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E. GLYCOL FREEZE PROTECTION
Only use food grade polypropylene glycol, FDA rated as GRAS (Generally Recognized As Safe), with
additives that provide resistance to breakdown during high temperatures. Glycol (pH) should be checked
periodically and replaced as specified by the manufacturer.
F. INSULATION
Heavily insulate all piping running to and from the manifold with high quality insulation of at least 0.6”
thickness, thicker in cold climates. Heat loss from the piping can be significant. Particular attention should
be taken to insulate any possible points of heat loss.
Ensure the insulation is tight against the manifold casing, thus minimizing heat loss from the inlet and
outlet. High quality silicone sealant should be used to prevent water from entering the temperature probe
port and/or in between the piping and insulation foam.
Insulation foam exposed to direct sunlight should be protected against UV related degradation by
wrapping/covering with UV protective material, such as adhesive back aluminum foil, PVC conduit or
similar.
For systems designed to allow stagnation, high temperature rated insulation such as glass wool or
mineral wool should be used on piping close to the collector (6’). Glass wool insulation may come with an
external foil wrap, but any cuts made during installation should be sealed with watertight, UV stabilized
material such as adhesive backed aluminum foil.
Circulation pumps can be a source of significant heat loss and should be insulated. Some pumps come
standard with a molded foam casing which has good insulation properties. If the pump does not have any
insulation, the same foam insulation used on the pipe can be used to cover the pump, secured in place
with good quality nylon cable ties or adhesive tape.
Note:
Certain pumps are not designed to be insulated. Please contact the pump manufacturer if in doubt.
All internal and external piping should be insulated. This includes at least the 3” closest to the hot water
outlet of the tank, as this copper pipe is a significant point of passive heat loss.
G. PUMP SELECTION
When selecting a pump, there are two basic solar designs to consider: pressure glycol and closed loop
drain back. In pressure glycol systems, two factors determine pump size. These are:
•
Flow Rate in gpm (gallons per minute)
•
Head Loss
In drain back systems, an additional factor must be considered along with the previous two:
•
Lift
Each HP-30SC collector has a flow rate of about .84 gpm.
When determining pumping head loss, consider the following:
•
Head loss pumping through panel(s).
•
Head loss pumping through piping and fittings.
•
Head loss pumping through heat exchanger.
•
(Drain back only) Determine the vertical lift from the water level in the drain back tank to the top of
the solar panels. (Vertical lift is the same as head loss.)
Summary of Contents for HP-30SC
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