air conditioning & duct replacement

Just a question on your Mini , most smaller hotels commonly use PTAC's which are noisey .
 
Breedlove said:
I built my own house it took a few years but as the person above said , if you want to really save money be efficient and really maintenance free go the route of the ductless mini split. ...
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Why would a mini-split be more efficient? Why maintenance free?

They aren't that different from a standard central A/C, just packaged differently. That could make installation cheaper, depending.

Generally, one large unit is more efficient than several small ones. And several small units have more moving parts than one central unit - seems like potentially more maintenance?

I suppose if you have rooms you don't need to cool, the mini-split might be cheaper to run? This can be accomplished (to a degree) by closing the ducts on a central A/C.

-ERD50
 
Go to you tube check out the new Mini splits.
1. no ductwork needed
2. Compressors are made to last as they do not run full blast all the time . When your whole house AC kicks on it runs full blast the mini's will modulate to match your temp demands . Depending on the size and how your house is designed ( ie ranch style ) you can get by with one handler and one compressor ( 2000sq ft home )
You can actually control the temps in individual rooms with one head Remote control temp .
HVAC has become a black art and it should not be .


A ductless mini split is not for everyone but for my money and my home it has been fine
 
Breedlove said:
Go to you tube check out the new Mini splits.
1. no ductwork needed
2. Compressors are made to last as they do not run full blast all the time . When your whole house AC kicks on it runs full blast the mini's will modulate to match your temp demands . Depending on the size and how your house is designed ( ie ranch style ) you can get by with one handler and one compressor ( 2000sq ft home )
You can actually control the temps in individual rooms with one head Remote control temp .
HVAC has become a black art and it should not be .


A ductless mini split is not for everyone but for my money and my home it has been fine
Click to expand...

I'd love to see some independent data on that.

"Compressors are made to last" - that strikes me as circular reasoning. They have less maintenance because they are built to last? And central A/C just aren't? Sources please, if you can.

You can buy central A/C that do not run "full blast". My new A/C is a two stage with full range variable speed fan (great for prioritizing humidity reduction when I want). I could have purchase a fully modulating A/C unit.

Talk about quiet - I literally cannot tell inside the house if mine is running w/o concentrating to try to hear/feel it. It runs at stage I most of the time, on stage II it is a little easier to detect, but just barely. Even outside the house, the compressor is right outside a window of my music room, and I can't hear it even if I strain - I have to look to see if I can tell if the fan is spinning. Ten feet away in my yard, the neighbor's A/C is louder than mine (theirs is maybe 40 feet away).

Individual room control is an advantage, but if duct adjustment is enough (and I think it is in many cases), then it is a mostly moot point.

I'm not saying mini-splits aren't right for some applications, just that your comments seem a bit out there for me.

-ERD50
 
Breedlove said:
Just a question on your Mini , most smaller hotels commonly use PTAC's which are noisey .
Click to expand...

Yes, those are much worse still. Don't get me wrong, my MIL's Mitsubishi Split is not as bad as the old window AC units used to be, but clearly, the mini room unit has to to turn over a significant amount of air in order to heat/cool (airflow is much higher than for vents in a ducted system (especially if the latter runs on a variable speed fan) and just the air movement itself creates significant noise. In addition, while the motors that drive the fan and adjust the louvers ARE very quiet, you definitely can hear them. All of this is ok, but not great, in my opinion, especially for a bedroom.
 
ERD50 said:
Why would a mini-split be more efficient? Why maintenance free?

They aren't that different from a standard central A/C, just packaged differently. That could make installation cheaper, depending.

Generally, one large unit is more efficient than several small ones. And several small units have more moving parts than one central unit - seems like potentially more maintenance?

I suppose if you have rooms you don't need to cool, the mini-split might be cheaper to run? This can be accomplished (to a degree) by closing the ducts on a central A/C.

-ERD50
Click to expand...

Actually the mini split units have variable speed compressors (which higher end regular units sort of 2 speeds for the higher end central ac units). This is done with an electrically commutated motor which also most modern air handler systems (the inside unit) have because it reduces the power used by the motor, but replacing the blower motor costs $700 or so.
 
meierlde said:
Actually the mini split units have variable speed compressors (which higher end regular units sort of 2 speeds for the higher end central ac units). This is done with an electrically commutated motor which also most modern air handler systems (the inside unit) have because it reduces the power used by the motor, but replacing the blower motor costs $700 or so.
Click to expand...

Yes, but as I mentioned, you can get variable speed compressors in a central A/C as well. I stopped at the two-stage with variable air handler, as it seemed like diminishing returns. We don't use our A/C a lot, but when we want it we want it to work well (handle a large crowd on a hot day, take out the humidity on a warm day).

From the article Texas Proud linked (which looked pretty good):

Of course, mini split AC systems do not come without their potential drawbacks. For starters, these units are not nearly as energy efficient as a forced-air system like central AC. In fact, according to Energy.gov, mini split AC units can cost 30% more to run than a central air conditioning unit.
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I suppose that is offset somewhat if you only need to cool a few rooms, and simple duct adjustments aren't adequate. OP will need to determine what is best for that situation, the mini-splits I think were being presented through rose-colored glasses.

-ERD50
 
Thanks everybody for all the good advice . While the mini system sounds tempting I am not sure if it would work in my house . The total size of the house is 3800 square. Feet 2800 is air conditioned and the living room is two stories high .
 
Moemg said:
Thanks everybody for all the good advice . While the mini system sounds tempting I am not sure if it would work in my house . The total size of the house is 3800 square. Feet 2800 is air conditioned and the living room is two stories high .
Click to expand...


It might.... I have a friend who has a very old house in Georgia... he put in mini split since it was not built with any AC... I think he has 3 stories and over 3,000 sf.... he said he needed it since the house would have huge temp differences with one standard unit... (well, also it would be a pain to put in ducts).....
 
I have bought and installed several heat pumps and gas furnaces I purchased from Ingrams Water and Heating on line. Both for my homes and rentals and well as commercial properties. They stand behind every order. Just an option for you to buy for a low cost and choose to install DIY or contract it out.

FWIW...I always buy the air handler with the GE varispeed motor, which drives to volume CFM required based on amps. The HP or AC unit should be dependent on cooling load in your case, and SEER is not as important as COP cooling. You should be able to buy a full AC system with strip heat, 3 ton or 3.5 ton high efficiency R410a 2 stage compressor and VS airhandler for <$2500. Install on ducts depends on your area and start up /Freon charge balance could cost $300 to $600. Being a mech eng still at heart, I tend to look at component quality, not the brand of products.
 
Back in 2010 I replaced the HVAC in my 1400 sq-ft tract house. No duct work except sealing. Tested good wrt leaks.

80,000 BTU/hr natural gas 95% efficient condensing furnace and 3.5 ton 15 SEER AC. Cost was $6700 installed. Nothing fancy, single speed York system.
 
We had another estimate today . It was $15,000 after several discounts .Guess who is not getting the job ?
 
samclem said:
If you really only use heat 7 days per year, I would go with heat strips (resistance heat) rather than a heat pump. Yes, resistance heat will cost a lot more to run, but the equipment will cost less and will be less complex (so, hopefully, more reliable).
Click to expand...

+1

As infrequently as you need heating, a heat pump is an unnecessary additional expense that may never pay for itself.
 
REWahoo said:
+1

As infrequently as you need heating, a heat pump is an unnecessary additional expense that may never pay for itself.
Click to expand...

I went with the heat strip unit . I only use heat maybe a few times each winter and rarely for the whole day .
 
RobbieB said:
Back in 2010 I replaced the HVAC in my 1400 sq-ft tract house. No duct work except sealing. Tested good wrt leaks.

80,000 BTU/hr natural gas 95% efficient condensing furnace and 3.5 ton 15 SEER AC. Cost was $6700 installed. Nothing fancy, single speed York system.
Click to expand...

Wow! That is way overkill for that square footage. Bigger is not better (in the case of HVAC).
 
It just a little bigger than what was in there stock, 60,000 BTH/hr and 3 tons. A lot more efficient though and the AC used to run constant when it was hot outside and now about 50%. The heater works good too and will raise the temp very quickly.

No need of programmable thermostats have I, just walk over and turn it up or down, don't have to wait long at all. It gets to freezing here in the winter, I'm not in San Diego and it gets hot here in the Central Valley summertime.
 
RobbieB said:
.......... the AC used to run constant when it was hot outside and now about 50%. ............
Click to expand...
In high humidity areas, having the AC run almost constantly is a good thing, as it allows the AC to dehumidify as well as cool the house.
 
This is not a high humidity area.
 
travelover said:
I was posting that for the benefit of the OP, who loves in Florida.
Click to expand...

I agree that with A/C size matters with regards to humidity removal, but I don't think the OP's love life should be discussed in a public forum.

-ERD50
 
ERD50 said:
I agree that with A/C size matters with regards to humidity removal, but I don't think the OP's love life should be discussed in a public forum.

-ERD50
Click to expand...
You are right . On reconsideration, we should only be aware that she lives in Florida. :LOL:
 
Moemg said:
We had another estimate today . It was $15,000 after several discounts .Guess who is not getting the job ?
Click to expand...
We paid that for two complete Rheem systems. That included duct cleaning, wireless transmitters, thermostats, 2.5 ton, 80k btu furnaces. This is not high efficiency but has ECM blowers. We dropped from top quintile of gas users to the bottom.

For OP, it may help to look at duct replacement as a separate issue.
 
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