[sammy37]

Can someone verify for me that a 410A unit will not cool as well as 22 does on a very hot day?
I'm wanting to replace the unit on my house with a smaller unit and have been told that a 410A unit will not keep up the same.
When you guys do manual J's, do you have to take this into account?

 

[digitalplumber]

Never heard this subscribing to see what the experts say.

 

[Technow]

A 24000BTUH R-22 condenser is the same as a 24000 BTUH R410A condenser

The manual J gives you the load on the house....a manual S is used to match the condenser to the manual J.

 

[sammy37]

This will be a package unit. I've heard in very hot weather that 410A cannot keep up like a 22 unit.

 

[sammy37]

Seems like I've heard beenthere mention this somewhere along the line, maybe he'll be along soon.

 

[Technow]

This will be a package unit. I've heard in very hot weather that 410A cannot keep up like a 22 unit.

Seems like I've heard beenthere mention this somewhere along the line, maybe he'll be along soon.

Yeah, I am sure he will:thumbsup:

Just make sure they don't give you a 22000BTUH R410A condenser instead of a 24000 BTUH R22 condenser. :whistling2:

 

[beenthere]

R410A does drop off in capacity at high outdoor temps. At 115°F outdoor temp a 2 ton R22 will have more capacity then a 2 ton R410A unit will. And as it gets hotter the difference increases. So it comes down to where you are located, and where you will have your condenser or package unit installed. My area, it doesn't matter. In Death Valley it will definitely matter.

A Manual J actually only tells you the capacity you need. Manual S is what tells you the size unit by giving you the derates and multipliers to use.

 

[sammy37]

So educate me here. As a person that has grown up in oversized country, what is the optimum setup for summer cooling? Should a unit run constantly on a hot day? Is it really cheaper to have a small unit run all day, as opposed to a larger unit that cycles off and on through the day?

I have only seen one example of a proper sized or possibly undersized setup, it was at my in laws house in Austin TX. They have a 1900 sq ft old 1980's tract house with a new 2 ton Bryant unit that runs all day long and doesnt really hold the set temp but the house was very comfortable and they say their power bills are quite cheap. I bet if someone was to run a load calc, it would come in higher than what they have. Is going smaller than what a load calc calls for bad? I wouldnt try it on a customers house but I dont mind trying it on my own.

There is a house in our neighborhood that is bigger than ours, it's 1920 sq ft, they are running a 3 ton unit. I wouldnt have believed it till I noticed the small unit on their roof and stopped to ask how they like it. He replied that they have all original insulation, windows and they run it at 78 with no problems. Their house originally came with a 4 ton unit.

 

[digitalplumber]

S37' what I can tell you in my home in Houston Texas. Originally builder installed 2 3 ton units. Changed them to 2 4 tons and could not be happier. 1 up and 1 down. Each is responsible for 1800 square feet.

Upstairs cycles even on super hot days and does the job!

 

[beenthere]

So educate me here. As a person that has grown up in oversized country, what is the optimum setup for summer cooling? Should a unit run constantly on a hot day? Is it really cheaper to have a small unit run all day, as opposed to a larger unit that cycles off and on through the day?

I have only seen one example of a proper sized or possibly undersized setup, it was at my in laws house in Austin TX. They have a 1900 sq ft old 1980's tract house with a new 2 ton Bryant unit that runs all day long and doesnt really hold the set temp but the house was very comfortable and they say their power bills are quite cheap. I bet if someone was to run a load calc, it would come in higher than what they have. Is going smaller than what a load calc calls for bad? I wouldnt try it on a customers house but I dont mind trying it on my own.

There is a house in our neighborhood that is bigger than ours, it's 1920 sq ft, they are running a 3 ton unit. I wouldnt have believed it till I noticed the small unit on their roof and stopped to ask how they like it. He replied that they have all original insulation, windows and they run it at 78 with no problems. Their house originally came with a 4 ton unit.

Just to cover the load, plus 15%.

The tightness of the home determines how comfortable the home will be with a "under sized" unit. if the humidity is kept down, it will feel comfortable. if it can't keep the humidity down it on't feel comfortable.

 

[beenthere]

S37' what I can tell you in my home in Houston Texas. Originally builder installed 2 3 ton units. Changed them to 2 4 tons and could not be happier. 1 up and 1 down. Each is responsible for 1800 square feet.

Upstairs cycles even on super hot days and does the job!

Unless you had your duct work altered, good chance your only getting 3 to 3.25 tons worth of cooling. And it was your under sized duct work that was the problem, not the A/C size.

What is the temp difference across the evap coil.

 

[sammy37]

Having been in many houses in Vegas that were set at the 77-80 degree range, I found them to be downright uncomfortable when the unit was off.

Spending a week in Texas with their house running at 78 degrees I was comfortable, because the unit was constantly running. With my oversized unit here at our house, I have to run it 75 degrees or less to stay comfortable with the cycling on and off. I know we can use ceiling fans and we do but it's not the same for me.

The main reason I asked about the r22 vs 410a, was because the small 3 ton unit on our neighbors house is r22.
I have an r22 3ton unit sitting in my garage that I was going to throw up on my roof but turns out it has a leaky evap coil and I dont want to mess with getting it fixed.

Now, I'm forced to buy a new 410a unit and dont want to screw up and buy one that is too small, it was all fine and good when I had the freeby unit to put up there.

 

[sammy37]

The other reason, I want to get rid of the heat pump and go back to gas.

 

[carmon]

115.... oh my.... no worries here.....410 it is...lol

 

[beenthere]

Having been in many houses in Vegas that were set at the 77-80 degree range, I found them to be downright uncomfortable when the unit was off.

Spending a week in Texas with their house running at 78 degrees I was comfortable, because the unit was constantly running. With my oversized unit here at our house, I have to run it 75 degrees or less to stay comfortable with the cycling on and off. I know we can use ceiling fans and we do but it's not the same for me.

The main reason I asked about the r22 vs 410a, was because the small 3 ton unit on our neighbors house is r22.
I have an r22 3ton unit sitting in my garage that I was going to throw up on my roof but turns out it has a leaky evap coil and I dont want to mess with getting it fixed.

Now, I'm forced to buy a new 410a unit and dont want to screw up and buy one that is too small, it was all fine and good when I had the freeby unit to put up there.

How tight is your home. The tighter it is, the lower the humidity will be.

 

[digitalplumber]

Unless you had your duct work altered, good chance your only getting 3 to 3.25 tons worth of cooling. And it was your under sized duct work that was the problem, not the A/C size.

What is the temp difference across the evap coil.

Cant tell you that right now, Winter. What I can tell you is that when we put a hood on each duct, we got darn near what it was suppose to be pushing.

Using rheem critereon furnaces.

We also added returns in all of the upstairs bedrooms (4) which also helped.

 

[sammy37]

How tight is your home. The tighter it is, the lower the humidity will be.

Fairly tight, I've done a few things to seal it up over the last few years and although I've talked about blowing in insulation over the last couple years, am finally doing it this spring.
I've also disconnected the evap cooler and have done away with that mess also.

 

[beenthere]

Cant tell you that right now, Winter. What I can tell you is that when we put a hood on each duct, we got darn near what it was suppose to be pushing.

Using rheem critereon furnaces.

We also added returns in all of the upstairs bedrooms (4) which also helped.

So it may be the addition of the returns which also makes it easier to get more air through the supply that did the most good and not the increase in size.

how did you know what it should be pushing? Did you do or have a load calc done?

 

[digitalplumber]

So it may be the addition of the returns which also makes it easier to get more air through the supply that did the most good and not the increase in size.

how did you know what it should be pushing? Did you do or have a load calc done?

BT, you are absolutely right, no doubt the additional returns were extremely helpful. But having said that, the additional ton made a world of difference on the extreme hot days here in houston.

What I meant by pushing was, if the Rheem Crit. was rated at 1600 for 4 tons, once we checked all of the discharge vents upstairs, we got darn near all of it. With the previous system we were way less on the the 3 ton. Even on our 100 plus days here, its been great! Unlike with the 3 ton that just ran and ran and never seemed to do anything.

Its one of those installs that I am sure the manual J would not support, but in this case I the customer am satisfied.

The home builders AC contractor would use a generic manual J on all like homes, not taking things like location, direction and or trees in consideration. You cant do that.

We have one side that is exposed to due west sun!

Thanks!:thumbsup:

 

[beenthere]

food for thought. how much better would the 3 ton have been with those same extra returns.