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3527 HVAC

First Thoughts

First thoughts:
  • mini-split with 3 zones
  • 1: 3rd floor bedroom
  • 2: 2nd floor rear bedroom
  • 3: kitchen

Need to determine:
  • BTUs
  • Is 3 zones a good choice?
  • placement of outdoor unit
  • refrigerant line lengths
  • routing for refrigerant lines, wiring, and condensate lines
  • placement of each indoor air handler

Want to order this soon because they may get hard to buy and it will get hot soon. The installation will take quite a bit of work, so it will interrupt the bathroom work.

BTUs: total house is 1834 sq ft by my reckoning, measuring inside dimensions of rooms (so: not counting area taken up by walls, and not including the basement). One online estimator gives 58,000 btu for this. But I also see an estimator that says 6000 btu per average room. And it is supposed to be better not to over-spec the BTU rating because then the thing will short cycle. But, mainly, all the units seem to be 24,000 - 30,000 or so.

My thinking is that the kitchen one will keep the whole ground floor cool and dry but mainly the kitchen. And the third floor one will do that room and let some cool air float down the steps. And the 2nd floor rear one will do the whole 2nd floor from the inside bathroom back. This leaves out our bedroom for now. So maybe later we will need a unit to do the front bedroom and potentially the dining room.

Area sketch:


-- BenDugan - 18 May 2022

New Plan:
  • mini-split with 2 zones
  • 1: 3rd floor
  • 2: Our bedroom

This is more manageable because there's no really long line and we kind of need our bedroom to be in the picture.

Need to determine:
  • BTUs: rooms are roughly 270 sq ft each so
  • placement of outdoor unit
  • refrigerant line lengths
  • routing for refrigerant lines, wiring, and condensate lines
  • placement of each indoor air handler

Went with 27,000 BTUs, 3x9,000, for 3rd floor bedroom, 2nd floor front, and ground floor front.

Most stuff arrive today but not line sets. Ordered 16', 25', and 50', but am getting 2x25's at same price b/c they're our of stock of 16'.

Let's call this the front unit.

Front Unit


What gauge wire? Here's the nameplate for the condenser:


I see online that the minimum circuit ampacity can be used for the wire gauge. This is presumably a current that it might run at normally, or occasionally.

The "whip" provided is 10 AWG. That seems to be rated for 30A. 12 AWG seems to be rated for 20A. So I guess it should be 10AWG.


Looks like what we need is 10/2 NMB (non metallic) and 100' is about $150.

What length? tbd

-- Main.BenDugan - 26 May 2022 - 20:35

Air Handler Strategies

The front chimney flues might be the best way to go here. Then the air handlers can be mounted on the bricks with holes going straight back into the flues. But what about the condensate lines?

Status Update 1

Boxed in spaces on 1st, 2nd, and 3rd floors for the lines and wires. But want to re-work the 3rd floor one because it doesn't line up well with the existing wall. It will look weird if it's not adjusted.

Refrigerant lines and wires are in place.

Today will do another layer of joint compound on 1st & 2nd floor and keep that moving this week so that the indoor units can be mounted. Then look into adjusting 3rd floor framing.

Need plan to get outdoor unit on to roof, and design for the frame that goes under it.

Also need to run power from basement to roof.

-- Main.BenDugan - 26 Jun 2022 - 08:57

I fired up this system for initial testing on July 24th if my memory is right. It's been running really well, keeping the house cool and dry, even back to the kitchen. As of today I have not covered the exposed refrigerant lines but I am almost ready to. I think the 2nd and 3rd floors are solid. The ground floor has a 3D printed wye coupler that isn't tight on 2 of the 3 pipes so that should get tweaked.

-- Main.BenDugan - 05 Aug 2022 - 12:58
Topic attachments
I Attachment Action Size Date Who Comment
FrontCondenserNameplate.jpgjpg FrontCondenserNameplate.jpg manage 210 K 27 May 2022 - 00:34 BenDugan  
FrontCondenserWhip.jpgjpg FrontCondenserWhip.jpg manage 674 K 27 May 2022 - 00:41 BenDugan  
floor_areas_sketch.pngpng floor_areas_sketch.png manage 743 K 18 May 2022 - 15:31 BenDugan  
Topic revision: r8 - 05 Aug 2022, BenDugan
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