Cli-mate CLI-AP30 Spezifikationen PDF herunterladen (Seite 18)

the heated fluid can reach the

tank. The hot fluid sits in the

return line and loses heat until

the next ON cycle, before it

finally is delivered back to the

tank. This is especially true

when high flow rates are used

and when there is a long pipe

run. A variable speed control

helps to prevent this from

happening by sending the heat

back into the tank as it is

produced and results in higher

overall system efficiency and

heat output.

f) Direct Flow - Flow Rate: A

high flow rate in a direct flow

system may cause turbulence in

the solar storage tank and

disturb stratification, which can

lower the entire tank temp during

low solar production periods. A

variable speed pump control will ensure that the flow rate matches the heat output and limit tank de-

stratification.

g) Correct Pump Choice: Any pump used for solar loop circulation must be able to handle continuous use

to at 232

F (110

C) and higher, if required by system design. The solar pump should always be installed on

the Supply (aka Flow) Line (i.e. pumping to the collector and away from the heat exchanger or tank) thus

limiting exposure to high temperatures. In addition, a check valve should always be installed after the pump

to prevent back flow, and nighttime thermo-siphoning, UNLESS the system is a drain-back, which should

never have a check valve installed in the solar loop. See Apricus OG-300 Schematics and Parts List

system diagrams for reference. The Apricus pump stations incorporate a flow meter, pump and check

valve. Refer to Closed Loop and Direct Flow Pump Station Installation instructions in this manual for more

details on pump station operation.

h) Flow Rate: The flow rate through the collectors should be determined under the following considerations:

i) Turbulent flow through the header is necessary for optimal heat transfer during high solar output and

is achieved at flow rates of 0.8 gpm (3 Lpm) and greater. In a single collector installation, this flow rate

will generally only be achieved during summer. Running a high flow rate during the winter to achieve

turbulent flow is NOT recommended or required as the heat output is not as high, and excessive ON/

OFF cycling of the pump will occur which can cause premature pump failure.

ii) Temperature rise of the heat transfer fluid during each pass through the collector manifold(s) can be

adjusted by changing the flow rate. Reducing the flow rate by half will double the temperature rise per

pass. Normally, a temperature rise of 10-30°F is an acceptable range. Lower delta-t levels

(temperature rise) attained at higher flow rates may cause the pump to turn ON/OFF too often.

Extremely high delta-t levels produced by low flow rates will decrease collector efficiency. This

decrease is far less acute with evacuated tubes than that experienced with a flat plate collector and

may be acceptable, especially if pressure drop is an issue.

A suitable flow rate range for each 30 tube collector is a 0.4-0.8 gpm (1.5-3 Lpm).

iii) The following table provides estimated temperature rise at various flow rates:

Flow Rate per 30 tubes

Temp Rise @ 150Btu/ft

(Clear Winter Day)

Temp Rise @ 320Btu/ft

(Clear Summer Day)

0.2 gpm (0.75 Lpm)

F (16.4

F (35

0.4 gpm (1.5 Lpm)

F (8.2

F (17.5

0.6 gpm (2.3 Lpm)

F (5.5

F (11.7

0.8 gpm (3 Lpm)

F (4.1

F (8.7

Apricus Solar Collector Installation & Operation Manual - USA

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