If you already have a dedicated hot water return line you can
use your Chilipepper hot water demand system with it instead of using the cold
water line as the return.
Homes that are plumbed with a hot water circulating
system have a dedicated hot water return line that connects the last fixture in
the loop with the water heater. The return line connects to either the
water heater inlet or the drain valve at the bottom of the heater.
Normally there will be a check valve between the end of the return line and the
connection with the water heater to prevent water from being drawn backwards
through the return line.
Why Replace A Hot Water Circulating
Pump With A Hot Water Demand System?
Traditional residential hot water circulating or
recirc systems eliminate the waste associated with running the hot water while
waiting for it to arrive, but they also waste a tremendous amount of energy.
The cost to heat water is far higher than the cost of the water you are heating,
and running a hot water pump continuously will make the water heater run more
often and longer to replace the heat energy being lost from the hot water
piping.
On the plus side there is no waiting for hot water, it is pretty much instant
hot water when you turn on the tap; You must of course, purge the cooled off hot
water from the hoses under the sink and perhaps a couple of feet of pipe, but
within two or three seconds you have piping hot water.
With a hot water demand
system you still have a wait for the hot water. Once that wait is over
then when you turn on the tap you will have nearly instant hot water. The
length of the wait depends on two things, the plumbing layout, and the power of
the pump being used.
How Long Will the Wait Be With a Demand
System
Pumping at 3 gallons per minute means the
water velocity in the pipe for a 3/4" diameter pipe would be about 2 feet per
second. With 1/2 inch pipe it's about 4 feet per second.
1/2" dia. Type L copper pipe has a pressure drop due to friction of
0.062 psi per foot with a flow rate of 3 gallons per minute. This means in
order to pump 3 gallons per minute through a 100 foot long 1/2" dia. Type L pipe
the pump will have to produce a pressure of at least 6.2 psi.
The Chilipepper demand pump is the most powerful pump on
the market and will pump at about 3 gallons per minute in most residential
plumbing layouts. The Chilipepper will only pump continuously for 3 minutes and
will then shut down to avoid over heating the motor. However, a gallon of
water will fill about 45 feet of 3/4" pipe or about 60 feet of 1/2" pipe.
So the nine gallons pumped during that 3 minutes would fill 405 feet of 3/4 inch
pipe or 540 feet of 1/2" diameter pipe. Few residential plumbing layouts have
anywhere near that much piping.
Here is a graph showing some typical pump curves for TACO pumps. Metlund D'mand
systems use TACO pumps for their hot water demand systems.
Way down in the bottom left hand corner, the second curve, the one labeled 006,
is the curve for the TACO 006 pump, the one used in the smallest Metlund System,
the Metlund D'mand model S-50T.
The pump "dead heads" at about 8 ft of head which is about 3.5 psi.
That means the the TACO 006 does not have enough pressure to produce a flow of 3
gallons per minute through a 1/2 inch pipe. Metlund, incidentally, states
the capacity of the pump in their literature as 8 gallons per minute or
something like that... somewhat misleading.
With tankless water heaters the
pressure drop through the heat exchanger is significant and must be added to the
piping pressure drop, probably 2 or 3 psi.
Installing a Demand
System With a Dedicated Hot Water Return Line
Typically a traditional hot water return line in a residential system
consists of a 1/2" pipe connecting from the supply pipe at the last fixture to
the inlet of the water heater. This forms a big loop of piping so the hot
water can be continuously circulated from the water heater through the loop and
back to the water heater. Usually the pump is located at the water heater
along with a check valve to prevent the pulling of cooler water from the bottom
of the tank into the recirc line when someone turns on a hot water tap.
Replacing the existing pump with a Chilipepper hot water demand pump is very
easy to do. Remove the old pump and plumb in the Chilipepper. Use hoses to
connect the Chilipepper inlet to the same fitting that was hooked to the old
pump's inlet and do the same with the outlet.
You can then either hard wire the buttons to the various fixtures, or if you
don't want to string wire in your attic or crawl space or there are other
impediments to hard wiring start buttons, use an X10 remote control system for
starting the pump from any location. Insteon remote control can also be
used but Insteon stuff is pretty pricey.
What to Expect
- Operating Your Hot Water Demand System with a Dedicated Return Line
Obviously there are major differences in the way a demand hot water system
and a hot water circulating system work. The hot water circulating or
recirc system is very simple. The most basic form is a continuously running pump
circulating a small amount of water around the hot water piping loop.
Since the water is continuously circulating it doesn't take much of a flow to
keep the loop full of hot water. However because a hot water recirculating
system wastes so much heat energy many home owners have used timers and or
temperature controls.
A timer can be used with the circulating pump to shut if
off during periods of no or little use. This does of course save oodles of
energy, but is quite inconvenient if you happen to need hot water during one of
those periods that the system is turned off.
Another method used to reduce the
energy wastage of recirc systems is to have the pump turn on when the
temperature drops below a set point and turn off when it reaches an upper set
point. The problem is that if you reduce the temperature low enough to
realize significant energy savings you don't end up with hot water in the loop,
just warm.
With a hot water demand system, when you want hot water you must
push the start button and then wait for the hot water to arrive. The hot
water will of course, reach the first fixture in the loop first, and then each
fixture along the loop until the pump senses the arrival of hot water.
When the Chilipepper detects a temperature increase of 3 to 12 degrees,
depending on the sensitivity setting, it shuts off. If you again push the
button the pump will again shut off when it sees a second temperature
increase... which typically would only be a second or two because the hot water
has arrived.
Once the temperature hits 96 degrees or above the pump locks out
and won't restart until the water temperature in the pump drops below 96
degrees.
Due to the time it takes hot water to cool off in the piping and the
pump there can be short periods of time where the occupant would like to use the
demand system to get hotter water than what is in the loop but the pump won't
respond because the water is just above 96 degrees. 96 degree water is
lower than human body temperature and therefore will feel cool, not hot.
Typically that time period would be 20 minutes or so.
That's all there is too
it. Be a little more green, conserve water, save time and water, install hot
water demand system in your home today!
