Quick expert HVAC system help?

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Quick expert HVAC system help?

Postby Tomas on Wed Jan 15, 2014 4:30 pm

My heating completely blew up, and so rather than paying $4k+ for all repairs, I decided to completely replace the whole system. Now, I know next to nothing about HVAC, so I need some advice:

My old (2003) system was 4 Ton 10 SEER (Ruud) + heat pump. It worked reasonably OK, though in the warmest months (NW Arkansas - where I live - probably goes to mid-to-high 90s in July + August) it had slight problems to keep the temperature down (say, if I put the termostat at 78, it would probably end up going to 80, until the the temperatures went down in the evening).

Today, the salesman did some calculations, and he came up with the following:
Besed on my square footage for heated areas (~2200 or 2300?) I am the candidate for 4 Ton, though once he factored in that most of my windows are east-west, the software spit out 4.9 Ton recommendation.

The salesman recommended going with 14 SEER (I would be getting Amana brand with the heat pump), even though they still sell 13 SEER, because - he said - 13 SEER will be disallowed after 2014.

So, my dilemma is to choose between 4T and 5T system (the difference in price is roughly $1,000). Any advice that could point me in the right direction?

Thanks!!
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Re: Quick expert HVAC system help?

Postby meow on Wed Jan 15, 2014 4:48 pm

Bigger is better. Go big or go home.
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Re: Quick expert HVAC system help?

Postby mac5155 on Wed Jan 15, 2014 4:58 pm

Tomas is the seer. way to go. we outed the seer.

lynch meow
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Re: Quick expert HVAC system help?

Postby ffemtreed on Thu Jan 16, 2014 9:03 am

meow wrote:Bigger is better. Go big or go home.



Not with an AC unit. Oversized can be a big problem!

The first question I would find out is why your old 4 ton unit couldn't keep up, was it a ducting problem (under sized? no returns?) or a size (tonage) problem. Whoever is going to install this unit should do a through inspection on your duct system.

The seer rating really isn't that important, all it is, is the energy efficiency of the unit. You need to figure out how much energy you would save with a 14 seer over a 13 seer per year and figure out how long it will take to pay back that extra $1000 (ROI). If you can afford the 1000 up front and plan on staying in the house longer than the ROI then go for it.


The only other advice i can give you is get multiple quotes and check out different brands and compare the warrenty's
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Re: Quick expert HVAC system help?

Postby mac5155 on Thu Jan 16, 2014 10:06 am

CERV96 is the resident HVAC dude iirc.
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Re: Quick expert HVAC system help?

Postby eddysnake on Thu Jan 16, 2014 11:44 am

Ours died recently as well. Just had a Trane XV95 2 stage variable blower gas furnace put in last week. This replaced an old Lennox Pulse furnace. I'm amazed at how small and quiet these things have become, it has made an incredible difference in our house. Also put in an AC unit, which should be a welcomed addition. The only thing I really know about it is that they are f'n expensive and couldn't have come at a worse time.
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Re: Quick expert HVAC system help?

Postby CERV96 on Thu Jan 16, 2014 10:59 pm

ffemtreed wrote:
meow wrote:Bigger is better. Go big or go home.



Not with an AC unit. Oversized can be a big problem!

The first question I would find out is why your old 4 ton unit couldn't keep up, was it a ducting problem (under sized? no returns?) or a size (tonage) problem. Whoever is going to install this unit should do a through inspection on your duct system.

The seer rating really isn't that important, all it is, is the energy efficiency of the unit. You need to figure out how much energy you would save with a 14 seer over a 13 seer per year and figure out how long it will take to pay back that extra $1000 (ROI). If you can afford the 1000 up front and plan on staying in the house longer than the ROI then go for it.


The only other advice i can give you is get multiple quotes and check out different brands and compare the warrenty's


This x10000

You do not want an oversized system. Be very careful with this. An oversized system can run your electrical bill through the roof. Your system is actually better off running all day on a 90 degree day(varies in different locations, humidity, and altitudes) then going on and off 8-10 times during every hour. Think about this. If it is going on and off 8-10 times on a 90 degree day imagine how many times it will go off and on a normal 80 degree day.

When I worked in the field we used to get calls every year when it was 90 degrees plus with high humidity. Most all of the systems are not designed to run and keep your house completely cool(1-2 degrees constantly off) on those days cause they just happen so rare. I am 100% with what the above poster has said. Also don't be afraid to ask around and look for the guys who do this stuff on the side for extra cash. They will be much cheaper in cost and are 100% more careful when they do their own work as opposed to what they are doing for the company they work for.
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Re: Quick expert HVAC system help?

Postby CERV96 on Thu Jan 16, 2014 11:02 pm

eddysnake wrote:Ours died recently as well. Just had a Trane XV95 2 stage variable blower gas furnace put in last week. This replaced an old Lennox Pulse furnace. I'm amazed at how small and quiet these things have become, it has made an incredible difference in our house. Also put in an AC unit, which should be a welcomed addition. The only thing I really know about it is that they are f'n expensive and couldn't have come at a worse time.


YES! Die Lennox pulse! Die!!!!!!!!!!!

Trane is even more expensive than Lennox. Great units but the Cadillac of A/C and furnace units.
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Re: Quick expert HVAC system help?

Postby Tomas on Fri Jan 17, 2014 12:39 am

CERV96 (and others) - this is really helpful!

What makes me a little concerned is that the original house owner put in 4T system (in 2003) - I would expect that somebody must have done a load calculation for him then, and 4T was the result.

Now, I do know that my system has been typically going the whole day (until, say, 9PM) during the typical summer months. And, based on the HVAC guy and some of my friends, this should not be typical, and might have contributed to the system's epic collapse after 11 years(?)

I have 2 quick questions:

1) how reliable are the programs computing loads? That is, if they say 4.9 T, can I indeed safely assume that 5 Ton is the ideal size?
2) Forget the software, just going by the "expert feel". Say, I have 2,700 sq feet single story house, with cathedral ceiling in the living room that has oversized living room windows (think floor-to-ceiling) facing west.
I live in the place that has the following average summer temperatures:
May: 75.5F
June: 83.5F
July: 88.7F
August: 89.4F
September: 80.8F
(all according to: http://en.wikipedia.org/wiki/Fayettevil ... as#Climate )
Just based on this - does it seem more like 4T or 5T system?

Thanks!!
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Re: Quick expert HVAC system help?

Postby CERV96 on Fri Jan 17, 2014 8:45 am

If your system is running non stop on typical days it is quite possible that it can be under sized(currently, but not at the time of the last installation). Things can change over times when the last load calculation could have been done. Insulation getting poorer, windows getting older, etc.

1) Most companies have their own type of load calculating programs. There is no real pattent on it so they all can vari pending on what the company wants you to do. Do not be afraid to ask him or the salesman to see it. Ask him whatever questions you want.

2) Wow! Thats a lot of open space you have. With that space, those types of average temperatures, what information you have given me, and just shooting from the hip sitting right here at my computer I would say a 5 ton is more than likely what you need instead of a 4 ton unit. Remember this is all just from what information you have given me without seeing any duct work, insulation, and all other things that can go in to play.
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Re: Quick expert HVAC system help?

Postby eddysnake on Fri Jan 17, 2014 9:35 am

CERV96 wrote:If your system is running non stop on typical days it is quite possible that it can be under sized(currently, but not at the time of the last installation). Things can change over times when the last load calculation could have been done. Insulation getting poorer, windows getting older, etc.


We went with a 2 stage (40,000-70,000) with a variable blower. In a week, it's never kicked to the 2nd stage. The HVAC guy said that's pretty typical. From my understanding, with the 2 stage it will run almost constantly, but it's running at 60% lower btu's than a 1 stage (my old Lennox Pulse) and that creates a more even and constant temperature in the house rather than the 1 stage blasting on full power, then shutting down, then blasting on, etc... It was more money, but so far I have to say it's made an incredible amount of difference
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Re: Quick expert HVAC system help?

Postby CERV96 on Fri Jan 17, 2014 9:53 am

It will also save you money on your gas bill as well 1st stage uses less gas than second as well. From what information the OP has told me it is possible it can be undersized. If a typical day in his area in the summer is 92 degrees and the system is not satisfying till 9-10 every night it can/could be a problem. A typical day for us(Pittsburgh) in the summer is based around 86 degrees. The system at this temperature will run and satisfy at least a couple long cycles a day. Any temperature above that it will cycle less and less and run all day in to the night (which is normal because you don't want to oversize) and really how many days in a year do we have where the temperature is above that? Not many. Also you are compairing heating to cooling and to boot a heat pump to a furnace(different applications). I also hate heat pumps but they a very common in his area.
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Re: Quick expert HVAC system help?

Postby Idoit40fans on Fri Jan 17, 2014 9:55 am

No pleasure, no rapture, no exquisite sin greater...than central air.
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Re: Quick expert HVAC system help?

Postby Digitalgypsy66 on Fri Jan 17, 2014 11:18 am

When my Goodman 2 ton system goes (installed in 2007), I'm going to have an Office Space style bat party for it. I may even have some gun enthusiast friends use it for target practice. For a brand new house, we've had nothing but troubles with HVAC.

I've documented it all here before...but we bought a spec house where the builder took the bid of the HVAC contractor that was $2K lower than the other contractors. The HVAC contractor used flex duct work throughout the house, even the main trunk line. The ridges in the ducts slow airflow down. He then strapped the ducts to crossbeams in the attic crawlspace...so the duct would leave the main trunkline and go up 3-4 feet over a crossbeam, and then back down to the vent in the ceiling. Air can't travel in two directions. We had next to no airflow, and that first summer in the house was miserable. We'd set the thermostat at 77 and it would usually read 83-84 in the late afternoon. Misery. The original HVAC contractor laughed at us, and the builder didn't really do anything until we threatened to have his license pulled. He finally had a second contractor come in and replace the duct work and add a second unit to our room over the garage (which should've been done in the first place).

Keep in mind I live in rural South Carolina, the Bible belt. The second contractor - who was friends with the builder - went up to our attic and saw the rat's nest of ductwork up there and blasphemed, and then dropped an f-bomb (JFC). That's the only time in my 23 years in the South that I've heard someone take the Lord's name in vain (other than it coming from own mouth). :lol:

CERV, what's the deal with geothermal heat pumps? Very expensive? I'll be looking to replace this system in a few years and I'd like something that works and is efficient. Basically, our current HVAC struggles below 35F and above 90F. Although it cools much better than it heats.
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Re: Quick expert HVAC system help?

Postby CERV96 on Fri Jan 17, 2014 2:49 pm

It uses the earth as a heat source (in the winter) or a heat sink (in the summer). They are pretty efficient and comon where you live. To be honest I have never worked on one around here. If there are any around here it is rare so I couldn't really be able to give you any type of ball park figure.

Heat pumps are not used in many houses around this area. Now I have seen a few of the richer people around here with a heat pump and a gas furnace. They use an outdoor air sensor and set their system to a certain temperature. The heat pump will remain in use until the outside air drops below a designed temperature. Once that happens the system then uses the forced air gas furnace.
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Re: Quick expert HVAC system help?

Postby Digitalgypsy66 on Fri Jan 17, 2014 4:56 pm

Yeah, that would work. I've heard some about gas assisted heat pumps, and all in one unit that does what you are talking about.
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