Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

Doesn't sound right to me, I don't have a tankless, but did you check to see
if the water going to the toilet is warm feel the supply tube at the bottom
of the tank.

Tom


wrote in message
oups.com...
Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

On 18 Dec 2005 07:31:08 -0800, wrote:

Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

Hey, somethings gotta keep the "****ter" warm.
Bubba

Nice... Nope, all water is cold like it should be. We do use the
Manabloc system in the house, would that be contributing to the water
flux? Looking at the manual, you have to have a significant amount of
flow to make it turn on.

It might be triggering by the fluctuation in the water pressure.

Maybe there is some sort of adjustment for this?



wrote in message
oups.com...
Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

My Bosch 125 never runs on cold water, New house, probably plumbed
wrong. Fix plumbing not the heater.

m Ransley wrote:
My Bosch 125 never runs on cold water, New house, probably plumbed
wrong. Fix plumbing not the heater.

If a drop in water presure cuases it, then putting a backflow preventer
valve in may help

your intelligent and worthwhile contributions to this newsgroup never cease
to amaze me
"Bubba " ReMoVe wrote in message
...
On 18 Dec 2005 07:31:08 -0800, wrote:

Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

Hey, somethings gotta keep the "****ter" warm.
Bubba

On a new house properly designed and installed plumbing should not have
an issue, when I open everything, drop pressure cold, the heater doesnt
run, it triggers on flow not pressure. Likely toilet is hooked to the
hot supply

In article .com,
says...
Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

If you don't have a backflow preventer on it, then when you flush the
toilet and drop the cold pressure, the water-hammer preventers on all
the hot fixtures in the house push a little bit of water back down
the pipes. If the Bosch turns on when it senses flow, it probably
can't distinguish forward flow from backward flow.

--
is Joshua Putnam
http://www.phred.org/~josh/
Braze your own bicycle frames. See
http://www.phred.org/~josh/build/build.html

Everybody talkes about backflow, but nobody commenting owns one or has
installed one. It isnt even mentioned in my manual, I have no backflow
device or issues.

"MC" wrote in message
...
m Ransley wrote:
My Bosch 125 never runs on cold water, New house,
probably plumbed
wrong. Fix plumbing not the heater.
If a drop in water presure cuases it, then putting a
backflow preventer valve in may help

a check valve.

Its making sense from what you all have put together. The main comes
in and splits. One to cold side of manabloc, the other to the Bosch -
then it goes into the hot side of the manabloc. If any cold service is
used, even if it's a hose bib, a drop in pressure is felt all of the
way into the Bosch. That reverse pressure is enough to kick it on.

Does that sound right? So maybe I need a backflow preventer?

Pressure doesnt trip the Bosch water flow does. It also wont trip on a
drip or a trickle flow, it takes apx 1/4 gpm. I say the toilet is hooked
to the HW line. I bet its only when the toilet is flushed, open a few
cold sinks at the same time, I bet nothing happens to fire the Bosch,
there goes your pressure theory. The volume needed to start tankless are
a drawback for trying to get minimal water flow and saftey against drips
and such. Try yours at a minimal HW sink flow it should not start.

In article ,
says...
Pressure doesnt trip the Bosch water flow does. It also wont trip on a
drip or a trickle flow, it takes apx 1/4 gpm.

When you have compressed air trapped at each fixture, a pressure drop
produces flow -- the compressed air expands as the pressure drops,
and pushes water back down the pipe.

I say the toilet is hooked
to the HW line.

If the toilet were hooked to the hot water line, the heater would
surely trigger for more than 15 seconds, unless he's got a toilet
that fills *really* fast. My toilets sure take more than 15 seconds
to fill the tank. I don't think a standard toilet stop can pass
10gpm, even if the toilet could take it that fast.

--
is Joshua Putnam
http://www.phred.org/~josh/
Braze your own bicycle frames. See
http://www.phred.org/~josh/build/build.html

wrote in message

Does that sound right? So maybe I need a backflow preventer?

A backflow preventer is a fairly complex piece of hardware that will cost
about $125. A simple check valve is all that is needed and will cost about
$15.

Thank You,
I cant say the same for you. If you were intelligent and worthwhile
you would know how to use a "kill-filter". Sucks sometimes, eh?
Bubba

On Sun, 18 Dec 2005 11:30:42 -0600, "A.D.C." wrote:

your intelligent and worthwhile contributions to this newsgroup never cease
to amaze me
"Bubba " ReMoVe wrote in message
.. .
On 18 Dec 2005 07:31:08 -0800, wrote:

Howdy ya'll,

My wife and I just built a home and moved in. We're using the Bosch
pro tankless 635 water heater. I notice every time the cold water is
demanded, ex- flushing any toilet or just turn on a cold water faucet,
this dang water heater fires up for about 15 seconds. It shouldn't do
that unless there is a demand for hot water. Is this normal???

Hey, somethings gotta keep the "****ter" warm.
Bubba

You are right JP 15 seconds is to short for firing to fill, but with 15
second start delay, or 30 second total it might work. A low flow tank of
3 gallon with high pressure might do it. The question is does the
heater run till its full or cut out early. Tankless take usualy 3- 10
seconds to fire. It still sounds like its hooked up to the HW to me as
it needs to sence 1/4-1/2 gallon moving to fire at all and that is alot
of volume and movement in pipe length, more than backflow. Hooking it to
the HW would be an understandable mistake, or there is another plumbing
issue. but it doesn`t happen when he runs his sink? Why not.

Okay guys, FORGET ABOUT THE TOILET.

It happens at any cold water demand - even a hose bib, and even when
the icemaker pulls water.

so you think a check valve would do?

Maybe its your heater not waiting for enough flow to trigger, I think it
can be adjusted, call Controlled Energy, I thinks that is the US
distributor.

Edwin Pawlowski wrote:
wrote in message

Does that sound right? So maybe I need a backflow preventer?


A backflow preventer is a fairly complex piece of hardware that will cost
about $125. A simple check valve is all that is needed and will cost about
$15.


Check valve, that is what I meant to say earlier.

Anyway, I have seen where a mixing valve was added to add a little hot
water to the cold water entering a toilet tank to prevent condensation
under heavy use. Not sure if that could be it.

MC