A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Jeff Wisnia wrote:

A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff


You're close. Maybe 150Amp (3 60 Amp brach circuits).
So now you're talking a 300-400 Amp service to the house ugh.

In Boston, a gas heater is the way to go.

Jim '58

Jeff Wisnia wrote:

A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Why would they not replace a gas tank type with a gas tankless type?
Either way, the tankless type have lower standby losses than the tank
type which may or may not matter much depending on the usage patterns
and unit location where the lost standby heat goes.

I don't know what the various utility rates are in Boston, but I though
I heard NU had like a 20% rate increase recently. Surely gas is cheaper
especially if they already have gas service in place vs. needing to
upgrade electric service.

Pete C.

On Apr 9, 1:03?pm, "Pete C." wrote:
Jeff Wisnia wrote:

A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Why would they not replace a gas tank type with a gas tankless type?
Either way, the tankless type have lower standby losses than the tank
type which may or may not matter much depending on the usage patterns
and unit location where the lost standby heat goes.

I don't know what the various utility rates are in Boston, but I though
I heard NU had like a 20% rate increase recently. Surely gas is cheaper
especially if they already have gas service in place vs. needing to
upgrade electric service.

Pete C.- Hide quoted text -

- Show quoted text -

gas will require a large new gas line directly to the tankless and may
require a new flue, all those BTUs have to go somewhere, the install
will be expensive, tankless will require routinue maintence by
qualified techniocians $$$ if the tankless quits working NO HOT WATER
AT ALL, the costs will exceed the standby losses, the paayback exceeds
the tankless warranty and expected life.....

a regular tank is a much better deal, if they complain about running
out of water upgrade to a 50 or 75 gallon tank with a 75 thousand BTU
burner, most regular tanks are half that, such a upgrade they will
never run out of hot water, it will double their capacity

regular tanks standby losses helps heat the home in the winter

Jeff Wisnia writes:

Comments from those in the know?

As an EE you should know enough thermodynamics and electricy to see that
these are a fool's errand.

Just do some simple calculations of water flow rates, times temperature
differential, to get the BTUs required, and then convert to watts, and
finally amps at 240 VAC. Heating 4 gallons/minute by 60 deg F takes 50
horsepower.

The capital cost of that much demand and wiring alone makes them
uneconomical, not to mention the device itself. And the horror of having a
50 horsepower electric appliance in your house.

On 2007-04-09, Jeff Wisnia wrote:
A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.
....
I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

They evidently have gas, so why not a gas tankless water heater? From
what I've read, those perform much better than electric ones for
whole-house use.

Richard J Kinch wrote:

Jeff Wisnia writes:


Comments from those in the know?


As an EE you should know enough thermodynamics and electricy to see that
these are a fool's errand.

Just do some simple calculations of water flow rates, times temperature
differential, to get the BTUs required, and then convert to watts, and
finally amps at 240 VAC. Heating 4 gallons/minute by 60 deg F takes 50
horsepower.

The capital cost of that much demand and wiring alone makes them
uneconomical, not to mention the device itself. And the horror of having a
50 horsepower electric appliance in your house.


Not to mention that only about 1/3 of the BTU's produced
in burning all that coal at the power station ever reaches
the appliance :-(

Jim

On 2007-04-09, Jeff Wisnia wrote:
The "family" is two adults living in a single family house in the Boston
Area.

You might also want to look into the smaller tankless heaters that
serve a single fixture, instead of a whole-house heater. One for the
kitchen sink, one for the washer, one for the shower, and one for the
bathroom sink.

I'm not saying these are any good--just suggesting considering all
options.

Go with a standard GAS 75 or 100 gallon 75,000 BTU tank. If their
existing tank is 35,000 BTU this will double the capacity.

Tankless on low flow like one fixture running slowly are often below
the minimum trip level to turn on the burner or turn on the electric
resulting in cold water for these applications.

Another thing a electric tankless or most gas tankless no electric
means no hot water at all.

Jeff Wisnia wrote:


A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff


Thanks guys, I think I'll tell my friend to "fughedit" and just get
another gas water heater (with tank) installed.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

wrote:
Go with a standard GAS 75 or 100 gallon 75,000 BTU tank. If their
existing tank is 35,000 BTU this will double the capacity.

Tankless on low flow like one fixture running slowly are often below
the minimum trip level to turn on the burner or turn on the electric
resulting in cold water for these applications.

Another thing a electric tankless or most gas tankless no electric
means no hot water at all.


It depends, the good ones do a good job sensing flow and regulating
temperature. Also the ignition is powered by electricity that is
generated by the flowing water.

One idea you might want them to consider is to add a heat exchanger to the
shower drain.

See this:

http://www.gfxtechnology.com/GFX.html

Looks to me like they might be able to downsize their current gas water tank
and still have plenty of hot water.

--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.

"Jeff Wisnia" wrote in message
...
Jeff Wisnia wrote:


A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff
I've read leads me to believe that installing a whole house tankless
unit as a replacement for their gas fired heater is very likely going to
require increasing the capacity of the electric service to their house,
along with the installation a new panel and heavier conductors from the
panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a
low flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff


Thanks guys, I think I'll tell my friend to "fughedit" and just get
another gas water heater (with tank) installed.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

"Speedy Jim" wrote in message
...
Jeff Wisnia wrote:

A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff I've
read leads me to believe that installing a whole house tankless unit as a
replacement for their gas fired heater is very likely going to require
increasing the capacity of the electric service to their house, along
with the installation a new panel and heavier conductors from the panel
to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a low
flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff


You're close. Maybe 150Amp (3 60 Amp brach circuits).
So now you're talking a 300-400 Amp service to the house ugh.

In Boston, a gas heater is the way to go.

Jim '58

Agreed - I can't think of any way that anything but a flame fired device is
going to work for tankless hot water system north of the Mason Dixon. Most
of the units I've seen that work well are gas, but the same basic principle
has been in use with oil fired furnaces for many years. I wouldn't touch an
electric tankless system, can't even think why they would make such a thing,
even worse try to sell it in New England! Usually even an electric hot
water tank can't keep up with one shower, how would a tankless unit do it?

Just my 2cents - FWIW.

"Richard J Kinch" wrote in message
. ..
Jeff Wisnia writes:

Comments from those in the know?

As an EE you should know enough thermodynamics and electricy to see that
these are a fool's errand.

Guess he told you, Jeff!
;-)


Just do some simple calculations of water flow rates, times temperature
differential, to get the BTUs required, and then convert to watts, and
finally amps at 240 VAC. Heating 4 gallons/minute by 60 deg F takes 50
horsepower.

The capital cost of that much demand and wiring alone makes them
uneconomical, not to mention the device itself. And the horror of having
a
50 horsepower electric appliance in your house.

"Jeff Wisnia" wrote in message
...
Jeff Wisnia wrote:


A friend who's facing replacement of a 60 gallon gas water heater asked
me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston
Area.

I've no firsthand experience with tankless heaters. The bit of stuff I've
read leads me to believe that installing a whole house tankless unit as a
replacement for their gas fired heater is very likely going to require
increasing the capacity of the electric service to their house, along
with the installation a new panel and heavier conductors from the panel
to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s
during the winter, requiring a pretty powerful tankless heater in order
to raise that to a comfortable temperature for showering, even with a low
flow showerhead.

And, if one person is showering and the other starts the clothes washer
and then decides to do the dishes, things could get coolish in the
shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the
heater, which will almost certainly necessitate the electrical changes
mentioned above.

Comments from those in the know?

Jeff


Thanks guys, I think I'll tell my friend to "fughedit" and just get
another gas water heater (with tank) installed.


I don't know, I would seriously consider a GAS tankless though, but I've got
a wood stove and live in redneck country.......




Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.