Special Controller Functions

Protect and Perfect Your Installations

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.

Control Optimization

I'd like call it a control optimization function for special Tube collectors. You see, the introduction of direct flow (Sydney type) vacuum tube collectors has made possible to mount collectors horizontally on flat roofs. The U-shaped tubing inside the vacuum tube conducts media to common headers.

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.

How the OTC Function Works:

When the solar pump is OFF (because the ∆T - 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 ∆T grows for additional 4 degrees, the controller will add additional 30 seconds of a run time. If ∆T becomes equal to delta T ON - programmed in DTO setting, then normal operation (load charging) begins.

Should the ∆T drop to DTF value - the solar pump will stop and collector temperature will be stored as new reference point. If the ∆T 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}

Collector Freezing Protection: OCF

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:

  1. For use in the regions where freezing is normally not an issue.
  2. For use in emergencies where glycol concentration couldn't be restored because an apprentice has forgotten the instructions and decided to do some 'creative improvisation'.

{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.