Michael Thomas, Paragon Property Services,
http://www.paragoninspects.com wrote:
On Dec 30, 7:39 pm, " wrote:

the bosch range of temp rise is likely not wide enough to accept pre
heated water, and scalding could result.

say water in 50 degrees out 130 degrees

pre heated water in 100 degrees, out 180 degrees.....

!!!OUCH !!!!

i suppose one could install a tempering valve to prevent too hot out.

but the too hot in may damage some delicate bosch input parts, perhaps
the impeller that trips the burners on.


Almost all "whole-house" tankless units have modulated burners or
heating elements, and raise the water temperature only to the pre-set
output temperature.

Not sure if you caught the original thread (which I wrote) from which
is quoting ... the question was why Bosch states in the
installation instructions that "The 2400 E is not approved or designed
for solar/preheat backup or high temperature booster use". I hadn't
planned on using it as such, but I was disappointed that a) the heater
cannot be used in a Solar hot water system e.g. be fed solar pre-heated
water, and b) I didn't learn this until after the purchase was made and
the box opened.

My thoughts were that it really *cannot* be used this way because
something will break, or else it is a corporate disclaimer to relieve
them of any liability if their heater is used in a solar heating system.
The latter I understand, but I can remember once upon a time installing
Paloma tankless heaters as part of a fresh-water solar hot water system.
The Paloma would get its water from a large storage tank of solar heated
water; if the water temperature was greater than the heater's thermostat
setting, the water would pass on through and the heater would remain off.

Do you know why this heater cannot be used in a solar preheat system?