Fan Coil Units & Reheat Cycle
Fan Coil Units & Reheat Cycle
(OP)
I plan to have fan coil units operating in a "Reheat Cycle) for the purpose of controlling humidity. Basically, I plan to cool down and de-humidify the air mass as it goes thru the cooling coil of the fan coil unit and then reheat the air mass as it goes thru the heating coil of the unit. I have both chilled and hot water available throughout the year. I'll be happy for any suggestions regarding this particular application for fan coil units.
Thanks,
Mike Orozco
Thanks,
Mike Orozco





RE: Fan Coil Units & Reheat Cycle
RE: Fan Coil Units & Reheat Cycle
RE: Fan Coil Units & Reheat Cycle
Regards,
RE: Fan Coil Units & Reheat Cycle
Control the heating coil hot water control valve with the room thermostat to close when temperature is 75deg. F (adjustable) and to open when the temperature is 73°F and below (adjustable). Valve should modulate between 75 & 73 degrees. If larger temperature swing can be tolerated, consider closing valve at 75 & opening at 70.
RE: Fan Coil Units & Reheat Cycle
Mike
RE: Fan Coil Units & Reheat Cycle
Initial condition repeated: Room starts with no reheat and no CHW, and is at 45% RH. With a constant moisture level in the air, and when temperature starts to RISE, what's to stop the rise? When temperature rises, RH goes down so then your cooling source would be disabled.
The controls would be interlocked. Changing one would affect the other, and vice-versa. This could turn into a one-foot-on-the-brake and one-foot-on-the-gas control that could lead to disastrous energy use during dehumidification and no cooling when needed.
If the CHW (or DX) always maintains a 55°F outlet temperature prior to the reheat coil and the HW controls as necessary to satisfy the room thermostat, I think that control would prevent these problems and perform better.
RE: Fan Coil Units & Reheat Cycle