Proper sizing and model question

[Drumrol]

I have a 1100' split level house. I have had 4 differnt contractors come over. 3 out of the 4 sized it for a 2 ton unit. 1 sized it for a 11/2 ton unit. The one 11/2 unit the contractor said the coil is 2 ton or compessor is 11/2 or reversed?
Second question is how is a Heil unit (N4H3)? And do all units come with a 10 year parts , 1 year labor?

[BaldLoonie]

Some mfrs don't make a 1.5 ton coil or approve of a 2 ton coil on a 1.5 ton unit for efficiency. How are they sizing? Guessing? Measuring and calculating?

Where are you? Is 1/2 of the first floor underground?

The N4H3 is a builder model, very similar to Carrier's basic unit.

[Drumrol]

They asked square footage, windows, insulation. I live in Rochester ,NY. No part of the 1st floor is underground. Im concerned because initally the Heil contractor mentioned a 2 ton unit and now he says this 11/2 ton unit. Would a 1/12 ton unit effiently cool a 1100' house?
The units that I were qouated on were Heil,York,Amanna,Armstrong. Who makes Heil?

[spark]

Make sure you have a load calculation done on the house. It's the only way you'll know for sure what size equipment you need.

And Heil is made by ICP - International Comfort products

-Mark

[udarrell]

Rochester, NY 2.5% summer design is 88F & 77F wet bulb for 43% RH outdoors.
An 88F outdoor air temp (OAT) doesn't carry near as high a ppm of moisture as say a 100F OAT.

Do you have factors in your home that create increased indoor humidity loads?
How tight do you think your home is; a high 0.8 Air Changes per Hour or 0.5 ACH?

The only way you'll know if a 1.5-Ton will handle the load is to run a whole house load-calc

You & your contractor can try this free online Whole House Load Calc but save your sf measurements somewhere else; then when you get everything right you'll need to print the results; as you can't save them. You'll need to use an infiltration rate between a real tight 0.4-ACH & say a 0.9-ACH, then using the cu/ft of air volume of your home & your guess of the % of ACH it will list the CFM number which you put in the make-up-air blank, so it will figure the cooling latent load, etc.

Then you use the Expanded Cooling Data on the 1.5-Ton Model unit you are planning to buy; a "Goodman Expanded Data" (search it) is easy to access online & may get you close enough using the same conditions criteria. It shows the 1.5 with a 2-Ton indoor cooling coil.

The 1.5-Ton A/C must be higher than the load-calc Results, by a decent margin in all 3 categories; Total Btuh, Sensible Btuh, & Latent Btuh.

To get the sensible Btuh, look at the S/T line on the Expanded Cooling chart & multiply it by the MBh in 1000' number; subtract the sensible from the total & you get the Latent Btuh.

Your contractor should know how to (or using other methods) do this for you... Manual S illustrates SIZING procedures; but may oversize a little bit

[udarrell]

Actually concerning what load-calc ACH to use; you really should use 0.40 or 0.45 ACH because you need to plug the holes to get the average infiltration ACH rate down to those levels.

Concerning sizing; you can do other things to get the heat-gain down to where the tonnage you selected will work; if you oversize you're out of options.

Also, for those very few exceptionally hot days, with the longer continuous runtime, 79-F plus 50% RH or less in your home, you will be well within the human comfort level conditions, and have more efficient operating runtimes during the other 90% of the seasonal operating times.

What % of the time will conditions be above the 75F indoor design & end up as high as 79F; an exceptionally few...the user has to agree with that selected design formula, or don't use it!

[AtticAce]

if you oversize you're out of options.

Not that you want to add unnecessary expense to a simple installation, but there is hope for those with mismatched or oversized condensing units. http://www.rawal.com/usrfiles/conten...s_brochure.pdf

[BaldLoonie]

Dang, spark, thems some credentials!

He's in your "hood", can you help him out or line him up with someone?

ICP/Heil is owned by Carrier. Same factories. The N4H3 is very much like the Carrier/Bryant basic units, slightly different grille.

If all 1100 ft is above ground, the 2 ton unscientifically doesn't sound too bad. But the load calc will tell if you want to do it right.

[udarrell]

Not that you want to add unnecessary expense to a simple installation, but there is hope for those with mismatched or oversized condensing units. http://www.rawal.com/usrfiles/conten...s_brochure.pdf

Hey AtticACE, after seeing your response to the parts changers; you're my kind of TECH PRO!
---------------
How low a tonnage do they go to with their reduction in output? Looked like they were primarily used on larger commercial applications.

Wonder what it cost to put one on a particular sized unit?

[spark]

Dang, spark, thems some credentials!

He's in your "hood", can you help him out or line him up with someone?

ICP/Heil is owned by Carrier. Same factories. The N4H3 is very much like the Carrier/Bryant basic units, slightly different grille.

If all 1100 ft is above ground, the 2 ton unscientifically doesn't sound too bad. But the load calc will tell if you want to do it right.

Thanks BL!

Drumrol,

What I would have done is an energy audit. They should include a load calculation and will check the rest of your house for issues. They are free to have done right now in NY state.
That way you can have a comprehensive report of your house, what can be improved on (if anything), the load calc, and learn about possible rebates/incentives for no cost.
I work for Isaac in the commercial service dept. Here's our home energy performance page with some additional info and phone #
http://isaachomeenergy.com/

Hopefully I'm not overstepping my bounds by plugging the company's info.

-Mark

[BadgerBoiler MN]

I like the 1.5ton contractor. Heating and cooling equipment should be sized properly--ACCA Manual 'J' heat loads--and left on most of the time. The only thing to improve a proper heat load is to predicate it with a proper blower door test and weather sealing.

Most equipment is over-sized as most customers don't understand comfort. "We shut everything down when we leave for work--summer and winter--and when we come home, it better be perfect before we set down to dinner!"

Set, forget it, be happy.

It is not unusual to oversize the condenser coil, and could be good, if you know what your doing.

One year labor is the standard for most mechanical trades.

[motoguy128]

In Rochester, NY, I'd have trouble imagining a typical 1100sqft residential configuration that would need more than 1.5 tons. But a load calculation is still needed to verify.

[motoguy128]

Most equipment is over-sized as most customers don't understand comfort. "We shut everything down when we leave for work--summer and winter--and when we come home, it better be perfect before we set down to dinner!"

Set, forget it, be happy.
.

+1. Worse you jsut deferred all of your run time to the tiem of day where you AC system is the least effcient and has the least capacity.

Most people would probably hate my house since it's a shrine to proper equipment sizing . It was 70F outside yesterday and I turned it down from 75 to 74F because my wife was a little warm. It took it almost 2 hours to drop it 1F. But when it was 85F and sunny earlier, it was only cycling about 50% of the time on 1st stage... as it should.

[Drumrol]

Thank you all for the great information and feedback. I will definetly check in to the home audit also. I have 2 more questions.
1. Currently my return air grills are on the bottom of the walls, the contractors say I should move them up towards the ceiling. Then rotate between the two between heating and cooling??
2. Condensate drain location. One contractor was going to pump it over to my sump pump pit, the other 3 said they would run a line to the space along the wall from the floating slab ??
I guess I'm going to want to keep the sun out of the house if I'm trying to cool it. Shades,curtains.

[dan sw fl]

2 ton ductless mini-split heat pump.

< 600 Cooling Degree Days
> 6400 Heating Degree Days

Similar to ..

http://www.climate-zone.com/climate/...york/syracuse/

[motoguy128]

gravity is more reliable than a pump but out needs to have adequate slope.

Return location isn't that critical. Supply location and register wealth make a bigger difference.

I might argue that you want grills lower in summer. Why...because ceilings are 8+ feet tall and humans ate usually 6 or less and only 4 when sitting. Allowing Souter to strategy at the ceiling means that you have less air that needs cooling.

All thing being equal, aesthetically a wall grill near the floor is the least noticeable

Sent from my DROID RAZR using Tapatalk 2

[sunnync]

Great information and a huge help. Thanks for everyone's efforts in helping each other. I have been quoted $13K + to change out two 2 ton units. I am thinking of going to one unit. After reading and looking at the threads on R22 vs R410A I am going with the R410A, even though it may cause a little more or quicker degradation of the system. It still should be cheaper in the end and there is the environmental factor. I do have some math under my belt and am going to enjoy trying to make the load calculation on my own first. I was surprised to find out I could over do the system size. At least that is what I think the comments on the thread are confirming. I hope my questions are fun for folks to take on. I generally get very creative when problem solving, so here they come: 1) Can someone expand on the need for accuracy regarding size of AC unit in a split system. The existing units are carrier 2 ton units. One for the up stairs and one for the down stairs. 2) Is going with a 4 ton unit a safe bet or is the load calculation still going to be a very important step? 3) Is the quoted price realistic? Thanks in advance, Jim

[udarrell]

I generally get very creative when problem solving, so here they come: 1) Can someone expand on the need for accuracy regarding size of AC unit in a split system. The existing units are carrier 2 ton units. One for the up stairs and one for the down stairs. 2) Is going with a 4 ton unit a safe bet or is the load calculation still going to be a very important step? 3) Is the quoted price realistic? Thanks in advance, Jim

Load calculation accuracy is important.

Simply going to a 4 ton system is not accurate, accurate load Calc's are critically important.

We cannot comment on quoted prices, I would get more quotes. Remove the price quote.

[dan sw fl]

Great information and a huge help. Thanks for everyone's efforts in helping each other. I have been quoted $01 to change out two 2 ton units.

I am thinking of going to one unit. After reading and looking at the threads on R22 vs R410A I am going with the R410A, even though it may cause a little more or quicker degradation of the system.

It still should be cheaper in the end and there is the environmental factor. I do have some math under my belt and am going to enjoy trying to make the load calculation on my own first. I was surprised to find out I could over do the system size. At least that is what I think the comments on the thread are confirming.

I hope my questions are fun for folks to take on.

3) Is the quoted price realistic? Thanks in advance, Jim

Anyone thinking of R-22, is Simply not thinking or had a recent RiP Van Winkle episode.

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