daestrom wrote:

"Robert Gammon" wrote in message
. com...
Power-Pipe now has a US web site that gets them around the customs
issue.

The pump with differential temperature control is the secret to
higher recovery rates. Flow rate thru the coil in excess of flow
rate of greywater will more efficiently transfer heat to the potable
water.

Actually you could take this a step further and use a water storage
tank intended for solar applications. It has an internal heat
exchanger, and you could route a working fluid thru Nick's, a GFX, or
a Power-Pipe that was NOT water for higher heat capacity.


What working fluid would that be? Water has a much higher heat
capacity than most any other fluid you're likely to find/afford. Best
to stick with simple water.

agreed that water is best, but think of Freon as an alternative.

As regards to increasing fresh-water flow, the GFX folks recommend
plumbing so that the cold water enters the heat-exchanger *before*
splitting to go to the hot-water heater and the cold tap in the
shower. So the 'cold' water side of the shower is pre-heated (need
less 'hot' water to stay comfortable) as well as the inlet to the
hot-water heater. This raises the flow on the fresh-water side to
equal the greywater flow.

Yes, and this works well in heating dominated climates where ground
water temps average less than 50F year round.

But not here with our ground water already in the high 60s to mid 70s (I
measured mine at 75F)

Putting a pump to circulate between the 'dip tube' into the heater,
and the drain could improve the circulation through the fresh-water
side of the gfx. But you best be sure to insulate the piping. But
with this setup would you still want the heat-exchanger's fresh-water
outlet going to the cold shower tap?

Yes, as that tempers the water to a reasonable temp. My water will come
from a well, and I need to set my hot water tank to at least 140F to
kill bacteria.

Foam insulation around piping and the heat exchanger seem to be useful
ideas to conserve energy as does a water heat blanket for the storage tank.

I'm a bit skeptical. After all, the greywater coming in is cooler
than the hot-water heater until you've cooled the bottom of the tank.
But the bottom of the tank is receiving fresh-water out of the hx.
Increasing the flow through the hx with a pump is going to put warm
water into the hx inlet, mixing with the cold water from the main.
Then sending the mixture of cold inlet water, and warm water from the
heater drain into the hx. Just so you can put warmer water back into
the bottom of the heater via the 'dip tube'. Net results seem to be
higher flow, but the average temperature of the fresh-water side of
the hx is higher and the greywater outlet temperature will be higher.
I would wonder if the increase in heat transfer due to higher flow on
one side only can make up for the lower temperature difference across
the heat-exchanger walls.

The flow is from the drain plug at the LOW point of the storage tank
thru the pump to mix with fresh water. Then thru the coil, and back in
to the lower third of the storage tank. There will be mixing that
occurs, however, this storage tank should achieve water temps in the
70-90F range depending on entering fresh water temp.

The idea is shown on the web site best under the solar hot water
retrofit. The application data shows efficiency rising as flow rate
thru the coil increases for a given flow rate down the drain.

Grey water temps may NOT increase at all due to the higher flow rate
(same idea as the heat exchanger itself). This higher flow rate comes
at a price of increased pressure loss and expense.

Coil inlet temp will be higher, but then so will coil outlet temp.