HVAC Automatic Duct Dampners 4

[flyinghigh]

An office building HVAC unit serves Zone 1 and Zone 2, which are connected by various hallways. Some Zone occupants are cold, while others in the other Zone are not. It is proposed to install a thermostat for each Zone, along with some Automatic Dampners to solve the problem. When one Zone demands air, the other will not get it and vice versa. How do these work?

 

[tys90]

Do you mean specifically how do they work or how do they work in the scheme of controlling temperature?

Specifically, a motor controls the damper blades based on a signal, usually from a thermostat.

In the scheme of controlling temperature, they modulate airflow to maintain temperature in a space. They shouldn't be designed so one zone starves the other though. Systems can be dumb, meaning they don't know what other zones are doing or systems can be extremely intelligent, switching over heating/cooling based on demand and settings, incorporating PID loops, resetting static pressure.

In your situation, the system is probably a constant volume system and the zone damper system will be fairly dumb. That means if you want to incorporate zone dampers, you will want to have a bypass to relieve pressure in the duct when your dampers close down. This can bypass directly back to the return duct or dump into the plenum. Either way, you will need a third damper that is either mechanically set to relieve pressure at a certain set point or automatically controlled based off a pressure sensor.

There's more to consider with these dampers, such as insuring that you maintain minimum ventilation rates, what do you do when one room needs heating and the other cooling, how much complexity do you want, etc. There should be some good articles on google.

 

[flyinghigh]

Originally, I was thinking they'd be tied electrically to a thermostat like you described, but later I was thinking the term automatic meant it was isolated from any controls and either opened upon air pressure or was spring-loaded.
Now I'm thinking if Zone 1 was too hot, we could place a thermostat in that Zone connected to an automatic dampner which would reduce the airflow to Zone 2, but give Zone 1 a larger, maybe more frequent shot of cold air to keep them happy.
Under that design, when Zone 2 wanted some cold air, everybody would get it. If the t-stats were set properly, it seems to me it would work.
I would try to avoid a third dampner in a new bypass duct to return air to simplify and reduce costs.
Comment?

 

[willard3]

Hire an HVAC Engineer and stop bootstrapping this.

 

[berkshire]

If you are going to work it that way, put a dummy thermostat next to the person who complains most about the heat or cold, then put them in charge of it.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[317069]

is it homework? if not, as far as you ar a structural and seems doing HVAC and electric and I guess architect too, so you can solve this problem by combind these two zones together and make them a one zon then no body will feel cold or hot.