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HVAC options - two installers, different approaches

Posted by mattshwink (My Page) on
Mon, Apr 30, 12 at 21:40

We are looking at getting a new HVAC system. We currently have a 10 SEER Carrier system that is roughly 10 years old. Ever since we have lived in the house (6 years) we have lived with a problem of air flow on the third floor (three story townhouse). When it gets warm in the summer (90+ degrees) we can't get the third floor to 77 degrees, at that point the AC runs constantly during the day. We have lived with it in the past, but now have a 7.5 year old and really want to regulate the temperature better on the third floor. Really, though, none of our vents (even the one coming right off the current air handler) would blow your hair back.

Our home is not open concept, the top and bottom floors have about 4 rooms each, and the second floor has three. By exterior dimension the home is about 2300 hundred square feet. (a little over 700 per floor).

We have talked with two different HVAC companies about the issue. The first suggested a Carrier Infinity 15 SEER system with a 3 ton variable speed air handler. He also talked about installing some directors in the vents to see if we could get some better flow on the third floor.

The second company suggested a 17 SEER Lennox system (he has some rebates right now that make it he same price as a 15 SEER, and the price is the same as the first installer) but recommended a 3.5 ton variable speed air handler to see if we could get better air flow that way. He also recommended trying (with a piece of cardboard at first) blocking the return on the first floor to see if that would help pull more air out the third floor return and better flow (if that worked he recommended partially sealing part of the 2nd floor return so that the third floor return would pull in more air). He said he recommended the 3.5 ton because of the number of registers we had (20).

So we called the first company back to ask for a quote on a 3.5 ton air handler, and he told he wouldn't do it, because it would cause back flow to the compressor that would shorten its lifetime and was a bad idea.

So the question is what should we do? I am no HVAC expert but I'm not sure who to believe here and would like some other opinions.

Thanks!
Matt


Follow-Up Postings:

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RE: HVAC options - two installers, different approaches

Matt

What is your location?

This is a HP system?

What size is existing system?

Air handler is located in attic?

Where are vents located both supply vents and return vents? You have a return vent on each floor?

Ok, here are my thoughts and you probably won't like it. It is near impossible to balance air flow for a three story townhouse that operates off one system and does not have zoning controls. Oh you can make modest improvements but comfort will still be lacking.

You need a thorough review of your ductwork system-size, insulation properties,adequate return. Does it ave damper control on the trunk lines to each floor? If not, can they be added? How are the insulation properties of the attic? Good windows on the third floor?

I personally think very little of the suggestions from both dealers. Has anyone suggested a separate small system for the third floor?

Your problem is quite typical and unfortunately can be very difficult and sometimes expensive to solve.

Post back.

IMO


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RE: HVAC options - two installers, different approaches

I would be suspect of any HVAC contractor who tries to fix an air flow problem by blocking return vents.

In your situation the SEER rating has no bearing on the problem. Don't get hung up on 15 vs 17 SEER. If you have duct work problems you will not see any gain in efficiency even compared to your old system.


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RE: HVAC options - two installers, different approaches

TD is correct. This is very typical of a townhouse.

Any chance you could put a small window unit in upstairs? Or a mini-split?


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RE: HVAC options - two installers, different approaches

I live in Alexandria, VA, just south of Washington DC.

The current system is a 10 SEER Carrier HP (3 ton) and the air handler is located in the utility room in the basement. There is a return on each floor (one in the bottom of the air handler, one in middle of the middle floor (hallway) and one at the top of the stairwell outside the master bedroom. No dampers on the lines, attic insulation is good, but probably could be improved.

No one has recommended window units.

How do I find someone who will do a ductwork review? I contacted four reputable (well reviewed companies) and none mentioned this. I did reach out to someone this morning and got a reply that they were looking at my inquiry, but nothing in 12 hours. It seems people that do duct reviews/analysis are few and far between.

If I went with a system on the 3rd floor, how would that work? I have approximately 730 sq feet of space, divided into a master on one side and two smaller bedrooms on the other (separated by a hallway with the split foyer stairwell in the middle. There is a bathroom in the master and in the hall by the other bedrooms.


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RE: HVAC options - two installers, different approaches

A good HVAC contractor will do a load calculation to size the equipment, and measure and inspect the duct work. If they are not doing that, then they are not very reputable in my opinion.

Do any of your neighbors have a similar townhouse? It would be interesting if they are facing the same issues and have tried to solve the problem.

Is there an internal chase which could be used to run a duct up to the third floor or attic? A duct could also be hidden inside a closet or you could make a chase in the corner of a room. If this is not viable, then adding a separate HVAC unit for the third floor is the only effective solution. You could install a unit in the attic with duct work to each room. I think a mini-split could work, but it may not be as effective for air flow movement throughout three rooms.


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RE: HVAC options - two installers, different approaches

Matt,

I was wondering if you ever found a solution to your HVAC problem. I also have a three story townhome in Alexandria and this past week has been brutal. My HVAC system runs non-stop throughout the day until halfway into the night. My first floor is cool, second floor mild, and third floor barely comfortable.

I have partially closed the vents on the first floor, got all new windows, and had insulation blown into the attic. My HOA will not let me put an attic fan in my unit which would probably alleviate at least some of the problem...


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