OT Educate me on home AC

moonlight machine · May 20, 2020

Looking to upgrade the AC in my house, a cool wife is a happy wife and all that. Currently have a 3 ton R22 system in a 100+ year old victorian. I would like to get something more efficient. How do I know how efficient a system is? How are they rated. What's the deal with the new refrigerant? A3 ton, what does that mean? Any online places to get good prices? I can do the instal my self.

Frederick Harvie · May 20, 2020

I suspect that given you are trying to cool a 100 year old victorian that the best bank for you buck will be more insulation

gustafson · May 20, 2020

Insulation and air sealing are cheaper than AC

Would you or your wife consider mini splits

I have installed half a dozen of them and it is mostly carpentry. Find a tech who will moonlight to commission them, or learn basic AC[if you don't already know] and they are pretty easy

central units are a bit more build to suit and can take some more knowledge to get right

another upside to minisplits is most will heat also, and that saves me some wife aggravation factor in the winter

GregSY · May 20, 2020

I'll be interested in what you learn. The AC business is an interesting one in that it is a protected industry....through some careful greasing of palms many years ago, the 'professionals' have achieved governmental protection. If you are not 'licensed', they work to keep you from doing anything yourself other them writing a check to someone who is.

Imagine that....you don't need a license to buy alcohol, a circular saw, an electrical circuit breaker box, or a 75" swing lathe...but you need one to buy a relay.

As for sizing, there is this prevailing idea that you are better off installing a 'barely enough' system that runs all the time rather than one that is oversized and runs sometimes. I hear that a lot...and I think it's a crock.

moonlight machine · May 20, 2020

Frederick Harvie said:
I suspect that given you are trying to cool a 100 year old victorian that the best bank for you buck will be more insulation

It is insulated and has a dead AC, High 70s low 80s this weekend it will be a hotbox.

310 Guy · May 20, 2020

GregSY said:
As for sizing, there is this prevailing idea that you are better off installing a 'barely enough' system that runs all the time rather than one that is oversized and runs sometimes. I hear that a lot...and I think it's a crock.

Nope, it's true if you live in a humid climate (like Houston.) A small unit will run for a longer time than a large unit, thereby removing more moisture from the air. The large unit will come on, quickly lower the temperature inside the house and then shut off, but it won't run long enough to remove the moisture. Then you wind up with a cool but clammy (damp) environment. Been there, done that.
Bill

Gordon Heaton · May 20, 2020

If you've already got a central system in place, I'd keep that and just upgrade the air handler and condenser. The efficiency ratings are SEER, I think it stands for 'Seasonal Energy Efficiency Rating' or something like that. A bigger number is better. You'll save a lot of money on electricity upgrading from an old R22 unit. I personally like the inverter driven stuff for both indoor and out. They're so quiet you can carry on a normal conversation standing right next to the compressor/condenser. You don't usually hear the indoor blower start or stop either unless you're listening for it.

Mini splits are neat, but it usually means a separate evap/blower for each living area. You can gang several off one condenser though. The other downside is of course that the odds of failure go up with the number of parts involved. If you don't already have the ductwork for central, minis would be a less expensive option.

ignator · May 20, 2020

moonlight machine said:
It is insulated and has a dead AC, High 70s low 80s this weekend it will be a hotbox.

By DEAD, does the compressor run? Does the condenser fan run? How about the fan in the house that most likely is the furnace blower?
If the compressor and condenser fan are not running, check for a bad capacitor out in the condensing unit. They typically share a common can. Does the contactor close in the outdoor unit when the thermostat is calling for cooling? I've seen contacts that are so corroded that the 240VAC will not flow.
Or has the system lost it's charge?
If you buy a new system, stay away from an aluminum condenser. You want copper tube with aluminum fins, the all aluminum that is a brazed assembly will fail early. Especially with R410a pressures being nominally double over the R22.

Larry Dickman · May 20, 2020

here what I know,

as mentioned above, insulation is extremely important. The second is your windows rating. If you're not interested in replacing your windows, never mind. But there are two ratings, the U factor and the SHGC, and they make a significant contribution to you houses overall efficiency.

Next is your condensers SEER factor. Bigger the better. To get a higher seer you need to go to a 2 stage pump and this is where the price takes off. So that's a judgement call, is the savings in power going to justify the added cost.

I forget how the tonnage rating came to be, but it works out to about 20,000 btu per ton. My understanding is, bigger is not better, it needs to be matched to the heat loss of the house. That depends on materials, roofing, siding, insulation. It's not all that hard to calculate. (look online)

Lastly, HVAC contractors are the most crooked of all the trades. Don't trust them as far as you can spit. Only problem, you will need one to do the install. Like Gregsy said, you CANNOT buy a condenser without a license. (I tried, almost got away with it.)

DDoug · May 20, 2020

You take your outdoor woodstove, and refill it with an ammonia & water solution for the summer....just like a Servel unit....

Seriously, this guy is on the radio with callers asking these kind of questions:
Dieter The Heater | Canfield OH

GregSY · May 20, 2020

Here in Houston, even an 'overized' AC unit will run a loooong time before it shuts off.

The way I see it, nothing can begin to match the efficiency of a unit that is not running.

I would aggressively avoid buying any product with an inverter. Yes, they might offer some creature comfort benefits...right up until they break and you can't fix them. I find it very uncomfortable opening my wallet.

I recently tossed a 4-1/2 year old $3700 GE Cafe fridge because of its inverter-fed compressor. Even though some good troubleshooting verified it was the compressor, it didn't matter - the compressors, because they are inverter fed, are so expensive it was not worth fixing. An old school, normal compressor woulda been $300 installed. And probably wouldn't have broken in the first place. Of course, I did enjoy a $2 lower electricity bill each month thanks to the inverter fed compressor, and I trust they knew what they were telling me when they said my lettuce would be crisper.....

Gordon Heaton · May 20, 2020

Larry Dickman said:
. . . you CANNOT buy a condenser without a license. . .

That depends on where you are, I guess. I've never had a problem. It's more likely you can't buy refrigerant without a license. Most units these days come pre-charged with enough refrigerant to install with a 'typical' length lineset. All you need to do is install, vacuum and check the numbers in operation, which usually comes out in spec if the lineset was in the specified length range. Of course, there are things like inerting the lines before brazing, etc. that some might not be aware of, but still no biggie if you have the equipment.

Doozer · May 20, 2020

3 tons means equivalent cooling capacity compared to 3 tons of ice.

-Doozer

Guest · May 20, 2020

GregSY said:
I'll be interested in what you learn. The AC business is an interesting one in that it is a protected industry....through some careful greasing of palms many years ago, the 'professionals' have achieved governmental protection. If you are not 'licensed', they work to keep you from doing anything yourself other them writing a check to someone who is.

I found that out when Trane would not sell me parts to fix a unit myself. Total BS.

ignator · May 20, 2020

moonlight machine said:
Looking to upgrade the AC in my house, a cool wife is a happy wife and all that. Currently have a 3 ton R22 system in a 100+ year old victorian. I would like to get something more efficient. How do I know how efficient a system is? How are they rated. What's the deal with the new refrigerant? A3 ton, what does that mean? Any online places to get good prices? I can do the instal my self.

3 ton is 36000 BTU's per hour refrigeration effect. This was based on melting ice at one time, hence 1 ton of ice can produce 288000BTU melting (2000lbs at 144BTU/lb phase change from solid to liquid), at 24 hours this is 12000 BTUs/hr.
I would suggest a multi zone mini split system, 2-3 zones.
Brand is everything. Daikin still has a good name for reliability. And the inverter will keep the unit running as the air temperature is reduced, but continue removing humidity. It does this by throttling the speed of the compressor with an inverter. So over capacity of the system does not cause any problems.

A 2 zone unit:
36,000 Btu 17.7 Seer Daikin Multi Zone Mini Split Heat Pump System - 12K-24K 658515781206 | eBay

eBay search "daikin mini split".

edit;
The other solution is they are less expensive in non zone, if you can live with multiple condensing units outside. Also lets you reduce the plumbing length. However you never want to install a condensing unit in direct sunlight (south or west side of home).

crossthread · May 20, 2020

Here in Virginia they will not sell you anything if you don't have a license. I do have a license (class 11 and class 111) so I do a lot of straw purchasing for friends that just want a filter and jet for their oil furnace or something like that. It's total BS but that's the way it is. I can maybe see not selling a large amount of refrigerant that will kill our atmosphere.

moonlight machine · May 20, 2020

Well more good news, The problem with my AC is the evaporator coil is bad, supposedly new ones are not available for R22 systems. So I have to go with a whole new system. Here's another problem,I just found out my Lennox pulse furnace is too tall to put the new high pressure evaporator on top of. so now they are telling me I need a new furnace as well!

ignator · May 20, 2020

moonlight machine said:
Well more good news, The problem with my AC is the evaporator coil is bad, supposedly new ones are not available for R22 systems. So I have to go with a whole new system. Here's another problem,I just found out my Lennox pulse furnace is too tall to put the new high pressure evaporator on top of. so now they are telling me I need a new furnace as well!

Or find one surplus;
https://www.ebay.com/itm/Rheem-Ruud-3-ton-R-22-Indoor-Coil-Heat-Pump-or-SC-Evaporator-Coil/202808267411?hash=item2f38509293:g:m64AAOSwovNdtFMh

[url]https://www.ebay.com/itm/Advanced-Distributor-Products-M-Series-18-in-3-Ton-Evaporator-Coil-Air-Handler/133402581049?hash=item1f0f69d839:g:N40AAOSwSTJerHs0

[/URL]

gustafson · May 20, 2020

GregSY said:
I'll be interested in what you learn. The AC business is an interesting one in that it is a protected industry....through some careful greasing of palms many years ago, the 'professionals' have achieved governmental protection. If you are not 'licensed', they work to keep you from doing anything yourself other them writing a check to someone who is.

Imagine that....you don't need a license to buy alcohol, a circular saw, an electrical circuit breaker box, or a 75" swing lathe...but you need one to buy a relay.

As for sizing, there is this prevailing idea that you are better off installing a 'barely enough' system that runs all the time rather than one that is oversized and runs sometimes. I hear that a lot...and I think it's a crock.

A lot of it is just people protecting their own jobs, HVAC is the worst. GO to an HVAC site and watch what happens when a 'homoaner' asks a question

As for sizing, the tendency is to massively oversize, and that causes problems with not removing moisture. You are more comfortable at 80 degrees and dry than 72 degrees and damp

Many contractors work from outdated rules of thumb and end up with unhappy customers

I still suggest moonlight look at minisplits, or ducted minisplits if he wants to do some DIY

I have bought online from acwholesalers dawt com personally, worth checking out the pricing to see if it is attractive for what you want to do

markz528 · May 20, 2020

moonlight machine said:
Looking to upgrade the AC in my house, a cool wife is a happy wife and all that. Currently have a 3 ton R22 system in a 100+ year old victorian. I would like to get something more efficient. How do I know how efficient a system is? How are they rated. What's the deal with the new refrigerant? A3 ton, what does that mean? Any online places to get good prices? I can do the instal my self.

3 ton 14 SEER HEAT PUMP 410a Goodman GSZ14036+ARUF37C14+25FT Lineset INSTALL PKG | eBay

Between my buddies and I we have several versions of the Goodmans bought from these folks on ebay. Prices have gone up since I bought my 2 1/2 ton heat pump from them.

You basically need an EPA license. Google it - its quite easy to get. Spend another $1000 for a good vacuum pump, gages, micron gage, small nitrogen tank and regulator, 30 lbs of 410A refrigerant and ???? and go install it. With this investment you are still way ahead of the game.

The biggest things is you want to purge with nitrogen when brazing - need to silver solder with sil-phos - hopefully you know how. Many pros don't purge and that is a mistake. The other big thing is getting a very good vacuum to the micron level and then check properly for leaks.

Can be a little intimidating at first, but its pretty easy to find guidance and then you are not at the mercy of the HVAC folks price gouging you.

But Goodman won't warranty it of you install it yourself - I find that to be low risk given the huge cost savings.

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