Air Flow Rate: Summer vs Winter

[Axe34]

Hello

This is more of a conceptual question. I'm fairly new to all of this so bear with me.

Say I have a 'constant' volume system (Air Handling Unit) with no recirculation that operates both during the summer and winter external conditions and maintains the same internal conditions (temp, relative humidity) all year round.

If I size my Air Handler fan, say, for providing the required volumetric flow in the summer, what is the normal procedure for during the winter?:

- accept that the pressure losses through the system will be different, and so the fan will output a different volume flow rate?
- control the fan speed to ensure constant volume?

Hope this makes sense
Thanks

[WAYNE3298]

With no recirculation you have a make-up air unit. Provide the same amount of airflow year around. Size the heat and cooling source to handle it. The flow rate shouldn't vary enough to matter.

[teddy bear]

Furnaces have specific needs for air flow to avoid overheating. A/c air flow is adjusted to provide ideal moisture removal. They may be different.
Keep us posted.
Regards Teddy Bear

[WAYNE3298]

Make-up air units are sized for a specific purpose and with no recirculation that purpose normally requires the same amount of airflow year around. For that reason design of the heating and cooling will handle the airflow. There are some MAU'S now that will do a lot of things. It depends on what you want them to do.
I recently balanced a school that had three MAU'S with three different purposes. One was a football locker room that traditionally had odor problems. The supply and return both had VFD'S. I set the football locker room up to exhaust at 100% 24/7. The supply CFM varied to help control temperature and humidity. The heat wheel speed varied. Heating and cooling percentages varied. This unit would do anything you wanted and performed beautifully.
One of the other MAU'S had to control room temperature and more importantly room pressure. The exhaust fan was set up to follow the supply fan at whatever speed necessary to keep the room at a positive pressure. The supply fan speed varied to control temperature and humidity. With both fans at 100% the room was positive.
As you can see it depends on what you want the MAU to do and how much you are willing to spend.