HVAC central air in particular

[cornutt]

We built our house 12 years ago and specified three heat pump units, with strip heat secondary (no gas service in our neighborhood) for three zones. The builder put in Frigidaire units, two 2.5 ton and one 3.5 ton. The larger unit was problematic from the start; the installer didn't get the line pumped down properly, and I had to call a veteran HVAC guy that I knew to evac and recharge it. It has also needed a defrost board and coil temp sensor, and I had to replace the outdoor fan motor and run capacitor on all three units. Three years ago the larger unit started leaking and the indoor coil was too corroded to be repaired, so the entire thing got replaced with a two-speed Carrier Infinity system. So far that system has been perfect, and we have seen a bit of improvement in our utility bills.

Cooling is no problem since the units, being heat pumps, are oversized for cooling. The house has an HAI/Leviton home automation system, so that controls all three units.

 

[artcurus]

about 2007 Carrier with Puron.
Lately it's been running really humid inside the house, but I replaced the filter and it seems to be doing better. I do need to clean the evap coil. It will cool the house down and works well during hot, humid days. The eco friendly refrigerant doesn't have the same air feel at all as my bedroom 2003 Friedrich room a/c with R22. I love that Friedrich.

 

[gusherb]

It seems there is a stigma associated with R410A vs R22 and R410 not running as cold as R22 or performing as well overall. The real difference is actually the design of the system and not the refrigerant. Higher SEER systems rely more on larger coils for their capacity and efficiency and operate on smaller compressors. What this means with larger coils is a much lower delta T (warmer indoor coil and cooler outdoor coil) which effects the latent capacity of the system therefore resulting in less dehumidification than before. With the higher efficiency systems this also means that they need to be kept clean and made sure they're getting proper airflow more so than old systems because capacity will drop off faster due to the use of smaller compressors. Older systems had a higher tolerance for this because the compressor was much larger.

In real world use a 13 or 14 SEER system will perform about the same as a 10 SEER system In terms of latent cooling. It's when you get above 15 SEER that what I explained starts coming into the equation. We have two 13 SEER R410A systems at home that replaced two 1990 model R22 9 SEER systems, in real world use the new systems function exactly the same as the old ones but much cheaper to run. I still get about 52 degree air out of the vents which is a 20 degree delta T, just like the old systems. The evaporators are matched exactly to the condensing units (keep an eye on that, some system configurations require oversized evaporators to meet efficiency requirements to get utility rebates). An An oversized evaporator will result in reduced latent cooling.

As for window units, I've yet to see any R410 model that doesn't perform the same or better then it's R22 counterpart. I had a 12,000 BTU R410 GE (rebadged Electrolux) that blew 29 degree air, or a few different LG's that blew in the lower 40s. I don't think you can get much colder than that without a freeze up.

I noticed something new at the Homo Depot the other day speaking of window units, the LG they were selling said it had R32 refrigerant in it...

 

[gusherb]

[No message]

 

[washman]

I follow ya GusHerb

to a point. Including my digs with a matched Goodman furnace, air handler, coil, and outdoor unit along with 2 co-workers who also have 410a systems, I can say for sure the 25 year old Heil unit at the condo cooled much quicker than the 410 units.

Having said that, it is hard to go totally apples to apples, because my ductwork in my new digs is entirely in the attic. And it sho gets hot up there. In the condo, the ductwork was in the floor as are 2 co-workers digs.

Once the Goodman has run for a few, the air is indeed nice and cold and I don't see excessive cycle on times to bring down the temp from say 79 to 76 (when I get home) or to maintain a constant 76.

One year and 16 mortgage payments in, I am satisfied with the Goodman setup. Let me get back to you in 5,10,15 years with a more accurate assessment of the reliability of the thing. Recall that in the 15 years I lived at the condo, neither the furnace nor the AC needed any kind of repair. And yes, I used them both to whatever extent was necessary to stay comfortable.

 

[gusherb]

You see, the refrigerant has no effect on how quickly the system cools, starts to cool, etc. it's all in the design of the system, whether it has a piston or TXV etc etc.
Both our systems have TXV's, the attic system pretty much within 10 seconds of it starting from hot you can feel the outlet air cooling down, it starts to cool quite quickly. The downstairs system takes longer to start blowing cold, despite being a TXV system as well, could be because that condenser has a Climatuff scroll compressor in it while the upstairs unit has a rebadged Copeland scroll, could be the way the TXV functions. I'm not sure exactly.

The 25 year old Heil probably was oversized and of course ductwork in conditioned space makes a pretty significant difference in efficiency.

I think I forgot to mention, the system at work has a 13 year old 3 ton 10 SEER Heil with a matched 3 ton Heil coil on a piston. I don't notice any real difference in performance from it to the 13 SEER systems at home. One characteristic of a fixed metering system is that they cool better the hotter it gets/higher the head pressure gets, that is the only difference I notice between that system and the ones at home is that it tends to blow colder when it's real hot out.

 

[washman]

Piston on mine

not sure if the condo was TXV or nor. Being that it was rental, I would go with piston.

I did verify mine is right sized for the evap coil and condenser. Once it gets percolating, it puts out cool enough air. Like I said, it does not run excessively long or frequently to keep 76 on an 85 degree day or above.

 

[gusherb]

That might be why yours takes longer to start cooling, since with a piston the high side has to build pressure before it starts to cool. I think most TXV's hold the high side pressure when it's off so as soon as it kicks on it just starts cooling.

 

[circlew]

Gibson

I was surprised to see this brand on a central air unit that was recently installed at a home a few blocks from me.

I looked it up, and found it is a Nortek brand. They license the Electrolux owned brands, which also include Frigidaire, Kelvinator, Tappan, Philco & Westinghouse.

They also have the rights to the Maytag name for HVAC.

Nortek is the parent company of Broan-NuTone, in addition to several other brands.

 

[washman]

Nortek used to be Nordyne

a major supplier of HVAC to the mobile home industry. Miller and Intertherm are two known brands.

Nortek is fond of microchannel "technology" (read: cheap) and has 2 facilities in Mexico in addition to a non union facility in Dyersburg, TN.

FWIW after going back almost 40 years of headaches with the Intertherm furnace in our 1974 mobile home, plus what I have read on so-called microchannel "technology" I would not purchase any of these units. Add to that an increasing number of units are coming out of Mexico pretty much seals the deal for me should I need to replace the non-union Goodman outdoor unit.

(pretty asinine how they are slapping the word "technology" on a condenser design that has its roots in the 1970's on automobiles)

 

[gusherb]

I think Nordyne is pretty universally hated in the HVAC industry. Apparently their support is horrible.

 

[washman]

I concurGusHerb

based on HVAC forums, Nordyne closely followed by York products have a less than stellar reputation, mostly due to both using microchannel condensers.

 

[gusherb]

My first day back in town and it hits 95 degrees. Both Tranes are merrily chugging away keeping the downstairs 73 and upstairs 72. The downstairs runs continuously about this time because of the sun hitting the side of the house with the thermostat, and the upstairs cycles partly because it's oversized by about 6,000 BTU's (half a ton) and it's shaded right now. If it got to 110 it would still hold 72 im sure.

Edit: Fixed Freudian slip [this post was last edited: 6/10/2016-21:33]

 

[DADoES]

 
12,000 BTU is one ton, yes?

 

[washman]

Yes DADoES

12000 BTU = 1 ton.

 

[gusherb]

My bad, I meant 6,000 BTU's! Glad you caught that. It should be a 2.5 ton system not the 3 ton that it is.

 

[twintubdexter]

I decided to give my 2 American Standard units some shade, although from what I've read this does little to make them operate more efficiently. They're on the west side of my house which gets smokin-hot in the summer. I'm hoping they'll relax and think they're poolside at some resort. They are predicting 120 for Monday, maybe higher. At those temps you don't fry an egg on the sidewalk, you roast a turkey.

 

[iheartmaytag]

My central unit is on the North side of the house, so hence is exposed to the direct sun during the hottest part of the day.

 

There have been a few times that I felt sorry for it chugging away and sat the sprinkler by it so it was misted with cool water.  It seemed to cool better, don't know if it worked any more efficiently.

 

 

[circlew]

When the temp get above 90 or so, the washateria I go to sprays their outside AC unit with water. They have a hose & nozzle clamped to a pipe that's aimed at it.

 

[warmsecondrinse]

"... therefore resulting in less dehumidification than before."

 

I would guess that this is a large part of the reason for people living where summers are hot and humid insisting that their new 12,000 btuh air conditioner doesn't cool as well as the 10,000 unit it replaced? 

 

Jim