|
Drain
Down Solar Water Heating Systems
With Preheat
Tank
Drain
Down Systems are suitable for single
application systems, particularly domestic hot
water, in moderate climates. One or two
tanks can be used in various configurations and they retrofit easily
into existing systems.
The drain down valve provides system freeze
protection. Without power, the valve closes the supply and
return lines from the tank and the collector water drains away,
preventing freeze-ups. |
|
| 1.
Collector Supply |
4.
Tempering Valve |
7.
New DHW
Tank |
| 2.
Collector Return |
5.
Hot Water to Taps |
8.
Existing DHW Tank |
| 3.
Hot Out to Cold In |
6.
Cold Feed |
|
|
| Connecting
an Extra Tank in a Series - a Preheat Tank |
In
some situations, particularly integrating with an existing system, a two
tank system is necessary. The traditional arrangement is to have a solar
preheat tank, in which the tanks are plumbed in series. If the tanks can
be sited close together connecting tanks in parallel has some
advantages. Both these arrangements provide adequate backup. |
| Advantages
of a Preheat Tank |
- Easy to retrofit to existing tank with
minimum disturbance of existing piping
- Versatile system - the preheat tank can
be located away from the conventional tank.
- Useful if the conventional tank is gas
or oil fired. Many gas fired DHW tanks have high standby heat losses
and will waste solar energy.
- The "pretank"
is usually cold in the morning and ready to receive solar energy.
- Good control over the system and easily
monitored performance.
- Efficient if the house is occupied
through the day. Solar heated water will frequently be drawn into
the conventional tank, helping offset standby losses.
- A well insulated standard DHW electric
tanks is mass produced and reasonably priced.
- This solar system can be disassembled
easily, leaving the existing system intact, and moved to another
location.
|
| Disadvantages
of a Preheat Tank |
- Solar energy is only heating half of the
available storage. If no-one is home through the day the solar heat
remains in the preheat tank.
- A larger pre-heat tank will be necessary
than if a tank was added in parallel.
- Stand-by losses are more than twice
those of a single tank system.
|
|
E-Mail:
Thermo Technologies
Thermal Solar Collectors | Solar Controller
| Solar Tanks
| Home
9009 Mendenhall Court
Suite E
Columbia, Maryland 21045
Voice: (410) 997-0778 Fax:
(410) 997-0779 |
