VAV Reheat and convector control
VAV Reheat and convector control
(OP)
Hi, we have vav boxes with reheat and convectors at perimeter zones. Convectors are sized to offset envelope loss. Vav reheat valves are not commanded open before room temperature drops below set point (vav boxes set to min flow), and we have reheat valves 100% open when room temperature is 3 degrees below set point.
In this scenario,
1)when should the convectors kick in? When outside temp. is below, say 40F? (AHU SA set point is 55F)
2)How should they be operating? In unison with reheat? How do we control the convector valve? (single space thermostat)
Thanks for suggestions.
In this scenario,
1)when should the convectors kick in? When outside temp. is below, say 40F? (AHU SA set point is 55F)
2)How should they be operating? In unison with reheat? How do we control the convector valve? (single space thermostat)
Thanks for suggestions.





RE: VAV Reheat and convector control
RE: VAV Reheat and convector control
That wouldn't be funny except it's true.
RE: VAV Reheat and convector control
With just a single thermostat at a perimeter zone, trying to keep things simple (straight proportional control), a possibility would be:
+2°F to 0°F of set point, no heat, just VAV full flow to min flow
0°F to -1°F (and OAT <45°F), perimeter heat 0% to 100% open
-1°F to -2°F, reheat 0% to 100% open.
I'd probably also consider boosting up that 55°F set point a bit during winter if the loads allow. There would be a little more ventilation and fan power but less reheat needed. Energy should be roughly equal but could improve comfort and IAQ (overall more ventilation, generally better throw from diffusers, etc.).