Considering switching to tankless water heater. Busy house, lots of
kids, so the neverending supply seems attractive.
I have always heard that they have trouble really heating the water hot
enough, especially here in the upper midwest when water comes out of
the ground pretty cold (maybe 40 degrees??)
Any experiences out there?
If you size it right and install it right it will do the job, it just
takes research. I have a small 117000 btu Bosch that heats 34f incomming
for a hot shower not even being set to high. For a family you will need
one sized , it will im sure be 180000 btu +. Proper gas supply must be
measured since these pull more gas than most furnaces and when
everything is running-pulling gas a test must be done with a Manometer.
So install can cost to upsize Ng lines. The upside is even Sears for
example their best Ng tanks have an energy factor rating of only in the
60s, tankless go from 82-90+ and have efficiencies of up to 94 for a
Talagi tk1. An upside is you will save on gas and considering 1/3 of Ng
usage can be HW, it can be alot. The downside is Endless hot water,
that premotes waste. Look at Takagi and Rinnai 188000+ btu units with
remote thermostat. Measure incomming water temp, Im near Chicago and
incomming is not as cold this year as we are having a warm winter, so
take off 10f on your temp , or if incoming is 40f figure at -15 - 20f it
will be 33f for your calculations. You also need to measure Gpm that you
"Tankless" hot water is a system where the heating system boiler is designed
and fitted with a copper coil that installs into the boiler where the
domestic water is heated by the boilers water.
This is not to be confused with an "indirectly fired hot water" tank which
is a large storage tank much like a gas or electric hot water heater that
has coils inside the tank that run hot water from a separate zone on your
heating system boiler through the tank to heat up the domestic water inside
Tankless systems would never be considered if you are looking for endless
hot water. They produce between 4 to 7 gallons of hot water per minute
depending on brand, size of boiler, and age of unit. When large amounts of
cold water run through the tubes in a smaller system the water would barely
get warm. I have one in my own home with teenagers. Trust me on this one.
They work best in low volume households.
What you want is the indirectly fired hot water system. I have installed
many of these systems in new homes and my customers love them. Get a 74
gallon tank and you are good for 4 teenage girls and a wife with a whirlpool
Ground water is generally 55 degrees, globally, if not drawn from near the
earth's surface (dug wells).
I am not sure you really want a tankless system. You will need to get
one with a capacity large enough to supply the maximum amount of water being
used at any one time. That means if you have two showers and a dishwasher
and a clothes washer all running at the same time, you are going to need a
really large capacity unit. If you only have one shower and will not be
doing dishes and washing clothes all at the same time, you should be OK.
I might suggest that a conventional system should also work. The only
real difference is the buffer. You tank type heater heats up a large volume
of water and it is available for use. You can use very high volumes of hot
water, but only as long as the total gallons used does not go over the
standing capacity of the heater. Even when being used some heating can be
going on to allow a constant usage of hot water as long as it does not go
over the capacity of the heater.
The standard tank heaters can have different tank sizes and they can
have different recovery rates. I suspect you can find one that will have a
large enough tank and recovery rate to handle your needs, just as you should
be able to find a tankless unit with a high enough rating to handle your
How many showers do you have now, what size heater (gallons and recover
data)? Are the showers old pre-restricted shower heads?
I was researching the very same thing a few months back. I live in the
Philadelphia area so in the winter the water can get pretty cold. I
found a DYI article about an electric version (I don't have gas in my
house), and it looked pretty good, but I remember there being an issue
with a limit on the max temp the water could be raised as based on the
temp coming from the ground. I was looking for something for 3 baths,
washer, and dishwaser. Cost was about $800 for the unit.
One link I found was
I recently replaced an old State water heater with an outside Rinnai
tankless (model 2532) about a month ago. My water heater was in the attic
which I did not like, so I was planning to re-locate whatever replacement I
ended up choosing. My neighbor had gone with a tankless about a year
earlier and they had liked it, so I decided to go that route myself. No
issues whatsoever with it heating water hot enough, and plenty of it. I
have four people (two adults, two children) in a 2400 sq ft home in North
Carolina and so far am very pleased with my choice.
Just for comparison sake based on different price quotes I was given, the
tankless unit cost me $400 more than a traditional
tank unit would have cost me (in both cases I was moving the location of the
water heater). For me the extra cost was worth it to solve the attic
locaton problem I had with a solution that I did not have to deal with in my
already cramped garage.
Three years ago when I built a new house, I looked at tankless heaters; but
I opted for the forced-draft high-efficiency tank type. One thought I had
was that in a 2-story house with most of the water use on the first floor
that I would have 50 gallons upstairs to use via gravity feed for flushing,
washing and drinking in the event of a failure of the city system. "Doesn't
happen." the neighbors said.
But, since I've been in the house it has happened -- several times. Pipes
break, there was a regional power failure and then an overworked system for
a while one summer. Last one was a cold winter day 3 weeks ago when the
main down the street started leaking. My little gravity system worked
simply by closing the main house valve and opening a faucet upstair to break
the air lock.
I doubt that there is much of an energy use differential between a tankless
and high-efficiency tank system for the same volume of water (it would be
good to see an unbiased comparison); but, so far, I've found the tank system
to be worth the slight extra cost.
Tankless are rated on gpm and temp rise. If you have 6 gpm incomming
at the main and your tankless is rated for 6 gpm @ 100f then you can
open every faucet in the house and get water 100f hotter then incomming.
With units out putting near 200,000 btu as standard for Rinnai and
Takagi you have alot of power to heat. Tankless have modulating gas
valves, my small unit modulates from apx 25000-117000 Btu. Mistakes are
made by underestimating incoming flow and lowest winter water incoming
temp and undersizing the Ng line, wich must be tested with everything
Sears best Power miser Ng water heater have an energy factor in the
60s. Tankless are from 82-90+. This is your true energy rating of true
efficiency. My 800$ Tankless will pay for itself in 3 years from my well
insulated electric tank. That is an investment return of 33% per year, I
can think of no other better investment ive made.
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