Ac In decision

Gordy

 I have a home with ceiling radiant ranch style. Been kicking around ditching the window shakers for AC. So my chices are mini split, High velocity, or conventional FA.



The Mrs. does not care for the Gaudy as she puts it mini split diffusers on the wall.

I don't particularly like the idea of HV, or conventional duct work in the unconditioned attic space, or the single return on the HV systems, which is really the best option for distribution piping through out the house. Basement does not have good acess to the whole house due to already finished ceilings.



Have looked at the concealed mini split diffusers.



Any other ideas/options.



Also I have been reading about these 21-28 seer mini splits but do not see those numbers for cooling only mini splits.



Gordy 

Techman

Gordy

Good Day to you! HV is good AS LONG AS it is installed properly, like anything else. You are not restricted to a single return,any isolated area [doors shut for privacy] should have its own return. The HV supply should be divided EVENLY,but at most undivided at 60-40%.,if a full circle supply trunk is not feasable.  Any  AC unit in the unconditioned attic, vent the attic, and mastic seal the ducts and use thickerer [ lol ] insulation.Mini's usually require several indoor units ,especially the bedrooms. Convential AC two stage ,hi SEER ,ECM indoor blowers, zoned[if needed] w/ dampers [PROPERLY] makes for a nice system.

Gordy

Thanks for reply

Attic is vented but it can still get pretty hot up there say 115*. This is a u shaped ranch, and a looped supply is feasable. Would you recommend HV or Two stage conventional? The two stage would give higher seer Than HV. Don't know if I believe the more moisture removed hub bub of HV being equal to a higher seer conventional.



Also plan on blowing in more insulation but thought if I wait to run ac duct work Blow insulation over that plus insulate ducts normally. Anything wrong with that?



Gordy

Techman

HV or Convential

Hi again. The  HV systems lower indoor humidity levels vs energy savings is true because you raise the indoor air temp a few degrees.The HV operates at a lower cfm/ton ratio w/ lower evap/air temps,vs.  a regular convential  AC system as long as you live in a hi humidity  area . The big advantage of the two stage units is they usually operate on 1st stage 70-80 % of the time,[as Dan says" DEPENDING "].1st stage being 67% of capacity and 2nd stage being 100%. There is another new compressor/condensing on the market that operates off of VFD by Danfoss, and it is variable speed.But I'm not physically familiar with them,just classroom knowledge .Sounded REAL good though.Attic at 115* isn't so bad,been there done that,still here!!!!!!!!The more insulation the better,definately seal the ducts, moisture and all that stuff.

Jack

on the Mini-splits

What I typically say is that the longer you live with them the better looking they become...because they are quiet, save money and they work. I went thru this at home and my wife was more than a bit opposed to the high wall evap. I put it in any way and she is thrilled with the comfort and quietness.

You do not have to put in high wall units in the ranch. You can do a multi and use the small ceiling cassettes, either 9, 12 or 18 kbtu. I have another place I am putting in two of them in a couple weeks to handle the second floor and I'll go high wall on the first. 22 1/2" square. They work very well.

NRT_Rob

got an ERV?

if so, maybe it's ceiling radiant cooling time

Gordy

Ribbing me

 Ya ribbing me Rob.No I don't have an ERV, Could put one in though. Midwest summers a little humid for ceiling radiant is my belief. If I'm going to control that much humidity to stay below dew point may as well AC it.....But if you have other thoughts please share, and elaborate.



Gody

NRT_Rob

some have done this in chicago

as long as all air in the home is dehumidified, it can work. run an ERV slightly unbalanced for positive pressure and then it's just the ERV airstream.



depends on your cooling load though. rad ceiling is supposed to be able to do 20-25 BTUs/sq ft of heat removal.



still need a chiller though. that plus ERV and dehumidification coil... and if you haven't needed an ERV because you're not that tight, it may not be a good idea. I am just in love with the concept lately

Gordy

Hmmmm

20Btus/sqft would get us comfy thats what I got in with window shakers. Losey gosey with four masonary fireplace chimneys, and 35% window area though. Thoughts Rob?  I'm wanting to experience some radiant cooling,



Gordy

NRT_Rob

I'm new to this gordy

be gentle



So far I've assumed a fairly tight envelope was a must... not sure how easy it is to stay "positive" on a loose envelope, and that's a key design element... if you have infiltration that doesn't go through the ERV, you can get pooched pretty quick.



Maybe you shouldn't be on the bleeding edge

GREG LAUER

option

Use a VRV heat pump and install a air handler in attic this will eliminate the issue with the Mrs's

Gordy

Greg

Air handler = duct work which I do not have.  If I do a FA system ductwork would be in the attic with diffusers in the ceiling. Just don't know if I like the idea of ductwork in an unconditioned space.



Gordy