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Old 06-07-2020, 01:05 PM   #16
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Re: This is a 2 ton condenser right?


Experience counts for a lot if you work a certain area and are very familiar with the age and how house certain houses were constructed.

I can size most ACs by square footage in my area and after 35 yrs of working in these houses you get to know how well certain sizes of ACs work PLUS they way people run them.

Lots of people still wait until the sun gets high and then slam on the AC and expect it to cool like crazy and catch up so we don't always size them to specs.

In theory the minimum size is a good idea but in reality people expect cool fast air and you have to factor in whether they do a lot of cooking, have several dogs, many kids etc and a bit of extra capacity is a good idea IMO.
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Old 06-07-2020, 01:09 PM   #17
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Re: This is a 2 ton condenser right?


Certainly

http://efficientcomfort.net/assets/d...ty_Control.pdf

http://efficientcomfort.net/assets/d...ent_Sizing.pdf

http://efficientcomfort.net/assets/d...ign_Issues.pdf

http://efficientcomfort.net/assets/d...s_Properly.pdf

Basically, as your equipment gets larger in size it tends to short cycle. It takes 15-20 minutes of consistent runtime for the unit to reach its full capacity and efficiency. Increased runtime also removes humidity from the space, which doesn’t happen cycling the unit on and off.
Then there’s the fact that the vast majority of homes are built with undersized/inadequate duct. So that big new 3 ton unit, never actually puts out 3 tons of air.
When your unit was commissioned, and you received your commissioning/startup report, what was your CFM/static/CFM per ton?
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Old 06-07-2020, 01:13 PM   #18
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Re: This is a 2 ton condenser right?


The big new 3 ton will always put out 3 tons of cooling BTUs but if the ducts are too small will freeze the indoor coil.

You cannot lose cooling because of duct sizing. It may not flow well but the capacity is still there.
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Old 06-07-2020, 01:19 PM   #19
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Re: This is a 2 ton condenser right?


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The big new 3 ton will always put out 3 tons of cooling BTUs but if the ducts are too small will freeze the indoor coil.

You cannot lose cooling because of duct sizing. It may not flow well but the capacity is still there.
Depending on the duct some will never put out enough airflow. Equipment speaking you still have 3 tons, but not in airflow.
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Old 06-07-2020, 01:25 PM   #20
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Re: This is a 2 ton condenser right?


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Originally Posted by roughneck View Post
Certainly

http://efficientcomfort.net/assets/d...ty_Control.pdf

http://efficientcomfort.net/assets/d...ent_Sizing.pdf

http://efficientcomfort.net/assets/d...ign_Issues.pdf

http://efficientcomfort.net/assets/d...s_Properly.pdf

Basically, as your equipment gets larger in size it tends to short cycle. It takes 15-20 minutes of consistent runtime for the unit to reach its full capacity and efficiency. Increased runtime also removes humidity from the space, which doesnít happen cycling the unit on and off.
Then thereís the fact that the vast majority of homes are built with undersized/inadequate duct. So that big new 3 ton unit, never actually puts out 3 tons of air.
When your unit was commissioned, and you received your commissioning/startup report, what was your CFM/static/CFM per ton?
This is not a new home actually built in 1966. Also how do you know how long my unit runs? More run time = more electric bill. My house cools nicely and my unit runs according to how hot and humid it is outside. Much like the furnace in the winter. I can tell it's more efficient than my old unit because it cools the house faster than the old unit. My old unit used to be on more than off on hot days. So far this one on the few hot days runs about 40% less. Never had a commissioning report and don't care to pay for one. The installer 40 years experience matched the A coil with the furnace/AC unit and he did a good job.
Seems like you have a lot to learn. Hope I helped to educate you.
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Old 06-07-2020, 01:29 PM   #21
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Re: This is a 2 ton condenser right?


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This is not a new home actually built in 1966. Also how do you know how long my unit runs? More run time = more electric bill. My house cools nicely and my unit runs according to how hot and humid it is outside. Much like the furnace in the winter. I can tell it's more efficient than my old unit because it cools the house faster than the old unit. My old unit used to be on more than off on hot days. So far this one on the few hot days runs about 40% less. Never had a commissioning report and don't care to pay for one. The installer 40 years experience matched the A coil with the furnace/AC unit and he did a good job.
Seems like you have a lot to learn. Hope I helped to educate you.
If your comfortable doing things the wrong way, then thatís fine.
Please donít use that incorrect advice for others.
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Old 06-07-2020, 01:31 PM   #22
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Re: This is a 2 ton condenser right?


It is more efficient as your old unit had a reciprocating compressor with worn valves and probably put out about 80-85% of a new one.

New units use scroll compressors with no valves and should do better in the long run until a scroll or some metal part breaks. They may not lose capacity but can seize up or break.

Experience counts for a lot but the trick is to find a experienced old school tech or company and hang on to him.
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Old 06-07-2020, 01:39 PM   #23
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Re: This is a 2 ton condenser right?


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It is more efficient as your old unit had a reciprocating compressor with worn valves and probably put out about 80-85% of a new one.

New units use scroll compressors with no valves and should do better in the long run until a scroll or some metal part breaks. They may not lose capacity but can seize up or break.

Experience counts for a lot but the trick is to find a experienced old school tech or company and hang on to him.
That was the guy i had install the unit he's 65 and old school and very knowledgeable about AC. I could tell by the questions I asked and the answers he gave. I do that to so I can tell if someone is BS'n me. I'm no spring chicken either and I can usually tell when someone is full of it.
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Old 06-07-2020, 01:41 PM   #24
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Re: This is a 2 ton condenser right?


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If your comfortable doing things the wrong way, then thatís fine.
Please donít use that incorrect advice for others.
Evidently not, well I tried.
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Old 06-07-2020, 01:51 PM   #25
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Re: This is a 2 ton condenser right?


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Evidently not, well I tried.
Try this, itís a free version of a manual J heat load report. Itís how equipment is sized to the structure for residential applications.
Commercial/industrial has a different calculation.
You do a room by room manual J with a manual D to design duct.
This is for new, and existing structures.

www.loadcalc.net
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Old 06-07-2020, 01:56 PM   #26
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Re: This is a 2 ton condenser right?


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Originally Posted by roughneck View Post
Try this, itís a free version of a manual J heat load report. Itís how equipment is sized to the structure for residential applications.
Commercial/industrial has a different calculation.
You do a room by room manual J with a manual D to design duct.
This is for new, and existing structures.

www.loadcalc.net
So now I'm supposed to install new duct work in my home. You're not very financially intelligent are you.
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Old 06-07-2020, 02:03 PM   #27
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Re: This is a 2 ton condenser right?


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So now I'm supposed to install new duct work in my home. You're not very financially intelligent are you.
Duct needs to fit the equipment, yes.
But how am I supposed to know how big to make a new takeoff to a room? Or fix old existing duct.
Itís not a guessing game.
Your throwing insults to cover up your lack of knowledge on the subject.
Iím trying to show you the real world of things, rather then just accepting someone telling you ďyou need a bigger unitĒ.
Sizing is very important. Even more important in humid climates. If I followed your instructions Iíd have no customers.
In many cases weíve gone in and pulled out a 5 ton unit for something substantially smaller. And the customer has been elated with how much better the system runs.
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Old 06-07-2020, 02:23 PM   #28
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Re: This is a 2 ton condenser right?


It's true that after doing a lot of houses with load calculations, it's possible to do a good job sizing based on experience.

But it's never directly proportional to sq ft.

The more humid the climate is, the more important it is not to oversize.

Quote:
Also how do you know how long my unit runs? More run time = more electric bill.
No, the bigger units draw more current when they run and the cycling reduces efficiency.

Best case, the larger unit uses the same amount of energy, in the real world, the combination of cycling (it takes 10 to 20 minutes to reach full capacity), reduced airflow or higher fan power required to maintain proper airflow increases operating costs.
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Old 06-07-2020, 02:28 PM   #29
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Re: This is a 2 ton condenser right?


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Originally Posted by roughneck View Post
Duct needs to fit the equipment, yes.
But how am I supposed to know how big to make a new takeoff to a room? Or fix old existing duct.
Itís not a guessing game.
Your throwing insults to cover up your lack of knowledge on the subject.
Iím trying to show you the real world of things, rather then just accepting someone telling you ďyou need a bigger unitĒ.
Sizing is very important. Even more important in humid climates. If I followed your instructions Iíd have no customers.
In many cases weíve gone in and pulled out a 5 ton unit for something substantially smaller. And the customer has been elated with how much better the system runs.
But I don't need new duct work just an AC unit, and it works much better than the old unit and it was efficiently installed. Partially by the installer and by me insulating the cold line better. My old unit was 2.5 tons not 5. How much do you charge for installing a new unit and duct work?
Never mind I don't want to know. I'll use the extra few thousand for the electric bill for the inefficient system I just had installed.
Do you wrap the insulation with electrical tape to improve efficiency?
Never mind I know the answer to that question.
Too bad your customers don't know how much money they could have saved.
Take care...
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Old 06-07-2020, 02:31 PM   #30
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Re: This is a 2 ton condenser right?


Your old unit was probably not properly charged, had a dirty evap coil or a compressor with bad valves. (or all of the above)

Also going from a 10 to a 13-14+ seer, there can be energy savings even if the unit is upsized.

btw the main reason to insulate the suction line is to prevent condensation. The extra heat picked up is pretty minimal, it's all vapour by that point and most of the heat absorption occurs when the refrigerant boils off, it's latent heat.
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