From our series on best-practices with RESOL DeltaSol Controllers.
RESOL controllers include a built-in control process optimization algorithm. This optimization is based custom setup options - so the installer should learn to recognize and use these features effectively.
One of the Special Functions for control optimization is OTC - Tube Collector Special Function.
The heat produced in the tube will not freely rise to the sensor well if the collector is installed horizontally. The resulting delay in the temperature readings necessary to start the circulator could create a problem, especially for systems with large collector arrays.
But this will not happen with the RESOL controller , my friends! The use of OTC function for that application will do the trick.
When the solar pump is OFF (because the âÂÂT - delta T is too small), the controller is actively measuring the collector temperature and storing that value as a reference point.
As soon as the collector temperature rises 4 degrees (2K) higher then previously recorded, the solar pump will be turned ON for a 30 seconds purge. The newly measured temperature is recorded as new reference value. The run time is preprogrammed and is not adjustable.
If during that purge exercise the âÂÂT grows for additional 4 degrees, the controller will add additional 30 seconds of a run time. If âÂÂT becomes equal to delta T ON - programmed in DTO setting, then normal operation (load charging) begins.
Should the âÂÂT drop to DTF value - the solar pump will stop and collector temperature will be stored as new reference point. If the âÂÂT drops for 4 degrees more, the reference point will be recalculated.
{xtypo_warning}Important Tip: The OTC Special Function is not applicable for every system with Vacuum tube collectors, don't turn it ON if is not necessary, or you will get an unpaid service call!{/xtypo_warning}
Another Special Function is OCF- collector freezing protection. It activates the solar loop circulator if a collector temperature drops below CFR - the freezing temperature of antifreeze set point.
But why use antifreeze if it freezes?
The OCF function is designed for two purposes:
{xtypo_warning}Important Tip: Never leave glycol at low concentrations on your installs! Antifreeze protection works only as long as some residual heat is in the tank and electrical power is on. It could be a BIG PROBLEM if the heat exchanger (especially a flat plate) frizzes up and cracks, or power goes out in the winter storm! By BIG PROBLEM I mean the kind of problem where ten thousand dollars can't make it go away.{/xtypo_warning}
Stay Tuned! In our next article we will discuss the RESOL Controller communication interface - the VBus.
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