Hot water at summer camp [RE-wrenches]

Mon Mar 19 06:11:56 PDT 2007

Hi Darryl,

Just to clarify to those not so familiar with the tankless products- "the
Takagi" (one _manufacturer_ of tankless water heaters) makes multiple
models, none of which are electric. The only time I would recommend
installing _any_ electric "whole house" tankless would be in an all electric
home. The _minimum_ of 80 Amperes at or below the sunbelt or 120 A above,
for a single shower in US applications is problematic on several counts.

Many of the gas tankless manufacturers offer what I will call "workarounds".
Strap on enough mixing valves (and their higher priced brethren) and if
everything goes well and stays well and there is no scaling, etc. etc. ad
Infinitum then the system might work well. The only current production
tankless, that I am aware of, that is specifically manufactured for solar
backup is the Bosch 125BS, which is a totally different control strategy
(temperature modulated) than the 125B or any of the other 117,000 BTU/hour
Bosch (flow modulated) machines. Unfortunately, the 125BS is a dated design
which uses a standing pilot (and its resulting efficiency numbers do not
permit the current $300 tax credit).

If you are using a non ICS solar system you may already have a
"conventional" tank, chances are that the tank has an electric element(s) or
provisions for same. Use them for backup, it's simple, effective, (and
cheap). Switch them off when you don't need them. (I'm slowly updating my
website to include tips on how to most effectively use your solar hot water
and even how to get the most out of your plain old tank.)

Bill Loesch
Solar 1 - Saint Louis Solar
314 631 1094

PS Darryl, if you are installing the whole house electric tankless in
Minneapolis, MN you might want to think about a bigger unit than 70 Amperes.
Unless you are able to wean the users to a single _ultra_ _ultra_ low flow
shower, 70 Amperes during the wintertime, when inlet water temperatures are
oftentimes _much_ lower, may not be enough. Proper sizing is critical for
any tankless. YMMV. Good luck.

PPS If any ICS systems are to be installed in a freezing climate, please
make sure you can drain the "system" sufficiently to prevent freezing
damage. Same caveat for any tankless that is going to suffer freezing
conditions during the unoccupied portion of the year. Did I remember Holt
wanted low maintenance? <G>

----- Original Message ----- 
From: "Darryl Thayer" <daryl_solar at yahoo.com>
To: <RE-wrenches at topica.com>
Sent: Sunday, March 18, 2007 8:31 AM
Subject: Re: Hot water at summer camp [RE-wrenches]

>
> Hello
> I agree, except for the back-up heater.  I have
> installed up to 70A-240 volt instant heaters with
> unhappy customers.  I have installed even the TAGAI
> which is rated for solar with unhappy customers
> because of the tricks that must be played to get a
> shower of uniform temperature.  If the goal is
> reasonable showers then use a tank type back up
> heater.
> Darryl
> --- Bill Loesch <solar1online at charter.net> wrote:
>
> >
> > Hi Holt,
> >
> > Good thinking! If the hot water load is after the
> > sun can work all day, the
> > ICS heaters are probably a good bet for simplicity
> > (and relatively low
> > cost). You have checked the structure for your dual
> > ICS installation?
> >
> > You need to choose a backup heater that is
> > compatiable with preheated water
> > (not all are). As a minimum, a temperature sensor
> > for _incoming_ water would
> > be required. Be aware of the very large electrical
> > demands of an electric
> > tankless capable of providing heated water for a
> > single shower. Compute the
> > temperature rise with the _lowest_ water temperature
> > that will reach the
> > heater, probably in winter, not the _average_ water
> > temperature that so many
> > of the clueless tankless marketing folks promote.
> > Add dual drain valves
> > inboard of the dual shutoff valves so that manual
> > descaling is a relatively
> > simple operation if/when the tankless heat exchanger
> > becomes blocked.
> >
> > Finally, for both the benefit of the ICS and the
> > tankless (and any other
> > appliance in the hot water distribution) if you have
> > hard water (and
> > especially very hard water) you _NEED_ a water
> > softener (preferably
> > installed only on the hot water side) for minimal
> > maintenance.
> >
> > Good luck,
> >
> > Bill Loesch
> > Solar 1 - Saint Louis Solar
> > 314 631 1094
> >
> >
> > ----- Original Message ----- 
> > From: "Holt Kelly" <holtek at sbcglobal.net>
> > To: <RE-wrenches at topica.com>
> > Sent: Friday, March 16, 2007 10:42 AM
> > Subject: Hot water at summer camp [RE-wrenches]
> >
> >
> > >
> > > I have been asked to design a hot water system at
> > a summer camp. 21
> > > seperate sytems. Hot water for showers is used
> > from 4:30pm to 5:30pm(14
> > > showers)per system, very little use the rest of
> > the day. Solar resource
> > > is excellent to fair. My initial thoughts were 2-
> > 40gal passive
> > > collectors with an electric tankless backup (need
> > to keep maintenance to
> > > a minimum). Or possibly Helio-flo with single
> > tank. Any thoughts out
> > > there?
> > >
> > > Holt E. Kelly
> > > Holtek Fireplace & Solar Products
> > > Waco, TX.
> > >
> > >
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