load calc calls for 2.5 ton, but go with 2 ton?

[hmmm]

according to contractor's load calc, a 2 ton condenser would be slightly undersized for the 2nd floor of my house. however it would be matched with a 2.5 variable blower and would be a good system for dehumidification.

here's my qustion: other contractors have suggested a 2.5 ton condenser, whereas this latest contractor suggests going with a 2 ton condenser and then installing gable fan(s) in the attic to blow out the 140+ degree air from the attic which he says should offset any undersizing of a 2-ton unit on the hottest days. sounds reasonable to me, but thought i'd throw it out there for a sanity check....

[beenthere]

A 2.5 ton condenser and a VS blower set up right will also give you good humidity control.

Might still want to install the gable fan.

[andserco]

Is this an existing house?

If the contractor went to the trouble to do a heat load, why dont they go with the results..:confused:

[beenthere]

Is this an existing house?

If the contractor went to the trouble to do a heat load, why dont they go with the results..:confused:


My guess, is he's trying to be low bidder.

[hmmm]

beenthere:

that's true. guess i should find out what the $ differential is between a 2 ton and a 2.5 ton. maybe not that much.

in terms of setting up right a VS blower with the condenser, in another post someone made the point that you have to have 2-stage condenser or else a VS blower isn't worth it. is this true? i hadn't seen that comment elsewhere and noone disputed/commented on this assertion. almost all of the proposals i've received include 1-stage condensers with VS blowers and even when i pressed the contractor today on this point, he said a one-stage condenser unit + a VS blower + VisionPro 8000 controls would work very well for dehumidication. does anyone else think a 2-stage condenser (which seems to significantly add $$) is necessary (ie., I'm wasting $$ on a VS blower without one)

andserco:

i hear your point. the calc showed that a 2 ton unit was only barely undersized. i think this contractor (who really seemed like a good guy and a good outfit) is just trying to be appropriately sensitive to my budget. the way he put it was something like, on a 95-degree day (and we only get so many of those fortunately in Conn.) this unit may only get you down to 75 degrees inside but with 55% humidity.....

[hmmm]

and yes, existing house.

[andserco]

IMO- ask him about the 2 1/2 ton, for the price, since it is an existing home , have him verify the existing ductwork is sized and installed correctly because if it not, it doesnt matter what size unit you have.....

On the dehumidification, the 8000 series is a good choice, there is several different models only one that will attempt dehumid mode, but my perference is the Honeywell IAQ series, it is almost the same as the 8000, but it control the fan a little different in the dehumid mode and it has some ventilation features that will also help in the overall comfort...But as usual they are more expensive... Good Luck........ come back and let us know how it goes.....

[beenthere]

Using a single stage condenser with a VS blower may get you to the next SEER rating.
Even with a single stage condenser, a VS blower enhances humidity control.

So, NO, you don't need a 2 stage condenser to get value from a VS blower.


I would sugest teh Honeywell IAQ thermostat over the Honeywell 8321.
The IAQ can run the A/C and slow down the VS blower to aid in humidity control.
The 8321 can only run the A/C and over cool to dehumidify.

There is a price difference, but it can be worth it.


The contractor that you "think is being sensitive to your buget", may be determining what your buget is for you, and what level comfort you deserve.

Thats your decision, NOT his.


Get the prices for the different systems, and then deside what your personal comfort in your home is worth to YOU. And if your buget can handle it.

[hmmm]

will certainly do. thanks.

when you say there is only model that will do dehumid well, which model in the 8000 series are you thinking of? would love to know.

i'm also going to ask about the honeywell control too as i have heard good things about this one before

btw, there is no existing duct work in the house and listening to each of the guys explain the design, fabrication, installation process has been a key area of focus for me. i totally get it that installation is king. this guy today talked about how the entire trunk line in the attic will be a long run of galvanized steel (with the blower sitting in the middle) with as small as possible branches running from it (as opposed to a short trunk with a bunch of flex piping). so i gave him points for that.....

[andserco]

Yea...........What Beenthere said..............:D :D :D :D

[hmmm]

each time i type you guys beat me to the punch. that's great.

all good points again, and thanks for the confirm regarding the 1-stage condenser (as the 2-stagers and all that came with them had me wondering which lottery tix i was going to have to buy...)

andserco, is the 8321 model that beenthere mentioens the same one you were thinking of? i am going to try to go the honeywell iaq route, but for some reason if have to "settle" for the visionpro, is want to make sure i'm getting the best model. thanks again.

[pstu]

>>...and then installing gable fan(s) in the attic to blow out the 140+ degree air from the attic...

If you simply exhaust air from the attic as nearly everyone does, there WILL be an equal amount of air entering the attic from somewhere. What guarantees it will not be from the house, leaking from the ceiling just under the attic?

If you are in a dry climate I guess that might not matter as much as in a humid one. I am in S.Texas, a homeowner who is concerned about random air infiltration.

Best wishes -- Pstu

[aircooled53]

I have tried using 2.0 ton condenser with larger coils on upstairs applications and didn't work very well. The amount of lift and length of line-set can pose a problem with small conmdensers.
\\I did home with 3.5 ton downstairs and 2.5 ton upstairs and used 2.ton condenser and found that we had alot of issues with keeping comfort level on HOT days. We changed out condenser with 2.5 ton and customer says it works great with the added 1/2 ton.

[beenthere]

Currently, the Vision Pro 8321 is the only 8000 series thermostat that can cool to dehumidify.

[hmmm]

>>...and then installing gable fan(s) in the attic to blow out the 140+ degree air from the attic...

If you simply exhaust air from the attic as nearly everyone does, there WILL be an equal amount of air entering the attic from somewhere. What guarantees it will not be from the house, leaking from the ceiling just under the attic?

Pstu

for a moment there i thought you were going to say that it wouldn't work because so many people are doing the same, which had me smiling

in my case, my sorry old house (apologies to my house) fortunately has lots of insulation on the floor of my attic (everyone who inspects the attic seems to point that out), so hopefully air seeping from 2nd floor into attic will be minimal

[beenthere]

>>...and then installing gable fan(s) in the attic to blow out the 140+ degree air from the attic...

If you simply exhaust air from the attic as nearly everyone does, there WILL be an equal amount of air entering the attic from somewhere. What guarantees it will not be from the house, leaking from the ceiling just under the attic?


Best wishes -- Pstu

If he would have said a mushroom fan, I'd be alittle worried.
But most gable fans are installed that they only exhaust have of their rated CFM. The rest comes bounces back from the gable lovours.


But your point is well put.

[andserco]

""but for some reason if have to "settle" for the visionpro""

Thats a good one--"settle" for a Vision Pro......:D

IMO-The two that has been mentioned are both excellent, Beenthere explained the difference in the operation of the fan, The IAQ just does it better and has a few more options. Hopefully your contractor can explain the differences.....

[hmmm]

easy to offend when you don't know what you're talking about ;)

wait a minute, in addition to offending, i think i just contradicted myself. i made the argument that blowing air out of my attic wouldn't compromise the cooler air inside the house b/c of a lot of insulation on the floor of the attic, yet the goal is to blow the hot air out of the attic so that it isn't "heating up" my house. uughhh

[beenthere]

""but for some reason if have to "settle" for the visionpro""

Thats a good one--"settle" for a Vision Pro......:D




LOL...

Exspecially when you consider that its not that much less then the IAQ.

I wouldn't exactly call it settling. :)