maxodyne wrote:

Robert Allison wrote:
I don't sell them. I am a general contractor. They are just one of the
new popular items since people have become aware of them and how much
energy use they can save. I haven't seen any of my customers complain
about them. The last one that I installed cost $845, the install was
300 dollars and she got a 200 dollar rebate from the city.

I have one, with two baths, a kitchen, dishwasher and wife and 2 kids.
Haven't run out of hot water since I put it in. I got a Rinnai and it
has been performing for 5 years now. I cannot compare energy savings
head to head, because I went from an electric water heater, to a gas
tankless, but my electric bill went down by $45 dollars a month (It
averages about 250-300 per month).

You seem to be trying to convince people that they are spawn from hell
and I am just trying to present the honest facts. I think you are the
one who is biased. It makes no difference to me what the homeowner
wants to install, I make money on the whole job, not just one part.


Greetings, Mr. Robert Allison General Contractor, and welcome to this
very interesting discussion about tank-type vs. tankless water heaters!

I'm moving your valuable contribution to an appropriately re-named
thread so that we can stay organized -- I hope you will follow it here.
The thread started out as rinnai vs. rheem tankless, but soon morphed
into a general tank-type vs. tankless water heater discussion. Then I
joined in, and renamed the thread as such. I won't ramble on about stuff
that I already covered. Hopefully you have picked up enough information
from the various posts in this thread.

Now then. You say that you have installed tankless heaters for your
clients, and they haven't complained about them. Plus, you own one
yourself. This is a good thing IMHO for this discussion group. I
recently installed a Bosch 2400E (natural gas) in my home a few weeks
ago, and have been mostly satisfied with the unit, as well as my own
installation. A dozen or more copper sweat-soldered joints and no leaks.
Anyway, I have a question that I hope you or someone else reading this
post can answer.

After installing my tankless heater, I discovered one thing the old
storage tank hot water heater was very good at: trickling a flow of hot
water into a sink. Tankless water heaters have trouble here, because
they depend upon a pressure drop to fire the heater. If that drop is
less than what the tankless sensor can detect (because so little hot
water is being demanded at any given moment), then no hot water. Or as I
have observed with my new tankless heater, after running full hot water
for a minute or so, and then turning down the hot mix down to below the
sensor threshold, the tap flows a combination of
hot-then-cold-then-hot-again kind of "checkerboard" hot water into the
sink. I know what's going on -- the tankless pressure or flow sensor is
reacting to my hot water demand and turning the burner on, off, and back
on again as I manipulate the sink hot and cold valves. So, the hot water
plumbing is delivering hot, then cold, then hot again water. That all
makes sense to me, but I want to improve on that if I can.

I know that tankless water heaters depend upon an inlet-outlet pressure
differential to trigger the burner (natural gas, in my case). I recall
reading that my Bosch 2400E has a pressure or flow sensor which detects
a 0.8 PSI water inlet/outlet differential. I have performance-tested my
home plumbing for any hot water "crossovers", and found none.

SO HERE COMES THE $64 QUESTION: Is there a way to adjust this pressure
sensor if it is adjustable, or to swap it out for a sensor of a
different, lower pressure differential value if it isn't adjustable; or,
is there any way to adjust the pressure parameters in the Bosch's
on-board computer/processor to lower the burner turn-on threshold so
that I can trickle some instantaneous hot water?

I hope all of that makes sense ... if not, someone please hammer on me
and I'll re-write my rather long-winded question into a shorter-winded
and more concise question if I can.

I have no idea. That would be a question for the Bosch
company or a company that repairs Bosch equipment. I know
that there are different thresholds on different units, but I
have never attempted to adjust the threshold (nor have I had a
need to do so).

I am sure that it is possible, but I can't answer your questions.

--
Robert Allison
Rimshot, Inc.
Georgetown, TX