A differential temperature controller manages solar water heating by comparing collector and tank temperatures. When the collector is hotter than the tank by a set threshold, it turns on the pump to transfer heat, then shuts it off when the temperature difference falls, maximizing efficiency.
/ˌdɪfəˈrenʃəl ˈtɛmprɪʧər kənˈtroʊlər/
A differential temperature controller manages solar water heating by comparing collector and tank temperatures. When the collector is hotter than the tank by a set threshold, it turns on the pump to transfer heat, then shuts it off when the temperature difference falls, maximizing efficiency.
What does a differential temperature controller do?
It compares collector and tank temperatures and runs the pump only when heat transfer is beneficial.
Source: The Cooling Company
Controllers start pumps only when useful heat is available.
In a solar water heating system, the controller activates circulation only when the collector is warmer than the tank, capturing free solar heat without wasting pump energy.
Adjust the differential set point seasonally to balance efficiency and hot‑water delivery.
“Adjust the differential set point seasonally to balance efficiency and hot‑water delivery.”
Differential controllers made solar water heating far more reliable by preventing circulation when heat gain is too low.
Can the differential setting be changed?
Yes. Technicians can adjust it to match system design and seasonal conditions.
What happens if sensors fail?
The controller may disable the pump or run it incorrectly; sensor checks are part of maintenance.
Do all solar water heaters use these controllers?
Most active solar thermal systems do, especially those with circulation pumps.
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