Will a new heat pump really make my house warmer?

pinstripeAugust 24, 2011

Hi there, hope you can help me. I live in Virginia, which gets hot humid summers and a bit of snow in the winter, and my house is all-electric. My 2.5 ton Carrier heat pump is 15 years old but still running; I'm told [by the HVAC sales guy] that it's about 8 SEER and 800 CFM. It delivers great service (heating and cooling) to the first and second floors of my 3-level 2300 sq ft townhouse when the damper is closed. My finished walkout basement is still comfortable in the summer with this arrangement, but gets really cold in the winter; when the damper is open, however, the second floor can get uncomfortable (both summer and winter). Given the system's age, I'm looking for a replacement that will heat the basement better.

HVAC Salesguy says that a new 2.5 ton, 15 SEER variable speed heat pump will heat my whole house (including basement) with the damper open, because it is 1400 CFM -- i.e., moving more air more constantly. Does this sound right? Can I expect to see significantly better performance (relative to my existing system) simply by improving the CFM?

Many thanks!

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ryanhughes

2.5 ton heat pump shouldn't be set up for 1400 cfm (3.5 ton). Nominally, a 2.5 ton heat pump would provide 1000 cfm at 400 cfm/ton. Increasing equipment size (even if 2.5 tons is what the home needs, which wouldn't surprise me for a 2300 sqft 3-story town home) is not a good way to make up for duct deficiencies or balancing issues. I would get a second opinion. Try to find a contractor willing to perform a load calculation and give a thorough overlook of your duct system and what improvements need to be made. The variable speed motor can help to an extent. An experienced pro needs to see what your duct system is capable of moving and what your home needs.

    Bookmark   August 24, 2011 at 11:59PM
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Jack_Mason

There are a couple of things going on here. First, is the performance of your old unit. It is definitely outdated, inefficient, and low power compared to the standard units on the market today. There is no question that moving from 8 SEER to 15 SEER is going to make a major difference in the system's heating and cooling capacity. It will definitely make your home feel significantly more comfortable during both summer and winter. Second, however, is your ducting system. A lot of systems lose as much as 30% to 50% of their energy and, by extension, cooling/heating capacity to leaks in the ducting. If you are going to upgrade the central unit, you should definitely spend a bit more to also upgrade your ducts. If you get it as a packaged deal from a local contractor, you should be able to get a competitive price, especially in this economy. Try Service Magic or Quality Smith - they are free services that get you estimates from pre-qualified local contractors. It's not just about getting a second or third opinion, but also about finding the best possible value for your money. In addition, you can learn a lot more about SEER, energy efficiency, and the importance of good ducting on www.hvacandwater.com under the Home Heating section. Good luck.

Here is a link that might be useful: www.HVACandWater.com

    Bookmark   August 25, 2011 at 12:08AM
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david_cary

Jack - you have crossed the line with pushing this website that I am guessing you have an interest in.

OP - please disregard his entire post as he is confusing terms and making unreasonable estimates for duct loses.

On the other hand, I'll second everything Ryan posted.

    Bookmark   August 25, 2011 at 4:06AM
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tigerdunes

pinstripe'>Pinstripe

I also Agree with Ryan.

Your post suggests you may be undersized. You need a load calculation before making a decision.

Ductwork needs a thorough evaluation both size and design. Do you have returns on each floor.

Cooling and heating loads for basement at or partially below grade usually are small. Insulation qualities should be reviewed for possible upgrade/improvements. Is basement area receiving adequate heating BTUs to keep it comfortable?

IMO

    Bookmark   August 25, 2011 at 8:22AM
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ckr74

Changing from 8seer to 15seer won't make any difference as far as capacity. You will use less energy though. Get a load calc done so sizing is right.

    Bookmark   August 25, 2011 at 8:43AM
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ionized_gw

A new heat pump is likely to have better low temperature performance, isn't it?

Echo the call to evaluate the whole house for insulation and infiltration

    Bookmark   August 25, 2011 at 10:48AM
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mike_home

Jack,

Can explain this statement?

"There is no question that moving from 8 SEER to 15 SEER is going to make a major difference in the system's heating and cooling capacity. It will definitely make your home feel significantly more comfortable during both summer and winter."

I am curious to know how improving the efficiency of the a pump increases the capacity and comfort level.

    Bookmark   August 25, 2011 at 3:07PM
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weedmeister

Echoing the sentiment to have someone do a ManualJ and check out your duct work.

Increasing the SEER will be most felt in your wallet.

The variable speed blower will do an excellent job on humidity reduction.

Which/what damper are you referring to?

    Bookmark   August 25, 2011 at 6:56PM
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pinstripe

Thank you all for the responses. I am having a different company come do an estimate tomorrow, and I will request that they do a load calculation. Do they need any advance warning for that?

I do have a return on each floor. About half the windows are from this century (the others are circa 1980).

I had an energy audit done this past spring (largely to address the cold basement) and, based on those results, recently added blown insulation to the attic and sealed some openings in the attic and basement. The auditor did not find other major sources of heat loss. He did offer a liquid sealant that gets blown inside the ducts; I declined, because of price and because he didn't really have evidence we were leaking badly from the ducts. If I should reconsider the duct sealant I would be interested in hearing that.

Thanks again!

    Bookmark   August 25, 2011 at 7:39PM
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energy_rater_la

OP did he recommend aeroseal?
would you share the cost and approx sq ft of your home??
I'd really like to compare these prices for my own research.
Ditto Ryann and above.

best of luck.

    Bookmark   August 26, 2011 at 6:53AM
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pinstripe

RE: the spray sealant, I wouldn't say he recommended it -- just discussed it as an option to cover all bases. I don't have a quote but recall the number discussed was between $1K and $2K. After declining, an HVAC guy told me that he had [theoretical] concerns about that process damaging the compressor; don't know how accurate that is.

Following up on questions I missed the first time:

- The 2.5 ton system quoted actually is a 3 ton air handler (4TEE3F39A1) and 2.5 ton compressor (4TWX5030A1), both Trane. Quoted price was $6K with some extras thrown in, which I thought was good for this area ... assuming this fix solves my problem. If this is not going to heat the basement better, I'm willing to trust the existing Carrier system to live another year or more.

- RE damper location, we have two ducts leading from the air handler to our living spaces. There is a damper in each one, just a few feet from the air handler. On the duct leading to the second floor, the damper is always open. On the duct leading to the basement, I keep the damper closed all the time. I'm not sure which of these feeds the main level, but I think it's the latter.

    Bookmark   August 26, 2011 at 7:36AM
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pinstripe

"damaging the compressor" in my 7:36 post should have been "damaging the coil," sorry.

    Bookmark   August 26, 2011 at 7:50AM
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Jack_Mason

I meant "efficiency", not "capacity". My bad and nice catch.

    Bookmark   August 27, 2011 at 10:08AM
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greendesigns_gw

I had a girlfriend who had a 3 story town home that was always hot on the third floor and cool on the first. The biggest improvement to the situation for the least amount of money was using a portion of a closet for a duct directly from the 3rd floor to the 1st and a reversible auxiliary fan to push the hot air down in the winter and to pull the cold air up in the summer. It helped to create a more uniform temperature in the whole dwelling without replacing a thing. I think it cost around $100 in materials for her to do.

    Bookmark   August 27, 2011 at 9:30PM
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pinstripe

Following up on the load calc advice -- the most recent estimator said I did not need a load calc because the tonnage of my existing heat pump was approved by the county when the house was built, and therefore is correct. Is this legit? This is not my preferred company (because of price) but they have a very good reputation and the rep was otherwise straight with me, e.g., very up front about no amount of new equipment making up for poor ducting design.

From looking at the county website, it appears a first-time HVAC install requires a permit and inspection, but replacements do not. My current unit is about 15 years newer than the house.

    Bookmark   August 29, 2011 at 8:36AM
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tigerdunes

Nonsense.

You do need one.

Dealers who refuse to perform a load calc don't deserve your business.

They usually fall into one of three categories.
1. They don't know how,ie they are ignorant
2. Too damn lazy
3. Don't give a damn about the customer.

IMO

    Bookmark   August 29, 2011 at 10:03AM
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