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Posted by stevek on March 1, 2007, 11:28 pm
I'm looking to install a new central system, and amongst the many
variables out there, I have one quandary.
First the background (skip right down to the question, if you'd like):
I'm in the NYC area, where humidity isn't a huge problem, (but it's an
annoyance), and electricity prices are a problem.
I'm quite interested in a two stage system with humidity control for
this reason.
I've had a couple of contractors come around and, they haven't done
manual J yet, but they both estimate I need about 3.5 tons. One gave
me quotes for a 4T single-state 15 SEER unit, and a 4T 21SEER unit
(carriers), and another was pushing the "comfortmaker" at 3.5T 15SEER.
It seems comfortmaker is carrier's unbranded line, and they do offer 2
stage units, and I've looked things up, and you can get a c4a648gka
with either FVM4x48 (16 SEER total) or fvm4x60 (16.5 SEER total), and
these both can take humidity controls to run with slightly lower fan
speeds for humidity control, etc.
The problem is, it seems that the two-stage units don't actually come
in 3.5T..
My logic is, that with a two stage unit, a little oversizing isn't as
bad for either humidity, or energy usage: It just means you'll be
running on the low stage a bit more than the high stage.
Is that logic right?
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Posted by on March 2, 2007, 12:37 am
Look with-in for my replies...
>
> I'm looking to install a new central system, and amongst the many
> variables out there, I have one quandary.
>
> First the background (skip right down to the question, if you'd like):
>
> I'm in the NYC area, where humidity isn't a huge problem, (but it's an
> annoyance), and electricity prices are a problem.
>
> I'm quite interested in a two stage system with humidity control for
> this reason.
>
> I've had a couple of contractors come around and, they haven't done
> manual J yet, but they both estimate I need about 3.5 tons.
No manual J, they recieve No work!!!!!!!!!
> One gave
> me quotes for a 4T single-state 15 SEER unit, and a 4T 21SEER unit
> (carriers), and another was pushing the "comfortmaker" at 3.5T 15SEER.
>
> It seems comfortmaker is carrier's unbranded line,
Not exactly true...
United Technologies owns two divisions Carrier and ICP ('International
Comfort Products' formally 'Inter-Cirt Products')
Under the Carrier branch falls 'Carrier, Bryant and Payne' (they no longer
use Day & Night)
The Carrier products are very similair, but each brand has it's own little
differences.
Under the ICP branch falls 'Arcoaire, Air Quest, Comfortmaker, Heil,
Tempstar, KeepRite, ICP International, ICP Commercial' (many other names
were used previously, like Whirpool, Sears, Heil Quaker, Etc)
The ICP products are practically the same from one to the other. There are
very little cosmetic changes from one to the other.
> and they do offer 2
> stage units, and I've looked things up, and you can get a c4a648gka
> with either FVM4x48 (16 SEER total) or fvm4x60 (16.5 SEER total), and
> these both can take humidity controls to run with slightly lower fan
> speeds for humidity control, etc.
You don't want to use a larger evaporator coil, if your whole concern is
humidity removal.
So in short, forget the FVM4X60 with the .5 higher S.E.E.R. rating. Getting
the matching FVM4X48 is the better choice.
> The problem is, it seems that the two-stage units don't actually come
> in 3.5T..
> My logic is, that with a two stage unit, a little oversizing isn't as
> bad for either humidity, or energy usage: It just means you'll be
> running on the low stage a bit more than the high stage.
>
> Is that logic right?
Yep...
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Posted by udarrell on March 2, 2007, 9:08 am
stevek wrote:
>I'm looking to install a new central system, and amongst the many
>variables out there, I have one quandary.
>
>First the background (skip right down to the question, if you'd like):
>
>I'm in the NYC area, where humidity isn't a huge problem, (but it's an
>annoyance), and electricity prices are a problem.
>
>I'm quite interested in a two stage system with humidity control for
>this reason.
>
>I've had a couple of contractors come around and, they haven't done
>manual J yet, but they both estimate I need about 3.5 tons. One gave
>me quotes for a 4T single-state 15 SEER unit, and a 4T 21SEER unit
>(carriers), and another was pushing the "comfortmaker" at 3.5T 15SEER.
>
>It seems comfortmaker is carrier's unbranded line, and they do offer 2
>stage units, and I've looked things up, and you can get a c4a648gka
>with either FVM4x48 (16 SEER total) or fvm4x60 (16.5 SEER total), and
>these both can take humidity controls to run with slightly lower fan
>speeds for humidity control, etc.
>
>The problem is, it seems that the two-stage units don't actually come
>in 3.5T..
>
>My logic is, that with a two stage unit, a little oversizing isn't as
>bad for either humidity, or energy usage: It just means you'll be
>running on the low stage a bit more than the high stage.
>Is that logic right?
>
>
The summer design for NYC Central Park area is 89-design dry bulb,
73-design wet bulb.
Madison, WI is 88-DB & 73-WB.
The number of run-time hours in the NYC area is not enough to justify
buying ultra high SEER rated A/C equipment.
I had a graphic of run-time hours across the U.S. but misplaced it.
I would insulate and do everything possible to reduce the heat-loss &
heat-gain because that will save on energy costs the year around.
Proper sealing will reduce air infiltration to a minimum & thus reduce
the humidity latent load to a small load effect.
In my opinion, that is your best payback option.
Unless the ductwork & airflow is right you will gain nothing, & lose on
payback, with ultra high efficiency high cost equipment.
http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
- udarrell
--
WISDOM PRINCIPLED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and PEOPLE EMPOWERMENT
http://www.udarrell.com/
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Posted by udarrell on March 2, 2007, 9:17 am
stevek wrote:
>I'm looking to install a new central system, and amongst the many
>variables out there, I have one quandary.
>
>First the background (skip right down to the question, if you'd like):
>
>I'm in the NYC area, where humidity isn't a huge problem, (but it's an
>annoyance), and electricity prices are a problem.
>
>I'm quite interested in a two stage system with humidity control for
>this reason.
>
>I've had a couple of contractors come around and, they haven't done
>manual J yet, but they both estimate I need about 3.5 tons. One gave
>me quotes for a 4T single-state 15 SEER unit, and a 4T 21SEER unit
>(carriers), and another was pushing the "comfortmaker" at 3.5T 15SEER.
>
>It seems comfortmaker is carrier's unbranded line, and they do offer 2
>stage units, and I've looked things up, and you can get a c4a648gka
>with either FVM4x48 (16 SEER total) or fvm4x60 (16.5 SEER total), and
>these both can take humidity controls to run with slightly lower fan
>speeds for humidity control, etc.
>
>The problem is, it seems that the two-stage units don't actually come
>in 3.5T..
>
>My logic is, that with a two stage unit, a little oversizing isn't as
>bad for either humidity, or energy usage: It just means you'll be
>running on the low stage a bit more than the high stage.
>Is that logic right?
>
>
The summer design for NYC Central Park area is 89-design dry bulb,
73-design wet bulb.
Madison, WI is 88-DB & 73-WB.
The number of run-time hours in the NYC area is not enough to justify
buying ultra high SEER rated A/C equipment.
I had a graphic of run-time hours across the U.S. but misplaced it.
I would insulate and do everything possible to reduce the heat-loss &
heat-gain because that will save on energy costs the year around.
Proper sealing will reduce air infiltration to a minimum & thus reduce
the humidity latent load to a small load effect.
In my opinion, that is your best payback option.
Unless the ductwork & airflow is right you will gain nothing, & lose on
payback, with ultra high efficiency high cost equipment.
http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
Do NOT Oversize the unit! Longer run times to reduce costly cycling is
paramount to efficient operation & does more toward reduction of
humidity than slowing the blower speed on oversized short-cycling
equipment!
Take the other gentlemen's advice & Require a manual J, D for ductwork,
& S for equipment Sizing.
In your climate I would rather have the condensing unit slightly
undersized than oversized!
- udarrell
--
WISDOM PRINCIPLED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and PEOPLE EMPOWERMENT
http://www.udarrell.com/
http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
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