HVAC return in slab - questions

[NoPro]

Our home (built in 50's) is an L-shaped brick ranch with the returns in the slab. We just replaced all the in-slab plumbing and the plumbers noted how much of the "tunneling" was collapsed and had water in it. The HVAC system was replaced about 14 years ago. It's a Lennox combined electric ac/ gas heat. We can feel air coming out of the return registers from time to time when the system is not on and we'd like to just cement the openings into the house so we don't get that musty odor. First question is, how can we tell if the returns in the slab are still being used by our current system? Second question is, if it is still being used how do we bypass it?
Thanks for your help.

[skippedover]

Your question is logical but your information is lacking. Do you have any attic space? Room enough for the appropriate equipment and a new duct system? Of just enough room for ducts? Or no attic and just a flat roof? If the plumbers found water in their tunnels, then it's likely the entire heating/cooling system in the slab is compromised. In that case, you could either relocate the entire system as mentioned above or as a path of last resort, dig up the system and have a sealed PVC duct system installed. That will be impervious to the water and should stay dry for as long as you own it. Mind you, I said as a last resort. If it were mine, I'd find a way to put in an overhead duct system, even if it means soffets in every room. I think in the long run it will be less $$$$ than doing any slab work. So attic 1st choice, soffets 2nd choice, slab last on the list.

[genduct]

follow your plumbers advice, based on his obserrvations i.e. return colapsed

A central return with transfer or jump ducts should work just fine

[NoPro]

Thank you for your responses genduct and skippedover! However, we're not quite ready to do any duct work just yet. The attic space can handle it, though, when we're ready. What would happen if we sealed the 2 existing openings (one under the unit itself and one in a nearby hallway)?

[tinner73]

be careful...if you seal off any returns you have the possibility of damaging the heat exchanger or the compressor from lack of airflow.

[Gross]

Thank you for your responses genduct and skippedover! However, we're not quite ready to do any duct work just yet. The attic space can handle it, though, when we're ready. What would happen if we sealed the 2 existing openings (one under the unit itself and one in a nearby hallway)?

:worthless:

lets see exactly what youre talking about

[NoPro]

Sorry, I don't have pics of the situation in the slab, only descriptions given by the plumber. There are currently 2 openings in the slab coming into the house through the floor. One is directly underneath the HVAC system, the other is in another hallway nearby. Each also opens into the house and there is a register vent over them. The larger opening is about the size (side to side) of the HVAC unit. The other is under a linen closet and is smaller (about 2' x 1').

[second opinion]

Sorry, I don't have pics of the situation in the slab, only descriptions given by the plumber. There are currently 2 openings in the slab coming into the house through the floor. One is directly underneath the HVAC system, the other is in another hallway nearby. Each also opens into the house and there is a register vent over them. The larger opening is about the size (side to side) of the HVAC unit. The other is under a linen closet and is smaller (about 2' x 1').

The answer to your question is no. The system would not function. Air in equals air out, no air in equals no air out.