My homebuilder says upgrading my electric service to 300 or even 400 Amps
will result in more "efficient" use of electricity by my appliances. Can one
of you experts out there please explain how this is so?
Only if you are planning to use up to 300 or 400 amps, otherwise he is full
of BS, sounds like a sales pitch to get you to pay a premium for the extra
amps. More important is to get a panel with as large a capacity of circuit
breakers as you can, which may take more than one panel to do the job, so
that there are a lot of lightly loaded circuits instead of loading each
circuit to the max. This will give you more "head room" in each circuit so
the ones that end up with a load are not overloaded. Also to provide a
separate circuit for each large load or critical load such as a separate
line for a freezer, etc.
I agree with you.
But you remind me of a long time question I've had.
When I lived in a 1930 apartment building, the fuse box in my apt. had
2 slo-blo 15 amp fuses, and in the basement the fuse that served my
apt. was 1 slo-blo 20 amp fuse.
I was told this was bad, because 2 x 15 = 30 which was more than 20.
I was told the sum of the fuses downstream should never be more than
the upstream fuse. Any truth to this????**
I sort of figured first, that the landlord would not rewire the whole
building and I needed my 30 amps, so I should keep my mouth shut.
second, the building had been working this way since
1930 and there were no electrical fires, and that's still true today,
75 years after construction.
and third, the 20 amp fuse in the basement would protect
the 12 gauge wire from the basement to the 5th floor. That was its
job. But there were sometimes I would use 14 amps through one fuse
and 5 through the other, and that would be under 15, and under 20
total so what's wrong with that. Anything higher would blow one fuse
or the other.
**If there is any truth to the idea that two 15 amp fuses can't feed a
20 amp fuse, why is it all right for the sum of all my circuit
breakers to be greater than the main serving my house. I have cb's
totally 200 or more amps now, and room in the box for in the box for
120 amps more. Maybe more. I'll never use anywhere near all of it
at once, but if this is ok, why was my apartment setup not ok??
BTW, slo-blo is only 5 or 10 seconds, right? It's more than 1/2
second like non-slo-blo, but no where near 30 seconds, is all of this
Nope. The current is limited to 20A max, no matter what the downstream fuses
are. Fuses are sized to the wiring they protect. Period.
You weren't getting 30A, only 20.
No surprise -- nothing inherently unsafe in what you've described. Silly,
perhaps, but not unsafe.
Ahh, now that's a different story. Two 15s feeding one 20 is not the same as
one 20 feeding two 15s.
It's just not a problem.
It is ok, and that's why -- you won't ever use anywhere near all of it at
once. For example, the probability is near zero that you'll ever use your air
conditioner and furnace simultaneously. It's also quite unlikely that all of
the lights in your house will be on at once, or that you'll simultaneously be
using all of your appliances.
It was ok, at least as you describe.
I never timed one, but yeah, it takes a little while, but only a little.
Doug Miller (alphageek at milmac dot com)
OK. I'm happy. It's been a long time but I thought one or two people
said it was bad at the time, and that 2 or 3 others have said it was
bad since then. Whoever did complain to me, it seemed like an
absolutist rule that didn't make sense. I'm glad it's not a rule
Thanks. Several more reply lines below, but this was the essence of
Right. My mistake. I really needed my 20 amps. 4 people for a few
years, and later 2 people and one room air conditioner. I also worked
things out so I could go to the basement to change the fuse in the
middle of the night without bothering the super. I think I replaced a
blown fuse about 10 times in 10 years. Somewhere between 8 and 18. I
vaguely remember a short period where I blew a whole bunch, but I
can't remember why. 18 in ten years doesn't seem like too many.
Compared to I guess 200 amps I have now, I really was not constrained
much by having only 20. Washing machine, no dryer or course, gas
stove. Plenty of lights, radios, I might have had two tv's on at once
once in a while (one in the kitchen), but iirc no roommate (I had
about 20) ever had even one tv. I wonder why not.
I think this is typical for 100's or thousands of buldings in NY.
Immigration was high all the time, but especially the 1880's to 1914,
I think it was, so there were plenty of buildings nicer than tenements
being built by the '30's. The war may have prevented much building in
until '45, and after that there was probably more electricity provided
for each apartment.
In the garbage room on our floor (where there was a chute that led to
the basement, where the garbage was first burned and then later
compacted, there was a sticker on the wall: "Save your cans. Defeat
the Axis." They only painted this tiny room every 20 years or so --
it didn't seem to get dirty -- and when they painted in 1980, they
didn't paint over this.
I meant to say it the other way. Or I was looking at "feeding" in a
different way. But regardless, I didn't mean anything different from
It better not be, because probably most people would be in violation
of it. The sum of the ampacities of branch breakers in a main panel
is _usually_ higher than the main feed breaker.
[IIRC, the breaker sum in our panel is > 3 times the size of the main
Slo-blos are _specifically_ designed to ride out the startup current surge
of a motor - typically 3-5 times higher than the steady state amp rating
of the motor. If that takes more than 5-10 seconds (eg: the motor is stalled),
the fuse better blow or the wiring might do something real bad (eg: melt).
So, no, you don't want a slo-blow to take much longer than that.
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
Only in the sense that if larger service entrance conductors were installed
you would have less of a voltage drop and losses from resistive heating that
you would otherwise under very heavy loads. A lot depends on the length of
the drop. If all the facts are known, it can be calculated with reasonable
accuracy (the resistance of the SE conductors and the resulting voltage drop
as a fuinction of current used).
You would have to be using most of that 300A most of the time to see a
difference though. It probably would reduce the incidence of lamp dimming
under heavy load conditions.
I don't think it would make any diffenence in your bill whatsoever since
metering is done after the SE conductors make it to your house. Any energy
lost in the SE conductors as heat (P=I*V or I^2*R) would not be metered.
It depends on your needs and the size of the home. I know a couple with
a 7000 SQ foot home they have two 250 amp main panels. I was told 250
is the largest main home panels available but dont know if this is
Frequently main entrance cable around here is alunimum, I would spend
the extra for copper from the meter can to the main breaker.
sounds like a big home have you included a standby generator for power
failures? thats $ well spent
Actually Al is better for heavy gague service entrance conductors. The
metal oxidizes less, it weighs less and it stands up to the elements better
than Cu if the jacket is damaged (due to the thin patina of oxide). You
only need slightly more metal to get the same resistivity as Cu but these
things are over engineered anyway. Al also expands less than Cu which is an
advantage for long overhead lines to reduce droop in the summer. Other than
that, in a poll, 4 out of 5 electrons don't care what metal they are in. :)
Rule of thumb, more house, more lights, plugs and loads. A smaller house
(~100SF) could justify so much current but it would need a big load like a
Kiln or an electrically heated pool.
replying to PipeDown, Mistert wrote:
I have a small 1800 sq foot home 2 full bath and 2 old fogies live here retired
and i want to go to the tankless Eco 36 but have 200 not 300 amp svce. and we
never have 2 showers at once just a load of clothes. Do I have to add more
On Friday, May 25, 2018 at 1:44:06 PM UTC-4, Mistert wrote:
It's 36KW, so it needs 150A. With 200A, you only have 50A left for everything
else. So, what are the other significant loads? AC? Electric ovens?
Cooktop? Dryer? Add it up and you'll have your answer. Even one of
those other loads and you're close to the limit. I think for
most people, tankless makes no sense, for a variety of reasons. Starting
with that I don't believe the operating cost savings justify the larger
upfront costs. The essential difference is you're eliminating the standby
losses of a tank type. Electric tank you can buy one of those extra
insulation blankets and pretty much totally enclose it in more insulation
which will reduce the losses.
On Fri, 25 May 2018 11:08:39 -0700 (PDT), trader_4
He might want to think about downsizing the heater to 24KW,
understanding that that might limit the hot water he can use at any
one time. The things that will end up competing will be an electric
range and the dryer but if you have 100a to work with that might not
be problem 99% of the time. Only having 50 could be problematic.
Without a load calc it is really hard to say what he can do.
I tend to agree with you, tankless water heaters may have a very long
payback time if you don't have natural gas.
To the OP, have you looked at what the cost will be to upgrade? You
can probably just put in a 320a "meter main" change the feeder from
there to your existing panel with "4 wire" add a grounding bus or two
and feed the new water heater from the meter main.
You are likely still talking about close to a grand by the time you
are done with the service. It will take a long time to make that back,
just saving the lostr heat from youe existing water heater. Remember
in the winter, there is no lost heat at all if you are running the
On Friday, May 25, 2018 at 2:38:36 PM UTC-4, firstname.lastname@example.org wrote:
The payback is even worse if you have natural gas. They suck up gas
like they suck up electricity, so you typically have to run a bigger
gas pipe from some big tap off, maybe even all the way from the
meter. And gas heats cheaper, so that makes the pay back take longer.
Here, the summer gas bill is under $20, which includes hot water and
some gas grilling. What you're saving is mostly the standby cost,
of the $20, that can't be all that much. Even if it's half, $10 x
12 months = $120. And I just have a basic water heater, for a couple
hundred more you can get higher efficiency too. Running gas, the cost
of the unit, it's a lot to pay back.
On Fri, 25 May 2018 15:04:14 -0700 (PDT), trader_4
It is worse than that. If the furnace is on, there is no lost heat at
all. It still goes to warming the house. It is like all of the other
energy you use in winter. The only real wasted energy is what escapes
the envelope of the house and the hot water you send down the drain.
My well water temperature is 48F.
I can't imagine what it would feel like to be taking a nice hot morning shower and all of a sudden the libtard energy-saving tankless water heater quits working. Suddenly I'd be standing in a stream of 48F water trying to rinse the shampoo out of my
hair. No thanks, I'll keep 50 gallon tank type water heater.
On Friday, May 25, 2018 at 8:29:35 PM UTC-4, Agua Caliente wrote:
hower and all of a sudden the libtard energy-saving tankless water heater q
uits working. Suddenly I'd be standing in a stream of 48F water tryin
g to rinse the shampoo out of my
That's true, with a failure on a tank type, you'd get a more gradual
shift that gives you warning. Also, if the power goes out, you have
40 or 50 gallons of hot water that will last for more than a day
if you use it sparingly. I guess some of the tankless gas units
will fire without power, but not the electric, obviously.
On Fri, 25 May 2018 14:38:01 -0400, email@example.com wrote:
Can be a pretty long payback on Natural Gas too if you need to
replace the meter and upsize the high pressure line from the street.
Since gas is cheaper per therm than electricity the payback will be a
lot longer because the cost savings are a lot smaller - even if it's
the same percentage savings.
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