16SEER, 18SEER, Variable speed, oy...

[joseywales]

So I'm curious. I have a gas, forced air HVAC unit. 4 ton unit I believe. Let's forget about any ROI with the better SEER, etc. If I get the 18SEER, it comes with a variable speed motor, but some pros believe those motors are more prone to issues, costly to repair, etc. They say best to stick with a 16SEER.

My unit is 25 years old. It's not broken, but i rarely get good air flow to the far bedrooms, etc. I'm not saying i want a new unit to solve that issue. That issue could be due to the labyrinth of duct work. My one question would be, will the variable speed make that better or worse?

Any thoughts?

 

[kwschumm]

Forget SEER, you have an air balance, duct design, restriction, or leakage, or an undersized air handler problem. If some rooms are starved for air it has nothing to do with the energy efficiency of the unit.

 

[mrpizza]

The duct system is the most important thing of all. Get a manual J and a manual D done to verify sizing of equipment and the ductwork. Anything less will leave you with heartache.

 

[Trey T]

18SEER is still conventional stuff w/ multiple stage pumping. 20seer+ is in the realm of inverter technology which is the same stuff as mini-split units and it's reliable. If money is no object, then get the highest efficiency units. Down here in Houston anything 16SEER+ unit doesn't make a sound investment for everyone because electricity here is so damn cheap, almost as cheap as NG.

A 4ton (straight cool) 14SEER is about $2500 wholesale and a 4ton (straight cool) 20SEER is about $4500 wholesale. It would takes 10-15yrs to recover the initial cost.

 

[Trey T]

The duct work has no replacement for any types of unit, it's a separate issue.

 

[theoldwizard1]

My one question would be, will the variable speed make that better or worse ?

Variable speed fan will not solve your problem.

 

[joseywales]

I realize the ducts are a separate issue. I just don’t want a variable speed to make it worse.

 

[Showkey]

Likely worse because those distance outlets will deliver even less air than they do now when the system is in low fan mode.

My current HVAC is only variable fan in heat mode and the burner is variable heat output, when in AC the blower is always on high speed. It my first variable heat system and I would do the variable heat mode again. Even heat distribution and quiet operation, low cost of operation.

 

[yeldogt]

Typically -- systems have restrictive ductwork. why -- it cheaper to install smaller ducts and often the use of flex. The next problem is .. bigger is always better ... often the units is oversized. Big unit pushing through small duct work. Most systems are a guess.

With the old system the fan just ran -- todays systems try and power through and burn up the newer designed fan motors.

All that said .. the new systems properly set up are a dream. Actually, zoning is often the answer when small ductwork is encountered. Since the ductwork can't be switched out of walls easily .. zoning allows the unit to provide the proper air to far flung rooms. If you just add a VS system to some houses the far away rooms will not get enough air when the system is running on low.


I did a three zone 2 stage AC carrier system about 12 years ago in a typical colonial 4 square with a back great room ..... solved all the problems. need a good installer and a room by room assessment of heat/cool and CFM

 

[Jackfre]

I agree that you have a duct issue first and that should be analyzed first, prior to making any decisions on equipment. Duct repair can be costly and in many cases you are putting lipstick on a pig. When we bought our current home I ended up pulling all the ducting out and making a dump run with it. Went mini-splits and happy to have done so. Point is, now that you are looking at the system, look at every option before moving forward with anything.

 

[kwschumm]

I've seen systems where everything is properly sized except the filter housing. If that is too small it will restrict airflow to the entire house.

 

[Mikeske]

I would be looking at mini-splits for the far flung rooms

 

[bonneyman]

I would be looking at mini-splits for the far flung rooms

I'm not a big fan of mini-splits but this is exactly the job they were originally designed to do.

 

[joseywales]

Ugh. It’s never a simple choice is it? I’m going to hold off on the unit for now. We’re having a mini-split installed in the basement and I’m optimistic about that. I’ll see how that goes, but I can’t imagine putting one in the bedrooms and there’s really no central area on the second floor it would work either.

If this guy isn’t up for it, I’ll have someone test the airflow.

I forgot about this, but last year, Oliver company was here to give me an estimate on an HVAC. Turns out, the salesman was part of the crew that installed the ductwork 25 years ago! He said the ductwork was a labyrinth of metal and not ideal. They just did what they were told to do.

I also know that the house plans changed midstream, when Zoning complained about the grade of the driveway. That forced them to dig down and the house ended up with a 7.5 foot ceiling in the garage and a 400sqf room above it, which now of course needed ductwork. That was originally just an insulated loft.

The laundry ended up on the first floor, with no vent. All kinds of fun stuff went on.

We had installed ceiling fans in the bedrooms and each has electric blankets.

 

[peter2772000]

Likely worse because those distance outlets will deliver even less air than they do now when the system is in low fan mode.

Exactly! I'm an HVAC contractor here in Mtl. Thankfully, we only service residences of our commercial clients (can't very well tell them we won't). It's mind-boggling how badly the ductwork is designed in many homes, especially older ones. We get complaints all the time about insufficient air to the rooms farthest away from the blower.

We've used in-line booster fans in a few extreme cases. It helps, but may cause problems elsewhere. I've also seen a powered nifty air-register for sale at Home Depot. Might help...

 

[yeldogt]

If you can get to and isolate the plenums .. zoning is the ticket with the newest systems. My carrier 3 zone 5 speed unit ramps up and down depending on what is required -- it will partially close off zones to push the air to far flung rooms.

When the unit is put into service it actually tests the various zones and temp changes -- slick set up. With zoning you don't want large ducts ... about 125% of the lower CFMs of the unit

 

[peter2772000]

That reminds me; There's a product out there (+/- $150/each) which consists of a motorized floor register controlled wirelessly by a controller. It has a built-in temp sensor and can be programmed to close air off to areas that don't need cooling/heating in order to pump more air into areas that need it.

Come out pretty pricey if you have 10 registers like myself. I recently added an extension to the kitchen (south-facing so it gets warm in summer) and the main supply duct is impossible to get to (finished basement). I was seriously considering the above for awhile, but drawing the blinds is so much easier LOL

 

[joseywales]

That reminds me; There's a product out there (+/- $150/each) which consists of a motorized floor register controlled wirelessly by a controller. It has a built-in temp sensor and can be programmed to close air off to areas that don't need cooling/heating in order to pump more air into areas that need it.

Come out pretty pricey if you have 10 registers like myself. I recently added an extension to the kitchen (south-facing so it gets warm in summer) and the main supply duct is impossible to get to (finished basement). I was seriously considering the above for awhile, but drawing the blinds is so much easier LOL

I had the poor man's version of that when my daughter was using the middle bedroom. I'll look into this version as well.

Bottom line, though, I'm thinking I won't see any benefit from a variable speed, unless I'm missing something here. That Carrier 3 zone, 5 speed unit sounds great, but it sounds like a lot things can go wrong with it. Again, maybe I'm wrong about that. I hated getting rid of my standard water heater, because the tankless units create more maintenance, etc. But I trade that for the extra space we gained, which ended up being an entire wall that can now have 12 foot shuffleboard table, if I chose to. It was literally in the middle of the wall!

 

[peter2772000]

Correction: $60/ea for the motorized registers. This is the product.

http://www.theactivent.com/index.php


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