Third 40 amp breaker for tankless water heater

C

Chasinmendo

Member
Location
Northern California
Occupation
Builder, Developer, Engineer
I have a customer who wants a specific brand water heater. The electrical requirements are for 3 40 amp breakers and 200amp total service.its too late today to check with the manufacturer. I installed double breaker, 50 amp each train and #8 wire anticipating an electric water heater but what is the third breaker for? It's not a three phase system?
 
C

Chasinmendo

Member
Location
Northern California
Occupation
Builder, Developer, Engineer
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Welcome to the forum.

To clarify, it wants three individual 2-pole, 240-volt, 1-phase circuits, delivered over three pairs of wire.

Please have an electrician wire this!
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
PaulMmn said:
...and this is cheaper-- er, more economical than a well-insulated storage-tank water heater??
"Oh-- it only uses power while the faucet is open!"
Click to expand...
But while the faucet is open, it uses a lot more power.
For me, the biggest advantage of a tankless unit is the ability to run unlimited appliances like dishwasher and washing machine loads and long relaxing showers. But the down side is that your choices may lead you to use more energy.
That said, I am much happier with an natural gas or propane heat source than electric. And a second downside of the tankless is that the total GPM from the heater is strictly limited, showering and running the washer at the same time, or two showers at once can be disappointing. And reversing direction again, that may work well with current limited flow showers.
 
T

TX+ MASTER#4544

Senior Member
Location
Texas
Occupation
electrical Code instructor and mentor
2023 NEC
Yeah, some of us 'lectricians are a real novel.
Who takes 2 showers in one day? Bathe with a friend?
Wash dishes by hand and save water. Use paper plates, we do.

If you gotta ask how much a water heater cost.....then you can't afford it. That's what they always told me when I asked.
Especially after you pay your friendly home town plumber.

I know, we spent almost a grand for a new tank of water and a new pickup for the young plumber. I shoulda never told him i was a wire twister.
Told him to call me when he needs replace burnt out bulbs.

OK, my plumber was in my electrical trade class at a high school where I taught electrical wiring, 20 something years ago.
I don't know what caused him to go left on me and take up plumbing.
Guess that's the younger gen xs on how to make more money than 'lectricians.
I still visit with him and were still good friends! Just wait till he needs me!

Thanks for reading.
Comments ACCEPTED.
TX+MASTER #4544
 
kwired

kwired

Electron manager
Location
NE Nebraska
PaulMmn said:
...and this is cheaper-- er, more economical than a well-insulated storage-tank water heater??
"Oh-- it only uses power while the faucet is open!"
Click to expand...
The concept here is that the storage tank heater is always losing some heat regardless how well it is insulated.

If you live in colder climate that heat is given up to your living space and isn't exactly an energy loss during heating season either though.

After factoring in initial investment, maintenance needed over the expected lifetime of either unit and energy costs, I bet you still come out ahead cost wise in most cases with a storage tank style water heater particularly if you are set on using electric as the energy source. Gas likely will come with less energy cost, but will have more up front cost and possibly more maintenance cost with some units.
 
Cartoon1

Cartoon1

Senior Member
Location
Florida
Occupation
Electrical Engineer
I think it depends on the water heater size. I have seen some with 4 breakers requirements. I believe waters heaters have different heater elements, the bigger the water heat KW the more heating elements involved.... the more breakers involved.
 
Barbqranch

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician Semi-retired
Another disadvantage of a tankless water heater is if you have a generator to use when the power is out. You can even wire a tank type to 120 volts in a pinch to use much less current. I did that when doing a remodel and moved the water heater into the garage. Still never ran out of hot water.
 
L

loboesso

Member
Location
Gilbert
Adding to the question - Do the breakers need to be GFCI? Also, since they dont used neutral, I I have a plug in neutral panel - I am guessing the neutral connection stays opens?

Thanks
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
kwired said:
The concept here is that the storage tank heater is always losing some heat regardless how well it is insulated.

If you live in colder climate that heat is given up to your living space and isn't exactly an energy loss during heating season either though.

After factoring in initial investment, maintenance needed over the expected lifetime of either unit and energy costs, I bet you still come out ahead cost wise in most cases with a storage tank style water heater particularly if you are set on using electric as the energy source. Gas likely will come with less energy cost, but will have more up front cost and possibly more maintenance cost with some units.
Click to expand...

And then there's a heat pump storage option, where any tank losses are offset by the lower energy input.
 
M

MD Automation

Senior Member
Location
Maryland
Occupation
Engineer
kwired said:
The concept here is that the storage tank heater is always losing some heat regardless how well it is insulated.

If you live in colder climate that heat is given up to your living space and isn't exactly an energy loss during heating season either though.

After factoring in initial investment, maintenance needed over the expected lifetime of either unit and energy costs, I bet you still come out ahead cost wise in most cases with a storage tank style water heater particularly if you are set on using electric as the energy source. Gas likely will come with less energy cost, but will have more up front cost and possibly more maintenance cost with some units.
Click to expand...
jaggedben said:
And then there's a heat pump storage option, where any tank losses are offset by the lower energy input.
Click to expand...

Earlier this year, in another Water Heater thread (about powering w/ 120 VAC) I mentioned that I had recently taken the time to document exactly how often a water heater in my house came "ON" with no water drawn - and how long it took for the thermostat to be satisfied during that recovery. The results surprised me.

I hooked up a cheap current sensing switch to a PLC and wrote a simple program to log the time(s) when that switch changed state.

With no water drawn from the tank, it takes roughly 11 hours before the thermostat kicks on. And it runs for about 8 minutes to get back up to temp. Pretty well insulated it would seem. Not just simple fiberglass blankets like 40 years ago. Now it's all foamed in and really well insulated from air flow. At least electric tanks anyway.

This water heater was a regular "nothing special" State 50 gallon water heater. Typical 4500 W elements (top and bottom). Not a Heat Pump model.

So - roughly - each recovery phase from simple tank heat loss uses ~ 0.6 kWh and happens 2x per day. At an electric rate of $0.15 per kWh that's 20 cents per day - so maybe like $6 per month.

And, as mentioned, part of that heat loss is mitigated in the winter if the "loss" is to indoor air you were trying to heat anyway.

If anybody is thinking that the On Demand Water Heater is going to pay for itself quickly by saving the heat loss from a modern water heater, I think those numbers say otherwise. Or, at least it won't be a quick payback ;)
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
MD Automation said:
Earlier this year, in another Water Heater thread (about powering w/ 120 VAC) I mentioned that I had recently taken the time to document exactly how often a water heater in my house came "ON" with no water drawn - and how long it took for the thermostat to be satisfied during that recovery. The results surprised me.

I hooked up a cheap current sensing switch to a PLC and wrote a simple program to log the time(s) when that switch changed state.

With no water drawn from the tank, it takes roughly 11 hours before the thermostat kicks on. And it runs for about 8 minutes to get back up to temp. Pretty well insulated it would seem. Not just simple fiberglass blankets like 40 years ago. Now it's all foamed in and really well insulated from air flow. At least electric tanks anyway.

This water heater was a regular "nothing special" State 50 gallon water heater. Typical 4500 W elements (top and bottom). Not a Heat Pump model.

So - roughly - each recovery phase from simple tank heat loss uses ~ 0.6 kWh and happens 2x per day. At an electric rate of $0.15 per kWh that's 20 cents per day - so maybe like $6 per month.

And, as mentioned, part of that heat loss is mitigated in the winter if the "loss" is to indoor air you were trying to heat anyway.

If anybody is thinking that the On Demand Water Heater is going to pay for itself quickly by saving the heat loss from a modern water heater, I think those numbers say otherwise. Or, at least it won't be a quick payback ;)
Click to expand...
Where on demand pays off, is where usage is very sporadic, such as a vacation cabin. Turning off the water heater when you leave means a cold shower when you come back the next weekend, or month. Daily use is where the payback is not as quick, if any.
 
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