Robert Gammon wrote:

Suppose we take a shower and collect 100 F greywater in the upper part of
a $30 100'x4" black plastic corrugated drainpipe coil containing 3 $20
100'x1" pieces of black plastic polyethylene pipe, with bidirectional
plug flow, like this, viewed in a fixed font like Courier:

shower
in
| ----------------------------------------- hot water to shower
| | Tl |
--------- sewer ---------
| | Tg | out | 120F |
| | | | |
| | | ^ | |
| | | | | |
| |1" |4" | | tank |
| | | | | water |
| | | | | heater |
| | | | | |
| | | | | |
| | | | | |
| | |---- | |
| | | | 55F |
--------- P ---------
| ---- Tc |
-----------------| - |------------------- cold water supply
----

This is so very very close to a GFX Star it isn't funny

I'm still not clear on that, after talking with Carmine again. One diff
might be beneficial stratification in the greywater drainpipe, vs full
mixing in a conventional greywater tank. At any rate, with 98.9% heat
recovery, we might heat 50K Btu/day of water with 550 Btu/day, eg
a 7 watt night light burning 24 hours per day :-)

Nick's figures and the Power-Pipe folks argue that the heat recovery is
equivalent to a 12-18KW electric heating element (for a 60 inch GFX).

Dr. V got US Customs to sieze Power Pipes at the border, based on a
theft-of-trade-secrets charge, but they seem to have gotten around that.

In testing of the the GFX done at at least a couple of universities,
they found that the upper heating element in an electric water heater
NEVER TURNED ON in ANY of their testing.

We also discussed some testing techniques that were biased against GFX.

The heat recovery of a GFX when used in this configuration jump 15-20
percentage points and becomes an almost level 65-75%

Maybe a lot more, with greywater plug flow.

One of the reasons for the higher heat recovery is that the flow rate
thru the coil LEAPS. The Taco pumps will move up to 20Gal/hr depending
on model to 20 feet. More realistically a Taco 006 or Taco 008 will
delvier upwards of 10Gal/hr at 10 feet of height. Now we have 2x-4x
MORE flow thru the coil than is flowing in the greywater.

That isn't part of my scheme, but another circulating pump could increase
the velocity through the coil and the conductance inside the coil...

GFX Star controls the pump via one of two methods

a. Timer - showers at KNOWN times EVERY day

b. Differential temperature controller -sensors on coil and inlet to the
heat exchanger (GFX or Nick's) will trigger the pump when temp
difference exceeds a set point - i.e. 2 or 3 degrees

That's quite different. No timing for me, and I'd turn on the pump when
the gw-fw temp diff at the output is LESS than 5 degrees.

Nick