Hi Group,

I did some Googling, and read a bunch on the issue of tankless water heaters
but didn't get a good feeling for whether one would be the right choice for
my brother and sister-in-law. Here's their situation:

Live in Ohio (USA)
All electric home, probably 10-15 yrs old.
Three sons ages 2yrs to 8 yrs
2.5 bath home, normal laundry, DW, etc.

I'm feeling that the initial cost of a 'whole house' unit large enough to
support them, coupled with the fact their actual hot water use is probably
going to be high enough that the heat loss of water just sitting in the tank
will offset the savings offered by 'on demand'. It seems the real savings of
on-demand is in the low usage level. Am I wrong here?

Additionally, with the fact that in mid winter the incoming water temp here
in Ohio would be around 50 degrees and they may not get the desired hot
water when they want it most.

Finally, the overall electric requirement seems it could be an issue as
well. The larger whole-house models seem to require 150 amps. I couldn't
find a rating for a standard electric tank (all gas in my house, so nothing
to look at to compare), but I didn't think a tank was more than 50-60 amp.

Any advice appreciated!

Mark

in general: for family with kids, electric tanks are slow recovery so
you get the biggest one you can afford that fits into the space and the
electrical service available.
think about how much energy it takes to bring 32 degree lake erie tap
water in buffalo ny to 150 degrees for plenty of hot water in our gas
fired 75 gallon tank for 4 adults, a dog, and dishwasher and laundry.
we overcame the running out of hot water with a high recovery 40 gallon
when we changed to a 75 gallon.
your ohio relatives have buffalo ny latitude's cold water.
also:
"On demand hot water system? from Noah Lamy The relative energy
efficiency of these systems depends a lot on other factors such as the
amount of heat loss from a more traditional storage tank system or the
length of time hot water is stored before it is used. In practice they
require a good deal more energy per volume of heated water than
conventional systems and they cannot usually provide enough hot water
for more than one fixture at a time. The traditional storage tank type
of water heater can be quite efficient if the tank and the hot water
pipes are properly insulated.
The on-demand type heaters have their uses in the appropriate
situation. I have found them practical and efficient in situations
where hot water is used only occasionally such as in some shop
situations or where a fixture is at a considerable distance from a
traditional storage tank water heater, such as in a guest house or pool
house. They can also be handy if you are adding hot water to a
structure that has been cold-water-only and the cost or inconvenience
of adding a complete hot water piping system will be prohibitive." it
says at:

comments from:
http://www.theplumber.com/faq.html#Water_Heater
various tankless models:
http://www.plumbingsupply.com//index...erheaters.html

"mwlogs" wrote in message
. ..
Hi Group,

I did some Googling, and read a bunch on the issue of tankless water
heaters but didn't get a good feeling for whether one would be the right
choice for my brother and sister-in-law. Here's their situation:

snip

I can't tell you whether a tankless heater is right for your brother and
sister in law. I can tell you that in our situation (central new england,
two kids, older home) it was NOT feasible for us. When we bought our
house, we were initially excited about the fact that there was a tankless
system, but after a year of lukewarm showers and not being able to wash in
hot enough water, we just had a tank put in. That works *much* better for
us.

HTH

Donna

mwlogs wrote:
Hi Group,

I did some Googling, and read a bunch on the issue of tankless water
heaters but didn't get a good feeling for whether one would be the
right choice for my brother and sister-in-law. Here's their
situation:
Live in Ohio (USA)
All electric home, probably 10-15 yrs old.
Three sons ages 2yrs to 8 yrs
2.5 bath home, normal laundry, DW, etc.

I'm feeling that the initial cost of a 'whole house' unit large
enough to support them, coupled with the fact their actual hot water
use is probably going to be high enough that the heat loss of water
just sitting in the tank will offset the savings offered by 'on
demand'. It seems the real savings of on-demand is in the low usage
level. Am I wrong here?
Additionally, with the fact that in mid winter the incoming water
temp here in Ohio would be around 50 degrees and they may not get
the desired hot water when they want it most.

Finally, the overall electric requirement seems it could be an issue
as well. The larger whole-house models seem to require 150 amps. I
couldn't find a rating for a standard electric tank (all gas in my
house, so nothing to look at to compare), but I didn't think a tank
was more than 50-60 amp.
Any advice appreciated!

Mark

Well, IF you get sufficient capacity to handle the load, you will have
lower electric bills. However you are likely going to need more than one
unit or you are going to need to manage the usage so you are not letting
anyone shower during laundry or you will not be able to wash dishes while
someone is showering etc.

Considering your household and the likely use of hot water in the coming
years, I would go for conventional tank type heater. You will save on the
installation and on the likely need for a new higher capacity electrical
supply.

--
Joseph Meehan

Dia duit

Do you know that even with Ng being much higher today your electric
cost is still apx 50% more than NG. They should convert to Ng heating
and apliances.

A whole house or more than 2 use Electric tankless will need 200 A. Do
they even have a 200A service or 200 Amps free, I dought it. Install and
upgrade would be thousands. A 160 Amp Bosch is rated 1-2 use, it is
rated near their 117000 Btu Ng unit. For a family you need a Bosch-
Rinnai-Takagi, Ng 190000 Btu unit, or maybe a 200 amp electric unit.
That means new service, and very heavy wiring, very very expensive.

A Tankless saves less the more people use it, especialy with Electric
tanks having less standby loss, a higher Energy Factor.

Add to that the kids Knowing unlimited HW is avalaible with Tankless
their bills may actualy go up.

I have A Ng tankless, it saves me 25$ a month, single use. But with a
family and Electric, I would pass, but I would go Ng on everything else.
Even a Ng tank would be an improvement. Research at "Energy Star" to
learn.

buffalobill wrote:
in general: for family with kids, electric tanks are slow recovery so
you get the biggest one you can afford that fits into the space and the
electrical service available.
"On demand hot water system? from Noah Lamy The relative energy
efficiency of these systems depends a lot on other factors such as the
amount of heat loss from a more traditional storage tank system or the
length of time hot water is stored before it is used. In practice they
require a good deal more energy per volume of heated water than
conventional systems


Anybody figure out how an on demand unit could require a good deal more
energy per volume of heated water? I could see how that might be
possible if one were comparing only gas units. It's possible the gas
tank type heater would be more efficient, recovering more of the
combustion heat. But I tend to doubt it could be a good deal more. As
for electric units, they are going to use exactly the same amount of
energy to raise water termp.




and they cannot usually provide enough hot water
for more than one fixture at a time. The traditional storage tank type
of water heater can be quite efficient if the tank and the hot water
pipes are properly insulated.
The on-demand type heaters have their uses in the appropriate
situation. I have found them practical and efficient in situations
where hot water is used only occasionally such as in some shop
situations or where a fixture is at a considerable distance from a
traditional storage tank water heater, such as in a guest house or pool
house. They can also be handy if you are adding hot water to a
structure that has been cold-water-only and the cost or inconvenience
of adding a complete hot water piping system will be prohibitive." it
says at:

People fail to Size the units, if Sized right they can heat any amount
of water needed. Sizing is flow, incomming temp lows, heat loss to the
shower head, Voltage drop or variations, of Ng pressure drop, competing
units and proper pipe sizing. They work, but few figure out what the
manuals specify and blame it on the units. Tankless anything takes alot
of research and testing to be sure you will be happy.

There is one other thing to consider: time of use rates (TOU). In
Ontario, *all* residential customers are being converted to TOU.

Under the new rate structure, it will be considerably cheaper to heat
water during off-peak times and store it for use during the shoulder
and peak periods. In this case, a large, well-insulated tank
controlled by a timer or similar control device would be a far better
choice.

In future, I wouldn't be surprised if more jurisdictions move to
mandatory TOU pricing, because it makes good sense for utilities to
flatten their load curves.

Cheers,
Paul

On Wed, 15 Mar 2006 04:12:28 GMT, "mwlogs"
wrote:

Hi Group,

I did some Googling, and read a bunch on the issue of tankless water heaters
but didn't get a good feeling for whether one would be the right choice for
my brother and sister-in-law. Here's their situation:

Live in Ohio (USA)
All electric home, probably 10-15 yrs old.
Three sons ages 2yrs to 8 yrs
2.5 bath home, normal laundry, DW, etc.

I'm feeling that the initial cost of a 'whole house' unit large enough to
support them, coupled with the fact their actual hot water use is probably
going to be high enough that the heat loss of water just sitting in the tank
will offset the savings offered by 'on demand'. It seems the real savings of
on-demand is in the low usage level. Am I wrong here?

Additionally, with the fact that in mid winter the incoming water temp here
in Ohio would be around 50 degrees and they may not get the desired hot
water when they want it most.

Finally, the overall electric requirement seems it could be an issue as
well. The larger whole-house models seem to require 150 amps. I couldn't
find a rating for a standard electric tank (all gas in my house, so nothing
to look at to compare), but I didn't think a tank was more than 50-60 amp.

Any advice appreciated!

Mark

Given that they are all electric, it would probably be cost prohibitive
as they would need multiple units to achieve a reasonable flow at the
temperature (city water temp vs. outlet temp) rise thye are likely to
experience. If they get a Nat Gas or Propane line then a single unit
might make sense (if they went with one of the largest available).

Nevertheless, to appropriately assess the situation you need some more
facts: Specifically you need to know what they believe their maximum
simultaneous hot water usage might be. For example, if they are
expecting to be able to take 2 showers, run the DW, and wash clothes
simulataneously then you get a very different answer than if they are
willing to live with never using more than 1 source of hot water at a
time. Figure on 2.5 GPM per outlet while in use and you'll quickly
come to a total GPM that the tankless unit needs to produce.

From there you can simply assess the various manufacturers specs for an
approx. 70-80 degree temp rise (depending on water inlet temp and how
hot they like their water) and see whether the unit can provide the
necessary volume of hot water.

Doug

wrote:
Given that they are all electric, it would probably be cost prohibitive
as they would need multiple units to achieve a reasonable flow at the
temperature (city water temp vs. outlet temp) rise thye are likely to
experience. If they get a Nat Gas or Propane line then a single unit
might make sense (if they went with one of the largest available).

Nevertheless, to appropriately assess the situation you need some more
facts: Specifically you need to know what they believe their maximum
simultaneous hot water usage might be. For example, if they are
expecting to be able to take 2 showers, run the DW, and wash clothes
simulataneously then you get a very different answer than if they are
willing to live with never using more than 1 source of hot water at a
time. Figure on 2.5 GPM per outlet while in use and you'll quickly
come to a total GPM that the tankless unit needs to produce.

From there you can simply assess the various manufacturers specs for an
approx. 70-80 degree temp rise (depending on water inlet temp and how
hot they like their water) and see whether the unit can provide the
necessary volume of hot water.

Doug


So with high 60s to mid 70s inlet water temp and a rise of 45F, the
large units (185K to 190K BTU input) will easily supply 3 simultaneous
use, and hot water recovery via GFX and/or geothermal heat pump could
make this even higher!!! Course, geothermal heat pump only assists in
this process UNLESS you get their option to produce all hot water (i.e
run heat pump JUST to generate DHW thru a heat exchanger inside a
dedicated DHW tank)

standby tank heat lost isnt wasted enegy in tthe winter since it helps
heat your home.

only in the summer is it wasted and since the entire building is warmer
the loss is less.

a 120 degree heater sitting in a 40 degree home looses lots more
standby heat than the same 120 degree heater sitting in a 80 degree
basement

there are super high gas condensing hot water tanks that elminate the
standing pilot and are fan vented like 90+ furnaces these 98% efficent
hot water tanks are a good solution. Pelonis is one brand

at very low flows a tankless may not trip on leaving you with cold
water for say a sink.

80 degree basement??????? Holy S^&% Batman - where the heck do you live that
your basement gets to 80? Even around here in central Ohio I don't think
even a partially exposed basement would get that hot on the hottest day of
summer!

All that said about heat loss from the storage tank I have to wonder. My
tank is in the basement where it is a pretty constant 60-70 degrees most the
time (I keep the heat off in winter and A/C on part way in summer to help
with moisture). I do spend a good bit of time down there and recently have
been listening for the tank to cycle thru when no water has been used. It
seems that it normally goes several hours before having to recover.

Based on this, I think the bigger loss I'd like to avoid is that which
occurs between the tank and the faucet. Not that I think there is any way
to prevent the loss between water uses - even insulated pipes will only hold
the heat for a short time - but if I'm losing 5-10 degrees while the water
runs from the tank and the faucet during each use and I can eliminate that,
I can set the tank that much cooler and save on both - the overall cost of
the hot I use, and the cost of keeping the tank hot bwtween uses.

Comments?

Mark

wrote in message
oups.com...
standby tank heat lost isnt wasted enegy in tthe winter since it helps
heat your home.

only in the summer is it wasted and since the entire building is warmer
the loss is less.

a 120 degree heater sitting in a 40 degree home looses lots more
standby heat than the same 120 degree heater sitting in a 80 degree
basement

there are super high gas condensing hot water tanks that elminate the
standing pilot and are fan vented like 90+ furnaces these 98% efficent
hot water tanks are a good solution. Pelonis is one brand

at very low flows a tankless may not trip on leaving you with cold
water for say a sink.