HVAC guy in North Jersey?

[Malsua 1,422]

I'm looking at putting in a Mini-split in my new construction. The walls are still open...for now.

 

My issue is that I simply don't know how to size the AC. Manual J you say? LOL. How do you calculate a room with 14 foot cathedral ceilings that ends in a balcony that drops 10 feet to another room? I did the heat loss calculation for my house for sizing the boiler and there's just no way to get it right as the living room essentially has a 24 foot ceiling on one end and an 8 foot ceiling on the other. All the heat goes up to the bedroom. By contrast...the AC will spill down the wall to the 14x22 bedroom, then continue on and spill right over the balcony and down the stairs which are at one end of the floor. The stairs aren't in yet. It's the big hole.

 

I'm not going to put AC in all rooms, all that I'm after is just to bring the temp down in the bedroom area.

 

Suggestions?

 

Here's a pic looking up and one looking down. stairs will have a bookcase/nick nack thing on 3 sides and the balcony will have a railing. This will help dam up some of the air. The room to the right(right on first pic, left on 2nd) on the 2nd floor will be closed off and that's it. It's a big open space. The AC will be high on the wall, all the way at the big windows at the top of the wall on the right in the first pic.

 

 

[tommy3rd 132]

if it was up to me, i'd just get the biggest window or wall AC i can afford, specially if all you're looking for is to cool the bedroom area. If you want to plan for the future, then I would put in the duct work and plumbing throughout the place while all the walls are open and plan to get central AC sometime.

[Dan 177]

I'm not an AC guy, but I stayed in a Holiday Inn express..

 

Kidding aside, I've spent the past month researching and having multiple contractors provide me quotes to upgrade my entire home HVAC system.

 

From my understanding mini-splits are mostly used when you can't get proper duct work in easily as in old homes, or ones with solid walls... or you just need to cool a small area. If you want to cool your bedrooms, why bother cooling the staircase loft area that opens to the living area below? Why not look at an attic unit and ducts that would feed all of the upstairs bedrooms with the single unit?

[Malsua 1,422]

if it was up to me, i'd just get the biggest window or wall AC i can afford, specially if all you're looking for is to cool the bedroom area. If you want to plan for the future, then I would put in the duct work and plumbing throughout the place while all the walls are open and plan to get central AC sometime.

 

I have casement windows so window units are out.

 

We're not going to ever put in Central, it's simply not necessary. We really don't have a good wall for a wall unit. We did....but a window moved so that eliminated that option.

 

From my understanding mini-splits are mostly used when you can't get proper duct work in easily as in old homes, or ones with solid walls... or you just need to cool a small area. If you want to cool your bedrooms, why bother cooling the staircase loft area that opens to the living area below? Why not look at an attic unit and ducts that would feed all of the upstairs bedrooms with the single unit?

 

Attic? What attic? heh. The only thing missing in that picture is drywall. There is no wall on the loft/bedroom. Upstairs it's a bedroom, bathroom and 10x10 walk in closet. The entire bedroom space is wide open 14x22 to the balcony edge and the stair comes up at that end. It's just my wife and I, so it's not like we need privacy. Someone buying the house might want to put up walls, but we're not. The Bathroom and Closet are walled but we're not interested in cooling them.

[alec.mc 180]

If the walls are all open and you have the space, I'd recommend installing a conventional split system ( central air ).

 

Sizing your new unit is very important, check out http://www.hvaccalc.com/main.asp , purchase the residential program. It's a step by step program that takes account all your parameters of your building and will give you your manual J calc.

 

Though, typically 400 sq ft per ton old construction ( old windows/installation , etc ) 600 sq ft per ton new construction ( nice energy efficient house ) or just average out 500sq/ft per ton.

[djg0770 481]

1) You can get a mini split with several internal units though they are more expensive.

2) Give me the floor plate sq ftg of the rooms you want cooled and I will make you a recommendation

3) Mini split wins the quiet award hands down on ANY system other than chilled beam (and I'm not a chilled beam believer).

[Malsua 1,422]

 

2) Give me the floor plate sq ftg of the rooms you want cooled and I will make you a recommendation

 

 

14x22, open on one end, drops 9 feet to different space.

 

That's it.

[djg0770 481]

Yeah - you're at one ton max for just that space, however:

 

Problem is the hot air from downstairs is going to migrate up to your bedroom. So either you oversize the unit to account for the remaining space or hang a curtain at that "balcony".

[Malsua 1,422]

Yeah - you're at one ton max for just that space, however:

 

Problem is the hot air from downstairs is going to migrate up to your bedroom. So either you oversize the unit to account for the remaining space or hang a curtain at that "balcony".

 

This is exactly the problem. I don't know how to account for that. Maybe I'll get 18k and run it on low if it short cycles.

[djg0770 481]

It's probably not going to short cycle...

[heaterbob 53]

why don't you find a place to run a duct from low wall down stairs to high wall upstairs with a reversable booster fan in the middle somewhere. that way in the summer you take cold air from downstairs and dump it upstairs, then from up to down in winter

[Malsua 1,422]

why don't you find a place to run a duct from low wall down stairs to high wall upstairs with a reversable booster fan in the middle somewhere. that way in the summer you take cold air from downstairs and dump it upstairs, then from up to down in winter

 

Not really any good space for it. We do have ceiling fans that will be able to drive the air down or up and that should help. One is just off the balcony so it can push cold air back upstairs.

[djg0770 481]

Stop being cheap and just A/C the whole house bro. Really...

 

Are you even at 1000 total sq ft?

[Malsua 1,422]

Stop being cheap and just A/C the whole house bro. Really...

 

Are you even at 1000 total sq ft?

 

I just doubled the size of my house and tripled the volume. If you saw how much money I'm laying out to get this done, you wouldn't even suggest I'm being cheap.

 

Not only am I not going to drop another 20k+ for central air, there's no place to run ducts.

[djg0770 481]

20k?? Wow you've been bent by someone. You could get a ductless split with two evaporators installed for less than that in my experience.

[Malsua 1,422]

20k?? Wow you've been bent by someone. You could get a ductless split with two evaporators installed for less than that in my experience.

 

Uhm...I'm talking about getting a 18k ductless with one evap. It's around 2k for the equipment plus whatever to get someone to check it for leaks and charge it. A double system with more BTU would probably run another 2k or so. Central air with ducts everywhere isn't even a possibility as the old part of the house is post and beam and the new part is open.

[djg0770 481]

OK so how did you get from $2k + $2k to $20k? Just asking.

[Malsua 1,422]

OK so how did you get from $2k + $2k to $20k? Just asking.

 

Central Air. Condenser + evaporator + air handler + duct work + installation

[djg0770 481]

Ahh well I was sticking with the minisplit approach either way.

[Malsua 1,422]

I ordered an 18k minisplit today. I'll run the liquid/suction/condensate lines this weekend and then the pressure is off until the sheet rock goes up.

[alec.mc 180]

I ordered an 18k minisplit today. I'll run the liquid/suction/condensate lines this weekend and then the pressure is off until the sheet rock goes up.

 

good deal, 18k should suffice from the dimensions you gave.

 

what are you doing for heat in the area?

[djg0770 481]

Don't forget cleanouts for condensate line. And I would oversize it, min 3/4" - much easier to snake clean if something happens...

[djg0770 481]

good deal, 18k should suffice from the dimensions you gave.

 

what are you doing for heat in the area?

 

He got's a wood stove.

[Malsua 1,422]

good deal, 18k should suffice from the dimensions you gave.

 

what are you doing for heat in the area?

 

I'm installing a 90k Mod/Con boiler. This is an area where I have pretty good knowledge on the subject. I did a heat loss and over-radiated for the space sufficiently enough to run a lower water temp and have enough delta-t to get condensation 90% of the year. I'm probably going to hang the boiler tonight. I ran the Fostapex for the zones over the July 4th week so now it's just getting the boiler up and doing all the copper, zone valves, exp tank, backflow preventer supply, etc. I'm stubbing out for IWH for when the electric one fails. After the drywall goes up, we'll finish the kicks and the fin tubes.

 

And I have a wood stove...we have to extend the chimney about 6 feet though. Yet another 2k or so in that.

[heaterbob 53]

I ordered an 18k minisplit today. I'll run the liquid/suction/condensate lines this weekend and then the pressure is off until the sheet rock goes up.

dont forget power wire from inside head to outside unit