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Need Help With HVAC Decision

Posted by slavetograss (My Page) on
Thu, May 10, 12 at 10:06

Kindly share your expertise and knowledge regarding the following:

Home:
3400 sq. ft., full sun exposure, facing West, gas-hot air heat, existing system is 19 yrs. old, R-50 insulation in 2/3 of attic, R-19 in remaining 1/3, house located in Phila., PA area. Existing system is Bryant 90+ AFUE, 132,000 BTU Furnace and 4 ton condenser and coil. The a/c struggles to cool the house on the hottest summer days and I have always wondered if a/c was undersized by the buider.

System Choices:
1. Rheem RGRM-10EZAJS, 105,000 BTU, 95% AFUE two stage, variable speed, furnace, Rheem 14AJM56 14.5 SEER, 54,000 BTU Condenser, and RCFLHM60 5 ton Coil. Price - $6100.

2. Lennox EL296UH110XV60C, 110,000 BTU, two stage, Variable Speed, 96% AFUE, furnace, Lennox XC17-060, 15 SEER, 5 ton a/c condenser unit, and Lennox CX34-62D-6F Coil. Price - $6100.

Your advise/input is most appreciated. I think I have two pretty good choices, but need your help in making final decision. The prices are the same due to price matching. Any other suggestions/input?

Many thanks,
Tom


Follow-Up Postings:

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RE: Need Help With HVAC Decision

Is house 2 story? 1700 ft each level?


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RE: Need Help With HVAC Decision

Both are nice systems. I just like Rheem better than Lennox. Any warranty difference?

Quote includes new lineset?

I would upgrade to a better Rheem AC condenser than the mdl quoted. You want to mke certain you get a true two stg thermostat, thermostat to control the staging not the timer from the furnace control board. This holds true for both Rheem and Lennox furnace. If you don't do this, you will be running off high stage when you don't need it.

If you have any hot/cold spots in your home, those need to be investigated for reason and improvements suggested. I would complete the attic insulation upgrade. Insulation is cheap and there is a payback.

I would want a filter cabinet as well.

IMO


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RE: Need Help With HVAC Decision

House is a 2 story and pretty much a split of the total sq. footage.

Warranties are pretty much equal.

New lineset is included.

Thanks for the tip on the thermostat. I agree on the insulation comment, but the remainder of the house is inaccessible to add insulation.

I will ensure that I add a filter cabinet as suggested.

So, one Rheem over Lennox vote.

Many thanks,


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RE: Need Help With HVAC Decision

Did the contractors perform load calculations? Don't assume 4 tons is not enough. If you do move to 5 tons, then you need to verify your duct work can handle the extra air flow. Most houses don't have duct work large enough to handle 2000 CFM of air.

What temperature do you usually set your thermostat? Can you be more specific when you say the AC struggles on the hottest days?


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RE: Need Help With HVAC Decision

Only some of the contractors performed heat load calcs., those that did feel that my system is undersized at 4 tons. They all measured my duct work however, and have determined that my system can support 5 tons.

Normally I set my thermostat at 80 dF during the day in summer. In mid-summer, mid-day, my unit does not cycle on/off; runs constantly, especially if some extra people are in the house w/ their added heat load. At night, I set my thermostat down to 74 dF so that the upstairs cools enough to be comfortable. The system will cool to 73/74 dF w/out the sun load at night.

Thanks again for your assistance,


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re: need help with hvac decision / imo

IMO / Tigerdunes,

Which 'better Rheem AC condenser' would you suggest?

Thanks,


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RE: Need Help With HVAC Decision

Mdl RAPM-JEZ


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RE: Need Help With HVAC Decision

fyi, and other tell me I'm wrong, but the furnaces quoted have less heat output that the one you're replacing. If that's ok, then continue.


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RE: Need Help With HVAC Decision

foe the previous poster

Quite typical for dealers then and now to oversize.

Unless there are special circumstances that ave not been mentioned, I feel very comfortable in his sizing.

In fact, I bet homeowner could even go down to 80k model if he had a professionally performed load calc. However, owner needs to keep in mind that he must have a 5 ton rated blower since he is going up in size. I hope dealer though has made a thorough ductwork system evaluation since he is going up in AC size from a 4 ton to a 5 ton. Very important. If owner has any hot/cold spots in his home, this needs investigation by dealer to properly address and make recommendations for improvement.

IMO


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RE: Need Help With HVAC Decision

Thanks to everyone who has posted on this thread. Your input has been most helpful!
Good day,


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RE: Need Help With HVAC Decision

Many cities require 2 systems. Upper/lower areas. If ur current system heats ok but struggles with cooling upstairs, why not add a mini split for warm bedrooms? Is the homeowner in 1 bedroom? Or are kids in additional rooms and have complaints of cooling? Why cool 3-4 bedrooms when only 1 bedroom might be used?


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RE: Need Help With HVAC Decision

Why not get damper controls on supply trunk lines to control airflow to each floor?

If ductwork is accessible, a much better and less expensive alternative than a mini split. And there are always zoning controls.

IMO


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RE: Need Help With HVAC Decision

I'd have a Home Energy Efficiency Audit performed & do whatever is cost effective to bring the heat-loss/heat-gain down so 4-Ton or say 46,000-Btuh will handle the heatload with ease. That is one size down to a 14AJM49 with a RHKL-HM4821 air handler with a ECM motor, it gets 16-SEER.

It is nearly always very difficult to achieve enough air flow for 5-ton of cooling. However, that Rheem 14AJM56 is actually 4.5-Ton @ 54,000-Btuh & 1600 to 1700-CFM would work okay if you match it with the RHKL-HM6024 air handler with the ECM motor, it gets 16-SEER. ARI#3799470

For 2-story home you probably should have a zoned system.

Phil, PA 2.5% summer design is 90-F dry bulb & 74-F wet bulb around 47.7% relative humidity.

That is 103 gr moisture per lb dry air; while indoors at 75-db & 62.5-wb is only 66 gr moisture per lb air. Infiltration would add considerable latent load; therefore you need long runtimes to keep humidity near 50%.

Here is a link that might be useful: Sizing Air Conditioning Systems & Ductwork Airflow


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RE: Need Help With HVAC Decision

Thanks much udarrell... you seem to really know your stuff; brings me back to my ME studies many yrs ago. At tigerdunes' suggestion, I've upgraded the quoted condenser. My quoted system now stands as:
RARL-JEC, 5 ton/56,000 BTU, Condenser,
RCQD 5 ton coil,and,
I'm trying decide btwn: RGRM-10ZAJ 2-Stage, or RGFG-10ZCM Modulating Furnace (I also have the option to take a left-over RFGE-12RCM furnace and save about $1K over this year's RGFG model; but it may be oversized at 120,000 BTUs?).
How do you feel about 2-Stage vs. Modulating Furnace, and the RGFG v. RGFE Furnace?
The Modulating Furnace is about $1200 more than the 2-Stage if I compare this year's model of each. I'm not sure the Modulating furnace is worth the extra $?

What do you think?

Thank you,


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RE: Need Help With HVAC Decision

I haven't seen any info on this thread as to where the ductwork is located. Is any of it in the attic? If so, they need to be very tightly sealed and insulated. A huge fraction of capacity can be lost through leakage and insufficient insulation when ducts are outside of conditioned space.

As others have suggested, you really need to have the shell of the house evaluated. There may be some fairly easy and inexpensive things that can be done to improve the shell, make it more comfortable year round, and reduce the heating/cooling needs.


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RE: Need Help With HVAC Decision

I got some prices for Carrier equip and they are way more than the 6100 you are quoting. Is that after any rebates and does it include install? I am in Camden County, NJ and my quote is 9821 after a 900 rebate and including a 10 year part/labor warranty.

It is Carrier 24ABC648 1-stage, 4 ton
Carrier 59TP5a100E21**20, 100,000 btu, 2-stage. (natural gas)

Can you tell me who you used and do you think they would come to South Jersey?

I am getting other quotes. This is from the company that came out to do my energy audit for njcleanenergy.com, which is a great program with huge rebates, but I think the companies mark it up to mark it down. This price was given when I asked for a price if I DON'T do the cleanenergy program. It's the same price as in the program, so I think I could get it down.

I am not too concerned with brand. I do have a company coming out next week that may try to sell me Amana, so I have to think about that.


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RE: Need Help With HVAC Decision

Cindy, - Call AAA Brothers (NE Philly/Huntingdon Valley, PA), they are a Lennox Dealer and seem to have the best pricing around. Not sure if they will come to S. Jersey, but call and ask. Their price for a comparable Lennox system should be under $6K for what you need (after rebates, includes install.). Some other HVAC contractors will price match once you have an offer in hand. I had quotes from $6,000 to $15,000 so there are many companies out there really trying to take advantage of the uninformed consumer. Best of luck,


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