On 11/10/2010 4:39 AM, mike wrote:
Prof Wonmug wrote:
Does anyone have experience with tnakless water heaters?

Are they really cheaper than a central water tank?

Do I need one installed next to every hot water tap?

What is the cost (roughly)?

Any detractors?

I just got a tour of my friend's new system.
It's about the size of a bathroom medicine cabinet.
Has three 240V 40Amp heaters. 120A is no big deal
for him cause he just put in 400A service.
For most people, that would be a problem.
Also, there's the major expense of the electrical
work if you have to pay to have it done.

Gas would have it's own set of issues.

Once you've picked an energy type, you pay
the same to heat water no matter what technology
you use. A BTU is a BTU.
The only difference is the losses in the system.
If you use a lot of hot water, I can't imagine it
saving much of anything. If you use no water,
the energy saved by not radiating
from your hot water tank and the pipes
between the source and the point of use might be
a significant percentage...but still maybe
not a big absolute number of $$.

Might be a different situation if your house
was optimized at design time to with all the
points of use a short distance from the tankless.

Me and my friend installed an electric two module instant water heater
for his sister. It's installed in the utility closet with the washing
machine and electrical panel so we didn't have to run a lot of wire.
The only problem with it is adjusting the rate of flow. For that, we
installed ball valves to adjust how fast water goes through the heater.
A gallon bucket and a stopwatch is what we used to determine rate of
flow so the heater will work. What most folks don't understand about
tankless water heaters is the fact that you're not going to get the
full flow of the rest of your water supply unless you install a very
high capacity heater. The water has to spend enough time in the heat
exchanger to absorb the heat. If I installed a tankless heater for
myself, I would add a tempering tank to help bring up the temp of the
incoming water.

TDD