[Shop-talk] tankless/instant water heater

[David Scheidt]

On Mon, Jan 24, 2022 at 6:04 PM Jim Franklin <jamesf at groupwbench.org> wrote:
>
>
>
> > On Jan 24, 2022, at 5:39 PM, David Scheidt <dmscheidt at gmail.com> wrote:
> >
> > On Mon, Jan 24, 2022 at 4:27 PM john niolon <jniolon at att.net> wrote:
> >>
> >> tired of just cold (really cold) water in the shop sink./..thinking about a tankless/instant water heater.  Would like to stay
> >> with 120v if possible to avoid additional wiring (me crawling around in attic dragging wire with bad knees and hips.  I have an available plug
> >> within 6 ' of sink
> >>
> >> pros and cons ? recommendations.
> >> This will strictly be a hand washing sink to be used after putting up my tools  (shop content)
> >>
> >
> > an 1800W tankless water heater (the biggest you can plug into 120V
> > outlet) will have a temperature rise of 25 degrees at 0.5 gpm.
> > (that's the physics of water.  they're all going to have similar
> > performance.  Anything that claims better is lying or has a tank)
> > That will turn cold water into less cold water, or warm water into hot
> > water.  you probably want something with a tank.
> >
>
> I'm pretty sure that you can change the 120 outlet to a 240 3 prong outlet and use the existing wiring, as long as you re-wire it in the breaker box to have a 240 breaker and stay within the current limits. A dumb heater will not need a neutral so the 14/2 or 12/2 (with ground) will work unless I'm having a senior moment.

You can do that if there's nothing else on that circuit, and you can
easily change the breaker.  a 20A 240V circuit lets you install a 4000
or 4200 W heater, which gives a heat rise of 65F at 0.5 gpm.  That's
probably enough temperature rise, even here where the incoming water
is currently less than 40F, but that's pretty low flow.  If you're
somewhere where 'cold' water is 60F, then it looks a lot better.  (a
gallon a minute is plenty for washing hands, it's slow if you want to
fill a sink or bucket).

It'll take a long time for the efficiency of tankless heater to pay
for the required changes though, and a plug in tank heater is cheap.




-- 
David Scheidt
dmscheidt at gmail.com