wiring for hot water heater

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  #1  
Old 05-21-06, 09:37 AM
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wiring for hot water heater

Hi. I'm very confused. My husband and I are trying to install an electric tankless water heater, and have had conflicting advice regarding the wiring. It's a 54 amp, 220-v water heater. We have been told by 3 different "experts":
1. we need a 60 amp breaker with #14 wire;
2. we need #10 wire with a 30-amp breaker;
3. we need #6 wire with a 30-amp breaker.

could you shed some light? The plumbing companies we've talked to want $600 to fix the wiring alone--before the actual plumbing part is handled. It seems that it would be very straightforward to wire it properly.
 
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  #2  
Old 05-21-06, 10:24 AM
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I'm not an expert, but I would use 10/3 wire fed from a dual 30 amp breaker. 6 ga wire from a dual 30 amp breaker would also work.

Whoever recommended 14 ga wire for this may be an expert, but his forte ain't electricity.
 
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Old 05-21-06, 10:28 AM
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Wayne Mitchell]I'm not an expert, but I would use 10/3 wire fed from a dual 30 amp breaker. 6 ga wire from a dual 30 amp breaker would also work.
No no no.
A two pole 30 amp breaker does not equal 60 amps
 
  #4  
Old 05-21-06, 11:26 AM
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Do you have ANY installation instructions with this thing? If not, look inside the unit either on the inside cover or near the electrical connections. There should be something there in the way of power requirements.

The size of wire is not only dependent on the breaker size but also the length of run from the breaker to the unit.
 
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Old 05-21-06, 11:56 AM
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If you do not know the difference between a 60A circuit and a 30A circuit, then you are not ready to do this installation yourself. A proper installation requires getting numerous details correct, far more than you even know to ask about or that we could even guess that you don't know. Before you continue on this project, you _must_ get several books on electrical wiring, read them, and ask questions about the points that you don't understand. If you are unwilling to pay for this installation with the effort to learn the appropriate background, then you have to be willing to pay a professional to do the job for you.

This installation is something that you _can_ do on your own with a small investment in learning, but you must make this investment.

On your questions:

1) A 54A water heater requires at least a 60A circuit, 70A if your local electrical authorities consider it a _continuous_ load. This requires a double pole breaker with 60A (or 70A as necessary) on the handle.

2) This circuit requires #6 copper conductors if this is _not_ considered a continuous load, #4 conductors if this is a continuous load.

The #10 conductors on a 30A breaker would have been the correct answer for a standard storage tank hot water heater.

-Jon
 
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Old 05-21-06, 12:27 PM
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If you are unwilling to pay for this installation with the effort to learn the appropriate background, then you have to be willing to pay a professional to do the job for you
Jon, thanks for the put-down. We actually have read numerous books, and asked numerous questions, and we have received numerous answers. One of the "professionals" you say we should be willing to pay gave us advice that directly contradicted what you said. Whether we finish this job ourselves or pay to have it done, we want good, safe wiring--and I am getting the impression that paying $600-$1500 is no guarantee of that.

This is what I don't understand, perhaps you can offer some clarity. This is what you said; 1) A 54A water heater requires at least a 60A circuit, 70A if your local electrical authorities consider it a _continuous_ load. This requires a double pole breaker with 60A (or 70A as necessary) on the handle.

This is what the "professional" said; 54 amps is the maximum amount of power that my hot water heater is supposed to handle. Therefore, if something goes wrong and too much power is running through the appliance, the 60 amp breaker will not trip the wire before it "arcs out". This sort of conflicting logic is precisely why we are perplexed and hesitant to proceed even with a professional at the helm.

My installation guide says only that "wire gauge depends on local requirements".
 
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Old 05-21-06, 01:05 PM
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I, for one, have to question the abilities and knowledge of the person claiming to be an electrician to you.

You heater does not "handle" the current per se, it draws or requires the current would be more accurately descriptive. The wire would more accurately be required to "handle" the current without damaging it.

The heater will draw up to 54 amps. Should you use a 30 amp breaker, it will overload the breaker and cause it to trip.

The thing is, the breaker has to allow the heater to draw the current it needs and is designed to draw. That would be the 54 amps. You cannot get a 54 amp breaker so you need to go to the next standard size (60) or if the heater is considered a continous use appliance 70 amp.(54 x 125%=67.5 then the next standard size is 70) The 125% is a "code" given figure to use when designing electrical systems.

The wire is designed and chosen to handle this current with no problem. When there is a short circuit, the current will go up and the breaker will trip, thus saving the wire from damage.

The thing is Jon is trying to do is avoid you getting hurt and avoid installing an electrical system that would not work and may even be dangerous. It is a very serious thing and should never be taken lightly. Those of us in the trade realize that what we do wrong could concievavbly cause the death of somebody. Something none of us ever wants to have happen.
 
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Old 05-21-06, 01:18 PM
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Please excuse any 'put-down' that you read in my words; no disrespect is intended. I have no way of knowing how much you have read, and your questions raised a couple of 'red flags' in my mind. But if you have been doing the reading, and have some questions that you don't understand, then you are doing exactly the right thing by asking questions here. None of use are perfect, either professional or experienced amateur, but since our answers are public and read by others, if we get it wrong, then we'll be corrected pretty quickly.

This is what the "professional" said; 54 amps is the maximum amount of power that my hot water heater is supposed to handle. Therefore, if something goes wrong and too much power is running through the appliance, the 60 amp breaker will not trip the wire before it "arcs out".
While there is a kernel of truth in this statement, it is so far wrong as to be nonsense.

Your heater is designed for 54A. If your supply voltage is slightly high, then it will draw a bit more current and run a small bit hotter. But appliances must be designed to tolerate expected voltage variation. 54A is not the _maximum_ that can flow through the device, but instead the current that the device will consume when connected to a source of its design voltage. All of the wiring feeding the device, and the circuit breakers, etc. must be able to carry at least this 54A. So this heater _must_ be placed on a circuit that is at least 54A or _larger_ in capacity.

The next standard size above 54A is a 60A circuit, however for _continuous_ loads (those that operate for 3 hours or more at a time), 25% more capacity is required, and you would need to calculate as though you had a 68A load, meaning a 70A breaker.

The kernel of truth in the above statement is that given two breakers which are _sufficient_ to supply a load, the lower A breaker will let less energy through in the event of a fault. But the breakers _must_ first be sufficient to supply the load.

-Jon
 
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Old 05-21-06, 03:28 PM
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What, we all got to be rocket scientists at every turn and confuse more than help?
Mama, plain and simple you need number 6 wire and a 60Amp breaker for this install. None of the 3 choices you listed are acceptable.
 
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Old 05-21-06, 04:26 PM
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My husband and I are trying to install an electric tankless water heater, and have had conflicting advice regarding the wiring. It's a 54 amp, 220-v water heater. We have been told by 3 different "experts":
1. we need a 60 amp breaker with #14 wire;
2. we need #10 wire with a 30-amp breaker;
3. we need #6 wire with a 30-amp breaker.
I was reading this question and it did raise serious red flag allready .

the NEC code is very strict with high load especally with electrical heating devices that including electric water heaters.

question #1
answer #1 NO it will burn up the wires fast

question #2
answer #2 this is very common set up with tank storage water heater

question #3
answer maybe if very long run away from breaker / fuse box

for myself i will just get the model number and read the electrical spec number and i am suspecting this 54 amp is above the 42 or 48 amp per nec code i think it will come in two circuits set up.

I did see few larger instat water heater have much as 3 circuit wires running to this unit


Please for safety sake here do not cut the corner with instat water heater unit they do draw power pretty good rate if you are not confortable with this then you have to get a electricican who know the code very well and make sure you metion the water heater wattage and number of circuits if possible so can able wire up safety.

Merci, Marc
 
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Old 05-21-06, 06:24 PM
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54amp= full load?
at 220 or 230volt?
is kw given?
does install manual call for breaker or fuses?

how many feet of wire from panel?

will some of wire be in attic?
how hot does your attic get during the 3& 4th wk of Jul?

what did your elec inspector state about this being a continuous load?

will any part of the wire be outside?
underground?
in conduit?

what is your normal voltage at your service panel?

NONE of the first suggested wire & bkr combinations are right!
AND, #1 would probably cause a fire quickly.
 
  #12  
Old 05-21-06, 06:24 PM
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I dont like these heaters for most things, in a house stored hot water is not a bad thing and as French said they add a LOT of load to an electric system, that need to be kept in mind before decicing on one, Whats the incoming service situation like to start with? One of my friends really isnt happy with one, designed into a new hope by proffesionals its another matter.
I think thats why we can get touchy about the answers here, its really more of a design and installation of a system than a simple hookup DIY hookup. A lot of factors could be involved.
 
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Old 05-21-06, 07:11 PM
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I can't add much to what has already been said, except to say that I don;t think anyone was trying to put you down for not knowing the answer to this question.

What I will say is that point of use water heaters are not generally treated as continuous. Most people don't run their hot water for that long all at once.
 
  #14  
Old 05-21-06, 07:11 PM
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I can't add much to what has already been said, except to say that I don;t think anyone was trying to put you down for not knowing the answer to this question.

What I will say is that point of use water heaters are not generally treated as continuous. Most people don't run their hot water for that long all at once.
 
  #15  
Old 05-22-06, 03:54 PM
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Originally Posted by mamasita
It's a 54 amp, 220-v water heater.
Only the instructions will tell.
Are you in USA or Canada?

In USA, it's 240V. It might take two double-pole 30A breakers or one double-pole 60A breaker.
If it's Canada, then it's the latter.
Only the manufacturer's direction will tell you for certain.

Wire size and count depends on breaker size and count.
 
  #16  
Old 05-22-06, 06:42 PM
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wiring for hot water heater

I agree that the answers given by the folks you consulted were, well, not very well thought out. That's putting it kindly- at the very least, they didn't listen to the question!

There are two key things here... "INSTANT hot water (different from the usual heater), and the NAMEPLATE info.

"Instant" suggests that the heater will need a LOT of power at one time. This in turn suggests big breakers and big wires.

The "code answer" would be....based upon the nameplate information, as follows:
220 volts : Two 'hot wires, a ground, and a "2-pole" breaker.
54 Amps : Wire at least #6 (assuming copper THHN) and
a 60 amp 2-pole breaker (the next larger standard size.


This is something even a second-year apprentice ought to be able to figure out. Anyone giving answere like the ones you received has no business doing electric work.
 
  #17  
Old 05-22-06, 08:16 PM
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ok , as few peoples try to give you a very good advice here but right now what i am suggest what to do next is get the model number and brand name so we can have better idea how to deal this in nice manner.

the other thing i want to head up if your home have 100 amp service you might be pushing the luck with the electrical system because when the instat water heater kick in it will make light flicker somehow what but i cant say for sure becuase there are too many variables to give you the honest answer.

But really for honest option from the electrician side this what we will like to do this ;

name plate of instat water heater
model number of unit
numbers of circuits if have on the listing

and we will go from there but be well aware about main house system a real electrician will give you a head up with warning if they think the main system is kinda " weak " probly have to upgrading to 200 amp main box and related wiring

so just think about this

Merci, Marc
 
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