Confusing Bids on HVAC replacement

[txgolfer45]

I live in the Dallas area of Texas. We did an addition about 12 yrs ago that increased our sq ft from 2100 to around 2700 (all one story). We have a 5 ton HVAC that covered the original sq ft and then added a 2 ton hvac to handle the addition.

I'm looking to replace the original 5 ton unit as the furnace is 22 yrs old and the AC is probably around 15 yrs old and is not keeping up with the cooling and has several repairs to it.

I originally thought of replacing both units. But, one contractor suggested keeping the small unit as I haven't had any problems with it to date. He suggested putting in an R16 SEER American Standard 2 stage/2 speed system using the new coolant R410A? with an 80% eff furnace. He also suggested keeping the original solid metal duct work and only replacing the flexible tube duct work. He also suggested an air filtration system.

Another contractor suggested changing out all the duct work and putting in a 5 ton R16 SEER Heil system with zones and eliminating both separate systems.

I'm concerned the one system will not get the job done and it is a single point of failure. It goes out and no AC!

I have two more bids coming tomorrow that hopefully will help clarify the solution.

Thoughts?

Thanks,
Scott

[jvillehvac]

i would stick with 2 systems, as you have said, one breaks, you have a place to retreat to. Also with a zone system, if only the smaller zone were calling, the rest of that air has to be bypassed or put into a dump zone where that area will be pretty cool.

[dash]

If tons with zoning will do it,as proved by a load calc., that would be sweet.But someone suggesting it without a load calc.,No Way.


If 5 tons did the original home,then adding an addition surely changed some outside windows and walls to interior ,so less A/C is needed for the original home,another reason for a load calc.!!!



Putting in another 5 ton and adding Better filtration,without testing the static(resistance to air flow) of the original duct system,to see if it can work with the additional static of the better filter ,is a mistake!!

[txgolfer45]

Dash,

We converted a garage and added a garage to the back of the original garage area. So, the changes to the original house were very minimal. We added a pocket door to close off the new area as needed. So, the 5 ton unit will still AC and heat the same area as the original house.

Your point about the duct work with air filtration is something I will follow up with the contractor. thanks!

I've already dropped the contractor suggesting one system to replace two existing systems due to bad references.

[dash]

Before you cooled the old garage ,that wall(s) was exposed to the heat in the garage,so the original load of the home has been reduced,maybe not enough to matter.

However coupled with the fact that the majority of homes were oversized when built,a load calc. is still a good idea.If you only need a 4 ton ,then the current duct system may be able to handle the better filtration.

You need ,like all homeowners a real Pro,few and far between.Likely one form your area on this board,might try a post looking for one.keep the conversation on the board,many here will help you out.