[Strawbale] [SB-r-us] re: Passive Heating

[Ryan McCulley]

I'm not Mark but thought I would share my experience with tankless
water heaters. It might be relevant for you and others considering
replacing their conventional water heaters.

I installed a small tankless unit on our house in midtown Tucson last
year, replacing our rumbling twenty-plus-year-old 40-gallon water
heater. We got it permitted, and the plumbing inspector informed us
that the gas line we had was too small to handle the load. Even the
smallest tankless units use a LOT of fuel to flash heat the water
on-demand. A common problem with tankless installs is that the gas
line capacity does not allow enough fuel to the unit, which prevents
it from working properly. We hadn't budgeted for it, and had to incur
a significant expense to bring the gas line to the proper size (we
actually moved the meter closer to the point of use).

Also, once the new water heater was installed, we noticed that the
water pressure in our newly-remodeled tub and shower fell so low that
the tub is effectively unusable. I understand (perhaps erroneously)
that in order to flash-heat the water on demand, the tankless water
heater has to reduce the water flow rate for the hot water. I believe
the anti-scald valve for the bath uses pressure-balancing to avoid
pressure drops and scalding water. This in combination with the
reduced pressure from the water heater basically reduces our flow rate
to a trickle. Be aware that, if you have a pressure-balancing valve
for your bath (such as a Delta Monitor), it will take a LONG time to
fill your tub and the water may not be hot enough to boot. We give
baths to our little kids, and when we do we have to fill up a bucket
at the bathroom sink with hot water to draw a bath! Crazy. Hopefully
replacing the Monitor tub valve will solve that problem. Anyone out
there have any suggestions?

We have noticed that the tankless unit uses much less fuel than a
conventional water heater, though. And we could install it outside, so
we were able to convert our old water heater closet into a pantry.

Hope that helps!

Ryan

On Jan 8, 2008 4:42 PM, Dot Rhodes <lacasapaja at theriver.com> wrote:
>  The main hot water tank (for those who haven't moved to a [tankless] combi
> boiler system)
>
>     Mark,
>     I am very interested in more information about a (tankless) combi boiler
> system for my radiant floor system and domestic hot water. I have a
> strawbale house in the mountains of SE Arizona, two stories, radiant floor
> heat in a slab on the two level ground floor (approx. 1560 sq ft) and
> radiant floor heat under a wooden  floor on the second floor (approx. 450 sq
> ft). The second floor is an open loft and only needs heat first thing in the
> morning. Warm air rising during the day from passive solar keeps the
> upstairs warm. On cloudy or cold days and nights I supplement the radiant
> heat with the Wells fireplace in the downstairs great room  Ceiling fans
> help to circulate the warm air.
>     The current heating and domestic hot water system is very simple, two
> zones, upstairs and downstairs, with a 60 gallon hot water heater fueled by
> propane and supplemented by two 30 gallon water solar panels on the roof. In
> the summer the solar panels provide about 98% of the domestic hot water. The
> hot water heater is ten years old, starting to rumble, propane is getting
> expensive, and I'm looking for a compact heating source to replace the
> current hot water heater. Thanks..
> Dot
>
>
>
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-- 
Ryan McCulley
ryan.mcculley at volny.cz

http://villagersonline.com