[RE-wrenches] tankless gas water heaters

[Kurt Albershardt]

On 2/10/09 12:20 AM, Bill Loesch wrote:
> What I can offer is that there are five (5) major _manufacturers_ of
> tankless water heaters that market to North America. Alphabetically: Bosch,
> Noritz, Paloma, Rinnai, and Takagi. A multitude of other companies market
> gas tankless. Even more market electric tankless. Sometimes these other
> companies simply change the decal on the machine to their own name. Not
> unlike buying a Mercury instead of a Ford (or vice versa). For example. A.O.
> Smith, a premier manufacturer of tank water heaters, also markets a tankless
> under the A. O. Smith label. Today A. O. Smith are marketing the Rinnai,
> earlier they were using a competitor tankless manufacturer.
>    
You could add to that a number of hydronic boiler manufacturers whose 
products work quite well for DHW.

> There are two classifications of gas water heater both tank and tankless -
> natural draft and power vented. The only commonality between the two are the
> fact they both use gas. If you have properly installed a natural draft tank
> or tankless you have zero experience (and carryover skills) with a power
> vented tank or tankless. Read the manual _before_ installation and save
> callbacks and frustration.
>    
I would add condensing and noncondensing variations.

Heat exchanger design is a critical area that has a complex relationship 
to service conditions (water chemistry, set points, usage patterns, 
venting, feed gas quality, etc.)

At a minimum, be aware that hard water and tankless generally do not 
play well together.  We are testing a new scale prevention system that 
shows great promise (a German technology marketed in the US by Watts.)