time for a new ac - inverter or not

Larry (from OSHA)

The carrier condenser was new in 1988 with the compressor replaced in 1992 or 03 when it blew its guts (warranty covered). The air handler is even older probably 1970's or so and in the attic. I'm getting tired of feeding it a few pounds of R22 every 2 years and will be in this house for 10 more years or so. I've been looking at Bryant and Trane. I like the variable speed units for comfort and sound levels but I know nothing about inverter systems. I am leaning towards the Trane. I appreciate any and all input. Thanks.

pecmsg

Inverter technology is here to stay. Variable speed Leeds to better comfort. Installation is more critical as far as sizing and following manufactures recommendations.  The only negative is finding techs that can service them. 

ChrisJ

My personal opinion for a split system, 2 stage.

80% of the benefits of inverter without the price.

JUGHNE

Hopefully the central AC inverters are more service friendly then Mini-split AC/Heat pumps.

I just finished rebuilding a 2 head Fujsi.
Took 3 new boards and fan motor.

Mother board had 2 fuses soldered on the bottom side, both blown.
Instructions say to change board and fan motor if fuse blown.
PB had 11 tiny molex connectors on the bottom with limited wire length to lift board to unplug.

Just rerouting the cables is not friendly. Fortunately had another next to it to look at.

So for this repair, it may be less than 2 G's.

I believe power surges may have cooked the boards.

These are 11 years old.
New double head mini's not available until fall, is what I have been told.

Larry (from OSHA)

Thank you all for your comments. Yes this is a central ac system, 3 ton. Do any of you have opinions on your preferred brand? I like the Trane because of the air handler but even with 10 year warranty, reliability is important. I appreciate all points of view.

Thanks, Larry

JUGHNE

IMO, I would avoid anything with Micro channel coils, inside or out.

pecmsg

Larry (from OSHA) said:

Thank you all for your comments. Yes this is a central ac system, 3 ton. Do any of you have opinions on your preferred brand? I like the Trane because of the air handler but even with 10 year warranty, reliability is important. I appreciate all points of view. Thanks, Larry

The name of the installing contractor is more important then the names on the box’s. 

jumper

Inverter or not we'll need whole house power safeties.

TAG

I have used the Carrier/ Bryant Infinity 5 speed in my last 4 projects and put one at my beach house. I'm in the mid Atlantic and the 5 speed is a nice compromise between the 2 speed and the full variable speed Greenspeed. Greenspeed is what they call the top model in the Infinity line.

I did the first 5 speed back in 2015 ... all have been flawless. 5 speed uses a Toshiba rotary compressor. The original Greenspeed from Carrier was a Scroll compressor and the problem I had with that unit was the 1st stage was still 40% and the 5 stage could run down to 25%. Important in humid areas. I noticed last year they came out with a full variable speed Toshiba rotary compressor and were selling both the rotary and the scroll units in the Greenspeed line. Looks like they dropped the scroll compressor unit.

The full variable speed is more money but the 5 speed still uses the same infinity thermostat and matches up to the same air handler or furnace. I always zone my projects and the Carrier infinity zoning is really slick. Not a cheap set up.

It just so happens that all mine are 3 ton units. Carrier makes an odd unit that fits the midatlantic .... it's a 37k BTU unit. Basically a 3T in a 4T case .. the heat and cool curves fit the climate a tad better. In NJ you have to use it to get all the rebates and that's why I know they make it.

Hot_water_fan

Not sure of your location, but now’s a great time to go with a heat pump, it’s an extremely cheap way to give yourself a lot of heating flexibility. The carrier infinity series exceed at both heating and cooling. The inverter benefits are just as good on the heating side and that might cover more of your year depending on location. 

The Steam Whisperer

I don't do any A/C installs, but I have done sizing. I tend to prefer simple and a properly sized 2 speed is probably the best choice if the step capacities match up well. Low speed should be just enough to cover typical days. Make sure it is sized right for good dehumidificaton. With a decently insulated home and west side shading you probably only need about 1 ton per 1200 sq ft. We run a single one ton window unit and it cools a single story 1600 sq ft space to 72 to 73F and will lose a couple degrees when we are in the upper 90s. Air circulation is quite good so temperatures are pretty even all around. We have a single layer of face brick all around and r-15 walls, r-25 ceiling and Low e storms on the west ( which really help alot).

ChrisJ

The Steam Whisperer said:

I don't do any A/C installs, but I have done sizing. I tend to prefer simple and a properly sized 2 speed is probably the best choice if the step capacities match up well. Low speed should be just enough to cover typical days. Make sure it is sized right for good dehumidificaton. With a decently insulated home and west side shading you probably only need about 1 ton per 1200 sq ft. We run a single one ton window unit and it cools a single story 1600 sq ft space to 72 to 73F and will lose a couple degrees when we are in the upper 90s. Air circulation is quite good so temperatures are pretty even all around. We have a single layer of face brick all around and r-15 walls, r-25 ceiling and Low e storms on the west ( which really help alot).

Mine stays in low until the high 80s.  Usually 85-88 it runs continuous in low.  By the mid 90s it runs continuous in high.

Humidity control is superior in low with my system.  I often see a 22-24f drop across the evap in low.   If I turn dehu mode on it drops the blower speed more but the thermostat doesn't log the temperature then so I have no idea how much drop I get.

EBEBRATT-Ed

Trane is usually pretty good equipment. I am not a Carier fan. I agree with @JUGHNE I would not by a unit with microchannel coils

TAG

With closed foam and decent windows + 1000sf per ton AC in the mid Atlantic is not a problem. My PA retrofit is almost 4k and the 3T can keep it comfortable. It's sort of an odd place/ space and we have a couple mini splits that get used when there are parties or lots of people there. One is in the kitchen and another in a loft.

The interesting thing about the 5 speed is how often it's running on stage 1 and 2 .... most days it is on 2 much of the time and on days when it's high 70's out having that stage 1 to keep the humidity out is really nice. It will go to 3 in the afternoon and sometimes 4 if hot. It will also bump to 4 if I turn it down. It's got to be hot for 5 to show up. It's also very cool how the zoning works on the unit .... the dampers are always moving and the unit knows the cfm of the zones.

Larry (from OSHA)

Thanks for all the comments. I am in Minnesota so the variable unit is overkill and the 2 stage would probably work great. The price difference is low enough to do the 19 seer inverter unit. Please tell me more about your dislike of micro-channel coils since I don't know anything about them.

Hot_water_fan

@Larry (from OSHA) great spot for a multi-speed heat pump then - no need to put all your eggs in one basket

Larry (from OSHA)

No heat pumps in my future. My Knight boiler takes care of cold season heating. 

ChrisJ

Larry (from OSHA) said:

No heat pumps in my future. My Knight boiler takes care of cold season heating. 

How cold does it get there Larry?

Larry (from OSHA)

I built the system around a design day of -16 several years ago and it certainly gets colder than that now and then. 

ChrisJ

Larry (from OSHA) said:

I built the system around a design day of -16 several years ago and it certainly gets colder than that now and then. 

Similar to International Falls?

TAG

Back in 15 when I did the first 5 speed the only way to get the full rebate was with the heat-pump .. straight AC was actually more expensive. NJ has a very good rebate program

Anyway -- it's great having the heat-pump with the boiler. On those chilly shoulder season mornings when you don't need much more than 10 min of heat .... the heat-pump is just the ticket.

ChrisJ

TAG said:

Back in 15 when I did the first 5 speed the only way to get the full rebate was with the heat-pump .. straight AC was actually more expensive. NJ has a very good rebate program Anyway -- it's great having the heat-pump with the boiler. On those chilly shoulder season mornings when you don't need much more than 10 min of heat .... the heat-pump is just the ticket.

I really thought about doing a heat pump.
But then I realized if I wanted to go that route I could just run a gas line up to the attic and do a furnace instead of an air handler.   Then I realized I'd have forced hot air in my house and dumped the entire idea and did straight cool.

I'm not saying it made sense I'm just explaining what happened.

TAG

The Steam Whisperer said:

I don't do any A/C installs, but I have done sizing. I tend to prefer simple and a properly sized 2 speed is probably the best choice if the step capacities match up well. Low speed should be just enough to cover typical days. Make sure it is sized right for good dehumidificaton. With a decently insulated home and west side shading you probably only need about 1 ton per 1200 sq ft. We run a single one ton window unit and it cools a single story 1600 sq ft space to 72 to 73F and will lose a couple degrees when we are in the upper 90s. Air circulation is quite good so temperatures are pretty even all around. We have a single layer of face brick all around and r-15 walls, r-25 ceiling and Low e storms on the west ( which really help alot).

My first Carrier Infinity was about 20 years ago. Rehab of me parents American four square w/ large rear addition. When they added on the rear (1950's) a local old school oil dealer did all the ductwork and installed a wax bulb Honeywell zoning system --- 3 zones. I did not come along until the 60's and by the early 00's the replacement motorized dampers and Amana HTM were failing. The same oil dealer was still my service provider even though the place had been NG since the early 80's -- they recommended the Carrier system to me. At that time 2 speed was the only option but, they already had the advanced Infinity zoning. We ended up going with the Bristol compressor vs the Scroll due to the former being about to do about 50%. Some of the two speeds don't have a very low first stage. The system is still working today even with the problematic compressor .... sold the place to a friend. Now the ductwork in that house was spot on because it was done by real pros at the time and multispeed just made a good layout better ... in many houses with oversized systems and small ductwork ... the 2 speed units fix some of that and the ability to zone can really make for a comfort upgrade.

TAG

ChrisJ said:

TAG said:

Back in 15 when I did the first 5 speed the only way to get the full rebate was with the heat-pump .. straight AC was actually more expensive. NJ has a very good rebate program

Anyway -- it's great having the heat-pump with the boiler. On those chilly shoulder season mornings when you don't need much more than 10 min of heat .... the heat-pump is just the ticket.

I really thought about doing a heat pump.
But then I realized if I wanted to go that route I could just run a gas line up to the attic and do a furnace instead of an air handler.   Then I realized I'd have forced hot air in my house and dumped the entire idea and did straight cool.

I'm not saying it made sense I'm just explaining what happened.





That first heat pump was a home/ office I did back in the 90's. Big (almost 5k) midcentury brick extended cape ... it was a rambling mess and uncomfortable. Heat fix was a combination of slab radiant, retrofit underfloor plates and panel radiators. When I did it originally both ducted systems were AC only. It was only after I was forced to do the heat pump that I discovered how handy it was as there was no furnace. NG boiler.

My latest place in PA is all floor radiant -- originally, I was only going to go with a heat pump air-handler .... ended up going with a full Infinity furnace. In PA we only have Propane so the heat pump can be cheaper to run at some times. It also a part time place so the furnace could give faster warm ups and liked the idea of a second heat source.

With the small up charge and efficiency of modern heat-pumps they make sense ...The NJ energy program basically mandates them (rebate wise) ..... but, those with NG forced hot air are still going to find the HP more $$ to operate.

Hot_water_fan

those with NG forced hot air are still going to find the HP more $$ to operate.

Depends! Much cheaper for me last winter to operate a HP. This year it will not even be close. Probably 50% cheaper than NG.

ChrisJ

Hot_water_fan said:

those with NG forced hot air are still going to find the HP more $$ to operate.

Depends! Much cheaper for me last winter to operate a HP. This year it will not even be close. Probably 50% cheaper than NG.

Depends on what?
Are you comparing HDD?

Hot_water_fan

Depends on what?
Are you comparing HDD?

On rates of course. Yes, adjusted for HDD. Natural gas is straight up uneconomic in my area and that was before the recent price spikes - once an area has high AC market penetration and use, the electric distribution costs are spread out so much that they approach irrelevancy, so you're comparing gas cost (for electricity) to gas cost (for combustion on-site).

Specifically, $.13/kwh x (1,000,000/3412) / 2.7 COP (for me) = $14.11/mmBTU. For my 80% efficient furnace, gas must be $1.13/therm to break even. As our per therm distribution cost is $.70, that means supply must be $.43/therm or less. Right now, our supply cost is $.89/therm.

The actual consumption data comes to the same conclusion.

Larry (from OSHA)

ChrisJ said:

Larry (from OSHA) said:

I built the system around a design day of -16 several years ago and it certainly gets colder than that now and then. 

Similar to International Falls?

Actually, I just checked the latest design day temp for Minneapolis and it is -12. That seems too warm for my experience. Things seem to be getting more extreme with whatever you call climate change. I think International Falls is more like -20 but that is just a guess.

ChrisJ

Hot_water_fan said:

Depends on what?
Are you comparing HDD?

On rates of course. Yes, adjusted for HDD. Natural gas is straight up uneconomic in my area and that was before the recent price spikes - once an area has high AC market penetration and use, the electric distribution costs are spread out so much that they approach irrelevancy, so you're comparing gas cost (for electricity) to gas cost (for combustion on-site).

Specifically, $.13/kwh x (1,000,000/3412) / 2.7 COP (for me) = $14.11/mmBTU. For my 80% efficient furnace, gas must be $1.13/therm to break even. As our per therm distribution cost is $.70, that means supply must be $.43/therm or less. Right now, our supply cost is $.89/therm.

The actual consumption data comes to the same conclusion.

That's fine and all.
But I think you need to change your name to HP Fan. The funny part is, heat pumps have fans........

Larry (from OSHA) said:

ChrisJ said:

Larry (from OSHA) said:

I built the system around a design day of -16 several years ago and it certainly gets colder than that now and then. 

Similar to International Falls?

Actually, I just checked the latest design day temp for Minneapolis and it is -12. That seems too warm for my experience. Things seem to be getting more extreme with whatever you call climate change. I think International Falls is more like -20 but that is just a guess.

I've tried to get the wife to move to International Falls but she refuses.

I love the cold she hates it.

EBEBRATT-Ed

@Larry (from OSHA)

Microchannel coils are made like car radiators not the tube and fin coils we are used too. They have been out for maybe 10 years and most all the mfgs were going to them. Don't know about now. They were prone to leak and leaks on those coils are considered non reparable by most.

I think at least some mfgs got away from them.

ChrisJ

EBEBRATT-Ed said:

@Larry (from OSHA) Microchannel coils are made like car radiators not the tube and fin coils we are used too. They have been out for maybe 10 years and most all the mfgs were going to them. Don't know about now. They were prone to leak and leaks on those coils are considered non reparable by most. I think at least some mfgs got away from them.

I thought automotive condensers and evaporators have been microchannel for decades?

I know Goodman / Amana do not seem to use it.  I just put in an 18 SEER 2 stage Goodman and that's a copper / aluminum condenser.

Hot_water_fan

@ChrisJ I’m holding out for widespread air to water heat pumps

JUGHNE

IIRC, automotive condensers are thicker and subject to only the pressures of 134A.

410A can run 3 times that pressure and are thinner aluminum.

Larry (from OSHA)

Thanks for the explanation of micro channel coils. I don’t think I need to be concerned.

I’ve seen that there seems to be 2 configurations of air handlers, blower either before the coil or after. So either pushing or pulling through the coil. From what I’ve seen, condensate can be an issue when pulling and more attention needs to be applied to the trap and static pressure. Does anyone have any thoughts one way or the other?

ChrisJ

JUGHNE said:

IIRC, automotive condensers are thicker and subject to only the pressures of 134A. 410A can run 3 times that pressure and are thinner aluminum.

If you're seeing 540 psig on a 410A system something is horribly wrong.

I think I've usually seen 275-300.  About 100 psi higher than r134a.

Dave Carpentier

Larry (from OSHA) said:

I’ve seen that there seems to be 2 configurations of air handlers, blower either before the coil or after. So either pushing or pulling through the coil. From what I’ve seen, condensate can be an issue when pulling and more attention needs to be applied to the trap and static pressure.

This has my interest too. When I go a/c, my air handler is filter-Acoil-blower-heater.
I knew I'd have to set up a drip tray, but didnt think about the condensation potentially misting the blower.

Larry (from OSHA)

There are YouTube videos that show how to convert to horizontal right configuration. A handful of steps to the a-coil and a few other pieces. If done wrong it’ll screw it up considerably.

GW

Inverter- BMW or Mercedes, it’s rad, has pizazz, bells and some whistles 

scroll compressor- an Accord or Camry, it’s like the sun coming up every day, does the job  

life is great with the cool car until the German automobile needs service. I know! 

TAG

Forget some have cheaper electric. The mid Atlantic my electric is $ .1954KW and my gas is $1.27 therm ... so even at 85% gas and COP of three ... gas is cheaper.

1m BTU of electric = $5726 .... NG is $1494. The problem I have is my place in PA is propane and at $3.24 gallon we are looking at $4173. Have multi homes that you can view as a blessing or curse.

Would have liked to have found a setup for air air to water heat pump ...

TAG

GW said:

Inverter- BMW or Mercedes, it’s rad, has pizazz, bells and some whistles 

scroll compressor- an Accord or Camry, it’s like the sun coming up every day, does the job  

life is great with the cool car until the German automobile needs service. I know! 

What issues have you had ?

When I was looking back in 2015 the Greenspeed using the VS Scroll compressor made a very annoying inverter noise .... My installer took me to a couple installs and the high pitched "whine" coming from the unit would have annoyed me. The Carrier rep told us the unit had and was still going through some redesigns but he thought the 5 speed was a better fit for my application anyway.

It would be interesting to know the difference between the the rotary compressors in the Carrier units -- I was told back in 2015 that the five speed was all in the inverter. Not different windings. I wonder if the full VS is the same compressor with a more advanced Inverter?

That installer has done hundreds of them every years since and has had very few issues. Time will tell .... I do always add the labor onto the 10 year parts just in case

pecmsg

TAG said:

Forget some have cheaper electric. The mid Atlantic my electric is $ .1954KW and my gas is $1.27 therm ... so even at 85% gas and COP of three ... gas is cheaper.

1m BTU of electric = $5726 .... NG is $1494. The problem I have is my place in PA is propane and at $3.24 gallon we are looking at $4173. Have multi homes that you can view as a blessing or curse.

Would have liked to have found a setup for air air to water heat pump ...

A google search brings a lot of hits!