vacation mode

[tandemsforus]

Hi
A question.
A neighbor said his solar system has a "vacation mode".
what exactly is "vacation mode"???
His system- two panels on the roof feeding a 60 gal or so hot water tank. He said it uses glycol so I am assuming its a closed loop but have no idea what kind of fluid.

[Naptown]

"vacation mode" is built into the controller
Most modern controllers, Resol and others will have this built in.
essentially you set a high limit above which the solar pumps will stop working. We usually set it about 160 degrees.
When you go away and there is no water being used the tank can get very hot.
When the high limit is reached the pump stops. When the temperature in the collectors gets to 240d the pumps start and run for about a minute then shut down again.
This will continue throughout the day.
When the sun sets and the collector cools down the tank is above the high limit. The controller sensing this will turn the pump back on to cool the tank. Assuming you have flat plate collectors this will work. It does not work with evacuated tube systems due to the extremely high insulation value of the tubes and the fact that they will only transfer heat in one direction.
If the system is evacuated tube it should be either a drain back or have a heat dump built in. Some people will also install a heat dump on the tank that either has an outdoor radiator or will dump some water when the high limit is reached.

[tandemsforus]

Naptown
Thanks for the answer, makes sense....

[Naptown]

You're Welcome

[bernard]

... When you go away and there is no water being used the tank can get very hot.
When the high limit is reached the pump stops.

Hi Naptown. Thank you for the upper explanation.

I am curious to know: If one is using evacuated tube collectors and a heat dump: is there even a need to keep the pumps turned on, while on vacation?
Can the pumps be turned off during vacation?

Thank you.