Issue
SVT Optimiser Controller does not enable the controlled space to recover to the required day temperature after an unoccupied period during which the inside air temperature has fallen to 12°C.
Environment
SVT4201 Optimiser Controller fitted with Analogue Time Switch.
SVT4251 Optimiser Controller fitted with Digital Time Switch.
Cause
SVT Optimiser Controller Time Switch settings do not allow for selected Design Preheat Hours (DPH)
Resolution
SVT Optimiser Controller Time Switch settings should allow for selected Design Preheat Hours (DPH)
SVT Optimiser Controller Time Switch settings should be carried out as follows :-
- Set Td to "Day" temperature required during occupancy.
- Set Tn to minimum "Night" temperature required during unoccupied periods.
-
Set DPH to design preheat time.
DPH is the maximum time required in order to enable the controlled space to recover to the required day temperature after an unoccupied period during which the inside air temperature has fallen to 12 deg. C.- Select the approximate time in whole hours on the rotary switch (1 to 5 hours)
- Fine trim +/- 1/2 hour on the associated setting potentiometer.
- Note. ALL "ON" times must be set earlier than the start of occupancy by the selected pre-heat time (DPH) set at (3) above.
Example :
DPH = 2 hours
Occupancy time = 8.00 a.m.
Set Time Switch "ON" time to 6.00 a.m.
Setting the Time Switch "ON" time to 6.00 a.m. will enable the SVT Optimiser Controller to switch the plant ON at any time between 6.00 a.m. and 8.00 a.m. depending on the heating loss experienced in the controlled space during the preceding plant OFF period.
N.B.
The setting method detailed in the example above applies equally to both SVT4201 Analogue Time Switch and SVT4251 Digital Time Switch versions of the SVT Optimiser Controller.
