4. Domestic Hot water
4.1
Single Pass Piping
There are several options for hooking up domestic hot water circuits. The standard
option, shown in fig. 4.1 is called a "single pass" system. The cold water line goes
through the solar heat exchanger and then to the inlet on the standard water heater.
Solar heated water is supplied on demand to the water heater.
4.2
Recirculator Piping
A second option is called a "recirculator" system, or "recirc" for short. This option has
an additional pump and controller installed on the solar tank to periodically transfer solar
heat into the standard water heater. Two lines are run from the solar tank to the
standard water heater -a supply (cold) line from the bottom of the water heater, and a
return (hot) line to the top of the water heater.
Figure 4.2 illustrates the piping diagram. The dip tube in the water heater must be cut in
half to prevent the solar heated water from short circuiting into the supply line at the
bottom. The check valve in the return line from the water heater lets the system act as
a single pass unit when the circulator pump is off. The recirculator option is
recommended only for certain special applications. It should not be used with gas water
heaters because they heat from the bottom where the (cold) supply line would be
located.
HoloTech
tm
Solar Installation Manual
18
!
Figure 4.1 Single Pass System Piping Diagram
Cold
Hot
Water
Heater
Figure 4.1 Single Pass System Piping Diagram
Figure 4.1 Single Pass DHW piping diagram.
