50
Chapter 8
HYDRAULIC SYSTEM
The hydraulic connection between the pipes and the solar panels must be realised using fl exible stainless
steel pipes. Direct connection of the panels tot he rigid pipes is not allowed.
The piping insulation must be suitable and without faults in a way to guarantee effi
cient transport of the
heat collected from the collector towards the tank. For pipe width up to 22 mm and insulation with heat
conductivity of 0.035 W/(m K) the minimum thickness of the insulator must be 20 mm. For diameters from
22 to 35 mm the minimum insulation thickness value must be 30 mm.
The following indications must be respected for pipes positioned inside:
The insulation must resist high temperatures (in proximity of the collector about 170°C, away from the
collector at least 120°C
The materials used must have low thermal conductivity
Only use open cell materials if there is no risk of humidity
The following indications must be respected for pipes positioned outside:
The insulation must resist environmental impact (atmospheric pollution, UV rays) and the action of
animals (pecking of birds, rodents, etc.) otherwise further coverings are required.
To prevent the risk of infi ltration of humidity, insulation must be carried out using closed cell materials,
as not even accurate covering can prevent the infi ltration of humidity. This seriously undermines the
effi
ciency of the insulation.
The following coverings for the insulators are available on the market:
Synthetic materials (to be used preferably on pipes located inside)
Galvanised steel
Aluminium 99.5
Salt-resistant aluminium
Stainless steel and aluminium-zinc alloy (special goods)
Single or double stainless steel or copper pipes complete with insulation, insulator covering and temperature
probe cable can be found on the market.
In order to minimise heat loss it is good practice to insulate all hydraulic parts involved in the transport of
the heat transfer fl uid: connections, branches, valves etc.
Closed cell elastome-
ric insulator
Drawn copper
without welding
Integrated
temperature
sensor cable
Black fi lm that pro-
tects from mecha-
nical wear and from
UV rays
fi gure 8.7
