HTP FP-40SC - Manual (Page 24)

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2. PRESSURE OPEN LOOP
Run the pump at the highest speed setting, forcing air out of the collector and back into the tank. If an
auto-air vent is installed on the outlet of the collector, air will automatically eliminate from the solar line. If
using a manual air vent, open it until all air is eliminated.
3. CLOSED LOOP
The solar loop may be filled with distilled water (drain back system) or glycol/water mix, unpressurized
(drain back system), or vented and pressurized. The exact process will depend on the design of the loop
and components used.
NOTE: A drain back system does not need to be purged.
D. PLUMBING CHECK
Water vapor may appear on the inside of the collector glass when initially installed. This is not a problem
and will disappear after a few days of operation. Consult your dealer or factory representative if water
vapor does not clear up after a week of sunny weather.
E. GLYCOL FREEZE PROTECTION
Only use food grade propylene 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 collector with high quality insulation of at least .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. Insulations should have a temperature rating
of 250
o
F.
Ensure the insulation is tight against the collector 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 wrap, 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 or PVC wrap.
Circulating pump volutes 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. This
insulation should be 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.