ACMV: Summer vs Winter
ACMV: Summer vs Winter
(OP)
Hi
I have come across ACMV systems that are designed for Summer time operation but seem to disregard Winter time operation. You have the typical setup. AC units, exhaust fans, and Make-up air fed into the AC units to compensate for the air that is thrown out. I was wondering what the scenario would be like when the AC is turned off come the Winter time. Now the AC and OA are OFF, but the exhaust is still ON. I see two issues with this
1- Is it not a problem that the Exhaust is ultimately pulling in cold air from the outside at a time when the occupants are trying to heat up the space? Or is this considered an equivalent penalty to the AC drawing in hot air in the Summer. Its not freezing here in the Winter (~16 degrees C/61 degrees F) on the coldest days of the year, and those temperatures around 6-8 weeks before the weather starts to warm up again. I'm thinking its not economic to spend money on systems that heat the air if its only cold for a maximum of 8 weeks a year.
2- Maybe cold air is less harmful when it comes to mold formation and similar issues since it carries much less water vapor than the hot air in the Summer, and thus is allowed into the occupancy during the colder months?
PS: I hope I'm not violating any forum policies with all these questions.
Thank you
Best Regards
I have come across ACMV systems that are designed for Summer time operation but seem to disregard Winter time operation. You have the typical setup. AC units, exhaust fans, and Make-up air fed into the AC units to compensate for the air that is thrown out. I was wondering what the scenario would be like when the AC is turned off come the Winter time. Now the AC and OA are OFF, but the exhaust is still ON. I see two issues with this
1- Is it not a problem that the Exhaust is ultimately pulling in cold air from the outside at a time when the occupants are trying to heat up the space? Or is this considered an equivalent penalty to the AC drawing in hot air in the Summer. Its not freezing here in the Winter (~16 degrees C/61 degrees F) on the coldest days of the year, and those temperatures around 6-8 weeks before the weather starts to warm up again. I'm thinking its not economic to spend money on systems that heat the air if its only cold for a maximum of 8 weeks a year.
2- Maybe cold air is less harmful when it comes to mold formation and similar issues since it carries much less water vapor than the hot air in the Summer, and thus is allowed into the occupancy during the colder months?
PS: I hope I'm not violating any forum policies with all these questions.
Thank you
Best Regards





RE: ACMV: Summer vs Winter
RE: ACMV: Summer vs Winter
RE: ACMV: Summer vs Winter
RE: ACMV: Summer vs Winter
Air Conditioning & Mechanical Ventilation
B.E.
You are judged not by what you know, but by what you can do.
RE: ACMV: Summer vs Winter
317069: Thank you for the response. That is one way to do it. The budget is available on this one, so I can go with something better. The fresh air to the fans will be supplied close to the face of the fan's filter rack. In the winter when the AC is OFF, the AHU will remain ON and will supply tempered air to the ceiling space which will be slowly drawn into the room through the AC return grills. This air will be tempered somehow, either by a heat recovery wheel, or an electric heater. Any comments are greatly appreciated.
Drazen: Thank you for the response. That makes sense.
willard3: As berkshire said.
Best Regards
RE: ACMV: Summer vs Winter
RE: ACMV: Summer vs Winter
ACMV is an acronym replacing HVAC in countries that do not normally require heating.
RE: ACMV: Summer vs Winter
Can you describe your system a little more, first you said fresh air come through AC, so this tell AC mean RTU or split system, then you said AC fan off and AHU fan on, what is your system, is it rooftop unit or split system (air conditioner and furnace for example)
what did you mean by AC?
RE: ACMV: Summer vs Winter
KiwiMace: Thank you for the response.
317069: Ok. It is a large palace with a chiller and FCU's. There is an Air Handling Unit that is bringing in Fresh Air and distributing it to the FCUs.
The fresh air is brought in at 110 DB (design day) and cooled down to 75 DB.
There is also a central exhaust fan + ductowrk
What I meant by A.C is Air conditioning System. In this case, Chiller and fan coil units.
Best Regards