# What do these numbers tell you?

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• 02-26-2005, 12:43 AM
fat eddy
[QUOTE]Originally posted by BamaCracker
[B]Well dang! You only undersized it by 1/2 a ton! That ain't too bad, since the original "expert" put in a 3 1/2 ton unit on a 2.5 ton load, and the house was so uncomfortable we hated it. I finally installed a 3 ton, 2 speed compressor, and converted it to heat pump. It was still oversized in cooling (maintained 67 degrees on a 107บ day) when on high speed, but the humidity control from running in 1/2 speed was awesome.

Let me break it down like this. I can see that you guys are having a lot of problems with this so I will simplify it even further.I will use capitols on the important parts of his quote.

It was STILL OVERSIZED IN COOLING (maintained 67 degrees on a 107 degree day) WHEN ON HIGH SPEED. ( KEY WORD HERE IS WHEN )apparently at 107 out it didn't need to run hi speed very often and probably never would if he didn't try to keep 67.

The HUMIDITY CONTROL from RUNNING 1\2 SPEED WAS AWESOME.

If it truly is half speed or half capacity it is at 18k, now lets do the math folks.

36k 2 Speed =107 OA 67space temp = unit cycles to low speed

24k =95 OA single stage 72 space temp = unit satisfies and cycles off.

Beleivable ? the only realistic is yes Fat Eddy I can beleive that, anything other than that would be pure stupidity.

And here is the topper the guy does a load calc and it comes out to 31k so whats he do he goes and puts in a 36k

Thats exactly how the whole thing got started to begin with.

[Edited by fat eddy on 02-25-2005 at 11:52 PM]
• 02-26-2005, 01:05 AM
rsmith46
Dang, now Fat Eddy's running circles around BamaCracker. I like FE, of course I miss Floor Furnace.
Never argue with an Idiot, they drag you down to their level and beat you at their own game.
• 02-26-2005, 01:09 AM
fat eddy
Whats your game? would you like to lose at that also ?
• 02-26-2005, 01:36 AM
bananaboy
Congrats Fat Edi. For some reasons we tink likewise, absolutely.

It happened to me to replace an Evap. coil which was 1/2 ton larger than the condensing unit. It was Sat. and I only had this size in my truck. Promised to the lady to come back and put the matching size. Of course when I charge up the system I had to put a bit more R22. To my suprise - when I went back on Monday with the correct size coil - the lady said she was very happy the way it is. What she did not understand was the that dehumidification was way better with the larger evap. coil.
• 02-26-2005, 01:38 AM
fat eddy
Thats because there is more surface area a point that many here can not grasp although it is in every decent HVAC book you can find.
• 02-26-2005, 01:46 AM
bananaboy
Right on, man !

Increased surface will increase the efficiency. Same idea on the increased Condensing coil surface to gain more subcooling, hence more efficient at the metering device.
• 02-26-2005, 01:49 AM
fat eddy
Yes, bigger condenser surface, closer approach, little extra subcooling, a little less flash and pow its more efficeint.
• 02-26-2005, 02:15 AM
41gasman
ColdBud.
This thread got a little side tracted
from the question you asked.Some peaple
guess right some of the time.but thier
not right all the time.It is your
money and your home.Spend the time
to find a honest and intelligent
hvac guy that will look at your
whole system.And knows that he
is spending your money and trust.
Even if he can eyeball it and tell
you nuts on.It should be no problem
to show you the numbers to help

Now as far as FatEddy goes.
He feels rather highly of himself.
And seems to be self righteous
in a angry sort of way.If you were
to hire him. Because he is so
intelligent that he can pick
out the size of the equipment
you need with just a little information.
Or a good look at your house.
Bear in mind who you would really
be hiring.I will refer you to
for your viewing in the residential
hvac forom.

After you read this. I think it will
substantiate why in this forom
it is said. It is the quality of
the install and the installer that
counts.
41Gasman

P.S SPLAT!!!
• 02-26-2005, 02:23 AM
Collin
Quote:

Originally posted by rsmith46
Dang, now Fat Eddy's running circles around BamaCracker. I like FE, of course I miss Floor Furnace.
Never argue with an Idiot, they drag you down to their level and beat you at their own game.

Why is it every few months someone shows up knowing everything? Then they want to argue with Bama?

I liked the floor furnace reference, Mr Smith.:D
• 02-26-2005, 03:47 AM
Quote:

Originally posted by swampfox
So lets get this straight, even after you find the load is 31k, you still think 24k will do the job at design conditions, and the oversized evap and 450 cfm/ton is for extra latent capacity, am I reading all this right?

Oversized evaporator coils DO NOT give you more latent. They give you the opposite. They give you more sensible and take away your latent (humidity) control. Increasing air flow also DECREASES your latent (HUMIDITY) control.

His 24K design wouldn't work. I will explain in a second.
• 02-26-2005, 04:06 AM
Quote:

Originally posted by fat eddy
What part was I wrong on, do tell me please. he did a load calc it came out to 31k which is less than 2.5 ton but close, load calcs in general tend to oversize by 20% that puts me right on the money and I assure that the size I chose would handle his home on any design day.

He also stated that he chose to go with a two speed compressor and that he got good dehum when it was running at low speed ( which is probably all the time) low speed is typically 60%, 60% of 36k is about 21k.

You are always better off undersizing than oversizing if you undersize you will get better pressures in your system.

The 36k unit kept his home at 67 when it was 107 out, would that make you think that it is still grossly oversized?

He actually ended up with exactly what I recommended a two ton unit with an oversized coil. And thats all he needed for design conditions. Case Closed,

What part was I wrong on, do tell me please. he did a load calc it came out to 31k which is less than 2.5 ton but close,
31K is more than 2 ฝ tons, which is 30K actually, and most only put out 29K, so you are wrong here since you asked to have it brought to your attention.
load calcs in general tend to oversize by 20% that puts me right on the money and I assure that the size I chose would handle his home on any design day.
.there is slop built in for a reason, and you do not even understand why. By you trying to take the slop out and make your sizing work in this application is unprofessional and not the way it should be engineered.
He also stated that he chose to go with a two speed compressor and that he got good dehum when it was running at low speed ( which is probably all the time) low speed is typically 60%, 60% of 36k is about 21k.
..here you are again trying to show where low speed will fit your high speed load. Not comparing apples to apples here are we?

You are always better off undersizing than oversizing if you undersize you will get better pressures in your system.
.Since when do we size a system by the pressures, and last I looked, it is superheat or subcooling which matters, but being a fitter as you proclaim to be, well

The 36k unit kept his home at 67 when it was 107 out, would that make you think that it is still grossly oversized?
..no, it shows he has excellent insulation.

He actually ended up with exactly what I recommended a two ton unit with an oversized coil. And thats all he needed for design conditions. Case Closed,
..wrong. He ended up with a system perfectly matched. 31k is over 2 ฝ tons, so going up to 3 tons is correct.

• 02-26-2005, 04:14 AM
[QUOTE]Originally posted by fat eddy
[B]
Quote:

Originally posted by BamaCracker
Well dang! You only undersized it by 1/2 a ton! That ain't too bad, since the original "expert" put in a 3 1/2 ton unit on a 2.5 ton load, and the house was so uncomfortable we hated it. I finally installed a 3 ton, 2 speed compressor, and converted it to heat pump. It was still oversized in cooling (maintained 67 degrees on a 107บ day) when on high speed, but the humidity control from running in 1/2 speed was awesome.

Let me break it down like this. I can see that you guys are having a lot of problems with this so I will simplify it even further.I will use capitols on the important parts of his quote.

It was STILL OVERSIZED IN COOLING (maintained 67 degrees on a 107 degree day) WHEN ON HIGH SPEED. ( KEY WORD HERE IS WHEN )apparently at 107 out it didn't need to run hi speed very often and probably never would if he didn't try to keep 67.

The HUMIDITY CONTROL from RUNNING 1\2 SPEED WAS AWESOME.

If it truly is half speed or half capacity it is at 18k, now lets do the math folks.

36k 2 Speed =107 OA 67space temp = unit cycles to low speed

24k =95 OA single stage 72 space temp = unit satisfies and cycles off.

Beleivable ? the only realistic is yes Fat Eddy I can beleive that, anything other than that would be pure stupidity.

And here is the topper the guy does a load calc and it comes out to 31k so whats he do he goes and puts in a 36k

Thats exactly how the whole thing got started to begin with.

[Edited by fat eddy on 02-25-2005 at 11:52 PM]

You are trying to justify putting in your system here which would only keep up to the correct sized system when it is running in low speed.

What are you going to do during the 3 months he needs full load in HOT Oklahoma when he needs it?

This is better than some of the jokes on David Letterman.
• 02-26-2005, 04:20 AM