7.5 ton unit need help

[keeplearnin]

I have a restaurant cust. that has an above t-bar air handler [Old] no name plate left. TXV slant coil with a trane 7.5 ton condenser. The problem is air flow. When system installed the installer hooked a 16 inch return to to air handler which is way too small. The compressor was changed about one yr ago, before I inherited. My question is; would disconnecting return flex duct and using t-bar ceiling as return, increase the air flow? I believe it would, but before I dive in would like some feedback please.

[second opinion]

I have a restaurant cust. that has an above t-bar air handler [Old] no name plate left. TXV slant coil with a trane 7.5 ton condenser. The problem is air flow. When system installed the installer hooked a 16 inch return to to air handler which is way too small. The compressor was changed about one yr ago, before I inherited. My question is; would disconnecting return flex duct and using t-bar ceiling as return, increase the air flow? I believe it would, but before I dive in would like some feedback please.

Firs start with what type of material is above the ceiling.

[dlove]

Firs start with what type of material is above the ceiling.

If you pull air from a plenum, wiring in the ceiling needs to be fire rated. than you need a smoke detector on the return. Unless its not considered a fire rated plenum. check code

[Chris_Worthington]

Being that it is a restaurant what does it have in place to run 365?

Hot gas? Auto reset Freeze stats on the Evap? Condenser fan control? etc?

[keeplearnin]

Freeze stats on coil, no smoke alarm in return. I think there might be a prob with a restriction at txv screen, I have replaced driers already and pressures way off. There does exist a smoke detector laying on t-bar??? who knows why, Remember New Orleans is the Big Easy and probably never inspected- you should see this place, terrible.

[jburchstead]

An additional question that I would ask is how tight is the air space above the ceiling and is this a one story? You have the potential for creating a humidity problem given your location.

[keeplearnin]

No two story and I would add return grills. Even though I know there exist a return air flow problem I am going to inspect txv screen and try to adjust the txv to get suction pressure up.

[HighTekk^]

I would drop a bunch of open top t-bar diffusers in to pull from the conditioned area, using the ceiling as a giant plenum. That would eliminate the humidity issues because it would still be pulling from the "comfort" area.

[Gunslinger]

If the area above the ceiling is not sealed, I believe you will be pulling all sorts of garbage and humidity into the return. Plenum returns are not advised. Why not add the proper ductwork? You short on return. Cure the airflow problem and then adjust the TXV and charge. What is the static pressure? I'll bet the return is out of sight.

[keeplearnin]

If the area above the ceiling is not sealed, I believe you will be pulling all sorts of garbage and humidity into the return. Plenum returns are not advised. Why not add the proper ductwork? You short on return. Cure the airflow problem and then adjust the TXV and charge. What is the static pressure? I'll bet the return is out of sight.

No room and I mean none.

[ckartson]

If you make a plenum return along with what everyone else mentioned you will increase the conditioned space area. Can the equipment handle the load?