[elky] Re: Summer....
- From: Robert Adams <elcam84@xxxxxxxxx>
- To: elky@xxxxxxxxxxxxx
- Date: Sat, 9 Jul 2011 09:44:38 -0500
The two stage or variable ones run pretty much constantly
which is more efficient cause it reduces start ups and maintains temp
instead of trying to knock it down all at once. The problem is when you do
a manual J for AC sizing it doesn't take into account 100*+ summer temps
here and humidity. Yes it slightly oversizes it in it's numbers but not for
our extreme temps. The problem with oversizing old single stage systems was
short cycling. With staged this isn't really an issue.
In our weather here I prefer to run an oversized
unit. In the hot part of the summer set the thermostat to keep a 2*
differential and when it's cooler out set it to 3* or 4*. So in cooler days
it'll drop the air temp say 4* instead of the standard 2* and eliminate
short cycling. But not all stats will do that and most you have to reprogram
that temp manually.
Our system is actually sized pretty close and I'm getting
15-20* temp drop across the coils, closer to 15 when it's 105-110* outside.
The air out of the condenser is about 120-130* or so. We have rockwool
insulation everywhere with blown in in the attic but nowhere near enough up
there. The house is brick too which really hurts. It sucks up heat and stays
hot all night.
Running the numbers for the attic insulation... In
fiberglass blow in it's going to be about $700 and cellulose about $500 just
materials. The average recommended R value in the attic here is 45(30-60).
So would need about 70-80 bags of cellulose to
get R45 or something like 25 bags of owens pink blow in....
We have 3 gable vents and two whirly birds. I am going to
put a powered fan in the south facing gable which is in the center of the
house. Ridge vent does help but it flows very little air for the cost and
you still need whirly birds or other vents on the attic to get enough flow.
Soffit vents are always a benefit too. I have to put those in still. I put
in 52 on my parents house and it only has ridge vent and we are going to put
a powered vent on the roof cause it needs it... It had two before it was re
roofed.
I found a local place that sells the reflective film cheap
cause they are cosmetic damaged. I plan to put it on the roof rafters all
the way tight to the top plate to serve as my air channel to the soffits and
keep insulation out of the soffits.
Anyway. Benadryl kicking in and to take a nap.
Robert Adams
On Sat, Jul 9, 2011 at 8:56 AM, Chris Lindh <chris@xxxxxxxxxxxxxxxxx> wrote:
> AC experts recommend smaller, more efficient systems now, and they
> want the fan running all the time. They want the air "changed" more
> often. I don't like the white noise of the fan running all the
> time... but I guess I understand if you want X temperature then a
> system running more often is more likely to keep the temperature
> closer to the goal.
>
> The blown in fiberglass we had done was the best $700 I ever spent.
> When we have to do the roof I'll get a ridge vent too.
>
>
> Rules: Please play nicely with others.
>
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