Setting Holiday function on solar controller

Anthonyk2010

Going on holiday next week and im not sure how this function works.
below is from the controller manuel. Is it saying the pump will come on and circulate when it hits 10 degs below set temp.
Will this keep system cool?

Holiday function/recooling

If the user extracts too little hot water, or none at all (e.g. during holidays),
a completely heated storage tank can cause the solar energy system to
begin evaporation prematurely, and the system is thus subjected to a
higher thermal load.
When the holiday function is activated, and the temperature in the storage
tank reaches 10 deg below the set maximum storage tank temperature(35Deg C),
the controller attempts to systematically unload the lower part of the storage
tank, until the set minimum storage tank temperature is reached.

This function always works with the lowest priority storage tank.

quentingargan

That is a different version to what I have seen. It won't keep the system cool during the day, but generally this holiday system cools the bottom half of the cylinder at night.

It does this by pumping from the bottom coil back up to the panel at night when the panel is cool. This works better with flatplates than it does with tubes, but should still get the temperature of the bottom half of the cylinder down at night. The the system will start heating as normal during the day again.

How well this works depends on the size of your solar array, and the amount of fluid below the top of your solar coil (). If your solar coil is tucked in at the very bottom of the cylinder with only 100L of water below its top, and you have 6 SqM of panels, it will only cool 100L of water. The system would still go into stagnation sometime the following afternoon. So this system has its limits, but is better than n'owt.

Hedgecutter

I have a heat dump that kicks in at 68 deg c, should I reduce this down to may be 55 while I'm away.

jj58

excess stagnation, can cause a degrading antifrezze, and will reduce bits freezing properties, i have seen a solar system in for 12 years now, and a year ago the copper inside the tubes burst in the frost, the system was stagnating alot and never changed antifreezes like your meant to every 5-7 years
so holiday mode is important, its easy do