HVAC Pros

[Stanley]

I got estimates for a couple of options on a replacement ac system for the downstairs in my house. One is a two stage system with a zone system and one is a variable speed system. The two stage is a Lennox XC16 and the variable system is the Lennox XC20. While I feel like the variable system would be a more efficient option, I'm not sure it would justify the extra cost.

Is it worth the extra $3k for the variable speed system compared to the two stage system?

From the AC guy.
"Option B is a 5 ton two stage system with a variable speed furnace which we could put a zone system into and be able to control the common area separately from the master. The only catch with this option is that we would have to put a few registers from the common area on the master zone because there is too much airflow on a 5 ton system even in first stage for you master bedroom and bathroom space."

"Option C is a 5 ton XC20 variable speed complete system which would allow us to more precisely adjust airflow in your bedroom area."

 

[CV355]

Deja-vu, I had the same conversation when we had our HVAC system replaced in February. You're at the mercy of your existing vents/ductwork, unless you add more to have better control over flow. At the end of the day, it's dollars for comfort levels.

Personally, I didn't feel like springing the extra money for crazy levels of control.

The owner of the company said (paraphrasing) "Most modern 14/16 SEER systems are going to get you a little better efficiency than what you had when it was operating normally. Beyond that, you can pay out like crazy for higher levels of efficiency, but the return just isn't there. Where the money goes is towards comfort. I can sell you a system that keeps your house comfortable for $5500. Or I can sell you a system that controls each room individually within 2 degrees for $15k. It's up to you."

Your Option B is already a step above what I had my entire system replaced with. It comes down to your personal preference, if you need that level of control. Just remember, more control = more hardware = more potential failure modes. A faulty zone control system cost me a LOT of money in 2014, so I said screw it and went as simple as possible.

Was the option B to C cost delta of $3k including the cost of the added registers for the flow concerns?

I find that our EcoBee with a single sensor helps regulate the temperature just fine by circulating air on regular intervals until the average of the two temp sensors (one in the t-stat, one remote sensor) hits the set point. Never really have a problem.

 

[Stanley]

Was the option B to C cost delta of $3k including the cost of the added registers for the flow concerns?

Yes, total cost. I'm not sure if they were going to add new registers or just tie a couple of existing registers to that zone. So it would be our bedroom plus the dinning room being run by the thermostat in our bedroom.

 

[ford fanatic]

How old is your existing system? My guess is you are already stepping up significantly in SEER rating with a new unit, no need for fancy variable speed system.

 

[CV355]

Yes, total cost. I'm not sure if they were going to add new registers or just tie a couple of existing registers to that zone. So it would be our bedroom plus the dinning room being run by the thermostat in our bedroom.

$3k extra is a lot for the extra levels of control, but it also comes down to your current situation. Are you finding that airflow to certain rooms is terrible, more than 5 degree difference? If the current layout isn't that great, then it would be worthwhile to consider the extra control- that's how it was in my first house. Bedroom was 10 degrees warmer than the office during the winter, and 15 degrees warmer than the 1st floor. $3k would be worth it there. In my current house, the max difference is like 5 degrees. $3k for 5 degrees doesn't seem worth it.

 

[wellby]

Keep in mind that you will save money with the higher seer units but when it comes time to make repairs the cost of repairs skyrocket when a control finally fails. I would go with the first option unless you were building from scratch , the ductwotk has to be perfect for the higher end 20+ seer units to perform like they are designed to. I have 25 years in the design and service of residential HVAC and a Lennox dealer. Keep it simple is almost always the best route when upgrading a existing system.

 

[Stanley]

How old is your existing system? My guess is you are already stepping up significantly in SEER rating with a new unit, no need for fancy variable speed system.

The existing system is 19 years old I think. Original to the house. The current unit is a single stage system. The 3k saved could go toward replacing the windows on the sun side of the house which might make up the difference.

Keep in mind that you will save money with the higher seer units but when it comes time to make repairs the cost of repairs skyrocket when a control finally fails. I would go with the first option unless you were building from scratch , the ductwotk has to be perfect for the higher end 20+ seer units to perform like they are designed to. I have 25 years in the design and service of residential HVAC and a Lennox dealer. Keep it simple is almost always the best route when upgrading a existing system.

Good point. I doubt my 19yo setup is optimal from a design perspective.

 

[03cobra#694]

No advise, but I'll need to have the duct work redone when we replace ours that's like 17 years old. Knocks on wood.

 

[08mojo]

No advise, but I'll need to have the duct work redone when we replace ours that's like 17 years old. Knocks on wood.

Out of curiosity, why do you say you'll need to have duct work redone? We replaced our 25+ year old system and duct work was never mentioned--wondering if it should have been mentioned.

 

[Stanley]

Out of curiosity, why do you say you'll need to have duct work redone? We replaced our 25+ year old system and duct work was never mentioned--wondering if it should have been mentioned.

In my old house we were going to have to replace the ductwork because we still had the old metal non flex ducts that had to be insulated. The new flex ductwork is insulated. It probably flows better as well.

 

[08mojo]

In my old house we were going to have to replace the ductwork because we still had the old metal non flex ducts that had to be insulated. The new flex ductwork is insulated. It probably flows better as well.

Makes sense.

 

[03cobra#694]

Out of curiosity, why do you say you'll need to have duct work redone? We replaced our 25+ year old system and duct work was never mentioned--wondering if it should have been mentioned.

My friend, who owns the HVAC place that does my stuff and my work were talking when he was replacing the system in the office. I asked about our home system that the put in years ago, and he said "you have gray ducts IIRC", yeah we do. He said those will need to be replaced and we need more returns. I understand the returns, but I never asked why the gray flex stuff is bad.