Do I need 200 amp?

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  #1  
Old 01-28-13, 01:43 AM
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Do I need 200 amp?

Hey guys.. I wanted to ask you a question.. (maybe it's too late) since I'm getting wired today.. but..

I want to use electric for just about everything in my house.. so..

- Electric stove
- Electric dryer (likely)
- 2 tankless electric water heaters (both needing 50 amp circuit breaker) (possibly wired to 2 different breaker box's )
- (possible) Electric furnace
- My usual household items are computers other than that..

Does that justify a 200 amp panel.. or is 100-125 fine?
 
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Old 01-28-13, 03:43 AM
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I hope you are prepared for your electric bill after installing the electric tankless heaters. "Electric furnace", not sure I am familiar with that one, so fill us in.

To answer your question......I hope a 200 amp panel will be large enough. I think you will find the water heaters will require two 50 amp breakers, each. Some do, some don't. Just check that out before you buy them.
 
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Old 01-28-13, 04:28 AM
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I've already read experiences where people used 1 50 amp or 60 amp with this water heater So I'm pretty sure that's right

I hope you are prepared for your electric bill after installing the electric tankless heaters.
Really, do you really think that.. showers and washing dishes add up to that much?? To bring in a gas meter from the 'gas company' costs $28 a month.. hmm.. you think it costs $28 a month?

I'm more worried about long term use myself.. will it last 5 years?

You can see.. electric furnaces here.. electric furnace in Furnaces & Heating Systems | eBay
 
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Old 01-28-13, 05:31 PM
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Electric furnaces are sized by KW; how big does your electric furnace need to be? Considering that you may have an average size home of 1500 square feet or so and you want to be all electric with two electric tankless water heaters, figure on a 400 amp service (320 amps actually). If you can give us more load information and square footage of home, we can quickly determine if a 200 amp service will handle all the proposed loads. Load calculations need to be done to properly size a furnace, but we can get pretty close with 10 watts per square foot. That would be 15 KW for 1500 square feet, 20 KW for 2000 square feet, 25 KW for 2500 square feet, etc. We also would like to know the KW of the 2 tankless water heaters.
 
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Old 01-28-13, 08:43 PM
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The link went to furnaces for mobile homes. Is that what you have?

Really, do you really think that.. showers and washing dishes add up to that much?? To bring in a gas meter from the 'gas company' costs $28 a month.. hmm.. you think it costs $28 a month?
Using electricity to make heat is both one of the least efficient uses of electricity and one of the least effective ways to make heat. I'm an electrician and, in my house, if it makes heat it burns gas. That means the furnace, the water heater, the cookstove and the clothes dryer.

Our gas bill is $40/mo. Our electric bill is more than $150/mo.

It would be well over $200/mo. if everything was electric.
 
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Old 01-28-13, 09:13 PM
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Not to get off topic......but I'm all natural gas here in New Jersey. Based on our electric rates I shudder to think of the utility bill bill without natural gas.

I've noticed here on this site, from other posters, some states have really low electric rates....so that would need to be figured in also.

......and to answer your question.....yes....you need a 200 amp service.
 
  #7  
Old 01-29-13, 02:35 AM
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Electric furnaces are sized by KW; how big does your electric furnace need to be? Considering that you may have an average size home of 1500 square feet or so and you want to be all electric with two electric tankless water heaters, figure on a 400 amp service (320 amps actually).
My home is only 1350? sqf according to the taxes.. and since it's a duplex your really only heating 675 sqf tops...

We also would like to know the KW of the 2 tankless water heaters.
According to its fact page.. it's 9.9 Kw a hour.. so that's x2

Amazon.com: Customer Reviews: Ks-94 Electric Tankless Water Heater - 9.9Kw @ 220V

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Hmm.. my electrician talked me into 100 amp service yesterday.. 80 amp being usable.. so now it's just a question if that's gonna fail horribly (the furnace is just a maybe.. the water heaters I'm definitely going to try.. I could stomach a $28 meter fee for winter.. I guess.. )

Seemed like I was going to pay $700 or more for 200 amp.. whereas I am going to pay $425 in materials for 100 amp.
 
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Old 01-29-13, 02:39 AM
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The link went to furnaces for mobile homes. Is that what you have?


Really, do you really think that.. showers and washing dishes add up to that much?? To bring in a gas meter from the 'gas company' costs $28 a month.. hmm.. you think it costs $28 a month?


Using electricity to make heat is both one of the least efficient uses of electricity and one of the least effective ways to make heat. I'm an electrician and, in my house, if it makes heat it burns gas. That means the furnace, the water heater, the cookstove and the clothes dryer.

Our gas bill is $40/mo. Our electric bill is more than $150/mo.

It would be well over $200/mo. if everything was electric.
That makes sense.. well, then my gas bill would probably be at least $60 a month

The link was just "electric furnaces" on ebay.. I don't know if those were mobile or what?
 
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Old 01-29-13, 02:43 AM
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I guess I should ask.. are there any trade secrets to easily getting cheap materials for electrical masts, can meter heads and ground wires etc.? (as my ground wire cost $40 yesterday )

My duplex can meter head is expensive too at $185.. (the 400 amp version may be much higher.. not sure.. maybe $225)
 
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Old 01-29-13, 03:01 AM
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We also would like to know the KW of the 2 tankless water heaters.

We also would like to know the KW of the 2 tankless water heaters.
Actually, according to the pictures at amazon.. and the sellers websites.. they are 11.78KW @ 240V. or 9.9KW @ 220V.

Home

This page also indicates that they can only do a 40F temperature rise.. which means 2 would be nice/needed.. also there price is down again

K's 94 Electric Tankless Water Heater
 
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Old 01-29-13, 03:52 AM
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So your water enters at a modest 50 degrees and you will be satisfied with a maximum of 90 degree water. Two units will only make it more expensive as they each will only put out 40 degree above incoming water temperature.
 
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Old 01-29-13, 05:06 AM
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Two units will only make it more expensive as they each will only put out 40 degree above incoming water temperature
Actually the unit has a heat dial on it.. so it's possible to balance the 2 units out on heat and load and theoretically that reduces the electricity cost

Someone did some math in one of their reviews.. (and I'm not saying this is right!) said a shower costs $.01 a minute.. obviously $.015 or $.02 a minute for 2 of e'm
 
  #13  
Old 01-29-13, 05:22 AM
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Hmm.. so I calculated the amps "based on" 11.78 Kwh and 240V and that makes 49.08 amps.. hmm.. that's 49 out of 80.. for 1 water heater

I'm gonna double check this with my electrician..

Also it makes sense why you need a 60 amp fuse.. cause 80% of 60 amp fuse is 48 amps (which is 1 amps lower than this unit supposedly takes/runs at)
 
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Old 01-29-13, 09:36 AM
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Originally Posted by theemaster View Post
Actually the unit has a heat dial on it.. so it's possible to balance the 2 units out on heat and load and theoretically that reduces the electricity cost

Someone did some math in one of their reviews.. (and I'm not saying this is right!) said a shower costs $.01 a minute.. obviously $.015 or $.02 a minute for 2 of e'm
Sorry, but there's no way I would pay anything for an 80-90 degree shower. Sorry, but that thing is junk. It's basically designed for trailers in Florida or Texas where the incoming water temp is 65 degrees, not places where it actually gets cold in the winter.

Not only that, but you can forget about using this thing with a dishwasher. Dishwashers require 120 degree water at MINIMUM. If the water is not hot enough, it heats has to heat it up, wasting even more electricity.

And Nashkat was referring to his TOTAL gas bill, not just the price of gas.. I have a 50 gal tank with an "instant hot" recirculation system, gas dryer, and a gas stove, and I still only use about $15 worth of gas per month. With the fixed fees my gas bill is about $35 during the non-heating months (it has actually gone down a little because gas has gotten cheaper over the past year, while electric rates have gone up). When I junked my electric stove for gas, my electric bill went down by $60 per month (yes, I do a LOT of cooking and baking), while my gas bill only went up by $5.
 
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Old 01-29-13, 09:42 AM
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Sorry, but there's no way I would pay anything for an 80-90 degree shower. Sorry, but that thing is junk. It's basically designed for trailers in Florida or Texas where the incoming water temp is 65 degrees, not places where it actually gets cold in the winter.
Actually this is what the guy that sells it says..

About the questions about the heater:
1)If you have 220 volts the unit load will be 45 amps, if you have 240 volts the load will be 53 amps, if you have 2 units the load will be double (90 or 106 amps.)
2) You can install 2 units in parallel, not in series, if you install in parallel you will double the rise (to 90F) with the same flow of 2 gpm, if you increase the flow to 4 gpm you will obtain 45f rise( same as one unit but more flow)
 
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Old 01-29-13, 12:14 PM
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Originally Posted by Nashkat1
Our gas bill is $40/mo. Our electric bill is more than $150/mo.

It would be well over $200/mo. if everything was electric.
That makes sense.. well, then my gas bill would probably be at least $60 a month
I don't understand. If we're paying $40/mo. to heat a 3-story townhouse with more than 2,000 ft.[SUP]2[/SUP] of conditioned space, to heat the water for four lavatories, two shower/tubs, a kitchen sink, the dishwasher and the washing machine, to dry the clothes and to cook, how would your gas bill be likely to be 50% more than ours? How many heat-generating appliances are you planning to install in your 675 ft.[SUP]2[/SUP] duplex, and what is the BTU rating of each of them?

The insta-hot toys you link to might work for a lavatory. They are too small for a shower and, as others have said, the heat rise is negligible. Hot water should come out of a faucet or shower head or any other outlet at 120[SUP]o[/SUP] F.

If I decided to put one of those in my house, it would burn gas too.
 
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Old 01-29-13, 12:35 PM
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About the questions about the heater:
1)If you have 220 volts the unit load will be 45 amps, if you have 240 volts the load will be 53 amps, if you have 2 units the load will be double (90 or 106 amps.)
2) You can install 2 units in parallel, not in series, if you install in parallel you will double the rise (to 90F) with the same flow of 2 gpm, if you increase the flow to 4 gpm you will obtain 45f rise( same as one unit but more flow)

Well....Unless I'm really mistaken....that makes no sense at all and tells me the seller doesn't have a clue and doesn't care.

How can you possibly double the rise if the incoming water to each unit is the same temp? As to the electrical...that's just bassackwards. If a unit draws X watts and you increase the voltage, then the amperage will decrease.

I wouldn't touch these with a 4 ft stick.
 
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Old 01-29-13, 01:31 PM
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As to the electrical...that's just bassackwards. If a unit draws X watts and you increase the voltage, then the amperage will decrease.
Sorry, Vic, but you are wrong. When calculating the amperage draw vs. applied voltage regarding a resistance heating element you MUST use the resistance of that element in calculating the amperage.

In the example given with an applied voltage of 220 and a stated amperage of 45 the resistance must be 4.89 ohms. (R=E/I) Transposing (I= E/R) and using 240 volts you will have an amperage draw of 49.08 amperes which then multiplied by the voltage equals 11,77.14 watts.
 
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Old 01-29-13, 02:24 PM
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Well....I did say unless I'm mistaken....lol.

Pretty sure the temp rise thing still doesn't make sense......and I still wouldn't use them.
 
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Old 01-29-13, 02:34 PM
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Absolutely.......the sales pitch regarding the temperature is incorrect.

If you put two heaters in parallel.....specifically plumbed with the correct sized piping.....then you can double the flow rate.....but the output temperature is the same as one heater. If they are plumbed in series.....then you double the temperature rise but only maintain the flow rate of one heater.


.
 
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Old 01-29-13, 03:07 PM
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No I think the premise behind it is if you halve the flow rate through each heater (by paralleling them - since the pressure and inlet/outlet pipe size remains constant), the water picks up more heat because it is spending more time in the heater.. You wouldn't double the flow rate because the piping to the rest of the house is still the same (probably 1/2"). Although it probably would flow a bit more due to less restriction, it wouldn't be anywhere near double. Maybe 1.1x.

But it doesn't change the fact that it's a dumb way to do it, and it totally flies in the face of logic when gas is a much cheaper fuel.

This day in age the only reason to use electric appliances is if you co-generate and want to take full advantage of a large solar array.
 
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Old 01-29-13, 06:07 PM
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This page also indicates that they can only do a 40F temperature rise.. which means 2 would be nice/needed.. also there price is down again
That page also has a little comment you maybe didn't pay any attention to, it says, "in warm climates".

Hmm.. so I calculated the amps "based on" 11.78 Kwh and 240V and that makes 49.08 amps.. hmm.. that's 49 out of 80..
I'm gonna double check this with my electrician..
Yes, please do check with your handyman.....I am interested in how two units can run on a 100 amp service.
 
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Old 01-30-13, 05:41 AM
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Pretty useless to list specs for the unit at 220 when the voltage in the US is 240.

For two units in one house they may need two services, one for the house, the other for the tankless.
 
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Old 01-30-13, 06:09 AM
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Not to be rude, but you sound like someone who's already decided what to do and doesn't want to hear that it's not the best way to go. You would be crazy not to opt for 200 amp service. As for the tankless heaters, the electric ones are far more exensive to operate than gas units (especially now when gas is dirt cheap) and the one you want to use is obviously not correctly sized. I have a gas tankless in my home. My heat pump's backup is a gas furnace. My propane bill averages about $30 a month. If I could get natural gas, it would be a lot less.
 
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Old 01-30-13, 09:34 AM
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Not sure it would be "a lot" less.. Because there are fixed fees with NG service. I'm not sure how you are set up, or what your capacity to use ratio is, but my dad has propane with bi-monthly delivery, and his delivery charges are far less than what I pay in fixed fees for natural gas.. But my actual gas usage cost is far less than his (this also takes into account that propane has less BTU per cu.ft. than natural gas does). I usually pay more in fixed fees per month than I do for the actual gas usage (in off-heating months). Depending on what the oil market is doing, our bills are usually pretty close.

So basically what I'm getting at is unless the price of propane skyrockets (which is not entirely outside the realm of possibility either, given the current happenings in Washington and around the world), the price difference between propane and NG on a monthly basis would be a wash.

It's impressive though that you only use $30 a month worth with a tankless.. I figured they'd use more than that..
 
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Old 01-30-13, 05:23 PM
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the price difference between propane and NG on a monthly basis would be a wash.
I seriously doubt that. Propane goes for about double the price of natural gas. The Us avg price for 100 cubic ft of natural gas (100,000 btu) in Oct. was $1.17. Propane for this week was $2.47 per gallon (91,000 BTU)
 
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Old 01-31-13, 02:26 AM
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Yes, and like I said, the fixed fees for NG are much higher than the fixed fees (delivery) for propane. He's only using $30 worth of propane per month, and with that usage, and depending on his tank size he probably gets delivery every other month, maybe even quarterly. Unless he doesn't own the tank, he shouldn't have any recurring fees beyond the delivery charge (if there even is one.. Some suppliers don't charge delivery with a minimum fill amount, and they max out at like $20-30 per delivery). I pay $25 a month in fixed fees even if I don't use any gas.
 
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Old 01-31-13, 04:53 PM
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I pay $25 a month in fixed fees even if I don't use any gas.
Yep, that's what I'll pay $28 though

Unless I get this electric tankless water heater setup.. then "maybe" not
 
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Old 01-31-13, 05:15 PM
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Not to be rude, but you sound like someone who's already decided what to do and doesn't want to hear that it's not the best way to go.
Well, you are being rude

Umm.. yes, I do already have my mind made up.. the question is not.. "what's the right water heater for me?" but if I can get by without 200 amps..?? the answer seems to be no.. I talked directly with the water heater selling guy..

He says each heater needs 53 amps.. now a 100 amp box is only supposed to do 80% of 100 amps.. really 80 amps.. so 200 seems like I have to have..

Right now I'm at about $440 to do 100 amp service for both sides of my duplex.. now I'm trying to figure how much higher the cost is for 200 amps

My need for 200 amps is 100% based on the water heaters (it's like the 200 amps is part of the water heater cost) I'm not sure I'd need it for anything else.. except "air conditioners" can be a draw here in MO
 
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Old 01-31-13, 07:40 PM
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I'm not sure I'd need it for anything else.. except "air conditioners" can be a draw here in MO
That's a fact! Where in MO are you?
 
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