daestrom wrote:

wrote in message
...
daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2,
60% is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design choice.


Guess again. If your setup was restricted to just 5 feet long, would
its performance be anywhere near as good as the GFX??? And that's the
point. To get performance on par with GFX, you have to resort to
something several tens of feet long.

Heck, If I had someone build a GFX that was 100 feet tall, I'm sure
it's performance would put your setup to shame. But who has space for
100' of 4" pipe (vertical, coiled or otherwise).

The issue with a 100 foot tall GFX is the required size of the potable
water tubing and the pressure required to get a reasonable flow rate
thru the 100ft stack.

As it is on a 60 inch GFX, manifolding is performed to limit pressure
loss (coil height is about 27 inches each) with the base of each coil
tied to the inlet water, and the top of each coil tied to the outlet.

The engineering drawings on gfxtech's web site clearing indicate an
asymptotic behavior. Adding additional length brings lower and lower
incremental benefit. Still with two S4-40s in series, pressure loss is
about 2.5psi on a 2 gal/hr flow rate. and 80 inches of gfx recovery
will get efficiency up another 5-10% over a 60 inch model and a 40inch
height is easier, in many cases, to find a spot for.

daestrom is doing us a great service by pointing out the issues with the
home brew system. I too do not believe that the home brew system
proposed will work as well as a 60 inch GFX to recover waste heat from
grey/black water and pump that heat to DHW and cold side showers.