long ago the customer installed 24 KW tankless waterheater and blew the POCO transfomer and they were not happy camper they have to find the cuprit and bill to that customer for the transfomer

The other thing is the tankless waterheater don't like hard water at all they will get scaled up and need to clean out pretty often.

So my suggest is stay with tank waterheater it cheaper and it very durable and not much can go wrong at all.

Merci,Marc
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Old 08-25-2009, 11:22 AM   #12
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How to determine amps coming to main panel?


Quote:
Originally Posted by frenchelectrican View Post
If you going tankless route you will need to increase the service size to at least 400 amp singlephase { some area may force you go with three phase due the distubation size }

The other thing with electric tankless waterheaters that it will make the light flicker no question asked that why many POCO is getting strict with this.

The other thing is the tankless waterheater don't like hard water at all they will get scaled up and need to clean out pretty often.

So my suggest is stay with tank waterheater it cheaper and it very durable and not much can go wrong at all.

Merci,Marc
How come they get along with these things in Germany?
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Old 08-25-2009, 11:56 AM   #13
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How to determine amps coming to main panel?


WOW....120 amps.....Personally, I'm not so sure I'd use this in my home. 120 amps being used, say, while taking a shower. That only leaves 40% of the available safe amperage (assuming a 200 amp main) for other high amp loads in your home for things like cooking, heating, drying clothes etc, if these items are electric. IF they were gas appliances with a 200 amp main you'd probably be fine. But, then again, with gas heating and cooking you'd probably only have a 150 amp service in a normal sized home and only 20% left, depends on local codes of course. At least, I wouldn't take a long hot shower while the wife is cooking Thanksgiving or Christmas dinner and it's 30 degrees outside.....you'd probably be maxing out your main breaker. At least though, it's a balanced load so you wouldn't load up the neutral. Just some thoughts to consider......
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Old 08-25-2009, 12:22 PM   #14
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How to determine amps coming to main panel?


gotta agree.... 120 amps.... wow....
electric hot waters can be as much as 20% of your bill.
my 50g HWH electric is worth every penny. it's heavily insulated and stays hot forever when the power goes out.
installed it myself easily and i've had 0 problems with it.

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Old 08-25-2009, 12:28 PM   #15
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How to determine amps coming to main panel?


Quote:
Originally Posted by DangerMouse View Post
electric hot waters can be as much as 20% of your bill.
my 50g HWH electric is worth every penny. it's heavily insulated and stays hot forever when the power goes out.
installed it myself easily and i've had 0 problems with it.

DM
Mine takes 35 therms/mon of NG for two of us, which would be $160/mon at my kwh rate.

Before insulating my WH [30 yrs ago] the element was on 5 min each 5 hrs; after, 5 min each 7 hrs.

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