Adding Garage to the cooling loop???

Gents,

Short version of my situation is:

New home. Humidity issues (SE Georgia). HVAC Consult is that the unit is oversized for the home (4 Ton when calcs indicate a 3 Ton is all that's needed) so it's somewhat short cycling, particularly when it's not super hot outside.

I had the home built with the attached garage insulated/sheetrocked with an insulated door. Sq footage is about 550 with a ~ 10 foot ceiling.

I had them wire for a mini split I was planning to install but It just occurred to me... could I have them add duct work and dampers to include the garage in the cooled area and that extra capacity would be able to handle the load?

I'm thinking dedicated supply and return with some type of controllable dampers so I could isolate that zone when I need to have the doors open.

How far off the reservation am I?

Isn’t it against code to tie in garage space with living space? Carbon monoxide and all that?

RonnieC said:

Isn’t it against code to tie in garage space with living space? Carbon monoxide and all that?

Click to expand...

This. Needs to be separate.

I'd add dedicated dehumidification

Code violation makes it a no go.

Mini split it is.

We did put in a whole house dehumidifier but the operation of it is not optimal (yet), but that's another discussion.

Thanks Guys... I'm off to source mini splits.

How do you know it should only be 3 ton?

Go after the builder or HVAC contractor if you have properly documented this "fact".

The longer version....

New house, immediate humidity issues.

Got another HVAC company to come look at the system (At least part of it was Bosch) and right off the bat he IDs that the air handler and condenser are miss matched (not sure how) and the system is over sized for the home and short cycling (Which I had already noticed).

Initial contractor's guy lets out that they were "switching suppliers" of equipment so I suspect we got installed with some units they had left over, thus the "mismatch".

Initial contractor replaces both units with a Trane System. Says home calcs to need 3 tons but they only have 2 or 4 (again, my gut says he just wants to install what he has, or has access to). This is SE Georgia so going over a little seems to make sense to me if you have to error.

Humidity issues continue so we have them install a whole house AprileAire dehumidifier for the "shoulder" times where it's a problem. This works for the most part.

It would not work properly some times. It'd shut down with a "High Refrigerant pressure" error and the Initial Contractor's guy decided the damper on the DH (Just a plastic flap) was occasionally hanging up so he installed an electric one. (It still has done this so I'm wondering if even this one hangs up occasionally. There's no way for me to see it's position so it'd be nice to have one of the type that has an indicator on the outside).

We still get spikes of humidity but now when it's stinking hot the AC keeps the humidity down and when it's cooler the dehumidifier takes the load although, since they have it plumbed into the supply/return, it appears the humidity spikes when the DH comes on I'm guessing from the air handler pushing air past the damp AC coil, thus the DH has to overcome that before the numbers start to drop.

The other miner issue is that it seems both running at the same time is not optimal. There's a setting on the DH to not run while the AC is running and it appears the wiring is hooked up properly but it still runs while the AC is on.

All in all we are doing better and I was just brain storming my Garage setup and it occurred to me, "Extra capacity??? Why not use it??" but as we have seen, that's a no go and I'm good with that.

I suspect that the system isn't variable (as you wouldn't have as many problems as the unit would adjust as needed), but is there a chance the outdoor unit is two stage?

It's all single stage.

Being as it's been "hot" the past few days, it is actually doing well.

The short term solution is that I'll ride the humidistat when it's "in between" temps.

What kind of humidity numbers are you seeing? Are you actually feeling it or having mold or just watching the RH numbers and are worried?

Is this a house with a crawl space? I've had good results with just throwing a $50 amazon DH in the crawl space and setting it to 60%. Been under there for around 3 years and the humidity in the house never gets over the upper 50% range even during the cool times of the year (so no A/C) when its raining.

Before doing that, it would creep up into the 60% range inside the house.