R22 vs 410a & Sizing

[Arizona John]

I would appreciate some guidance on a replacement system (2) for our home.

I've had 4 bids from ACCA contractors and no one agrees on tonnage. Sizing is ranging from 3.5 to 5t to replace a Goodman 4t unit, from 1997, and is for a downstairs living space of 1900 ft2 (up is 1100 ft2, and they agree 3t for upstairs).

I want a 410a system. Some contractors warn me that the 410a will NOT cool like the R22, or about 10% less capable, so I have to go up 25% to a 5t unit. Others tell me that it is the same, don't worry.

So do I need more tonnage with 410a system? It's confusing, please advise.

Thank you-- Arizona John

[jimj]

They may be ACCA members, but did they do a load calc? They should be able to show you there manual J and a manual S extended rating for the system there recommending. Ask for it.

[pecmsg]

I've had 4 bids from ACCA contractors and no one agrees on tonnage. Sizing is ranging from 3.5 to 5t to replace a Goodman 4t unit, from 1997, and is for a downstairs living space of 1900 ft2 (up is 1100 ft2, and they agree 3t for upstairs).

Click on the tab HVAC CALC above Do your own calculations. Then request there’s to compare notes. (Granted some will not leave a copy with you but should be more then willing to sit down one more time to compare.) 2 ½ - 3-Ton, 3 to 3 1/2-Ton fine. 3 ½ to 5 there’s a problem.


I want a 410a system. Some contractors warn me that the 410a will NOT cool like the R22, or about 10% less capable, so I have to go up 25%to a 5t unit.

BS Find another contractor.

[Sonicview]

I have a 2 stage 3 ton R-410a HP unit and it cools my 1600sqft area just fine....maybe too much ... I have it zoned now though...so much of the 3 tons was pushing into 800 sqft at a time...way too much ... I have since modified the settings on the zone panel to get the fan speed a bit lower and to only run in 1st stage when 1 zone is calling. that helped out alot with the humidity also... so based on my particular experience I would say 3 tons is alot for 1100 sqft but I dont know the specifics on your house, how much glass,southern exposure to sun, shade, age of home, insulation etc.... you need a good reputable company that knows what the hell is going on and how to measure these variables and determine exactly what you should need... they are hard to find but are out there.. interview as many as you can and ask questions that you know the answers to and see how they respond... (I had one guy I interviewed tell me that "there was no need to do a static pressure test on a variable speed system because it adjusted itself") good luck...

[beenthere]

I would appreciate some guidance on a replacement system (2) for our home.


I want a 410a system. Some contractors warn me that the 410a will NOT cool like the R22, or about 10% less capable, so I have to go up 25% to a 5t unit. Others tell me that it is the same, don't worry.

So do I need more tonnage with 410a system? It's confusing, please advise.

Thank you-- Arizona John

In certain areas, a larger R410A system may be required.
You may or may not be in one of those areas.
What is your outdoor design temp.

Normally, if you need a bigger R410A system for one floor, you would also need a larger unt for the second floor. Unless it was already over sized.

[jimj]

In certain areas, a larger R410A system may be required.
You may or may not be in one of those areas.
What is your outdoor design temp.

Normally, if you need a bigger R410A system for one floor, you would also need a larger unt for the second floor. Unless it was already over sized.

When the heck do you sleep, isn't it past your bedtime:D.
Your rite though, Phoenix design that most people use is 110 ( record high 122). My city we use 118 (record high 128). R410A will have large capacity drops and very high pressures at those temps.

[beenthere]

Its only 11:15 PM here. :)

[Arizona John]

Thank you all for your great comments. Best part is the unvarnished comments, thanks again!

Firstly, I will do my own Manual J calcs. Should be interesting. You know, I chose the contractors due the ACCA and also the high percentage of NATE techs. But not one did a calculation, they just swagged it in my opinion since they "had the answer" on the spot.

A brand question: I am leaning to the American Standard. Cheaper than Trane and I am told they are the same. Lennox is competitive, better SEER for the money. But even the Lennox dealers slam the brand and steer me to Trane or American Standard saying Lennox doesn't stand behind the dealers. Are Lennox good?

I'm looking to spend about $14,000 on the 2 systems so I have to get this right. Do you think the extra 10 year parts and labor is worth it (extra $350)?

Appreciate the advice.

[Arizona John]

Jimj--

I am in Phoenix so we get some heat. So when it gets to 110, the R410a is not going to keep up, right, so I need some extra tonnage?




When the heck do you sleep, isn't it past your bedtime:D.
Your rite though, Phoenix design that most people use is 110 ( record high 122). My city we use 118 (record high 128). R410A will have large capacity drops and very high pressures at those temps.

[beenthere]

Edit out your pricing, not allowed on this site, Thank you.

Yes, get teh extended parts and labor warranty.

I f you need to increase size on the one unit, you should need to increase size on the other. Ask them why you only need to increase the size of the one unit.

[hvaclover]

Jimj--

I am in Phoenix so we get some heat. So when it gets to 110, the R410a is not going to keep up, right, so I need some extra tonnage?

:eek::eek::eek::eek::eek::eek::eek:

[jimj]

Jimj--

I am in Phoenix so we get some heat. So when it gets to 110, the R410a is not going to keep up, right, so I need some extra tonnage?

John all systems will have capacity drops as the ambient temps rise, R22 and 410A. The trick is to have a properly sized system. That is where manual j and s come in. Manual j will tell you how many BTU's you need at your design temps (Phoenix) and manual s will tell you how many BTU's a system will deliver at a particular condition. In you case 110 degrees dry bulb, 75 degree indoor dry bulb and 63 degree indoor wet bulb. Do that and you have the start of a good system ( this assumes you have a duct system that was properly designed, but thats another story and another manual :D).

[beenthere]

John all systems will have capacity drops as the ambient temps rise, R22 and 410A.

True. But thats not what I was refering to.

Check your performance for R410A, it does have a greater loss then R22 at higher outdoor ambients.
110°F is within R410A's operating range without excess drop off.

Some of the guys that work in areas that have higher ambients then that have already run into troubles.

The death vally boys will have their work cut out for them.

[jimj]

True. But thats not what I was refering to.

Check your performance for R410A, it does have a greater loss then R22 at higher outdoor ambients.
110°F is within R410A's operating range without excess drop off.

Some of the guys that work in areas that have higher ambients then that have already run into troubles.

The death vally boys will have their work cut out for them.

Been no argument, I agree 100%. We have had problems in my area already. But IF you do a manual s you can overcome those issues.

[beenthere]

Been no argument, I agree 100%. We have had problems in my area already. But IF you do a manual s you can overcome those issues.
Using Manual S, is will indicate when to increase size when switching to R410A in high ambient areas.


But.

Some places, when replacing 5 ton units, they will have to add a second unit, because the R410A system won't meet sensible load no matter what. Its heat transfer efficiency drops off too much.

[jimj]

Been I work in 2 of the hottest cities in the country. Check it out Lake Havasu City Az. and Bullhead Az. I don't think you can find hotter cities:D. Gotta go to a wine tasting see ya.:D

[beenthere]

Deathvally ca, may not count as a city.
But they got hotter temps. :)

[Andy Schoen]

Check your performance for R410A, it does have a greater loss then R22 at higher outdoor ambients.


Due to the fact that R-410A reaches critical temperature at 160°F, while R-22 reaches critical temperature at 205°F.

[hvaclover]

Due to the fact that R-410A reaches critical temperature at 160°F, while R-22 reaches critical temperature at 205°F.

Owtch. I asllep at the wheel. I should knows that.

Well that sure make 410 a sucky R22 replacement.

I'm wondering if that isn't the reason and a lot of Asia and Europe are still holding on to 407?

Gotta look it up.

[hvaclover]

Owtch. I asllep at the wheel. I should knows that.

Well that sure make 410 a sucky R22 replacement.

I'm wondering if that isn't the reason and a lot of Asia and Europe are still holding on to 407?

Gotta look it up.

I was right. 407's critical temp is 180F*.

[Arizona John]

Okay, I am getting this slowly... so if 410a degrades at a lower temp than the R22, I can correct this by going to more tonnage... right? I will dazzle the contractor in question with my request for a manual J, and R.

[jimj]

Deathvally ca, may not count as a city.
But they got hotter temps. :)

Your rite they don't count, we run about 8 degrees warmer than Phoenix ( on average) a few cooler than Death Valley. If you look at city's high temps over the last ten years with the highest number of days in a year with the warmest temps in the country on a given day you will find my part of the country. Lake Havasu has the highest temp ever recored in a city, 128 degrees.

Been, I still agree with you thou, there will be some BIG problems in western Arizona and parts of California ( Palm Desert, Palm Springs and Rancho Mirage). Put a 410A unit on a 135 degree roof with a slightly dirty condenser or slight over charge and the 625 high pressure control is a joke. I have a good friend ( was my service manager 20 years ago)that was a territory manager for the Carrier / Bryant distributor for Palm Desert and Indio Calif for many years and 675lb high pressure controls were a stock replacement for factory HP controls.

[hvaclover]

I guess when Global Warming hits only the R22 units are going to survive:D

[jimj]

Okay, I am getting this slowly... so if 410a degrades at a lower temp than the R22, I can correct this by going to more tonnage... right? I will dazzle the contractor in question with my request for a manual J, and R.

John here is my point. As an example if you take Trane's 2TWR3060 unit( R22) and tie it to its most common air handler it will give you 47,900 total BTU's and 37,900 sensible BTU's at 115 degrees DB ambient, 75 degree indoor DB 63 WB. If you take its R410A version under the same conditions it will give you 47,800 total BTU's and 38,750 sensible BTU's. Yes from there the 410A system will drop off faster, but so what thats what manual s is for. Match the system to YOUR requirements. Your contractor should be able to give you this information, if not walk away.